<PAGE>

                                                                 EXHIBIT 10.34


                                      LEASE

                                  KILROY REALTY

                                SORRENTO GATEWAY

                                   BUILDING A





                              KR-GATEWAY PARTNERS,

                     a Delaware limited liability company,

                                  as Landlord,

                                       and

                              DIVERSA CORPORATION,

                             a Delaware corporation,

                                   as Tenant.
<PAGE>

                                TABLE OF CONTENTS
                                -----------------

                                                                          Page
                                                                          ----

ARTICLE 1       PREMISES, BUILDING, PROJECT, AND COMMON AREAS.............  5
ARTICLE 2       INITIAL LEASE TERM; OPTION TERM...........................  6
ARTICLE 3       BASE RENT................................................. 10
ARTICLE 4       ADDITIONAL RENT........................................... 10
ARTICLE 5       USE OF PREMISES........................................... 18
ARTICLE 6       SERVICES AND UTILITIES.................................... 19
ARTICLE 7       REPAIRS................................................... 20
ARTICLE 8       ADDITIONS AND ALTERATIONS................................. 21
ARTICLE 9       COVENANT AGAINST LIENS.................................... 23
ARTICLE 10      INSURANCE................................................. 24
ARTICLE 11      DAMAGE AND DESTRUCTION.................................... 27
ARTICLE 12      NONWAIVER................................................. 29
ARTICLE 13      CONDEMNATION.............................................. 29
ARTICLE 14      ASSIGNMENT AND SUBLETTING................................. 30
ARTICLE 15      SURRENDER OF PREMISES; OWNERSHIP AND
                REMOVAL OF TRADE FIXTURES................................. 35
ARTICLE 16      HOLDING OVER.............................................. 35
ARTICLE 17      ESTOPPEL CERTIFICATES..................................... 36
ARTICLE 18      SUBORDINATION............................................. 37
ARTICLE 19      DEFAULTS; REMEDIES........................................ 38
ARTICLE 20      COVENANT OF QUIET ENJOYMENT............................... 40
ARTICLE 21      SECURITY DEPOSIT; LETTER OF CREDIT........................ 41
ARTICLE 22      TELECOMMUNICATIONS EQUIPMENT.............................. 43
ARTICLE 23      SIGNS..................................................... 44
ARTICLE 24      COMPLIANCE WITH LAW....................................... 46
ARTICLE 25      LATE CHARGES.............................................. 47
ARTICLE 26      LANDLORD'S RIGHT TO CURE DEFAULT; PAYMENTS BY TENANT...... 47
ARTICLE 27      ENTRY BY LANDLORD......................................... 48
ARTICLE 28      TENANT PARKING............................................ 48
ARTICLE 29      MISCELLANEOUS PROVISIONS.................................. 49


                                     (iv)
<PAGE>

                                      INDEX
                                      -----
                                                          Page(s)
                                                          -------

                    Accountant...........................   18
                    Additional Rent......................   10
                    Advocate Arbitrators.................    9
                    Affiliate............................   34
                    Alterations..........................   22
                    Award................................    9
                    Bank Prime Loan......................   47
                    Base Building........................   22
                    Base Rent............................   10
                    BOMA.................................    6
                    Brokers..............................   54
                    BS Exception.........................   20
                    Builder's All Risk...................   23
                    Building Monument Sign...............   45
                    Building Signage.....................   45
                    Building Structure...................   20
                    Building Systems.....................   20
                    CC&Rs................................   19
                    CGCC.................................   34
                    Comparable Area......................    8
                    Comparable Buildings.................    8
                    Comparable Deals.....................    7
                    Comparable Term......................    8
                    Cosmetic Alterations.................   21
                    Direct Expenses......................   11
                    Environmental Laws...................   55
                    Estimate.............................   17
                    Estimate Statement...................   17
                    Estimated Direct Expenses............   17
                    Excess...............................   17
                    Exclusive Negotiation Period.........   57
                    Exercise Notice......................    8
                    Expense Year.........................   11
                    First Offer Notice...................   57
                    Force Majeure........................   52
                    Hazardous Material(s)................   55
                    Holdover Notice......................   36
                    HVAC.................................   19
                    Landlord.............................    1
                    Landlord Parties.....................   24
                    Landlord Repair Notice...............   27
                    Landlord Response Date...............    8
                    Landlord Response Notice.............    8
                    Landlord's Option Rent Calculation...    8


                                      (v)
<PAGE>

                                                          Page(s)
                                                          -------

                    L-C..................................   41
                    L-C Amount...........................   41
                    L-C Security Deposit.................   42
                    Lease................................    1
                    Lease Commencement Date..............    6
                    Lease Expiration Date................    6
                    Lease Term...........................    6
                    Lease Year...........................    6
                    Lines................................   55
                    Mail.................................   52
                    Market Rent..........................    7
                    Net Worth............................   34
                    Neutral Arbitrator...................    9
                    Nondisturbance Agreement.............   37
                    Notices..............................   52
                    Objectionable Name...................   45
                    Operating Expenses...................   11
                    Option Rent..........................    7
                    Option Term..........................    7
                    Option Term TI Allowance.............    8
                    Original Improvements................   25
                    Other Improvements...................   56
                    Outside Agreement Date...............    9
                    PCA..................................    6
                    Permitted Holdover Term..............   36
                    Premises.............................    5
                    Proposition 13.......................   15
                    Rent Concessions.....................    7
                    Rent.................................   10
                    Sign Specifications..................   45
                    Statement............................   17
                    Subject Space........................   30
                    Summary..............................    1
                    Tax Expenses.........................   15
                    TCCs.................................    5
                    Telecommunications Equipment.........   43
                    Tenant...............................    1
                    Tenant Parties.......................   24
                    Tenant Work Letter...................    5
                    Tenant's Option Rent Calculation.....    8
                    Tenant's Share.......................   16
                    Tenant's Signage.....................   45
                    Transfer.............................   33
                    Transfer Notice......................   30
                    Transfer Premium.....................   32



                                     (vi)
<PAGE>

                                                          Page(s)
                                                          -------
                    Transferee...........................   30
                    Transfers............................   30















                                    (vii)
<PAGE>

                                SORRENTO GATEWAY
                                ----------------

                                      LEASE
                                      -----

     This Lease (the "LEASE"), dated as of the date set forth in Section 1 of
the Summary of Basic Lease Information (the "SUMMARY"), below, is made by and
between KR-GATEWAY PARTNERS, LLC, a Delaware limited liability company
("LANDLORD"), and DIVERSA CORPORATION, a Delaware corporation ("TENANT").

                       SUMMARY OF BASIC LEASE INFORMATION
                       ----------------------------------
<TABLE>
<CAPTION>
TERMS OF LEASE                                                     DESCRIPTION
----------------------------------------------   -----------------------------------------------
<S>                                              <C>
1.   Date:                                       February 11, 2000

2.   Premises
     2.1  Building:                              That certain two (2) story building to be
                                                 located on lot 5 of the "Project," which
                                                 building shall contain approximately 75,520
                                                 rentable square feet of space, and shall be
                                                 commonly referred to in Project as "BUILDING
                                                 A", as indicated on the Project Site Plan
                                                 attached to the Lease as EXHIBIT A, and
                                                 referred to herein as the "BUILDING."

     2.2  Premises:                              All of the approximately 75,520 rentable feet
                                                 of space located the Building, as further set
                                                 forth in EXHIBIT A to the Lease.

     2.3  Project:                               The Building is part of an office project
                                                 known as "SORRENTO GATEWAY", as further set
                                                 forth in Section 1.1.2 of this Lease.
3.   Lease Term
     (Article 2).

     3.1  Length of Term:                        Fifteen (15) years and no (0) months.

     3.2  Lease Commencement Date:
                                                 The earlier to occur of (i) the date upon which
                                                 Tenant first commences to conduct business
                                                 in the Premises and (ii) the date upon which the
                                                 Premises are Ready for Occupancy, which is
                                                 anticipated to be November 15, 2000.

     3.3  Lease Expiration Date:                 The date immediately preceding the 15th
                                                 anniversary of the Lease Commencement Date.
</TABLE>
<PAGE>

4.   Base Rent (Article 3):
                                                                    Monthly
                                               Monthly            Rental Rate
                          Annual             Installment          per Rentable
    Lease Year          Base Rent            of Base Rent         Square Foot
    ----------        -------------          ------------        --------------

       1 - 2          $2,129,664.00          $177,472.00           $2.3500
       3 - 4          $2,278,740.48          $189,895.04           $2.5145
       5 - 6          $2,438,238.72          $203,186.56           $2.6905
       7 - 8          $2,608,974.34          $217,414.53           $2.8789
       9 - 10         $2,791,581.70          $232,631.81           $3.0804
      11 - 12         $2,986,967.04          $248,913.92           $3.2960
      13 - 14         $3,196,036.61          $266,336.38           $3.5267
         15           $3,419,787.26          $284,982.27           $3.7736


To the extent Tenant reduces the amount of the Tenant and Core Improvement
Allowance pursuant to Section 2 of the Tenant Work Letter, for each $1.00 per
Rentable Square Foot of such reduction (up to a cumulative reduction of $10.00
per Rentable Square Foot of the Premises), the Monthly Rental Rate per Rentable
Square Foot attributable to the Premises shall be lowered by $0.01 (and the
corresponding amounts of Monthly Installment of Base Rent and Annual Base Rent
shall be reduced accordingly and the Base Rent for all 15 years recalculated,
based on a 7% increase on the first day of the 3rd, 5th, 7th, 9th, 11th, 13th,
and 15th Lease Years). To the extent Tenant elects to increase the amount of the
Tenant and Core Improvement Allowance pursuant to Section 2 of the Tenant Work
Letter, for each $1.00 per Rentable Square Foot of such increase (up to a
cumulative increase of $10.00 per Rentable Square Foot of the Premises), the
Monthly Rental Rate per Rentable Square Foot attributable to the Premises shall
be increased by $0.01 (and the corresponding amounts of Monthly Installment of
Base Rent and Annual Base Rent shall be increased accordingly and the Base Rent
for all 15 years recalculated, based on a 7% increase on the first day of the
3rd, 5th, 7th, 9th, 11th, 13th, and 15th Lease Years).


5.  Intentionally Omitted
    (Article 4):

6.  Tenant's Project Share         Approximately eleven and 55/100 Percent
    (Article 4):                   (11.55%).

7.  Permitted Use                  Tenant shall use the Premises solely for
    (Article 5):                   general office, research and development,
                                   labs, and any other legally permitted use
                                   pursuant to the MIB zoning and Sorrento
                                   Gateway P.I.D. applicable to the Building.



                                      -2-
<PAGE>

8.  Security Deposit               Tenant shall fund a letter of credit in an
    (Article 21):                  initial amount of either (i) $2,129,664.00,
                                   (ii) $4,259,328.00 or (iii) $6,388,992.00
                                   (which amounts equal 12, 24, and 36 months
                                   of the initial Monthly Installment of Base
                                   Rent, respectively), depending upon Tenants
                                   financial condition as more particularly set
                                   forth in Article 21, and subject to
                                   reductions and/or reinstatements pursuant to
                                   the provisions of Article 21. Such amounts
                                   shall be recalculated in the event the amount
                                   of Base Rent is adjusted as provided in
                                   Paragraph 4 of this Summary, and Article 3
                                   of the Lease.


9.  Parking Pass Ratio             Tenant shall have the exclusive right to use
    (Article 28):                  the uilding parking area to be constructed
                                   along with the construction of the Building,
                                   in the location and with the number of spaces
                                   indicated on the Project Site Plan attached
                                   hereto as Exhibit A-1, and as more
                                   specifically set forth in Article 28. Such
                                   parking shall be provided at no charge to
                                   Tenant.

10.  Address of Tenant             Diversa Corporation
     (Section 29.18):              10665 Sorrento Valley Road
                                   San Diego, California  92121
                                   Attention:  Mr. Pat Simms,
                                   Vice President of Operations
                                   (Prior to Lease Commencement Date)

     and                           at the Premises to the
                                   attention of Mr. Pat Simms
                                   (After Lease Commencement Date)

                                   with a copy to:

                                   Cooley Godward LLP
                                   One Maritime Plaza, 20th Floor
                                   San Francisco, California  94111
                                   Attention:  Elizabeth A. Willes, Esq.

11.  Address of Landlord           See Section 29.18 of the Lease.
     (Section 29.18):



                                      -3-
<PAGE>

12.  Broker(s)
     (Section 29.24):              Mr. Shaun Burnett
                                   Senior Vice President
                                   The Irving Hughes Group
                                   501 West Broadway, Suite 2020
                                   San Diego, California  92101

                                   and

                                   Brian Driscoll
                                   Colliers International
                                   4660 LaJolla Village Drive, Suite 200
                                   San Diego, California  92121

13.  Tenant and Core Improvement   $110.00 per Rentable Square Foot of the
     Allowance                     Premises ($8,307,200.00 based on 75,520
     (Section 2 of EXHIBIT B):     Rentable Square Feet of Space), subject to
                                   increase or decrease (with a maximum of
                                   $120.00 and a minimum of $100.00) pursuant
                                   to Section 2 of the Tenant Work Letter.




                                      -4-
<PAGE>

                                   ARTICLE 1
                                   ---------

                  PREMISES, BUILDING, PROJECT, AND COMMON AREAS
                  ---------------------------------------------

     1.1   PREMISES, BUILDING, PROJECT AND COMMON AREAS.
           ---------------------------------------------

           1.1.1 THE PREMISES. Landlord hereby leases to Tenant and Tenant
                 ------------
hereby leases from Landlord the premises which are to be constructed
by Landlord in accordance with the Tenant Work Letter which premises shall
contain the approximate number of square feet set forth in Section 2.2 of the
Summary (the "PREMISES"). The parties hereto agree that the lease of the
Premises is upon and subject to the terms, covenants and conditions (the "TCCS")
herein set forth, and Tenant covenants as a material part of the consideration
for this Lease to keep and perform each and all of such TCC's by it to be kept
and performed and that this Lease is made upon the condition of such
performance. The parties hereto hereby acknowledge that the purpose of EXHIBIT A
                                                                       ---------
is to show the approximate location of the "BUILDING," as that term
is defined in Section 1.1.2, below, only, and such Exhibit is not meant to
constitute an agreement, representation or warranty as to the construction of
the Premises, the precise area thereof or the specific location of the "COMMON
AREAS," as that term is defined in Section 1.1.3, below, or the elements thereof
or of the accessways to the Premises or the "PROJECT," as that term is defined
in Section 1.1.2, below. Except as specifically set forth in this Lease and in
the Tenant Work Letter attached hereto as EXHIBIT B (the "TENANT WORK
                                          ---------
LETTER"), Landlord shall not be obligated to provide or pay for any improvement
work or services related to the improvement of the Premises. Tenant also
acknowledges that neither Landlord nor any agent of Landlord has made any
representation or warranty regarding the condition of the Premises, the Building
or the Project or with respect to the suitability of any of the foregoing for
the conduct of Tenant's business, except as specifically set forth in this Lease
and the Tenant Work Letter. The taking of possession of the Premises when the
Premsies are Ready for Occupancy, by Tenant shall conclusively establish that
the Premises is at such time in good and sanitary order, condition and repair,
subject only to punchlist items and Landlord's obligations set forth in Article
7 of this Lease, including, without limitation, Landlord's obligation to
maintain in accordance with Section 7.1 the "Building Structure" as that term is
defined in Section 7.1 of this Lease.

           1.1.2  THE BUILDING AND THE PROJECT.  The Premises consist of all
                  ----------------------------
of that certain two (2)-story building set forth in Section 2.1 of the Summary
(the "BUILDING"). The Building is part of an office project known as "SORRENTO
GATEWAY." The term "PROJECT," as used in this Lease, shall mean (i) the Building
and the Common Areas as shown on the Project Site Plan attached hereto as
Exhibit A-1, (ii) the land (which is to be improved with landscaping, and other
improvements) upon which the Building and the Common Areas are located and which
is known as "LOT 5", and (iii) the other future buildings to be located adjacent
to the Building and the land (commonly known as Lots 1 through 4, and 6 through
9) upon which such adjacent buildings are to be located after completion of
construction of such buildings.

           1.1.3  COMMON AREAS.  Tenant shall have the non-exclusive right to
                  ------------
use in common with other tenants in the Project, and subject to the rules and
regulations referred to in Article 5 of this Lease, those portions of the
Project which are provided, from time to time, for use in common by Landlord,
Tenant and any other tenants of the Project (such areas, together with such
other portions of the Project designated by Landlord, in its discretion,
including certain

                                      -5-
<PAGE>

areas to be shared by Landlord and certain tenants, are collectively referred to
herein as the "COMMON AREAS"). The Common Areas shall consist of the portion of
the Project reasonably designated as such by Landlord; provided, however, such
Common Areas shall not include building common areas within the buildings to be
built within the Project. The manner in which the Common Areas are maintained
and operated shall be at the reasonable discretion of Landlord and the use
thereof shall be subject to such reasonable rules, regulations and restrictions
as Landlord may make from time to time as provided in Section 5.2 of this Lease,
provided that Landlord shall at all times maintain and operate the Common Areas
in a first-class manner consistent with the "Comparable Buildings, as such term
is defined in Section 1.5.2 of this Lease. Landlord reserves the right to close
temporarily, make alterations or additions to, or change the location of
elements of the Project and the Common Areas, as long as such changes do not
change the nature of the Project to something other than a first-class project
or materially, adversely effect Tenant's use of the Premises for the Permitted
Use, as set forth in Section 7 of the Summary, Tenant's ingress to or egress
from the Project, Building, the Premises or the parking areas servicing the
same, or reduce the parking area available for use by Tenant. In connection with
the foregoing, Tenant hereby acknowledges that Landlord shall, pursuant to the
"Building B Lease," as that term is set forth in Section 29.37 of this Lease,
construct "Building B," as that term is set forth in Section 29.37 of this
Lease, and other improvements and Common Areas within the Project. Except when
and where Tenant's right of access is specifically excluded as the result of (i)
an emergency, (ii) a requirement by law, or (iii) a specific provision set forth
in this Lease, Tenant shall have, throughout the Lease Term, the right of
ingress and egress to the Premises, the Building and the Building parking areas
twenty-four (24) hours per day, seven (7) days per week.

     1.2  VERIFICATION OF RENTABLE SQUARE FEET OF PREMISES AND BUILDING.  For
          -------------------------------------------------------------
purposes of this Lease, "rentable square feet" and "usable square feet" shall be
calculated pursuant to Standard Method of Measuring Floor Area in Office
Building, ANSI Z65.1 - 1996 ("BOMA") for single tenant buildings. Within thirty
(30) days after the Lease Commencement Date, Pacific Cornerstone Architects
("PCA") shall measure the rentable and usable square feet of the Premises. The
determination of PCA shall be conclusive and binding upon the parties. In the
event that PCA determines that the amounts thereof shall be different from those
set forth in this Lease, all amounts, percentages and figures appearing or
referred to in this Lease based upon such incorrect amount (including, without
limitation, the amount of the "RENT" and any "SECURITY DEPOSIT," as those terms
are defined in Section 4.1 and Article 21 of this Lease, respectively) shall be
               ------------    -----------
modified in accordance with such determination. If such determination is made by
PCA as set forth above, it will be confirmed in writing by Landlord to Tenant.

                                   ARTICLE 2
                                   ---------

                         INITIAL LEASE TERM; OPTION TERM
                         -------------------------------

     2.1  Initial Lease Term.  The TCC's of this Lease shall be effective as of
          ------------------
the date of this Lease.  The term of this Lease (the "LEASE TERM") shall be as
set forth in Section 3.1 of the Summary, shall commence on the date set forth in
             -----------
Section 3.2 of the Summary (the "LEASE COMMENCEMENT DATE"), and shall terminate
-----------
on the date set forth in Section 3.3 of the Summary (the "LEASE EXPIRATION
                         -----------
DATE") unless this Lease is sooner terminated as hereinafter provided. For
purposes of this Lease, the term "LEASE YEAR" shall mean each consecutive twelve
(12)

                                      -6-
<PAGE>

month period during the Lease Term; provided, however, that the first Lease Year
shall commence on the Lease Commencement Date and end on the last day of the
eleventh month thereafter and the second and each succeeding Lease Year shall
commence on the first day of the next calendar month; and further provided that
the last Lease Year shall end on the Lease Expiration Date. At any time during
the Lease Term, Landlord may deliver to Tenant a notice in the form as set forth
in EXHIBIT C, attached hereto, as a confirmation only of the information set
   ---------
forth therein, which Tenant shall execute and return to Landlord within ten (10)
days of receipt thereof.

     2.2  OPTION TERM.
          -----------

           2.2.1  OPTION RIGHT.  Landlord hereby grants the Original Tenant and
                  ------------
its Affiliates two (2) five (5)-year options (each, an "OPTION TERM") to extend
the Lease Term for the entire Premises. Such option(s) shall be exercisable only
by Notice delivered by Tenant to Landlord as provided below, provided that, as
of the date of delivery of such Notice, Tenant is not in Default under this
Lease. Upon the proper exercise of such option to extend, and provided that, as
of the end of the then applicable Lease term, Tenant is not in Default under
this Lease, the Lease Term, as it applies to the entire Premises, shall be
extended for a period of five (5) years. The rights contained in this
Section 2.2 shall only be exercised by the Original Tenant and its Affiliate
-----------
(and not any other assignee, sublessee or other transferee of the Original
Tenant's interest in this Lease) if Original Tenant and/or its Affiliate is in
possession of the entire Premises.

           2.2.2  OPTION RENT.  The Rent payable by Tenant during each Option
                  -----------
Term (the "OPTION RENT") shall be equal to the Market Rent; provided, however,
that the average annual, effective (including free rent, if applicable, spread
on a straight line basis) base rent component of Market Rent, shall not be lower
than the Base Rent for the month immediately preceding such Option Term.

For purposes of this Lease, the term "MARKET RENT" shall mean the base rent,
which shall be adjusted to reflect a "triple net" transaction, including all
escalations, at which tenants, as of the commencement of the applicable term
are, pursuant to transactions completed within the prior twenty-four (24)
months, leasing non-sublease, non-encumbered, non-synthetic, non-equity space
(unless such space was leased pursuant to a definition of "fair market"
comparable to the definition of Market Rent) comparable in size, location and
quality to the Building for a "Comparable Term," as that term is defined in this
Section 2.2.2 (the "COMPARABLE DEALS"), which comparable space is located in the
-------------
"Comparable Buildings," as that term is defined in this Section 2.2.2, giving
                                                        -------------
appropriate consideration to the annual rental rates per rentable square foot
(adjusting the base rent component of such rate to reflect a net value after
accounting for whether or not utility expenses are directly paid by the tenant
such as Tenant's direct utility payments provided for in Section 6.1 of this
Lease), the standard of measurement by which the rentable square footage is
measured, the ratio of rentable square feet to usable square feet, and taking
into consideration only, and granting only, the following concessions (provided
that the rent payable in Comparable Deals in which the terms of such Comparable
Deals are determined by use of a discounted fair market rate formula shall be
equitably increased in order that such Comparable Deals will not reflect a
discounted rate) (collectively, the "RENT CONCESSIONS"): (a) rental abatement
concessions, if any, being granted such tenants in connection with such
comparable

                                      -7-
<PAGE>

spaces; (b) tenant improvements or allowances provided or to be provided for
such comparable space, taking into account the value of the existing
improvements in the Building, such value to be based upon the age, quality and
layout of the improvements, and (c) all other monetary concessions, if any,
being granted such tenants in connection with such comparable space; provided,
however, that notwithstanding anything to the contrary herein, no consideration
shall be given to (x) the fact that Landlord is or is not required to pay a real
estate brokerage commission in connection with the applicable term or the fact
that the Comparable Deals do or do not involve the payment of real estate
brokerage commissions, and (y) any period of rental abatement, if any, granted
to tenants in Comparable Deals in connection with the design, permitting and
construction of tenant improvements in such comparable spaces. The term
"COMPARABLE TERM" shall refer to the length of the lease term, without
consideration of options to extend such term, for the space in question. If in
determining the Market Rent for an Option Term, Tenant would, pursuant to the
Comparable Deals and the Rent Concessions set forth therein, otherwise be
entitled to a tenant improvement or comparable allowance for the improvement of
the Premises (the "OPTION TERM TI ALLOWANCE"), Tenant shall not be entitled to,
and shall not be compelled, to receive such Option Term TI Allowance, and
Landlord shall reduce the rental rate component of the Market Rent to be an
effective rental rate which takes into consideration that Tenant will not
receive any Option Term TI Allowance. The term "COMPARABLE BUILDINGS" shall mean
other office buildings in the Project, and other first-class lab buildings which
are comparable to the Building in terms of age (based upon the date of
completion of construction or major renovation as to the building containing the
portion of the Premises in question), quality of construction, level of services
and amenities, size and appearance, and are located in the Sorrento Mesa,
University Towne Center and Torrey Pines areas (the "COMPARABLE AREA").

           2.2.3  EXERCISE OF OPTION.  The option contained in this Section 2.2
                  ------------------                                -----------
shall be exercised by Tenant, if at all, only in the manner set forth in this
Section 2.2.3. Tenant shall deliver notice (the "EXERCISE NOTICE") to Landlord
-------------
not more than fifteen (15) months nor less than nine (9) months prior to the
expiration of the then Lease Term, stating that Tenant is exercising its option.
Concurrently with such Exercise Notice, Tenant shall deliver to Landlord
Tenant's calculation of the Market Rent (the "TENANT'S OPTION RENT
CALCULATION"). Landlord shall deliver notice (the "LANDLORD RESPONSE NOTICE") to
Tenant on or before the later to occur of (i) the date which is thirty (30) days
after Landlord's receipt of the Exercise Notice and Tenant's Option Rent
Calculation, or (ii) the date which is nine (9) months prior to the expiration
of the then Lease Term (the "LANDLORD RESPONSE DATE"), stating that (A) Landlord
is accepting Tenant's Option Rent Calculation as the Market Rent, or (B)
rejecting Tenant's Option Rent Calculation and setting forth Landlord's
calculation of the Market Rent (the "LANDLORD'S OPTION RENT CALCULATION").
Within ten (10) business days of its receipt of the Landlord Response Notice,
Tenant may, at its option, accept the Market Rent contained in the Landlord's
Option Rent Calculation. If Tenant does not affirmatively accept or Tenant
rejects the Market Rent specified in the Landlord's Option Rent Calculation, the
parties shall follow the procedure, and the Market Rent shall be determined as
set forth in Section 2.2.4.
             -------------

           2.2.4  DETERMINATION OF MARKET RENT.  In the event Tenant objects or
                  ----------------------------
is deemed to have objected to the Market Rent, Landlord and Tenant shall attempt
to agree upon the Market Rent using reasonable good-faith efforts. If Landlord
and Tenant fail to reach agreement within sixty (60) days following Tenant's
objection or deemed objection to the

                                      -8-
<PAGE>

Landlord's Option Rent Calculation (the (the "Outside Agreement Date"), then (i)
in connection with the Option Rent, Landlord's Option Rent Calculation and
Tenant's Option Rent Calculation, each as previously delivered to the other
party, shall be submitted to the arbitrators pursuant to the TCCs of this
Section 2.2.4, and (ii) in connection with any other contested calculation of
Market Rent, the parties shall each make a separate determination of the Market
Rent and shall submit the same to the arbitrators pursuant to the TCCs of this
Section 2.2.4. The submittals shall be made concurrently with the selection of
the arbitrators pursuant to this Section 2.2.4 and shall be submitted to
                                 -------------
arbitration in accordance with Section 2.2.4.1 through 2.2.4.7 of this Lease,
                               -------------------------------
but subject to the conditions, when appropriate, of Section 2.2.3.
                                                    -------------

                  2.2.4.1 Landlord and Tenant shall each appoint one arbitrator
who shall by profession be a real estate broker, appraiser or attorney who shall
have been active over the five (5) year period ending on the date of such
appointment in the leasing (or appraisal, as the case may be) of first-class
office properties in the Comparable Area. The determination of the arbitrators
shall be limited solely to the issue of whether Landlord's or Tenant's submitted
Market Rent, is the closest to the actual Market Rent as determined by the
arbitrators, taking into account the requirements of Section 1.5.2 of this
                                                     -------------
Lease. Each such arbitrator shall be appointed within fifteen (15) days after
the applicable Outside Agreement Date. Landlord and Tenant may consult with
their selected arbitrators prior to appointment and may select an arbitrator who
is favorable to their respective positions. The arbitrators so selected by
Landlord and Tenant shall be deemed ("ADVOCATE ARBITRATORS").

                  2.2.4.2 The two Advocate Arbitrators so appointed shall be
specifically required pursuant to an engagement letter within ten (10) days of
the date of the appointment of the last appointed Advocate Arbitrator agree upon
and appoint a third arbitrator ("NEUTRAL ARBITRATOR") who shall be qualified
under the same criteria set forth hereinabove for qualification of the two
Advocate Arbitrators except that neither the Landlord or Tenant or either
party's Advocate Arbitrator may, directly or indirectly, consult with the
Neutral Arbitrator prior to subsequent to his or her appearance. The Neutral
Arbitrator shall be retained via an engagement letter jointly prepared by
Landlord's counsel and Tenant's counsel.

                  2.2.4.3 The three arbitrators shall within thirty (30) days of
the appointment of the Neutral Arbitrator reach a decision as to Market Rent and
determine whether the Landlord's or Tenant's determination of Market Rent as
submitted pursuant to Section 2.2.4.1 and Section 2.2.3 of this Lease is closest
                      ---------------     -------------
to Market Rent as determined by the arbitrators and simultaneously publish a
ruling ("AWARD") indicating whether Landlord's or Tenant's submitted Market Rent
is closest to the Market Rent as determined by the arbitrators. Following
notification of the Award, the Landlord's or Tenant's submitted Market Rent
determination, whichever is selected by the arbitrators as being closest to
Market Rent shall become the then applicable Market Rent.

                  2.2.4.4 The Award issued by the majority of the three
arbitrators shall be binding upon Landlord and Tenant.

                  2.2.4.5 If either Landlord or Tenant fail to appoint an
Advocate Arbitrator within fifteen (15) days after the applicable Outside
Agreement Date, either party may petition the presiding judge of the Superior
Court of San Diego County to appoint such Advocate

                                      -9-
<PAGE>

Arbitrator subject to the criteria in Section 2.2.4.1 of this Lease, or if he or
                                      ---------------
she refuses to act, either party may petition any judge having jurisdiction over
the parties to appoint such Advocate Arbitrator.

                  2.2.4.6 If the two Advocate Arbitrators fail to agree upon and
appoint the Neutral Arbitrator, then either party may petition the presiding
judge of the Superior Court of San Diego County to appoint the Neutral
Arbitrator, subject to criteria in Section 2.2.4.1 of this Lease, or if he or
                                   ---------------
she refuses to act, either party may petition any judge having jurisdiction over
the parties to appoint such arbitrator.

                  2.2.4.7  The cost of arbitration shall be paid by Landlord and
Tenant equally.


                                    ARTICLE 3
                                    ---------

                                    BASE RENT
                                    ---------

     Tenant shall pay, without prior notice or demand, to Landlord or Landlord's
agent at the management office of the Project, or, at Landlord's option, at such
other place as Landlord may from time to time designate in writing, by a check
for currency which, at the time of payment, is legal tender for private or
public debts in the United States of America, base rent ("BASE RENT") as set
forth in Section 4 of the Summary, payable in equal monthly installments as set
forth in Section 4 of the Summary in advance on or before the first day of each
and every calendar month during the Lease Term, without any setoff or deduction
whatsoever. The Base Rent for the first full month of the Lease Term shall be
paid at the time of Tenant's execution of this Lease. If any Rent payment date
(including the Lease Commencement Date) falls on a day of the month other than
the first day of such month or if any payment of Rent is for a period which is
shorter than one month, the Rent for any fractional month shall accrue on a
daily basis for the period from the date such payment is due to the end of such
calendar month or to the end of the Lease Term at a rate per day which is equal
to 1/365 of the applicable annual Rent. All other payments or adjustments
required to be made under the terms of this Lease that require proration on a
time basis shall be prorated on the same basis.


                                   ARTICLE 4
                                   ---------

                                 ADDITIONAL RENT
                                 ---------------

     4.1  GENERAL TERMS.  In addition to paying the Base Rent specified in
          -------------
Article 3 of this Lease, Tenant shall pay "TENANT'S SHARE" of the annual "DIRECT
EXPENSES," as those terms are defined in Sections 4.2.6 and 4.2.2 of this Lease.
Such payments by Tenant, together with any and all other amounts payable by
Tenant to Landlord pursuant to the TCC's of this Lease, are hereinafter
collectively referred to as the "ADDITIONAL RENT", and the Base Rent and the
Additional Rent are herein collectively referred to as "RENT." All amounts due
under this Article 4 as Additional Rent shall be payable for the same periods
and in the same manner as the Base Rent. Without limitation on other obligations
of Tenant which survive the expiration of the Lease Term, the obligations of
Tenant to pay the Additional Rent provided for in this Article 4 shall survive
the expiration of the Lease Term. Landlord and Tenant understand and agree that

                                      -10-
<PAGE>

this Lease is a "Triple Net" Lease. Tenant recognizes and acknowledges, without
limiting the generality of any other TCC's of this Lease, that it is the intent
of the parties hereto that the Base Rent provided to be paid by Tenant to
Landlord shall be net to Landlord, and any and all expenses incurred in
connection with the Premises, the Building and a pro-rata portion of the Common
Areas, or in connection with the operations thereof, include any and all taxes,
assessments, general or special license fees, insurance premiums, public utility
bills and costs of repair, maintenance and operation of the Premise and the
Project and all buildings, structures, permanent fixtures and other improvements
comprised therein, together with the appurtenances thereto, shall be paid by
Tenant in addition to the Base Rent specified in this Lease.

     4.2   DEFINITIONS OF KEY TERMS RELATING TO ADDITIONAL RENT.  As used in
           ----------------------------------------------------
this Article 4, the following terms shall have the meanings hereinafter set
forth:

           4.2.1  Intentionally Omitted.

           4.2.2  "DIRECT EXPENSES" shall mean "Operating Expenses" and "Tax
Expenses."

           4.2.3 "EXPENSE YEAR" shall mean each calendar year in which any
portion of the Lease Term falls, through and including the calendar year in
which the Lease Term expires, provided that Landlord, upon notice to Tenant, may
change the Expense Year from time to time to any other twelve (12) consecutive
month period, and, in the event of any such change, Tenant's Share of Direct
Expenses shall be equitably adjusted for any Expense Year involved in any such
change.

           4.2.4 "OPERATING EXPENSES" shall mean all expenses, costs and
amounts of every kind and nature which Landlord pays or accrues during any
Expense Year because of or in connection with the ownership, management,
maintenance, security, repair, replacement, restoration or operation of the
Project, or any portion thereof, except as specifically set forth below to the
contrary. Without limiting the generality of the foregoing, Operating Expenses
shall specifically include any and all of the following: (i) the cost of
supplying all utilities, the cost of operating, repairing, maintaining, and
renovating the utility, telephone, mechanical, sanitary, storm drainage, and
elevator systems, and the cost of maintenance and service contracts in
connection therewith; (ii) the cost of licenses, certificates, permits and
inspections and the cost of contesting any governmental enactments which may
affect Operating Expenses, and the costs incurred in connection with a
transportation system management program or similar program; (iii) the cost of
all insurance carried by Landlord in connection with the Project; (iv) the cost
of landscaping, relamping, and all supplies, tools, equipment and materials used
in the operation, repair and maintenance of the Project, or any portion thereof;
(v) costs incurred in connection with the parking areas servicing the Project;
(vi) fees and other costs, including management fees (which management fee shall
equal two percent (2%) of the Base Rent due under this Lease), consulting fees,
legal fees and accounting fees, of all contractors and consultants in connection
with the management, operation, maintenance and repair of the Project; (vii)
intentionally omitted; (viii) wages, salaries and other compensation and
benefits, including taxes levied thereon, of all persons engaged in the
operation, maintenance and security of the Project at the property manager level
or below; (ix) costs under any recorded instrument pertaining to the sharing of
costs by the Project; (x) operation, repair, maintenance and replacement of all
systems and equipment and components thereof of the Building; (xi) the cost of
security and other

                                      -11-
<PAGE>

services, and fixtures in common areas, maintenance and replacement of curbs and
walkways, and repair to the Building roof membrane; (xii) amortization
(including interest on the unamortized cost) of the cost of acquiring or the
rental expense of personal property used in the maintenance, operation and
repair of the Project, or any portion thereof; (xiii) the cost of capital
improvements or other costs incurred in connection with the Project (A) which
are intended to effect economies in the operation or maintenance of the Project,
or any portion thereof, (B) that are required to comply with present or
anticipated conservation programs, (C) which are replacements or modifications
of nonstructural items located in the Common Areas required to keep the Common
Areas in good order or condition or are replacements or modifications of the
"Building Structure," as that term is set forth in Section 7.1 of this Lease, or
(D) that are required under any governmental law or regulation; provided,
however, that any capital expenditure shall be amortized with interest over its
useful life, as reasonably determined by Landlord pursuant to sound real estate
accounting and management principles, consistently applied; (xiv) costs, fees,
charges or assessments imposed by, or resulting from any mandate imposed on
Landlord by, any federal, state or local government for fire and police
protection, trash removal, community services, or other services which do not
constitute "Tax Expenses" as that term is defined in Section 4.2.5, below; and
(xv) payments under any easement, license, operating agreement, declaration,
restrictive covenant, or instrument pertaining to the sharing of costs by the
Building.

     Notwithstanding anything in this Section 4.2.4 to the contrary, for
purposes of this Lease, Operating Expenses shall not, however, include the
following:

           (A) all costs relating to the maintenance and repair of the following
     structural items: (i) the foundation slab structure under the Building (ii)
     exterior wall structure of the Building, and (iii) the roof structure of
     the Building (excluding the membrane).

           (B) marketing costs, costs of leasing commissions, attorneys' fees
     and other costs and expenses incurred in connection with negotiations or
     disputes with prospective tenants or other occupants of the Project;

           (C) except as otherwise specifically provided in Section 4.2.4(xiii)
     above, costs incurred by Landlord in the repairs, capital additions,
     alterations or replacements made or incurred to rectify or correct defects
     in design, materials or workmanship in connection with the Base Building
     portions of the Project;

           (D) costs (including permit, license and inspection costs) incurred
     in renovating or otherwise improving, decorating or redecorating rentable
     space for prospective tenants or vacant rentable space;

           (E) cost of utilities or services sold to Tenant or others for which
     Landlord is entitled to and actually receives reimbursement (other than
     through any operating cost reimbursement provision identical or
     substantially similar to the provisions set forth in this Lease);

           (F) except as otherwise specifically provided in this Section 4.2.4,
     costs incurred by Landlord for capital repairs, improvements, equipment and
     alterations to the

                                      -12-
<PAGE>

     Project which are considered capital improvements and replacements under
     generally accepted accounting principles, consistently applied;

           (G) costs incurred due to the violation by Landlord or any licensee
     of the TCC's of any lease or license of space in the Project;

           (H) costs of general overhead and general administrative expenses,
     not including management fees and building office expenses which are
     included in operating expenses by landlords of Comparable Buildings;

           (I) costs of any compensation and employee benefits paid to clerks,
     attendants or other persons in a commercial concession operated by
     Landlord;

           (J) marketing costs, legal fees, space planner's fees, and
     advertising and promotional expenses and brokerage fees incurred in
     connection with the original development, subsequent improvement, or
     original or future leasing of the Project;

           (K) costs of electrical power for which Tenant directly contracts
     with and pays a local public service company

           (L) any bad debt loss, rent loss, or reserves for bad debts or rent
     loss;

           (M) costs associated with the operation of the business of the
     partnership or entity which constitutes the Landlord, as the same are
     distinguished from the costs of operation of the Project (which shall
     specifically include, but not be limited to, accounting costs associated
     with the operation of the Project, costs of partnership accounting and
     legal matters, costs of defending any lawsuits with any mortgagee (except
     as the actions of the Tenant may be in issue), costs of selling,
     syndicating, financing, mortgaging or hypothecating any of the Landlord's
     interest in the Project, and costs incurred in connection with any disputes
     between Landlord and its employees, between Landlord and Project
     management, or between Landlord and other tenants or occupants, and
     Landlord's general corporate overhead and general and administrative
     expenses);

           (N) the wages and benefits of any employee who does not devote
     substantially all of his or her employed time to the Project unless such
     wages and benefits are prorated to reflect time spent on operating and
     managing the Project vis-a-vis time spent on matters unrelated to operating
     and managing the Project; provided, that in no event shall Operating
     Expenses for purposes of this Lease include wages and/or benefits
     attributable to personnel above the level of Project manager or Project
     engineer;

           (O) interest, charges and fees incurred on debt, payments on
     mortgages and amounts paid as ground rental for the real property
     underlying the Project by the Landlord;

           (P) costs for sculpture, paintings, fountains or other objects of
     art, other than those incurred in ordinary maintenance and repair;

                                      -13-
<PAGE>

           (Q) any costs expressly excluded from Operating Expenses elsewhere in
     this Lease;

           (R) costs arising from Landlord's charitable or political
     contributions;

           (S) any gifts provided to any entity whatsoever, including, but not
     limited to, Tenant, other tenants, employees, vendors, contractors,
     prospective tenants and agents;

           (T) any costs covered by any warranty, rebate, guarantee or service
     contract which are actually collected by Landlord (which shall not prohibit
     Landlord from passing through the costs of any such service contract if
     otherwise includable in Operating Expenses);

           (U) interest, late charges and tax penalties incurred as a result of
     Landlord's gross negligence, inability or unwillingness to make payments or
     file returns when due;

           (V) all items and services for which Tenant reimburses Landlord;

           (W) any costs included as a Tax Expense pursuant to Section 4.2.5
     below;

           (X) any expense resulting from the gross negligence of Landlord, its
     agents, contractors or employees, or, to the extent landlord is entitled to
     reimbursement for such costs, to remedy damage caused by or resulting from
     the gross negligence of any licensees in the Project, including their
     agents, contractors and employees;

           (Y) reserves for anticipated future expenses;

           (Z) costs or repairs or other work occasioned by fire, casualty or
     other risk covered by insurance maintained (or obligated to be maintained
     pursuant to Article 10 of this Lease) by Landlord;

           (AA) costs, fines, or fees incurred by Landlord due to Landlord's
     violations of any federal, state or local law, statute or ordinance, or any
     rule, regulation, judgment or decree of any governmental rule or authority;

           (BB) any costs representing an amount paid to a person, firm,
     corporation or other entity related to Landlord which is in excess of the
     amount which would have been paid in the absence of such relationship;

           (CC) rentals for items (except when needed in connection with normal
     repairs and maintenance of permanent systems) which if purchased, rather
     than rented, would constitute a capital item which is specifically excluded
     in this Lease (excluding, however, equipment not affixed to the Building
     which is used in providing janitorial or similar services);

           (DD) advertising and promotional expenditures, and costs of signs in
     or on the Building identifying the owner of the Building;

                                      -14-
<PAGE>

           (EE) costs of development or initial construction within the Project
     (including, without limitation, such initial development or initial
     construction costs incurred to comply with any now-existing CC&Rs,
     development permits, design permit or use permit currently issued for the
     Project);

           (FF) reserves for depreciation, amortization and other expenses;

           (GG) costs occasioned by the active negligence or willful misconduct
     of Landlord or any other occupant of the Project or violations of
     applicable law by Landlord or any such occupant of the Project;

           (HH) deductibles payable under any earthquake insurance.

           4.2.5  TAXES.
                  -----

                  4.2.5.1 "TAX EXPENSES" shall mean all federal, state, county,
or local governmental or municipal taxes, fees, charges or other impositions of
every kind and nature, whether general, special, ordinary or extraordinary,
(including, without limitation, real estate taxes, general and special
assessments, transit taxes, leasehold taxes or taxes based upon the receipt of
rent, including gross receipts or sales taxes applicable to the receipt of rent,
unless required to be paid by Tenant, personal property taxes imposed upon the
fixtures, machinery, equipment, apparatus, systems and equipment, appurtenances,
furniture and other personal property used in connection with the Project, or
any portion thereof), which shall be paid or accrued during any Expense Year
(without regard to any different fiscal year used by such governmental or
municipal authority) because of or in connection with the ownership, leasing and
operation of the Project, or any portion thereof. Notwithstanding anything to
the contrary set forth in this Section 4.2.5, Tax Expenses shall specifically
exclude bonds and/or assessments which have been or, subsequent to the date
hereof are, levied for the purpose of funding the costs of construction of all
or any portion of the Project or capital improvements constructed therein or
about, or on-or off-site improvements with respect thereto, to the extent such
improvements are the sole responsibility of Landlord under the TCCs of this
Lease.

                  4.2.5.2 Tax Expenses shall include, without limitation:
(i) Any tax on the rent, right to rent or other income from the Project, or any
portion thereof, or as against the business of leasing the Project, or any
portion thereof; (ii) Any assessment, tax, fee, levy or charge in addition to,
or in substitution, partially or totally, of any assessment, tax, fee, levy or
charge previously included within the definition of real property tax, it being
acknowledged by Tenant and Landlord that Proposition 13 was adopted by the
voters of the State of California in the June 1978 election ("PROPOSITION 13")
and that assessments, taxes, fees, levies and charges may be imposed by
governmental agencies for such services as fire protection, street, sidewalk and
road maintenance, refuse removal and for other governmental services formerly
provided without charge to property owners or occupants, and, in further
recognition of the decrease in the level and quality of governmental services
and amenities as a result of Proposition 13, Tax Expenses shall also include any
governmental or private assessments or the Project's contribution towards a
governmental or private cost-sharing agreement for the purpose of augmenting or
improving the quality of services and amenities normally provided by
governmental agencies; (iii) Any assessment, tax, fee, levy, or charge allocable
to or measured by the area of the

                                      -15-
<PAGE>

Premises or the Rent payable hereunder, including, without limitation, any
business or gross income tax or excise tax with respect to the receipt of such
rent, or upon or with respect to the possession, leasing, operating, management,
maintenance, alteration, repair, use or occupancy by Tenant of the Premises, or
any portion thereof; and (iv) Any assessment, tax, fee, levy or charge, upon
this transaction or any document to which Tenant is a party, creating or
transferring an interest or an estate in the Premises.

                  4.2.5.3 Any costs and expenses (including, without limitation,
reasonable attorneys' fees) incurred in attempting to protest, reduce or
minimize Tax Expenses shall be included in Tax Expenses in the Expense Year such
expenses are paid. Except as set forth in Section 4.2.5.4, below, refunds of Tax
Expenses shall be credited against Tax Expenses and refunded to Tenant
regardless of when received, based on the Expense Year to which the refund is
applicable, provided that in no event shall the amount to be refunded to Tenant
for any such Expense Year exceed the total amount paid by Tenant as Additional
Rent under this Article 4 for such Expense Year. If Tax Expenses for any period
                ---------
during the Lease Term or any extension thereof are increased after payment
thereof for any reason, including, without limitation, error or reassessment by
applicable governmental or municipal authorities, Tenant shall pay Landlord upon
demand Tenant's Share of any such increased Tax Expenses included by Landlord as
Building Tax Expenses pursuant to the TCC's of this Lease. Notwithstanding
anything to the contrary contained in this Section 4.2.8 (except as set forth in
                                           -------------
Section 4.2.8.1, above), there shall be excluded from Tax Expenses (i) all
---------------
excess profits taxes, franchise taxes, gift taxes, capital stock taxes,
inheritance and succession taxes, estate taxes, federal and state income taxes,
and other taxes to the extent applicable to Landlord's general or net income
from all sources, (ii) any items included as Operating Expenses, (iii) any items
paid by Tenant under Section 4.5 of this Lease, and transfer taxes associated
                     -----------
with the sale or other transfer by Landlord of its interest in the Project.

           4.2.6 "TENANT'S SHARE" shall mean the percentage set forth in Section
6 of the Summary, which percentage is equal to a fraction, the numerator of
which is the acreage of Lot 5, and the denominator of which is the acreage of
the entire Project (i.e., Lots 1 through 9).

     4.3  ALLOCATION OF DIRECT EXPENSES; METHOD OF ALLOCATION.  The parties
          ---------------------------------------------------
acknowledge that the Building is a part of what is to be a multi-building
project and that the costs and expenses incurred in connection with the Project
(i.e. the Direct Expenses) should be shared between Tenant (as the tenant of the
Building) and the tenants of the other buildings in the Project. Accordingly, as
set forth in Section 4.2 above, Direct Expenses (which consists of Operating
                -----------
Expenses and Tax Expenses) are determined annually for the Project as a whole,
and a portion of the Direct Expenses, which portion shall be determined by
Landlord on a pro-rata basis as set forth in Section 4.2.6, shall be allocated
to the Building (as opposed to other buildings in the Project and the tenants of
such buildings) and such portion shall be the Direct Expenses for purposes of
this Lease. Such portion of Direct Expenses allocated to the Building shall
include all Direct Expenses attributable solely to the Building (e.g., 100% of
the Tax Expenses related solely to Lot 5) and a pro-rata portion of the Direct
Expenses attributable to the Project as a whole (provided, however, that for
purposes of determining the portion of Tax Expenses attributable to the Project
as a whole, only the Tax Expenses relating to the Common Areas (as opposed to
the Tax Expenses relating directly to another lot in the Project upon which
another building is to be built) shall be included in such determination).

                                      -16-
<PAGE>

     4.4   CALCULATION AND PAYMENT OF ADDITIONAL RENT.  Tenant shall pay to
           ------------------------------------------
Landlord, in the manner set forth in Section 4.4.1, below, and as Additional
Rent Tenant's Share of Direct Expenses for each Expense Year.

           4.4.1  STATEMENT OF ACTUAL DIRECT EXPENSES AND PAYMENT BY TENANT.
                  ---------------------------------------------------------
Within one hundred fifty (150) days after the end of each Expense Year, Landlord
shall give to Tenant a statement (the "STATEMENT") which shall state the Direct
Expenses incurred or accrued for such preceding Expense Year, and which shall
indicate the amount of Tenant's Share of Direct Expenses. Within thirty (30)
days of receipt of the Statement for each Expense Year commencing or ending
during the Lease Term Tenant shall pay, with its next installment of Base Rent
due, the full amount of Tenant's Share of Direct Expenses for such Expense Year,
less the amounts, if any, paid during such Expense Year as "Estimated Direct
Expenses," as that term is defined in Section 4.4.2, below. The failure of
Landlord to timely furnish the Statement for any Expense Year shall not
prejudice Landlord or Tenant from enforcing its rights under this Article 4.
Even though the Lease Term has expired and Tenant has vacated the Premises, when
the final determination is made of Tenant's Share of Direct Expenses for the
Expense Year in which this Lease terminates, if is greater than then amount of
estimated Direct Expenses previously paid by Tenant to Landlord (an "EXCESS"),
Tenant shall pay to Landlord such amount within thirty (30) days of request
therefor. The provisions of this Section 4.4.1 shall survive the expiration or
earlier termination of the Lease Term.

           4.4.2  STATEMENT OF ESTIMATED DIRECT EXPENSES.  In addition,
                  --------------------------------------
Landlord shall give Tenant a yearly expense estimate statement (the "ESTIMATE
STATEMENT") which shall set forth Landlord's reasonable estimate of Tenant's
Share of Direct Expenses (the "ESTIMATE") of what the total amount of Direct
Expenses for the then-current Expense Year shall be and the estimated excess
(the "ESTIMATED DIRECT EXPENSES"). Failure of Landlord to timely furnish the
Estimate Statement for any Expense Year shall not preclude Landlord from
enforcing its rights to collect any Estimated Direct Expenses under this Article
4, nor shall Landlord be prohibited from revising any Estimate Statement or
Estimated Direct Expenses theretofore delivered to the extent necessary. After
its receipt of the Estimate Statement, Tenant shall pay, with its next
installment of Base Rent due, a fraction of the Estimated Direct Expenses for
the then-current Expense Year (reduced by any amounts paid pursuant to the next
to last sentence of this Section 4.4.2). Such fraction shall have as its
numerator the number of months which have elapsed in such current Expense Year,
including the month of such payment, and twelve (12) as its denominator. Until a
new Estimate Statement is furnished (which Landlord shall have the right to
deliver to Tenant at any time), Tenant shall pay monthly, with the monthly Base
Rent installments, an amount equal to one-twelfth (1/12) of the total Estimated
Direct Expenses set forth in the previous Estimate Statement delivered by
Landlord to Tenant.

     4.5   TAXES AND OTHER CHARGES FOR WHICH TENANT IS DIRECTLY RESPONSIBLE.
           ----------------------------------------------------------------

           4.5.1 Tenant shall be liable for and shall pay ten (10) days before
delinquency, taxes levied against Tenant's equipment, furniture, fixtures and
any other personal property located in or about the Premises. If any such taxes
on Tenant's equipment, furniture, fixtures and any other personal property are
levied against Landlord or Landlord's property or if the assessed value of
Landlord's property is increased by the inclusion therein of a value placed upon
such equipment, furniture, fixtures or any other personal property and if
Landlord pays the taxes based

                                      -17-
<PAGE>

upon such increased assessment, which Landlord shall have the right to do
regardless of the validity thereof but only under proper protest if requested by
Tenant, Tenant shall upon demand repay to Landlord the taxes so levied against
Landlord or the proportion of such taxes resulting from such increase in the
assessment, as the case may be.

           4.5.2  Intentionally Omitted.

           4.5.3 Notwithstanding any contrary provision herein, Tenant shall pay
prior to delinquency any (i) rent tax or sales tax, service tax, transfer tax or
value added tax, or any other applicable tax on the rent or services herein or
otherwise respecting this Lease, (ii) taxes assessed upon or with respect to the
possession, leasing, operation, management, maintenance, alteration, repair, use
or occupancy by Tenant of the Premises or any portion of the Project, including
the Project parking facility; or (iii) taxes assessed upon this transaction or
any document to which Tenant is a party creating or transferring an interest or
an estate in the Premises.

     4.6   LANDLORD'S BOOKS AND RECORDS.  Within two (2) years after receipt of
           ----------------------------
a Statement by Tenant, if Tenant disputes the amount of Additional Rent set
forth in the Statement, a determination as to the proper amount shall be made,
at Tenant's expense, by an independent certified public accountant (the
"ACCOUNTANT") selected by Landlord and subject to Tenant's reasonable approval,
by inspecting Landlord's records with respect to the Statement at Landlord's
offices, provided that Tenant is not then in Default under this Lease and Tenant
has paid all amounts required to be paid under the applicable Estimate Statement
and Statement, as the case may be. In connection with such inspection, the
Accountant must agree in advance to follow Landlord's reasonable rules and
procedures regarding inspections of Landlord's records, and shall execute a
commercially reasonable confidentiality agreement regarding such inspection. If
such determination by the Accountant proves that Direct Expenses were overstated
by more than five percent (5%), then the cost of the Accountant and the cost of
such determination shall be paid for by Landlord. Tenant's failure to dispute
the amount of Additional Rent set forth in any Statement within two (2) years of
Tenant's receipt of such Statement shall be deemed to be Tenant's approval of
such Statement and Tenant, thereafter, waives the right or ability to dispute
the amounts set forth in such Statement. Tenant hereby acknowledges that
Tenant's sole right to inspect Landlord's books and records and to contest the
amount of Direct Expenses payable by Tenant shall be as set forth in this
Section 4.6, and Tenant hereby waives any and all other rights pursuant to
Applicable Law to inspect such books and records and/or to contest the amount of
Direct Expenses payable by Tenant.

                                   ARTICLE 5
                                   ---------

                                 USE OF PREMISES
                                 ---------------

     5.1   PERMITTED USE.  Tenant shall use the Premises solely for the
           -------------
Permitted Use set forth in Section 7 of the Summary and Tenant shall not use or
permit the Premises or the Project to be used for any other purpose or purposes
whatsoever without the prior written consent of Landlord, which may be withheld
in Landlord's reasonable discretion.

     5.2   PROHIBITED USES.  The uses prohibited under this Lease shall include,
           ---------------
without limitation, use of the Premises or a portion thereof for (i) offices of
any agency or bureau of the

                                      -18-
<PAGE>

United States or any state or political subdivision thereof; (ii) offices or
agencies of any foreign governmental or political subdivision thereof; (iii)
offices of any health care professionals or service organization; (iv) schools
or other training facilities which are not ancillary to corporate, executive or
professional office use; (v) retail or restaurant uses; or (vi) communications
firms such as radio and/or television stations. Tenant further covenants and
agrees that Tenant shall not use, or suffer or permit any person or persons to
use, the Premises or any part thereof for any use or purpose contrary to the
provisions of the Rules and Regulations set forth in EXHIBIT D, attached hereto,
                                                     ---------
or in violation of the laws of the United States of America, the State of
California, or the ordinances, regulations or requirements of the local
municipal or county governing body or other lawful authorities having
jurisdiction over the Project) including, without limitation, any such laws,
ordinances, regulations or requirements relating to hazardous materials or
substances, as those terms are defined by applicable laws now or hereafter in
effect. Tenant shall not do or permit anything to be done in or about the
Premises which will in any way damage the reputation of the Project or use or
allow the Premises to be used for any improper, unlawful or objectionable
purpose, nor shall Tenant cause, maintain or permit any nuisance in, on or about
the Premises.

     5.3   CC&RS.  Tenant shall comply with all recorded covenants, conditions,
           -----
and restrictions currently affecting the Project. Additionally, Tenant
acknowledges that it is anticipated that the Project will be subject to that
certain "Declaration of Covenants, Conditions and Restriction for Sorrento
Gateway," a substantially complete copy of which is attached hereto as
EXHIBIT F-1, and may be subject to amendments and modifications thereto as well
-----------
as additional future covenants, conditions and restrictions (collectively, the
"CC&RS") which Landlord deems reasonably necessary and/or desirable (provided,
however, such amendments and/or modifications do not prohibit the Permitted Use
in the Project and do not materially adversely interfere with Tenant's use and
enjoyment of the Premises, and Tenant agrees that this Lease shall be subject
and subordinate to such CC&Rs. Landlord shall have the right to require Tenant
to execute and acknowledge, within fifteen (15) business days of a request by
Landlord, a "Recognition of Covenants, Conditions, and Restriction," in a form
substantially similar to that attached hereto as EXHIBIT F-2, agreeing to and
                                                 -----------
acknowledging the CC&Rs.


                                   ARTICLE 6
                                   ---------

                             SERVICES AND UTILITIES
                             ----------------------

     6.1   STANDARD TENANT SERVICES.  Landlord shall keep the Building
           ------------------------
Structure in condition and repair materially consistent with the Comparable
Buildings and shall maintain the Common Areas of the Project.

     Notwithstanding the foregoing, Tenant shall directly pay for all utilities
(including without limitation, electricity, gas and water) attributable to its
use of the entire Premises. Such utility use shall include electricity, water,
and gas use for lighting, incidental use and heating and air-conditioning
("HVAC"). All such direct utility payments shall be excluded from Operating
Expenses (as opposed to the utility payments made by Landlord for the Common
Areas of the Project which shall be included in Operating Expenses) and shall be
paid directly by Tenant prior to the date on which the same are due to the
utility provider. The Premises shall be separately

                                      -19-
<PAGE>

metered as part of the Tenant Improvements to be constructed pursuant to the
Tenant Work Letter.

     Landlord shall not be required to provide any services other than with
regard to its maintenance and repair obligation relating to the Building
Structure and the Common Areas of the Project (subject to the TCCs of Section
4.3 above).

     6.2   INTENTIONALLY OMITTED.
           ---------------------

     6.3   INTERRUPTION OF USE.  Tenant agrees that Landlord shall not be
           -------------------
liable for damages, by abatement of Rent or otherwise, for failure to furnish or
delay in furnishing any service (including telephone and telecommunication
services), or for any diminution in the quality or quantity thereof, when such
failure or delay or diminution is occasioned, in whole or in part, by breakage,
repairs, replacements, or improvements, by any strike, lockout or other labor
trouble, by inability to secure electricity, gas, water, or other fuel at the
Building or Project after reasonable effort to do so, by any riot or other
dangerous condition, emergency, accident or casualty whatsoever, by act or
default of Tenant or other parties, or by any other cause; and such failures or
delays or diminution shall never be deemed to constitute an eviction or
disturbance of Tenant's use and possession of the Premises or relieve Tenant
from paying Rent or performing any of its obligations under this Lease.
Furthermore, Landlord shall not be liable under any circumstances for a loss of,
or injury to, property or for injury to, or interference with, Tenant's
business, including, without limitation, loss of profits, however occurring,
through or in connection with or incidental to a failure to furnish any of the
services or utilities as set forth in this Article 6.
                                           ---------

                                    ARTICLE 7
                                    ---------

                                     REPAIRS
                                     -------

     Landlord shall maintain in good condition and operating order and keep in
good repair and condition the structural portions of the Building, including the
foundation, floor/ceiling slabs, roof, curtain wall, exterior glass and
mullions, columns, beams, shafts (including elevator shafts), parking areas,
landscaping, exterior fountains, exterior water falls, exterior Project signage,
exterior plazas, exterior art work, exterior sculptures, and all exterior common
and public areas (collectively, "BUILDING STRUCTURE"). Tenant shall maintain in
good condition and operating order and keep in good repair and condition the
Base Building mechanical, electrical, life safety, plumbing, sprinkler systems
and HVAC systems, stairs, stairwells, elevator cabs, men's and women's
washrooms, and Building mechanical, electrical and telephone closets, including
those constructed by Tenant Parties (collectively, the "BUILDING SYSTEMS").
Notwithstanding anything in this Lease to the contrary, Tenant shall be required
to repair the Building Structure to the extent required because of Tenant's
negligence or willful misconduct, unless and to the extent such damage is
covered by insurance carried or required to be carried by Landlord pursuant to

Article 10 and to which the waiver of subrogation is applicable (such obligation
----------
to the extent applicable to Tenant as qualified and conditioned will hereinafter
be defined as the "BS EXCEPTION"). Tenant shall, at Tenant's own expense,
pursuant to the TCC's of this Lease, including without limitation Article 8
                                                                  ---------
hereof, keep the Premises, including all Tenant Improvements, "Alterations," as
that term is defined in Section 8.1 of this Lease, fixtures and the
                        -----------

                                      -20-
<PAGE>

floor or floors of the Building on which the Premises are located, in good
order, repair and condition at all times during the Lease Term (but such
obligation shall not extend to the Building Structure except pursuant to the BS
Exception), except for damage caused by ordinary wear and tear or beyond the
reasonable control of Tenant. Tenant shall, at Tenant's own expense, but under
the supervision and subject to the prior approval of Landlord, and within any
reasonable period of time specified by Landlord, pursuant to the TCC's of this
Lease, including without limitation Article 8 hereof, promptly and adequately
                                    ---------
repair all damage to the Premises and replace or repair all damaged, broken, or
worn fixtures and appurtenances (but such obligation shall not extend to the
Building Structure except pursuant to the BS Exception), except for damage
caused by ordinary wear and tear or beyond the reasonable control of Tenant;
provided however, that, at Landlord's option, but only if Tenant fails to make
such repairs and replacements, Landlord may, but need not, make such repairs and
replacements, and Tenant shall pay Landlord the cost thereof, including a
percentage of the cost thereof (to be uniformly established for the Building
and/or the Project) sufficient to reimburse Landlord for all overhead, general
conditions, fees and other costs or expenses arising from Landlord's involvement
with such repairs and replacements forthwith upon being billed for same.
Landlord may, but shall not be required to, enter the Premises at all reasonable
times (after reasonable notice) to make such repairs, alterations, improvements
or additions to the Premises or to the Project or to any equipment located in
the Project as Landlord shall desire or deem necessary or as Landlord may be
required to do by governmental or quasi-governmental authority or court order or
decree. Tenant hereby waives any and all rights under and benefits of subsection
1 of Section 1932 and Sections 1941 and 1942 of the California Civil Code or
under any similar law, statute, or ordinance now or hereafter in effect.
Landlord shall procure a fifteen (15) year warranty on the roof membrane and
assign such warranty (and all other warranties for the Building) to Tenant. If,
on or before the eighth (8th) anniversary of the Lease Commencement Date, Tenant
becomes obligated, at Tenant's sole cost and expense, to make a repair to the
Building Systems pursuant to the TCCs of this Article 7 which shall be capital
in nature, Tenant may elect, upon immediate notice thereof to Landlord, to have
Landlord make such repair to the Building Systems, the cost of which shall be
amortized with interest over its useful life as reasonably determined by
Landlord pursuant to sound real estate accounting and management principles,
consistently applied, and shall be paid by Tenant to Landlord as Additional
Rent; provided, however, (i) Tenant shall not have such option to the extent
such repair is necessary due to the negligence or willful misconduct of Tenant
or the Tenant's Parties, and (ii) to the extent Tenant's use of the repaired
item reduces the useful life of such repair, the cost of such repairs shall be
amortized with interest over such shorter time period.

                                   ARTICLE 8
                                   ---------

                            ADDITIONS AND ALTERATIONS
                            -------------------------

     8.1   LANDLORD'S CONSENT TO ALTERATIONS.  Tenant shall have the right,
           ---------------------------------
without Landlord's consent but upon five (5) business days prior Notice to
Landlord, to make strictly cosmetic, non-structural additions and alterations
("COSMETIC ALTERATIONS") to the Premises that do not (i) involve the expenditure
of more than $100,000.00 in the aggregate in any Lease Year; (ii) affect the
exterior appearance of the Building, or (iii) affect the Building Systems or the
Building Structure. Except in connection with Cosmetic Alterations, Tenant may
not make any improvements, alterations, additions or changes to the Premises or
any mechanical, plumbing or

                                      -21-
<PAGE>

HVAC facilities or systems pertaining to the Premises (collectively, the
"ALTERATIONS") without first procuring the prior written consent of Landlord to
such Alterations, which consent shall be requested by Tenant not less than
thirty (30) days prior to the commencement thereof, and which consent shall not
be unreasonably withheld by Landlord, provided it shall be deemed reasonable for
Landlord to withhold its consent to any Alteration which adversely affects the
structural portions or the systems or equipment of the Building or is visible
from the exterior of the Building. The construction of the initial improvements
to the Premises shall be governed by the TCC's of the Tenant Work Letter and not
the TCC's of this Article 8.
                  ---------

     8.2   MANNER OF CONSTRUCTION.  Landlord may impose, as a condition of its
           ----------------------
consent to any and all Alterations or repairs of the Premises or about the
Premises, such requirements as Landlord in its reasonable discretion may deem
desirable, including, but not limited to, the requirement that Tenant utilize
for such purposes only contractors, subcontractors, materials, mechanics and
materialmen selected by Tenant from a list provided and approved by Landlord,
the requirement that upon Landlord's request, Tenant shall, at Tenant's expense,
remove such Alterations upon the expiration or any early termination of the
Lease Term. If such Alterations will involve the use of or disturb hazardous
materials or substances existing in the Premises, Tenant shall comply with
Landlord's rules and regulations concerning such hazardous materials or
substances. Tenant shall construct such Alterations and perform such repairs in
a good and workmanlike manner, in conformance with any and all applicable
federal, state, county or municipal laws, rules and regulations and pursuant to
a valid building permit, issued by the City of San Diego, all in conformance
with Landlord's construction rules and regulations. In the event Tenant performs
any Alterations in the Premises which require or give rise to governmentally
required changes to the "Base Building," as that term is defined below, then
Landlord shall, at Tenant's expense, make such changes to the Base Building. The
"BASE BUILDING" shall consist of the Building Structure. In performing the work
of any such Alterations, Tenant shall have the work performed in such manner so
as not to obstruct access to the Project or any portion thereof, by any other
tenant of the Project, and so as not to obstruct the business of Landlord or
other tenants in the Project. Tenant shall not use (and upon notice from
Landlord shall cease using) contractors, services, workmen, labor, materials or
equipment that, in Landlord's reasonable judgment, would disturb labor harmony
with the workforce or trades engaged in performing other work, labor or services
in or about the Building or the Common Areas. In addition to Tenant's
obligations under Article 9 of this Lease, upon completion of any Alterations,
Tenant agrees to cause a Notice of Completion to be recorded in the office of
the Recorder of the County of San Diego in accordance with Section 3093 of the
Civil Code of the State of California or any successor statute, and Tenant shall
deliver to the Project management office a reproducible copy of the "as built"
drawings of the Alterations as well as all permits, approvals and other
documents issued by any governmental agency in connection with the Alterations.

     8.3   PAYMENT FOR IMPROVEMENTS.  If payment is made directly to
           ------------------------
contractors, Tenant shall comply with Landlord's requirements for final lien
releases and waivers in connection with Tenant's payment for work to
contractors. Except with regard to Cosmetic Alterations for which there shall be
no such charge, whether or not Tenant orders any work directly from Landlord,
Tenant shall pay to Landlord a percentage of the cost of such work (not to
exceed one percent (1%) of the total cost of such work) sufficient to compensate
Landlord for all overhead, general

                                      -22-
<PAGE>

conditions, fees and other costs and expenses arising from Landlord's
involvement with such work.

     8.4   CONSTRUCTION INSURANCE.  In addition to the requirements of Article
           ----------------------
10 of this Lease, in the event that Tenant makes any Alterations, prior to the
commencement of such Alterations, Tenant shall provide Landlord with evidence
that Tenant carries "BUILDER'S ALL RISK" insurance in an amount approved by
Landlord covering the construction of such Alterations, and such other insurance
as Landlord may require, it being understood and agreed that all of such
Alterations shall be insured by Tenant pursuant to Article 10 of this Lease
immediately upon completion thereof. In addition, Landlord may, in its
discretion, require Tenant to obtain a lien and completion bond or some
alternate form of security satisfactory to Landlord in an amount sufficient to
ensure the lien-free completion of such Alterations and naming Landlord as a co-
obligee.

     8.5   LANDLORD'S PROPERTY.  All Alterations, improvements, fixtures,
           -------------------
equipment and/or appurtenances which may be installed or placed in or about the
Premises, from time to time, shall be at the sole cost of Tenant and shall be
and become the property of Landlord, except that Tenant may remove any
Alterations, improvements, fixtures and/or equipment which Tenant can
substantiate to Landlord have not been paid for with any Tenant improvement
allowance funds provided to Tenant by Landlord, provided Tenant repairs any
damage to the Premises and Building caused by such removal and returns the
affected portion of the Premises to a building standard tenant improved
condition as determined by Landlord. Furthermore, Landlord may, by written
notice to Tenant prior to the end of the Lease Term, or given following any
earlier termination of this Lease, require Tenant, at Tenant's expense, to (i)
remove any Alterations or improvements in the Premises, and/or (ii) remove any
"Above Building Standard Tenant Improvements," as that term is defined in the
Tenant Work Letter, located within the Premises and replace the same with then
existing "Building Standard Tenant Improvements," as that term is defined in the
Tenant Work Letter, and to repair any damage to the Premises and Building caused
by such removal and returns the affected portion of the Premises to a building
standard tenant improved condition as reasonably determined by Landlord;
provided, however, if, in connection with its request for Landlord's approval
for particular Alterations, (1) Tenant requests Landlord's decision with regard
to the removal of such Alterations, and (2) Landlord thereafter agrees in
writing to waive the removal requirement when approving such Alterations, then
Tenant shall not be required to so remove such Alterations. If Tenant fails to
complete such removal and/or to repair any damage caused by the removal of any
Alterations or improvements in the Premises, and returns the affected portion of
the Premises to a building standard tenant improved condition as reasonably
determined by Landlord, then at Landlord's option, either (A) Tenant shall be
deemed to be holding over in the Premises and Rent shall continue to accrue in
accordance with the TCC's of Article 16, below, until such work shall be
completed, or (B) Landlord may do so and may charge the cost thereof to Tenant.
Tenant hereby protects, defends, indemnifies and holds Landlord harmless from
any liability, cost, obligation, expense or claim of lien in any manner relating
to the violation of the foregoing provisions, which obligations of Tenant shall
survive the expiration or earlier termination of this Lease.

                                      -23-
<PAGE>

                                   ARTICLE 9
                                   ---------

                             COVENANT AGAINST LIENS
                             ----------------------

     Tenant shall keep the Project and Premises free from any liens or
encumbrances arising out of the work performed, materials furnished or
obligations incurred by or on behalf of Tenant, and shall protect, defend,
indemnify and hold Landlord harmless from and against any claims, liabilities,
judgments or costs (including, without limitation, reasonable attorneys' fees
and costs) arising out of same or in connection therewith. Tenant shall give
Landlord notice at least twenty (20) days prior to the commencement of any such
work on the Premises (or such additional time as may be necessary under
applicable laws) to afford Landlord the opportunity of posting and recording
appropriate notices of non-responsibility. Tenant shall remove any such lien or
encumbrance by bond or otherwise within ten (10) days after notice by Landlord,
and if Tenant shall fail to do so, Landlord may pay the amount necessary to
remove such lien or encumbrance, without being responsible for investigating the
validity thereof. The amount so paid shall be deemed Additional Rent under this
Lease payable upon demand, without limitation as to other remedies available to
Landlord under this Lease. Nothing contained in this Lease shall authorize
Tenant to do any act which shall subject Landlord's title to the Building or
Premises to any liens or encumbrances whether claimed by operation of law or
express or implied contract. Any claim to a lien or encumbrance upon the
Building or Premises arising in connection with any such work or respecting the
Premises not performed by or at the request of Landlord shall be null and void,
or at Landlord's option shall attach only against Tenant's interest in the
Premises and shall in all respects be subordinate to Landlord's title to the
Project, Building and Premises.

                                   ARTICLE 10
                                   ----------

                                    INSURANCE
                                    ---------

     10.1  INDEMNIFICATION AND WAIVER.  Tenant hereby releases Landlord from
           --------------------------
all risk of damage to property or injury to persons in, upon or about the
Premises from any cause whatsoever (other than Landlord's and Landlord Parties'
negligence or willful misconduct) and agrees that Landlord, its partners,
subpartners and their respective officers, agents, servants, employees, and
independent contractors (collectively, "LANDLORD PARTIES") shall not be liable
for, and are hereby released from any responsibility for, any damage either to
person or property or resulting from the loss of use thereof, which damage is
sustained by Tenant or by other persons claiming through Tenant (other than
Landlord's and Landlord Parties' negligence or willful misconduct). Tenant shall
indemnify, defend, protect, and hold harmless the Landlord Parties from any and
all loss, cost, damage, expense and liability (including without limitation
court costs and reasonable attorneys' fees) incurred in connection with or
arising from any cause in or on the Premises (other than Landlord's and Landlord
Parties' negligence or willful misconduct), any acts, omissions or negligence of
Tenant or of any person claiming by, through or under Tenant, or of the
contractors, agents, servants, employees, invitees, guests or licensees of
Tenant (collectively, the "TENANT PARTIES") or any such Tenant Parties, in, on
or about the Project or any breach of the TCC's of this Lease, either prior to,
during, or after the expiration of the Lease Term, provided that the TCC's of
the foregoing indemnity shall not apply to the negligence or willful misconduct
of Landlord. Should Landlord be named as a defendant in any suit brought against
Tenant in connection with or arising out of Tenant's occupancy of the Premises,
Tenant shall pay to Landlord its costs and expenses incurred in such suit,
including without limitation, its actual professional fees such as appraisers',
accountants' and attorneys' fees. Further, Tenant's agreement to indemnify
Landlord pursuant to this Section 10.1 is not intended and shall not relieve any
                          ------------
insurance carrier of its obligations under policies required to

                                      -24-
<PAGE>

be carried by Tenant pursuant to the provisions of this Lease, to the extent
such policies cover the matters subject to Tenant's indemnification obligations;
nor shall they supersede any inconsistent agreement of the parties set forth in
any other provision of this Lease. The provisions of this Section 10.1 shall
                                                          ------------
survive the expiration or sooner termination of this Lease with respect to any
claims or liability arising in connection with any event occurring prior to such
expiration or termination.

     10.2  TENANT'S COMPLIANCE WITH LANDLORD'S FIRE AND CASUALTY INSURANCE.
           ---------------------------------------------------------------
Tenant shall, at Tenant's expense, comply with all commercially reasonable
insurance company requirements pertaining to the use of the Premises. If
Tenant's conduct or use of the Premises causes any increase in the premium for
such insurance policies then Tenant shall reimburse Landlord for any such
increase. Tenant, at Tenant's expense, shall comply with all rules, orders,
regulations or requirements of the American Insurance Association (formerly the
National Board of Fire Underwriters) and with any similar body.

     10.3  TENANT'S INSURANCE.  Tenant shall maintain the following coverages
           ------------------
in the following amounts.

           10.3.1 Commercial General Liability Insurance covering the insured
against claims of bodily injury, personal injury and property damage (including
loss of use thereof) arising out of Tenant's operations, and contractual
liabilities (covering the performance by Tenant of its indemnity agreements)
including a Broad Form endorsement covering the insuring provisions of this
Lease and, to the extent consistent with commercially standard policies of such
insurance coverage, the performance by Tenant of the indemnity agreements set
forth in Section 10.1 of this Lease, for limits of liability not less than:


Bodily Injury and                          $5,000,000 each occurrence
Property Damage Liability                  $5,000,000 annual aggregate

Personal Injury Liability                  $5,000,000 each occurrence
                                           $5,000,000 annual aggregate
                                           0% Insured's participation


           10.3.2 Physical Damage Insurance covering (i) all office furniture,
business and trade fixtures, office equipment, free-standing cabinet work,
movable partitions, merchandise and all other items of Tenant's property on the
Premises installed by, for, or at the expense of Tenant, (ii) the "Tenant
Improvements," as that term is defined in Section 2.1 of the Tenant Work Letter,
                                          -----------
and any other improvements which exist in the Premises as of the Lease
Commencement Date (excluding the Base Building) (the "ORIGINAL IMPROVEMENTS"),
and (iii) all other improvements, alterations and additions to the Premises made
by Tenant. Such insurance shall be written on an "special cause of loss" of
physical loss or damage basis, for the full replacement cost value (subject to
reasonable deductible amounts) new without deduction for depreciation of the
covered items and in amounts that meet any co-insurance clauses of the policies
of insurance and shall include coverage for damage or other loss caused by fire
or other peril including, but not limited to, vandalism and malicious mischief,
theft, water damage of any type, including sprinkler leakage, bursting or
stoppage of pipes, and explosion, and providing business interruption coverage
for a period of one year.

                                      -25-
<PAGE>

                  10.3.3 Worker's Compensation and Employer's Liability or
other similar insurance pursuant to all applicable state and local statutes and
regulations.

     10.4  FORM OF POLICIES.  The minimum limits of policies of insurance
           ----------------
required of Tenant under this Lease shall in no event limit the liability of
Tenant under this Lease. Such insurance shall (i) name Landlord, and any other
party the Landlord so specifies (if such party has an insurable interest), as an
additional insured, including Landlord's managing agent, if any; (ii)
specifically cover the liability assumed by Tenant under this Lease, including,
but not limited to, Tenant's obligations under Section 10.1 of this Lease to the
extent consistent with commercially standard policies of such insurance
coverage,; (iii) be issued by an insurance company having a rating of not less
than A-X in Best's Insurance Guide or which is otherwise acceptable to Landlord
and licensed to do business in the State of California; (iv) be primary
insurance as to all claims thereunder and provide that any insurance carried by
Landlord is excess and is non-contributing with any insurance requirement of
Tenant; (v) be in form and content reasonably acceptable to Landlord; and (vi)
provide that said insurance shall not be canceled or coverage materially changed
unless ten (10) days' prior written notice shall have been given to Landlord and
any mortgagee of Landlord. Tenant shall deliver said policy or policies or
certificates thereof to Landlord on or before the Lease Commencement Date and at
least ten (10) days before the expiration dates thereof. In the event Tenant
shall fail to procure such insurance, or to deliver such policies or
certificate, Landlord may, at its option, procure such policies for the account
of Tenant, and the cost thereof shall be paid to Landlord within ten (10) days
after delivery to Tenant of bills therefor.

     10.5  SUBROGATION.  Landlord and Tenant intend that their respective
           -----------
property loss risks shall be borne by reasonable insurance carriers to the
extent above provided, and Landlord and Tenant hereby agree to look solely to,
and seek recovery only from, their respective insurance carriers in the event of
a property loss to the extent that such coverage is agreed to be provided
hereunder. The parties each hereby waive all rights and claims against each
other for such losses, and waive all rights of subrogation of their respective
insurers, provided such waiver of subrogation shall not affect the right to the
insured to recover thereunder. The parties agree that their respective insurance
policies are now, or shall be, endorsed such that the waiver of subrogation
shall not affect the right of the insured to recover thereunder, so long as no
material additional premium is charged therefor.

     10.6  ADDITIONAL INSURANCE OBLIGATIONS.  Tenant shall carry and maintain
           --------------------------------
during the entire Lease Term, at Tenant's sole cost and expense, increased
amounts of the insurance required to be carried by Tenant pursuant to this
Article 10 and such other reasonable types of insurance coverage and in such
reasonable amounts covering the Premises and Tenant's operations therein, as may
be reasonably requested by Landlord.

     10.7  LANDLORD'S INSURANCE.  Landlord shall insure the Building (including
           --------------------
the Building Structure and Building Systems) and the Project during the Lease
Term against loss or damage due to fire and other casualties covered within the
classification of fire and extended coverage, vandalism coverage and malicious
mischief, sprinkler leakage, water damage and special extended coverage. Such
coverage shall be in such amounts, from such companies, and on such other TCCs,
as Landlord may from time to time reasonably determine, provided that to the
extent consistent with the practices of landlords of the Comparable Buildings,
such coverage

                                      -26-
<PAGE>

shall (i) be for full replacement of the Building and the Project in compliance
with all then existing Applicable Law; (ii) provide for rent continuation
insurance equal to at least twelve months rent; and (iii) be with companies and
have policies meeting the criteria set forth in Section 10.4(iii) in this Lease.
                                                -----------------
Additionally, at the sole option of Landlord, such insurance coverage may
include the risks of earthquakes and/or flood damage and additional hazards, a
rental loss endorsement and one or more loss payee endorsements in favor of the
holders of any mortgages or deeds of trust encumbering the interest of Landlord
in the Building or the ground or underlying lessors of the Building, or any
portion thereof. In addition, Landlord shall maintain a Commercial General
Liability Insurance policy covering the insured against claims of bodily injury
and personal injury, for limits of liability not initially less than $5,000,000
each occurrence and $5,000,000 annual aggregate for each of bodily injury and
personal injury. Notwithstanding the foregoing TCCs of this Section 10.6, the
                                                            ------------
coverage and amounts of insurance carried by Landlord in connection with the
Building need only, at the option of Landlord, be comparable to the coverage and
amounts of insurance which are carried by reasonably prudent landlords of
Comparable Buildings, and Worker's Compensation and Employee's Liability
coverage as required by Applicable Law. Upon inquiry by Tenant, from time to
time, Landlord shall inform Tenant of all such insurance carried by Landlord.

                                   ARTICLE 11
                                   ----------

                             DAMAGE AND DESTRUCTION
                             ----------------------

     11.1  REPAIR OF DAMAGE TO PREMISES BY LANDLORD.  Tenant shall promptly
           ----------------------------------------
notify Landlord of any damage to the Premises resulting from fire or any other
casualty. If the Premises or any Common Areas serving or providing access to the
Premises shall be damaged by fire or other casualty, Landlord shall promptly and
diligently, subject to reasonable delays for insurance adjustment or other
matters beyond Landlord's reasonable control, and subject to all other TCC's of
this Article 11, restore the Base Building and such Common Areas. Such
restoration shall be to substantially the same condition of the Base Building
and the Common Areas prior to the casualty, except for modifications required by
zoning and building codes and other laws or by the holder of a mortgage on the
Building or Project or any other modifications to the Common Areas deemed
desirable by Landlord, provided that access to the Premises shall not be
materially impaired. Upon the occurrence of any damage to the Premises, upon
notice (the "LANDLORD REPAIR NOTICE") to Tenant from Landlord, Tenant shall
assign to Landlord (or to any party designated by Landlord) all insurance
proceeds payable to Tenant under Tenant's insurance required under Section 10.3
of this Lease allocable to the Tenant Improvements and the Original
Improvements, and Landlord shall repair any injury or damage to the Tenant
Improvements and the Original Improvements installed in the Premises and shall
return such Tenant Improvements and Original Improvements to their original
condition; provided that if the cost of such repair by Landlord exceeds the
amount of insurance proceeds received by Landlord from Tenant's insurance
carrier, as assigned by Tenant, the cost of such repairs shall be paid by Tenant
to Landlord prior to Landlord's commencement of repair of the damage. In the
event that Landlord does not deliver the Landlord Repair Notice within sixty
(60) days following the date the casualty becomes known to Landlord, Tenant
shall, at its sole cost and expense, repair any injury or damage to the Tenant
Improvements and the Original Improvements installed in the Premises and shall
return such Tenant Improvements and Original Improvements to their original
condition. Whether or not Landlord delivers a Landlord Repair Notice, prior to
the

                                      -27-
<PAGE>

commencement of construction, Tenant shall submit to Landlord, for
Landlord's review and approval, all plans, specifications and working drawings
relating thereto, and Landlord shall select the contractors to perform such
improvement work. Landlord shall not be liable for any inconvenience or
annoyance to Tenant or its visitors, or injury to Tenant's business resulting in
any way from such damage or the repair thereof; provided however, that if such
fire or other casualty shall have damaged the Premises or Common Areas necessary
to Tenant's occupancy, Landlord shall allow Tenant a proportionate abatement of
Rent to the extent Landlord is reimbursed from the proceeds of rental
interruption insurance purchased by Landlord as part of Operating Expenses,
during the time and to the extent the Premises are unfit for occupancy for the
purposes permitted under this Lease, and not occupied by Tenant as a result
thereof; provided, further, however, that if the damage or destruction is due to
the negligence or willful misconduct of Tenant or any of its agents, employees,
contractors, invitees or guests, Tenant shall be responsible for any reasonable,
applicable insurance deductible (which shall be payable to Landlord upon demand)
and there shall be no rent abatement. In the event that Landlord shall not
deliver the Landlord Repair Notice, Tenant's right to rent abatement pursuant to
the preceding sentence shall terminate as of the date which is reasonably
determined by Landlord to be the date Tenant should have completed repairs to
the Premises assuming Tenant used reasonable due diligence in connection
therewith.

     11.2  LANDLORD'S OPTION TO REPAIR.  Notwithstanding the TCC's of
           ---------------------------
Section 11.1 of this Lease, Landlord may elect not to rebuild and/or restore the
------------
Premises, Building and/or Project, and instead terminate this Lease, by
notifying Tenant in writing of such termination within sixty (60) days after the
date of discovery of the damage, such notice to include a termination date
giving Tenant sixty (60) days to vacate the Premises, but Landlord may so elect
only if the Building or Project shall be damaged by fire or other casualty or
cause, whether or not the Premises are affected, and one or more of the
following conditions is present: (i) in Landlord's reasonable judgment, repairs
cannot reasonably be completed within ninety (90) days after the date of
discovery of the damage (when such repairs are made without the payment of
overtime or other premiums); (ii) the holder of any mortgage on the Building or
Project or ground lessor with respect to the Building or Project shall require
that the insurance proceeds or any portion thereof be used to retire the
mortgage debt, or shall terminate the ground lease, as the case may be; (iii)
the damage is not fully covered by Landlord's and Tenant's insurance policies;
or (iv) Landlord cannot, pursuant to the applicable laws then in effect, rebuild
the Building or Common Areas so that they will be substantially the same
structurally or architecturally; (v) the damage occurs during the last twelve
(12) months of the Lease Term.

     If the Premises, Building or Common Areas are damaged by any peril and
Landlord does not elect to terminate this Lease or is not entitled to terminate
this Lease pursuant to this Article 11, then as soon as reasonably practicable,
Landlord shall furnish Tenant with the written opinion of Landlord's architect
or construction consultant as to when the restoration work required of Landlord
is reasonably anticipated to be complete. Tenant shall have the option to
terminate this Lease in the event any of the following occurs, which option may
be exercised only by delivery to Landlord of a written notice of election to
terminate within thirty (30) days after Tenant receives from Landlord the
estimate of the time anticipated to be needed to complete such restoration.

                                      -28-
<PAGE>

           (A) If the anticipated time to substantially complete such
restoration exceeds twelve (12) months from and after the date the written
opinion of the architect or construction consultant is delivered to Tenant; or

           (B) If the date of such damage occurs within the last twelve (12)
months of the Lease Term.

     11.3  WAIVER OF STATUTORY PROVISIONS.  The provisions of this Lease,
           ------------------------------
including this Article 11, constitute an express agreement between Landlord and
Tenant with respect to any and all damage to, or destruction of, all or any part
of the Premises, the Building or the Project, and any statute or regulation of
the State of California, including, without limitation, Sections 1932(2) and
1933(4) of the California Civil Code, with respect to any rights or obligations
concerning damage or destruction in the absence of an express agreement between
the parties, and any other statute or regulation, now or hereafter in effect,
shall have no application to this Lease or any damage or destruction to all or
any part of the Premises, the Building or the Project.

                                   ARTICLE 12
                                   ----------

                                    NONWAIVER
                                    ---------

     No provision of this Lease shall be deemed waived by either party hereto
unless expressly waived in a writing signed thereby. The waiver by either party
hereto of any breach of any term, covenant or condition herein contained shall
not be deemed to be a waiver of any subsequent breach of same or any other term,
covenant or condition herein contained. The subsequent acceptance of Rent
hereunder by Landlord shall not be deemed to be a waiver of any preceding breach
by Tenant of any term, covenant or condition of this Lease, other than the
failure of Tenant to pay the particular Rent so accepted, regardless of
Landlord's knowledge of such preceding breach at the time of acceptance of such
Rent. No acceptance of a lesser amount than the Rent herein stipulated shall be
deemed a waiver of Landlord's right to receive the full amount due, nor shall
any endorsement or statement on any check or payment or any letter accompanying
such check or payment be deemed an accord and satisfaction, and Landlord may
accept such check or payment without prejudice to Landlord's right to recover
the full amount due. No receipt of monies by Landlord from Tenant after the
termination of this Lease shall in any way alter the length of the Lease Term or
of Tenant's right of possession hereunder, or after the giving of any notice
shall reinstate, continue or extend the Lease Term or affect any notice given
Tenant prior to the receipt of such monies, it being agreed that after the
service of notice or the commencement of a suit, or after final judgment for
possession of the Premises, Landlord may receive and collect any Rent due, and
the payment of said Rent shall not waive or affect said notice, suit or
judgment.

                                   ARTICLE 13
                                   ----------

                                  CONDEMNATION
                                  ------------

     If the whole or any part of the Premises or the Building shall be taken by
power of eminent domain or condemned by any competent authority for any public
or quasi-public use or purpose, or if any adjacent property or street shall be
so taken or condemned, or reconfigured or

                                      -29-
<PAGE>

vacated by such authority in such manner as to require the use, reconstruction
or remodeling of any part of the Premises or Building, or if Landlord shall
grant a deed or other instrument in lieu of such taking by eminent domain or
condemnation, Landlord shall have the option to terminate this Lease effective
as of the date possession is required to be surrendered to the authority. If
more than fifty percent (50%) of the rentable square feet of the Premises is
taken, or if access to the Premises is substantially impaired, in each case for
a period in excess of one hundred eighty (180) days, Tenant shall have the
option to terminate this Lease effective as of the date possession is required
to be surrendered to the authority. Tenant shall not because of such taking
assert any claim against Landlord or the authority for any compensation because
of such taking and Landlord shall be entitled to the entire award or payment in
connection therewith, except that Tenant shall have the right to file any
separate claim available to Tenant for any taking of Tenant's personal property
and fixtures belonging to Tenant and removable by Tenant upon expiration of the
Lease Term pursuant to the TCC's of this Lease, and for moving expenses, so long
as such claims do not diminish the award available to Landlord, its ground
lessor with respect to the Building or Project or its mortgagee, and such claim
is payable separately to Tenant. All Rent shall be apportioned as of the date of
such termination. If any part of the Premises shall be taken, and this Lease
shall not be so terminated, the Rent shall be proportionately abated. Tenant
hereby waives any and all rights it might otherwise have pursuant to Section
1265.130 of The California Code of Civil Procedure. Notwithstanding anything to
the contrary contained in this Article 13, in the event of a temporary taking of
                               ----------
all or any portion of the Premises for a period of one hundred and eighty (180)
days or less, then this Lease shall not terminate but the Base Rent and the
Additional Rent shall be abated for the period of such taking in proportion to
the ratio that the amount of rentable square feet of the Premises taken bears to
the total rentable square feet of the Premises. Landlord shall be entitled to
receive the entire award made in connection with any such temporary taking.

                                   ARTICLE 14
                                   ----------

                            ASSIGNMENT AND SUBLETTING
                            -------------------------

     14.1  TRANSFERS.  Tenant shall not, without the prior written consent of
           ---------
Landlord, assign, mortgage, pledge, hypothecate, encumber, or permit any lien to
attach to, or otherwise transfer, this Lease or any interest hereunder, permit
any assignment, or other transfer of this Lease or any interest hereunder by
operation of law, sublet the Premises or any part thereof, or enter into any
license or concession agreements or otherwise permit the occupancy or use of the
Premises or any part thereof by any persons other than Tenant and its employees
and contractors (all of the foregoing are hereinafter sometimes referred to
collectively as "TRANSFERS" and any person to whom any Transfer is made or
sought to be made is hereinafter sometimes referred to as a "TRANSFEREE"). If
Tenant desires Landlord's consent to any Transfer, Tenant shall notify Landlord
in writing, which notice (the "TRANSFER NOTICE") shall include (i) the proposed
effective date of the Transfer, which shall not be less than thirty (30) days
nor more than one hundred eighty (180) days after the date of delivery of the
Transfer Notice, (ii) a description of the portion of the Premises to be
transferred (the "SUBJECT SPACE"), (iii) all of the TCC's of the proposed
Transfer and the consideration therefor, including calculation of the "TRANSFER
PREMIUM", as that term is defined in Section 14.3 below, in connection with such
Transfer, the name and address of the proposed Transferee, and a copy of all
existing executed and/or proposed documentation pertaining to the proposed
Transfer, including all existing operative

                                      -30-
<PAGE>

documents to be executed to evidence such Transfer or the agreements incidental
or related to such Transfer, (iv) current financial statements of the proposed
Transferee certified by an officer, partner or owner thereof, business credit
and personal references and history of the proposed Transferee and any other
information required by Landlord which will enable Landlord to determine the
financial responsibility, character, and reputation of the proposed Transferee,
nature of such Transferee's business and proposed use of the Subject Space and
(v) an executed estoppel certificate from Tenant in the form attached hereto as
Exhibit E. Any Transfer made without Landlord's prior written consent shall, at
Landlord's option, be null, void and of no effect, and shall, at Landlord's
option, constitute a default by Tenant under this Lease. Whether or not Landlord
consents to any proposed Transfer, Tenant shall, within thirty (30) days after
written request by Landlord, reimburse Landlord for all reasonable and actual
out-of-pocket third-party costs and expenses incurred by Landlord in connection
with its review of a proposed Transfer; provided that such costs and expenses
shall not exceed One Thousand Five Hundred and No/100 Dollars ($1,500.00) for a
Transfer in the ordinary course of business. Landlord and Tenant hereby agree
that a proposed Transfer shall not be considered "in the ordinary course of
business" if such Transfer involves the review of documentation by Landlord on
more than two (2) occasions with regard to a single proposed Transfer.

     14.2  LANDLORD'S CONSENT.  Landlord shall not unreasonably withhold its
           ------------------
consent to any proposed Transfer of the Subject Space to the Transferee on the
TCC's specified in the Transfer Notice. Without limitation as to other
reasonable grounds for withholding consent, the parties hereby agree that it
shall be reasonable under this Lease and under any applicable law for Landlord
to withhold consent to any proposed Transfer where one or more of the following
apply:

           14.2.1 The Transferee is of a character or reputation or engaged in a
business which is not consistent with the quality of the Building or the
Project, or would be a significantly less prestigious occupant of the Building
than Tenant;

           14.2.2 The Transferee intends to use the Subject Space for purposes
which are not permitted under this Lease; 14.2.3 The Transferee is either a
governmental agency or instrumentality thereof; 14.2.4 Intentionally Omitted;

           14.2.5 The Transferee is not a party of reasonable financial worth
and/or financial stability in light of the responsibilities to be undertaken in
connection with the Transfer on the date consent is requested;

           14.2.6 The proposed Transfer would cause a violation of another lease
for space in the Project, or would give an occupant of the Project a right to
cancel its lease;

           14.2.7 The TCC's of the proposed Transfer will allow the Transferee
to exercise a right of renewal, right of expansion, right of first offer, or
other similar right held by Tenant (or will allow the Transferee to occupy space
leased by Tenant pursuant to any such right); or

                                      -31-
<PAGE>

           14.2.8 Either the proposed Transferee, or any person or entity which
directly or indirectly, controls, is controlled by, or is under common control
with, the proposed Transferee, (i) occupies space in the Project at the time of
the request for consent, or (ii) is negotiating with Landlord to lease space in
the Project at such time, or (iii) has negotiated with Landlord during the
twelve (12)-month period immediately preceding the Transfer Notice; or

           14.2.9 The Transferee does not intend to occupy the entire Premises
and conduct its business therefrom for a substantial portion of the term of the
Transfer.

     If Landlord consents to any Transfer pursuant to the TCC's of this Section
14.2 (and does not exercise any recapture rights Landlord may have under Section
14.4 of this Lease), Tenant may within six (6) months after Landlord's consent,
but not later than the expiration of said six-month period, enter into such
Transfer of the Premises or portion thereof, upon substantially the same TCC's
as are set forth in the Transfer Notice furnished by Tenant to Landlord pursuant
to Section 14.1 of this Lease, provided that if there are any changes in the
TCC's from those specified in the Transfer Notice (i) such that Landlord would
initially have been entitled to refuse its consent to such Transfer under this
Section 14.2, or (ii) which would cause the proposed Transfer to be more
------------
favorable to the Transferee than the TCC's set forth in Tenant's original
Transfer Notice, Tenant shall again submit the Transfer to Landlord for its
approval and other action under this Article 14 (including Landlord's right of
recapture, if any, under Section 14.4 of this Lease). Notwithstanding anything
                         ------------
to the contrary in this Lease, if Tenant or any proposed Transferee claims that
Landlord has unreasonably withheld or delayed its consent under Section 14.2 or
otherwise has breached or acted unreasonably under this Article 14, their sole
remedies shall be a declaratory judgment and an injunction for the relief sought
without any monetary damages, and Tenant hereby waives all other remedies,
including, without limitation, any right at law or equity to terminate this
Lease, on its own behalf and, to the extent permitted under all applicable laws,
on behalf of the proposed Transferee. Tenant shall indemnify, defend and hold
harmless Landlord from any and all liability, losses, claims, damages, costs,
expenses, causes of action and proceedings involving any third party or parties
(including without limitation Tenant's proposed subtenant or assignee) who claim
they were damaged by Landlord's wrongful withholding or conditioning of
Landlord's consent, unless a court of competent jurisdiction determines that
Landlord was wrongful in its withholding or conditioning of its consent.

     14.3  TRANSFER PREMIUM.  If Landlord consents to a Transfer, as a condition
           ----------------
thereto which the parties hereby agree is reasonable, Tenant shall pay to
Landlord fifty percent (50%) of any "Transfer Premium," as that term is defined
in this Section 14.3, received by Tenant from such Transferee. "TRANSFER
PREMIUM" shall mean all rent, additional rent or other consideration payable by
such Transferee in connection with the Transfer in excess of the Rent and
Additional Rent payable by Tenant under this Lease during the term of the
Transfer on a per rentable square foot basis if less than all of the Premises is
transferred, after deducting the reasonable expenses incurred by Tenant for (i)
any changes, alterations and improvements to the Premises in connection with the
Transfer, (ii) any free base rent reasonably provided to the Transferee, and
(iii) any brokerage commissions in connection with the Transfer. "Transfer
Premium" shall also include, but not be limited to, key money, bonus money or
other cash consideration paid by Transferee to Tenant in connection with such
Transfer. In the calculations of the Rent (as it relates to the Transfer Premium
calculated under this Section 14.3), and the Transferee's Rent and Quoted Rent
under Section 14.2 of this Lease, the Rent paid during each annual period for

                                      -32-
<PAGE>

the Subject Space, and the Transferee's Rent and the Quoted Rent, shall be
computed after adjusting such rent to the actual effective rent to be paid,
taking into consideration any and all leasehold concessions granted in
connection therewith, including, but not limited to, any rent credit and tenant
improvement allowance. For purposes of calculating any such effective rent all
such concessions shall be amortized on a straight-line basis over the relevant
term.

     14.4  LANDLORD'S OPTION AS TO SUBJECT SPACE.  In the event that a proposed
           -------------------------------------
Transfer, if consented to, would cause seventy-five percent (75%) or more of the
Premises to be assigned or subleased to a party other than Original Tenant
and/or its Affiliates, then notwithstanding anything to the contrary contained
in this Article 14, Landlord shall have the option, by giving written notice to
Tenant within thirty (30) days after receipt of any Transfer Notice, to
recapture the Subject Space. Such recapture notice shall cancel and terminate
this Lease with respect to the Subject Space as of the date stated in the
Transfer Notice as the effective date of the proposed Transfer until the last
day of the term of the Transfer as set forth in the Transfer Notice (or at
Landlord's option, shall cause the Transfer to be made to Landlord or its agent,
in which case the parties shall execute the Transfer documentation promptly
thereafter). In the event of a recapture by Landlord, if this Lease shall be
canceled with respect to less than the entire Premises, the Rent reserved herein
shall be prorated on the basis of the number of rentable square feet retained by
Tenant in proportion to the number of rentable square feet contained in the
Premises, and this Lease as so amended shall continue thereafter in full force
and effect, and upon request of either party, the parties shall execute written
confirmation of the same. If Landlord declines, or fails to elect in a timely
manner to recapture the Subject Space under this Section 14.4, then, provided
                                                 ------------
Landlord has consented to the proposed Transfer, Tenant shall be entitled to
proceed to transfer the Subject Space to the proposed Transferee, subject to
provisions of this Article 14.
                   ----------

     14.5  EFFECT OF TRANSFER.  If Landlord consents to a Transfer, (i) the
           ------------------
TCC's of this Lease shall in no way be deemed to have been waived or modified,
(ii) such consent shall not be deemed consent to any further Transfer by either
Tenant or a Transferee, (iii) Tenant shall deliver to Landlord, promptly after
execution, an original executed copy of all documentation pertaining to the
Transfer in form reasonably acceptable to Landlord, (iv) Tenant shall furnish
upon Landlord's request a complete statement, certified by Tenant's chief
financial officer, setting forth in detail the computation of any Transfer
Premium Tenant has derived and shall derive from such Transfer, and (v) no
Transfer relating to this Lease or agreement entered into with respect thereto,
whether with or without Landlord's consent, shall relieve Tenant or any
guarantor of the Lease from any liability under this Lease, including, without
limitation, in connection with the Subject Space. Landlord or its authorized
representatives shall have the right at all reasonable times to audit the books,
records and papers of Tenant relating to any Transfer, and shall have the right
to make copies thereof. If the Transfer Premium respecting any Transfer shall be
found understated, Tenant shall, within thirty (30) days after demand, pay the
deficiency, and if understated by more than five percent (5%), Tenant shall pay
Landlord's costs of such audit.

     14.6  ADDITIONAL TRANSFERS.  For purposes of this Lease, the term
           --------------------
"TRANSFER" shall also include (i) if Tenant is a partnership, the withdrawal or
change, voluntary, involuntary or by operation of law, of fifty percent (50%) or
more of the partners, or transfer of fifty percent (50%) or more of partnership
interests, within a twelve (12)-month period, or the dissolution of the
partnership without immediate reconstitution thereof, and (ii) if Tenant is a
closely held

                                      -33-
<PAGE>

corporation (i.e., whose stock is not publicly held and not traded through an
exchange or over the counter), (A) the dissolution, merger, consolidation or
other reorganization of Tenant or (B) the sale or other transfer of an aggregate
of fifty percent (50%) or more of the voting shares of Tenant (other than to
immediate family members by reason of gift or death), within a twelve (12)-month
period, or (C) the sale, mortgage, hypothecation or pledge of an aggregate of
fifty percent (50%) or more of the value of the unencumbered assets of Tenant
within a twelve (12)-month period. Notwithstanding anything to the contrary set
forth in this Article 14 to the contrary, in no event shall an offering of stock
to third parties by means of a public offering (either an initial public
offering or a subsequent public offering) through a recognized stock market
constitute a "Transfer."

     14.7  OCCURRENCE OF DEFAULT.  Any Transfer hereunder shall be subordinate
           ---------------------
and subject to the provisions of this Lease, and if this Lease shall be
terminated during the term of any Transfer, Landlord shall have the right to:
(i) treat such Transfer as cancelled and repossess the Subject Space by any
lawful means, or (ii) require that such Transferee attorn to and recognize
Landlord as its landlord under any such Transfer. If Tenant shall be in default
under this Lease, Landlord is hereby irrevocably authorized, as Tenant's agent
and attorney-in-fact, to direct any Transferee to make all payments under or in
connection with the Transfer directly to Landlord (which Landlord shall apply
towards Tenant's obligations under this Lease) until such default is cured. Such
Transferee shall rely on any representation by Landlord that Tenant is in
default hereunder, without any need for confirmation thereof by Tenant. Upon any
assignment, the assignee shall assume in writing all obligations and covenants
of Tenant thereafter to be performed or observed under this Lease. No collection
or acceptance of rent by Landlord from any Transferee shall be deemed a waiver
of any provision of this Article 14 or the approval of any Transferee or a
release of Tenant from any obligation under this Lease, whether theretofore or
thereafter accruing. In no event shall Landlord's enforcement of any provision
of this Lease against any Transferee be deemed a waiver of Landlord's right to
enforce any term of this Lease against Tenant or any other person. If Tenant's
obligations hereunder have been guaranteed, Landlord's consent to any Transfer
shall not be effective unless the guarantor also consents to such Transfer.

     14.8  NON-TRANSFERS.  Notwithstanding anything to the contrary contained
           -------------
in this Article 14, an assignment or subletting of all or a portion of the
Premises to (a) an affiliate of Tenant (an entity which is controlled by,
controls or is under common control, as such term is defined in California
General Corporations Code ("CGCC") Sections 160 and 5045, with, Tenant), (b) an
entity which merges with or acquires or is acquired by, Tenant or a parent of
Tenant, as defined in CGCC Sections 175 and 5064, or a subsidiary, as defined in
CGCC Sections 189 and 5073, of Tenant's parent or Affiliate, or (c) a transferee
of substantially all of the assets of Tenant (a, b and c to be collectively be
referred to herein as an "AFFILIATE") along with any other entity which will
qualify as an "affiliate" under CGCC 150 and 5031, shall not be deemed a
Transfer under this Article 14, provided that at least thirty (30) days prior to
                    ----------
such assignment or sublease (i) Tenant provides Landlord with reasonable
evidence, including a certified audit opinion of an independent certified public
accountant with a regional or national reputation, that any such entity
maintains a net worth, calculated in accordance with generally accepted
accounting principles, consistently applied ("NET WORTH"), equal to or greater
than the Net Worth of Tenant either immediately prior to the time of such
assignment or sublease or at the time this Lease is executed; (ii) Tenant
notifies Landlord of any such assignment or sublease and promptly supplies
Landlord with any documents or information requested by Landlord regarding such
assignment or sublease

                                      -34-
<PAGE>

and promptly supplies Landlord with any documents or information requested by
Landlord regarding such assignment or sublease or such Affiliate; and (iii) such
assignment or sublease is not a subterfuge by Tenant to avoid its obligations
under this Lease. In the event an assignment or sublease to an Affiliate is made
pursuant to the TCCs of this Section 14.8, Tenant shall be relieved of its
obligations under this Lease to the extent the same become the TCCs of such
Affiliate pursuant to such assignment or sublease.

                                   ARTICLE 15
                                   ----------

                      SURRENDER OF PREMISES; OWNERSHIP AND
                      ------------------------------------
                            REMOVAL OF TRADE FIXTURES
                            -------------------------

     15.1  SURRENDER OF PREMISES.  No act or thing done by Landlord or any
           ---------------------
agent or employee of Landlord during the Lease Term shall be deemed to
constitute an acceptance by Landlord of a surrender of the Premises unless such
intent is specifically acknowledged in writing by Landlord. The delivery of keys
to the Premises to Landlord or any agent or employee of Landlord shall not
constitute a surrender of the Premises or effect a termination of this Lease,
whether or not the keys are thereafter retained by Landlord, and notwithstanding
such delivery Tenant shall be entitled to the return of such keys at any
reasonable time upon request until this Lease shall have been properly
terminated. The voluntary or other surrender of this Lease by Tenant, whether
accepted by Landlord or not, or a mutual termination hereof, shall not work a
merger, and at the option of Landlord shall operate as an assignment to Landlord
of all subleases or subtenancies affecting the Premises or terminate any or all
such sublessees or subtenancies.

     15.2  REMOVAL OF TENANT PROPERTY BY TENANT.  Upon the expiration of the
           ------------------------------------
Lease Term, or upon any earlier termination of this Lease, Tenant shall, subject
to the provisions of this Article 15, quit and surrender possession of the
Premises to Landlord in as good order and condition as when Tenant took
possession and as thereafter improved by Landlord and/or Tenant, reasonable wear
and tear, casualty and condemnation, and repairs which are specifically made the
responsibility of Landlord hereunder excepted. Upon such expiration or
termination, Tenant shall, without expense to Landlord, remove or cause to be
removed from the Premises all debris and rubbish, and such items of furniture,
equipment, business and trade fixtures, free-standing cabinet work, movable
partitions and other articles of personal property owned by Tenant or installed
or placed by Tenant at its expense in the Premises, and such similar articles of
any other persons claiming under Tenant, as Landlord may, in its sole
discretion, require to be removed, and Tenant shall repair at its own expense
all damage to the Premises and Building resulting from such removal, provided
that the removal of Alterations shall be governed by Article 8 hereof.

                                   ARTICLE 16
                                   ----------

                                  HOLDING OVER
                                  ------------

     If Tenant holds over after the expiration of the Lease Term or earlier
termination thereof, with or without the express or implied consent of Landlord,
such tenancy shall be from month-to-month only, and shall not, except as set
forth below, constitute a renewal hereof or an extension for any further term,
and in such case Rent shall be payable at a monthly rate equal to

                                      -35-
<PAGE>

the product of (i) the Rent applicable during the last rental period of the
Lease Term under this Lease, and (ii) a percentage equal to the sum of (A) 200%
and (B) the percentage by which Rent was increased at the time of the last
increase of Rent during the Lease Term. Such month-to-month tenancy shall be
subject to every other applicable term, covenant and agreement contained herein.
Notwithstanding the foregoing, Tenant shall have the one-time right, upon notice
(the "HOLDOVER NOTICE") to Landlord not less than nine (9) months prior to the
expiration of the then Lease Term, to extend the Lease Term for a period of up
to six (6) months (in one (1) month increments), the length of which shall be
set forth in the Holdover Notice (the "PERMITTED HOLDOVER TERM"), in which case
the Rent payable by Tenant during such Permitted Holdover Term shall equal the
product of (a) the Rent applicable during the last rental period of the Lease
Term under this Lease, and (b) one hundred twenty percent (120%) during the
first three (3)-month period of such Permitted Holdover Term, and one hundred
fifty percent (150%) during the second three (3)-month period of such Permitted
Holdover Term. For purposes of this Article 16, a holding over shall include
Tenant's remaining in the Premises after the expiration or earlier termination
of the Lease Term, as required pursuant to the TCC's of Section 8.5, above, to
                                                        -----------
remove any Alterations or Above Building Standard Tenant Improvements located
within the Premises and replace the same with Building Standard Tenant
Improvements. Except with respect to the Permitted Holdover Term, Nothing
contained in this Article 16 shall be construed as consent by Landlord to any
holding over by Tenant, and Landlord expressly reserves the right to require
Tenant to surrender possession of the Premises to Landlord as provided in this
Lease upon the expiration or other termination of this Lease. The provisions of
this Article 16 shall not be deemed to limit or constitute a waiver of any other
     ----------
rights or remedies of Landlord provided herein or at law. Except with respect to
the Permitted Holdover Term, If Tenant fails to surrender the Premises upon the
termination or expiration of this Lease, in addition to any other liabilities to
Landlord accruing therefrom, Tenant shall protect, defend, indemnify and hold
Landlord harmless from all loss, costs (including reasonable attorneys' fees)
and liability resulting from such failure, including, without limiting the
generality of the foregoing, any claims made by any succeeding tenant founded
upon such failure to surrender and any lost profits to Landlord resulting
therefrom.

                                   ARTICLE 17
                                   ----------

                              ESTOPPEL CERTIFICATES
                              ---------------------

     Within ten (10) days following a request in writing by Landlord, Tenant
shall execute, acknowledge and deliver to Landlord an estoppel certificate,
which, as submitted by Landlord, shall be substantially in the form of EXHIBIT
                                                                       -------
E, attached hereto (or such other form as may reasonably be required by any
prospective mortgagee or purchaser of the Project, or any portion thereof),
indicating therein any exceptions thereto that may exist at that time, and shall
also contain any other information reasonably requested by Landlord or
Landlord's mortgagee or prospective mortgagee. Any such certificate may be
relied upon by any prospective mortgagee or purchaser of all or any portion of
the Project. Tenant shall execute and deliver whatever other commercially
reasonable instruments may be reasonably required for such purposes. At any time
during the Lease Term, Landlord may require Tenant to provide Landlord with its
most recently prepared financial statement and financial statements of the two
(2) years prior to the most recently prepared financial statement year. Such
statements shall be prepared in accordance with generally accepted accounting
principles and, if such is the normal practice of

                                      -36-
<PAGE>

Tenant, shall be audited by an independent certified public accountant. Failure
of Tenant to timely execute, acknowledge and deliver such estoppel certificate
or other commercially reasonable instruments shall constitute an acceptance of
the Premises and an acknowledgment by Tenant that statements included in the
estoppel certificate are true and correct, without exception. Any such financial
statement or other information which is marked "confidential" or "company
secret(s)" (or is otherwise similarly marked by Tenant) shall be confidential
and shall not be disclosed by Landlord to any third party (other than its
partners, administrators, consultants, financial, legal and a prospective or
current purchaser, mortgagee, or ground or underlying lessor of the Building or
the Project, a prospective Transferee, and except as required by applicable law
or in connection with a dispute or litigation hereunder or as required by a
subpoena) except as specifically provided in this Article 17 and then only if
the person to whom disclosure is made first agrees to be bound by the
requirements of this Article 17.

                                   ARTICLE 18
                                   ----------

                                  SUBORDINATION
                                  -------------

     Subject to Tenant's receipt of an appropriate non-disturbance agreement(s)
as set forth below, This Lease shall be subject and subordinate to all present
and future ground or underlying leases of the Building or Project and to the
lien of any mortgage, trust deed or other encumbrances now or hereafter in force
against the Building or Project or any part thereof, if any, and to all
renewals, extensions, modifications, consolidations and replacements thereof,
and to all advances made or hereafter to be made upon the security of such
mortgages or trust deeds, unless the holders of such mortgages, trust deeds or
other encumbrances, or the lessors under such ground lease or underlying leases,
require in writing that this Lease be superior thereto. As of the date of this
Lease, Landlord covenants that no deed of trust, mortgage, other encumbrance, or
ground or underlying lease encumbers the Premises, Building or Project.
Landlord's delivery to Tenant of commercially reasonable non-disturbance
agreement(s) (the "NONDISTURBANCE AGREEMENT") in favor of Tenant from any ground
lessor, mortgage holders or lien holders of Landlord who later come into
existence at any time prior to the expiration of the Lease Term shall be in
consideration of, and a condition precedent to, Tenant's agreement to be bound
by the terms and conditions of this Article 18; provided Tenant shall execute
and return such Nondisturbance Agreement to Landlord within four (4) days of its
receipt thereof. Any such Nondisturbance Agreement shall include an express
agreement by the lessor, mortgage holder or lien holder to complete the
construction of the Building and fund the Tenant and Core Improvement Allowance
in accordance with the terms of this Lease and the Tenant Work Letter. Tenant
covenants and agrees in the event any proceedings are brought for the
foreclosure of any such mortgage or deed in lieu thereof (or if any ground lease
is terminated), to attorn, without any deductions or set-offs whatsoever
(excepting any unfunded portion of the Tenant and Core Improvement Allowance),
to the lienholder or purchaser or any successors thereto upon any such
foreclosure sale or deed in lieu thereof (or to the ground lessor), if so
requested to do so by such purchaser or lienholder or ground lessor, and to
recognize such purchaser or lienholder or ground lessor as the lessor under this
Lease, provided such lienholder or purchaser or ground lessor shall agree to
accept this Lease and not disturb Tenant's occupancy, so long as Tenant timely
pays the rent and observes and performs the TCC's of this Lease to be observed
and performed by Tenant. Landlord's interest herein may be assigned as security
at any time to any lienholder. Subject to Tenant's receipt of a Nondisturbance
Agreement, Tenant shall, within five (5) days of request by

                                      -37-
<PAGE>

Landlord, execute such further instruments or assurances as Landlord may
reasonably deem necessary to evidence or confirm the subordination or
superiority of this Lease to any such mortgages, trust deeds, ground leases or
underlying leases. Tenant waives the provisions of any current or future
statute, rule or law which may give or purport to give Tenant any right or
election to terminate or otherwise adversely affect this Lease and the
obligations of the Tenant hereunder in the event of any foreclosure proceeding
or sale.

                                   ARTICLE 19
                                   ----------

                               DEFAULTS; REMEDIES
                               ------------------

     19.1  EVENTS OF DEFAULT.  The occurrence of any of the following shall
           -----------------
constitute a default of this Lease by Tenant:

           19.1.1 Any failure by Tenant to pay any Rent or any other charge
required to be paid under this Lease, or any part thereof, when due unless such
failure is cured within three (3) days after notice; or

           19.1.2 Except where a specific time period is otherwise set forth for
Tenant's performance in this Lease, in which event the failure to perform by
Tenant within such time period shall be a default by Tenant under this
Section 19.1.2, any failure by Tenant to observe or perform any other provision,
--------------
covenant or condition of this Lease to be observed or performed by Tenant where
such failure continues for ten (10) days after written notice thereof from
Landlord to Tenant; provided that if the nature of such default is such that the
same cannot reasonably be cured within a ten (10) day period, Tenant shall not
be deemed to be in default if it diligently commences such cure within such
period and thereafter diligently proceeds to rectify and cure such default, but
in no event exceeding a period of time in excess of sixty (60) days after
written notice thereof from Landlord to Tenant; or

           19.1.3 To the extent permitted by law, a general assignment by Tenant
or any guarantor of this Lease for the benefit of creditors, or the taking of
any corporate action in furtherance of bankruptcy or dissolution whether or not
there exists any proceeding under an insolvency or bankruptcy law, or the filing
by or against Tenant or any guarantor of any proceeding under an insolvency or
bankruptcy law, unless in the case of a proceeding filed against Tenant or any
guarantor the same is dismissed within sixty (60) days, or the appointment of a
trustee or receiver to take possession of all or substantially all of the assets
of Tenant or any guarantor, unless possession is restored to Tenant or such
guarantor within thirty (30) days, or any execution or other judicially
authorized seizure of all or substantially all of Tenant's assets located upon
the Premises or of Tenant's interest in this Lease, unless such seizure is
discharged within thirty (30) days; or

           19.1.4 A default (beyond any applicable notice and cure periods) by
Tenant under the "Building B Lease," as that term is set forth in Section 29.37;
or

           19.1.5 The failure by Tenant to observe or perform according to the
provisions of Section 5.2 of this Lease or Articles 14, 17 or 18 of this Lease
where such failure continues for more than ten (10) business days after notice
from Landlord.

                                      -38-
<PAGE>

     The notice periods provided herein are in lieu of, and not in addition to,
any notice periods provided by law.

     19.2  REMEDIES UPON DEFAULT.  Upon the occurrence of any event of default
           ---------------------
by Tenant, Landlord shall have, in addition to any other remedies available to
Landlord at law or in equity (all of which remedies shall be distinct, separate
and cumulative), the option to pursue any one or more of the following remedies,
each and all of which shall be cumulative and nonexclusive, without any notice
or demand whatsoever.

           19.2.1 Terminate this Lease, in which event Tenant shall immediately
surrender the Premises to Landlord, and if Tenant fails to do so, Landlord may,
without prejudice to any other remedy which it may have for possession or
arrearages in rent, enter upon and take possession of the Premises and expel or
remove Tenant and any other person who may be occupying the Premises or any part
thereof, without being liable for prosecution or any claim or damages therefor;
and Landlord may recover from Tenant the following:

                  (i)   The worth at the time of any unpaid rent which has been
earned at the time of such termination; plus

                  (ii)  The worth at the time of award of the amount by which
the unpaid rent which would have been earned after termination until the
time of award exceeds the amount of such rental loss that Tenant proves
could have been reasonably avoided; plus

                  (iii) The worth at the time of award of the amount by which
the unpaid rent for the balance of the Lease Term after the time of award
exceeds the amount of such rental loss that Tenant proves could have been
reasonably avoided; plus

                  (iv)  Any other amount necessary to compensate Landlord for
all the detriment proximately caused by Tenant's failure to perform its
obligations under this Lease or which in the ordinary course of things would be
likely to result therefrom, specifically including but not limited to, brokerage
commissions and advertising expenses incurred, expenses of remodeling the
Premises or any portion thereof for a new tenant, whether for the same or a
different use, and any special concessions made to obtain a new tenant; and

                  (v)   At Landlord's election, such other amounts in addition
to or in lieu of the foregoing as may be permitted from time to time by
applicable law.

     The term "RENT" as used in this Section 19.2 shall be deemed to be and to
mean all sums of every nature required to be paid by Tenant pursuant to the
TCC's of this Lease, whether to Landlord or to others. As used in Paragraphs
19.2.1(i) and (ii), above, the "worth at the time of award" shall be computed by
allowing interest at the rate set forth in Article 25 of this Lease, but in no
case greater than the maximum amount of such interest permitted by law. As used
in Paragraph 19.2.1(iii) above, the "worth at the time of award" shall be
computed by discounting such amount at the discount rate of the Federal Reserve
Bank of San Francisco at the time of award plus one percent (1%).

           19.2.2 Landlord shall have the remedy described in California Civil
Code Section 1951.4 (lessor may continue lease in effect after lessee's breach
and abandonment and recover

                                      -39-
<PAGE>

rent as it becomes due, if lessee has the right to sublet or assign, subject
only to reasonable limitations). Accordingly, if Landlord does not elect to
terminate this Lease on account of any default by Tenant, Landlord may, from
time to time, without terminating this Lease, enforce all of its rights and
remedies under this Lease, including the right to recover all rent as it becomes
due.

           19.2.3 Landlord shall at all times have the rights and remedies
(which shall be cumulative with each other and cumulative and in addition to
those rights and remedies available under Sections 19.2.1 and 19.2.2, above, or
any law or other provision of this Lease), without prior demand or notice except
as required by applicable law, to seek any declaratory, injunctive or other
equitable relief, and specifically enforce this Lease, or restrain or enjoin a
violation or breach of any provision hereof.

     19.3  SUBLEASES OF TENANT.  Whether or not Landlord elects to terminate
           -------------------
this Lease on account of any default by Tenant, as set forth in this Article 19,
                                                                     ----------
Landlord shall have the right to terminate any and all subleases, licenses,
concessions or other consensual arrangements for possession entered into by
Tenant and affecting the Premises or may, in Landlord's sole discretion, succeed
to Tenant's interest in such subleases, licenses, concessions or arrangements.
In the event of Landlord's election to succeed to Tenant's interest in any such
subleases, licenses, concessions or arrangements, Tenant shall, as of the date
of notice by Landlord of such election, have no further right to or interest in
the rent or other consideration receivable thereunder.

     19.4  FORM OF PAYMENT AFTER DEFAULT.  Following the occurrence of an event
           -----------------------------
of default by Tenant, Landlord shall have the right to require that any or all
subsequent amounts paid by Tenant to Landlord hereunder, whether to cure the
default in question or otherwise, be paid in the form of cash, money order,
cashier's or certified check drawn on an institution acceptable to Landlord, or
by other means approved by Landlord, notwithstanding any prior practice of
accepting payments in any different form.

     19.5  EFFORTS TO RELET.  No re-entry or repossession, repairs, maintenance,
           ----------------
changes, alterations and additions, reletting, appointment of a receiver to
protect Landlord's interests hereunder, or any other action or omission by
Landlord shall be construed as an election by Landlord to terminate this Lease
or Tenant's right to possession, or to accept a surrender of the Premises, nor
shall same operate to release Tenant in whole or in part from any of Tenant's
obligations hereunder, unless express written notice of such intention is sent
by Landlord to Tenant. Tenant hereby irrevocably waives any right otherwise
available under any law to redeem or reinstate this Lease.

                                   ARTICLE 20
                                   ----------

                           COVENANT OF QUIET ENJOYMENT
                           ---------------------------

     Landlord covenants that Tenant, on paying the Rent, charges for services
and other payments herein reserved and on keeping, observing and performing all
the other TCC's, provisions and agreements herein contained on the part of
Tenant to be kept, observed and performed, shall, during the Lease Term,
peaceably and quietly have, hold and enjoy the Premises subject to the TCC's,
provisions and agreements hereof without interference by any

                                      -40-
<PAGE>

persons lawfully claiming by or through Landlord. The foregoing covenant is in
lieu of any other covenant express or implied.

                                   ARTICLE 21
                                   ----------

                       SECURITY DEPOSIT; LETTER OF CREDIT
                       ----------------------------------

     21.1  DELIVERY OF LETTER OF CREDIT.  Tenant shall deliver to Landlord
           ----------------------------
within thirty (30) days of mutual execution of this Lease, an unconditional,
clean, irrevocable letter of credit (the "L-C") in an amount (the "L-C AMOUNT")
initially equal to the "Initial L-C Amount," as that term is set forth in
Section 21.2, below, which L-C shall be issued by a money-center bank (a bank
------------
which accepts deposits, maintains accounts, has a local San Diego office which
will negotiate a letter of credit, and whose deposits are insured by the FDIC)
reasonably acceptable to Landlord, and which L-C shall be in the form of EXHIBIT
                                                                         -------
G, attached hereto.  Tenant shall pay all expenses, points and/or fees incurred
-
by Tenant in obtaining the L-C.

     21.2  L-C AMOUNT.
           ----------

           21.2.1  INITIAL L-C AMOUNT.  For purposes of this Lease, the
                   ------------------
"Initial L-C Amount" shall be (i) an amount equal to twelve (12) months of the
initial Monthly Installment of Base Rent (estimated to be $2,129,664.00) if
Tenant's "Market Capitalization," as that term set forth hereinbelow, is
$500,000,000 or greater, and Tenant has "Working Capital," as that term is set
forth hereinbelow, of $50,000,000 or greater; (ii) an amount equal to
twenty-four (24) months of the initial Monthly Installment of Base Rent
(estimated to be $4,259,328.00) if Tenant's Market Capitalization is between
$350,000,000 and $500,000,000 and Tenant has Working Capital of at least
$35,000,000; and (iii) an amount equal to thirty-six (36) months of the initial
Monthly Installment of Base Rent (estimated to be $6,388,992.00), if Tenant's
Market Capitalization is less than $350,000,000 or if Tenant has less than
$35,000,000 of Working Capital. "Market Capitalization" means product of (A) the
number of outstanding shares of Tenant, and (B) the average closing share price
during the last thirty (30) days of the applicable financial quarter. "Working
Capital," means then- current assets of Tenant less then-current liabilities
from Tenant's previous quarterly financial statements, which Working Capital
shall include then-current receivables (zero (0) to sixty (60) days only).
"Minimum Financial Requirements" means Tenant maintains a Market Capitalization
of no less than $350,000,000 and has Working Capital of no less than
$35,000,000.

           21.2.2  CONDITIONAL REDUCTION OF L-C AMOUNT.  The L-C Amount shall
                   -----------------------------------
be reduced as follows: (A) to fifty percent (50%) of the Initial L-C Amount if
Tenant maintains the Minimum Financial Requirements, for four (4) consecutive
financial quarters, or (B) to $0.00 if Tenant maintains the Minimum Financial
Requirements for eight (8) consecutive financial quarters, or (C) to $0.00 in
the event Tenant achieves either (i) an investment grade rating of no less than
"BBB" (Standard & Poor's) or "Baa3" (Moody's), or (ii) a Market Capitalization
of $1,000,000,000 or greater and Working Capital of no less than $100,000,000.

           21.2.3  REESTABLISHMENT OF INITIAL L-C AMOUNT.  Throughout the
                   -------------------------------------
initial Lease Term and any Option Terms, if any, in the event the L-C Amount has
been reduced to less than the Initial L-C Amount (i) pursuant to the TCC's of
Section 21.2.2(A) or (B) and Tenant
------------------------

                                      -41-
<PAGE>

thereafter fails, at the end of any quarter, to meet the Minimum Financial
Requirements, or (ii) pursuant to the TCC's of Section 21.2.2(C) and Tenant
                                               -----------------
thereafter fails, at any time thereafter, to maintain a Market Capitalization of
at least $1,000,000,000 and Working Capital of no less than $100,000,000, then,
in such event, Landlord shall be entitled to require that the L-C be
reestablished with an L-C Amount equal to the Initial L-C Amount on the TCC's
set forth in this Article 21. Tenant shall, upon its receipt of written notice
                  ----------
from Landlord (the "REESTABLISHMENT NOTICE"), cause the L-C to be immediately
re-issued/reestablished with an L-C Amount equal to the Initial L-C Amount.

           21.2.4  FAILURE TO REINSTATE PENALTY.  In the event that Tenant
                   ----------------------------
fails, within ten (10) days following Tenant's receipt of a Reestablishment
Notice, to cause the L-C to be re-issued/reestablished, then Tenant's Monthly
Installment of Base Rent shall be increased by one hundred fifty percent (150%)
of its then existing level during the period commencing on the date of ten (10)
days after such Reestablishment Notice and ending on the earlier to occur of (i)
the date such L-C is re-issued/reestablished pursuant to the terms of this
Section 21.2, or (ii) the date which is ninety (90) days after the date of such
------------
Reestablishment Notice. In the event that Tenant fails, during such three (3)
month period following the date of the Reestablishment Notice, to cause the L-C
to be reissued/reestablished, then Tenant's Monthly Installment of Base Rent
shall be increased by two hundred percent (200%) of its then existing level
during the period commencing on the date which is ninety (90) days after the
date of such Reestablishment Notice and ending on the date such L-C is
re-issued/reestablished pursuant to the terms of this Section 21.2.
                                                      ------------

     21.3  APPLICATION OF LETTER OF CREDIT.  The L-C shall be held by Landlord
           -------------------------------
as security for the faithful performance by Tenant of all the TCC's of this
Lease to be kept and performed by Tenant during the Lease Term. The L-C shall
not be mortgaged, assigned or encumbered in any manner whatsoever by Tenant
without the prior written consent of Landlord. If Tenant defaults with respect
to any provisions of this Lease, including, but not limited to, the provisions
relating to the payment of Rent, or if Tenant fails to renew the L-C at least
thirty (30) days before its expiration, Landlord may, but shall not be required
to, draw upon all or any portion of the L-C for payment of any Rent or any other
sum in default, or for the payment of any amount that Landlord may reasonably
spend or may become obligated to spend by reason of Tenant's default, or to
compensate Landlord for any other loss or damage that Landlord may suffer by
reason of Tenant's default. The use, application or retention of the L-C, or any
portion thereof, by Landlord shall not prevent Landlord from exercising any
other right or remedy provided by this Lease or by law, it being intended that
Landlord shall not first be required to proceed against the L-C and shall not
operate as a limitation on any recovery to which Landlord may otherwise be
entitled. Any amount of the L-C which is drawn upon by Landlord, but is not used
or applied by Landlord, shall be held by Landlord and deemed a security deposit
(the "L-C SECURITY DEPOSIT"). If any portion of the L-C is drawn upon, Tenant
shall, within ten (10) days after written demand therefor, either (i) deposit
cash with Landlord (which cash shall be applied by Landlord to the L-C Security
Deposit) in an amount sufficient to cause the sum of the L-C Security Deposit
and the amount of the remaining L-C to be equivalent to the amount of the L-C
then required under this Lease or (ii) reinstate the L-C to the amount then
required under this Lease, and if any portion of the L-C Security Deposit is
used or applied, Tenant shall, within ten (10) days after written demand
therefor, deposit cash with Landlord (which cash shall be applied by Landlord to
the L-C Security Deposit) in an amount sufficient to restore the L-C Security

                                      -42-
<PAGE>

Deposit to the amount then required under this Lease, and Tenant's failure to do
so shall be a default under this Lease; provided, however, that upon Tenant's
satisfaction of its economic obligations and restoration of the L-C Security
Deposit pursuant to this sentence, any unused portion of the drawn upon funds
shall be returned to Tenant. Tenant acknowledges that Landlord has the right to
transfer or mortgage its interest in the Real Property and the Center and in
this Lease and Tenant agrees that in the event of any such transfer or mortgage,
Landlord shall have the right to transfer or assign the L-C Security Deposit
and/or the L-C to the transferee or mortgagee, and in the event of such
transfer, Tenant shall look solely to such transferee or mortgagee for the
return of the L-C Security Deposit and/or the L-C. Landlord shall pay all costs
associated with the transfer or re-issuance of the L-C due to Landlord's
transfer or assignment. Tenant shall, within five (5) days of request by
Landlord, execute such further instruments or assurances as Landlord may
reasonably deem necessary to evidence or confirm Landlord's transfer or
assignment of the L-C Security Deposit and/or the L-C to such transferee or
mortgagee. If Tenant is not then in default under this Lease, the L-C Security
Deposit and/or the L-C, or any balance thereof, shall be returned to Tenant
within thirty (30) days following the expiration of the Lease Term.

     21.4  AFTER SALE TO A THIRD PARTY NON-INSTITUTIONAL BUYER.  In the event
           ---------------------------------------------------
the initial Landlord entity (KR-Gateway Partners LLC) or its Affiliates
transfers or sells its interest in the Project to a person or any entity other
than an institutional buyer (a "NON-INSTITUTIONAL BUYER"), Tenant shall have the
right to require that the L-C Security Deposit be held by the lender, if any,
providing the financing for such Non-Institutional Buyer, which account shall be
subject to escrow instructions specifying that (i) Landlord shall only have the
right to draw on the L-C to the extent the Landlord is entitled to pursuant to
the TCCs of this Article 21, (ii) Landlord shall deliver a statement to the
escrow holder prior to any draw down, certifying that Landlord is entitled to
draw on the L-C pursuant to the TCCs of this Article 21, and (iii) that within
ninety (90) days after the expiration of this Lease, the escrow holder shall
release the L-C to Tenant consistent with the terms of this Lease and this
Article 21. For purposes of this Section 21.4, the term "institutional buyer"
shall include, without limitation, life insurance companies, banks, pension
funds, pension fund advisors, opportunity funds, hedge funds, private owners who
directly or indirectly own more than $75,000,000 of real estate, or publicly
traded real estate investment trusts.

                                   ARTICLE 22
                                   ----------

                          TELECOMMUNICATIONS EQUIPMENT
                          ----------------------------

     At any time during the Lease Term, subject to the TCCs of this Article 22
and Article 8 of this Lease, Tenant may install, at Tenant's sole cost and
expense, but without the payment of any Rent or a license or similar fee or
charge, a satellite or microwave dish or other communications, HVAC or other
equipment servicing the business conducted by Tenant from within the Premises
(all such equipment, including non-telecommunication equipment is, for the sake
of convenience, defined collectively as the "TELECOMMUNICATIONS EQUIPMENT") upon
the roof of the Building. The physical appearance and the size of the
Telecommunications Equipment shall be subject to Landlord's reasonable approval,
the location of any such installation of the Telecommunications Equipment shall
be designated by Tenant subject to Landlord's reasonable approval and Landlord
may require Tenant to install screening around

                                      -43-
<PAGE>

such Telecommunications Equipment, at Tenant's sole cost and expense, as
reasonably designated by Landlord. Tenant shall maintain such Telecommunications
Equipment, at Tenant's sole cost and expense. In the event Tenant elects to
exercise its right to install the Telecommunication Equipment, then Tenant shall
give Landlord prior notice thereof. Tenant shall remove such Telecommunications
Equipment upon the expiration or earlier termination of this Lease and shall
restore such area to the condition the same existed prior to the installation of
such Telecommunications Equipment. Such Telecommunications Equipment shall be
installed pursuant to plans and specifications approved by Landlord, which
approval will not be unreasonably withheld. Such Telecommunications Equipment
shall, in all instances, comply with applicable governmental laws, codes, rules
and regulations. The rights contained in this Article 22 shall be personal to
the Original Tenant and its Affiliates and may only be exercised by the Original
Tenant or an Affiliate (and not any assignee, subleasee or other transferee of
the Original Tenant's interest in this Lease) if the Original Tenant and/or an
Affiliate occupies the entire Building. Landlord shall reserve the concurrent
right to use the roof for its own use and for third-party use for installation
of satellite dish and antenna devices similar to Tenant's Telecommunications
Equipment (collectively, the "LANDLORD TCE"), provided such Landlord TCE shall
not interfere with Tenant's operations on the roof of the Building, and provided
Landlord maintains, restores and repairs the Building rooftop space associated
with such Landlord TCE. To the extent Landlord elects to install Landlord TCE on
the Building rooftop, Landlord shall be responsible for the maintenance, repair
and restoration of such Landlord TCE and shall notify Tenant no less than
twenty-four (24) hours in advance of any entry/access onto the Building rooftop.
Landlord shall be responsible for (and shall make all necessary repairs and
replacements for) any damage to Tenant's Telecommunications Equipment due to the
actions or omissions of Landlord or Landlord Parties (or any third party to whom
Landlord has granted roof access rights). Tenant shall be responsible for (and
shall make all necessary repairs and replacements for) any damage to the
Landlord TCE due to the negligence or willful misconduct of Tenant.

                                   ARTICLE 23
                                   ----------

                                      SIGNS
                                      -----

     23.1  FULL FLOORS.  Subject to Landlord's prior written approval, in its
           -----------
reasonable discretion, Tenantat its sole cost and expense, may install
identification signage anywhere in the Premises including in the elevator lobby
of the Premises.

     23.2  INTENTIONALLY OMITTED.
           ---------------------

     23.3  PROHIBITED SIGNAGE AND OTHER ITEMS.  Any signs, notices, logos,
           ----------------------------------
pictures, names or advertisements which are installed and that have not been
separately approved by Landlord may be removed without notice by Landlord at the
sole expense of Tenant. Any signs, window coverings, or blinds (even if the same
are located behind the Landlord-approved window coverings for the Building), or
other items visible from the exterior of the Premises or Building, shall be
subject to the prior approval of Landlord, in its reasonable discretion.

     23.4  TENANT'S SIGNAGE.
           ----------------

                                      -44-
<PAGE>

           23.4.1  TENANT'S SIGNAGE RIGHTS.  For purposes of this Lease,
                   -----------------------
"Tenant's Signage" shall mean the "Building Signage" as that term is defined
below; provided, however, Tenant's Signage is personal to Original Tenant and
its Affiliates, is non-transferable, and is conditioned upon the Original Tenant
and its Affiliates being in occupancy of at least sixty percent (60%) of the
Premises. Tenant shall be entitled to install the following signage in
connection with Tenant's lease of the Premises (collectively, the "BUILDING
SIGNAGE"):

                   (i)  Two (2) signs identifying Tenant's name and logo
located at the top of, or on the eyebrow of, the Building and/or next to
Tenant's main entrance to the Premises; and

                   (ii) One (1) monument sign located adjacent to the main
entrance point to the Building (the "BUILDING MONUMENT SIGN"); provided,
however, that in any event Landlord shall be able to locate its standard
identification signage, in a size to be mutually and reasonably determined, on
the Building Monument Sign (with lowest/least prominent position, and provided
the size of the lettering on such Landlord identification signage is no greater
than 25% of the lettering on Tenant's portion of such Building Monument Sign);
and

                   (iii) One (1) monument sign located on the patio plaza wall
located adjacent to the Building (the "PLAZA WALL SIGN").

           23.4.2  SPECIFICATIONS AND PERMITS.  Tenant's Signage shall set
                   --------------------------
forth Tenant's name and logo as determined by Tenant in its sole discretion;
provided, however, in no event shall Tenant's Signage include an "Objectionable
Name," as that term is defined in Section 23.4.3, of this Lease. The graphics,
materials, color, design, lettering, lighting, size, illumination,
specifications and exact location of Tenant's Signage (collectively, the "SIGN
SPECIFICATIONS") shall be subject to the prior written approval of Landlord,
which approval shall not be unreasonably withheld, conditioned or delayed, and
shall be consistent and compatible with the quality and nature of the Project
and the Building Standard Signage Specifications. Provided, however, that with
respect to the sign(s) at the top of the Building, Tenant may have the maximum
signage available by Applicable Law and the CC&R's. In the preceding sentence,
the reference to "name" shall mean name and/or logo. In addition, Tenant's
Signage shall be subject to Tenant's receipt of all required governmental
permits and approvals and shall be subject to all Applicable Law and to any
covenants, conditions and restrictions affecting the Project. Landlord shall use
commercially reasonable efforts to assist Tenant in obtaining all necessary
governmental permits and approvals for Tenant's Signage. Tenant hereby
acknowledges that, notwithstanding Landlord's approval of Tenant's Signage,
Landlord has made no representation or warranty to Tenant with respect to the
probability of obtaining all necessary governmental approvals and permits for
Tenant's Signage. In the event Tenant does not receive the necessary
governmental approvals and permits for Tenant's Signage, Tenant's and Landlord's
rights and obligations under the remaining terms and conditions of this Lease
shall be unaffected.

           23.4.3  OBJECTIONABLE NAME.  To the extent Original Tenant or its
                   ------------------
Affiliates desires to change the name and/or logo set forth on Tenant's Signage,
such name and/or logo shall not have a name which relates to an entity which is
of a character or reputation, or is associated with a political faction or
orientation, which is inconsistent with a first-class project, or which would
otherwise reasonably offend a landlord of the Comparable Buildings (an
"OBJECTIONABLE NAME").

                                      -45-
<PAGE>

           23.4.4  COST AND MAINTENANCE.  The costs of the actual signs
                   --------------------
comprising Tenant's Signage and the installation, design, construction, and any
and all other costs associated with Tenant's Signage, including, without
limitation, utility charges and hook-up fees, permits, and maintenance and
repairs, shall, subject to the terms and conditions of this Lease, be the sole
responsibility of Tenant; provided that Landlord shall install the Project
Monument Sign(s), at Landlord's sole cost and expense, and Tenant shall be
responsible for the cost of Tenant's sign on the Project Monument Sign(s), but
Landlord shall maintain all monument signs set forth in this Article 23 in good
condition and repair, the cost of which in connection with the Project Monument
Sign(s) shall be included in Operating Expenses. Should Tenant's Signage require
repairs and/or maintenance, as determined in Landlord's reasonable judgment,
Landlord shall have the right to provide Notice thereof to Tenant and Tenant
(except as set forth above) shall cause such repairs and/or maintenance to be
performed within thirty (30) days after receipt of such Notice from Landlord, at
Tenant's sole cost and expense; provided, however, if such repairs and/or
maintenance are reasonably expected to require longer than thirty (30) days to
perform, Tenant shall commence such repairs and/or maintenance within such
thirty (30) day period and shall diligently prosecute such repairs and
maintenance to completion. Should Tenant fail to perform such repairs and/or
maintenance within the periods described in the immediately preceding sentence,
Landlord shall have the right to cause such work to be performed and to charge
Tenant as Additional Rent for the actual cost of such work plus interest at the
Interest Rate from the date of Landlord's payment of such actual costs to the
date of Tenant's reimbursement to Landlord. Upon the expiration or earlier
termination of this Lease, Tenant shall, at Tenant's sole cost and expense,
cause Tenant's Signage to be removed and shall cause the areas in which such
Tenant's Signage was located to be restored to the condition existing
immediately prior to the placement of such Tenant's Signage. If Tenant fails to
timely remove such Tenant's Signage or to restore the areas in which such
Tenant's Signage was located, as provided in the immediately preceding sentence,
then Landlord may perform such work, and all actual costs incurred by Landlord
in so performing, plus interest at the Interest Rate from the date of Landlord's
payment of such costs to the date of Tenant's reimbursement to Landlord, shall
be reimbursed by Tenant to Landlord within ten (10) days after Tenant's receipt
of an invoice therefor. The terms and conditions of this Section 23.4.4 shall
survive the expiration or earlier termination of this Lease.

                                   ARTICLE 24
                                   ----------

                               COMPLIANCE WITH LAW
                               -------------------

     Tenant shall not do anything or suffer anything to be done in or about the
Premises or the Project which will in any way conflict with any law, statute,
ordinance or other governmental rule, regulation or requirement now in force or
which may hereafter be enacted or promulgated. At its sole cost and expense,
Tenant shall promptly comply with all such governmental measures. Should any
standard or regulation now or hereafter be imposed on Tenant by a state, federal
or local governmental body charged with the establishment, regulation and
enforcement of occupational, health or safety standards for employers,
employees, landlords or tenants, then Tenant agrees, at its sole cost and
expense, to comply promptly with such standards or regulations. Tenant shall be
responsible, at its sole cost and expense, to make all alterations to the
Premises as are required to comply with the governmental rules, regulations,
requirements or standards described in this Article 24, except for any such
                                            ----------
alterations to the Building Structure,

                                      -46-
<PAGE>

which shall be performed by Landlord pursuant to the TCCs of this Lease. The
judgment of any court of competent jurisdiction or the admission of Tenant in
any judicial action, regardless of whether Landlord is a party thereto, that
Tenant has violated any of said governmental measures, shall be conclusive of
that fact as between Landlord and Tenant. If, on or before the eighth (8th)
anniversary of the Lease Commencement Date, Tenant becomes obligated, at
Tenant's sole cost and expense, to make an improvement or alteration to the
Building Systems which shall be capital in nature, Tenant may elect, upon
immediate notice thereof to Landlord, to have Landlord make such improvement or
alteration to the Building Systems, the cost of which shall be amortized with
interest over its useful life as reasonably determined by Landlord pursuant to
sound real estate accounting and management principles, consistently applied,
and shall be paid by Tenant to Landlord as Additional Rent; provided, however,
(i) Tenant shall not have such option to the extent such improvement or
alteration is necessary due to the negligence or willful misconduct of Tenant or
the Tenant's Parties, and (ii) to the extent Tenant's use of the improvement or
alteration reduces the useful life (as determined pursuant to GAAP) of such
improvement or alteration, the cost of such improvement or alteration shall be
amortized with interest over such shorter time period.

                                   ARTICLE 25
                                   ----------

                                  LATE CHARGES
                                  ------------

     If any installment of Rent or any other sum due from Tenant shall not be
received by Landlord or Landlord's designee within five (5) days after said
amount is due, then Tenant shall pay to Landlord a late charge equal to five
percent (5%) of the overdue amount plus any attorneys' fees incurred by Landlord
by reason of Tenant's failure to pay Rent and/or other charges when due
hereunder. The late charge shall be deemed Additional Rent and the right to
require it shall be in addition to all of Landlord's other rights and remedies
hereunder or at law and shall not be construed as liquidated damages or as
limiting Landlord's remedies in any manner. In addition to the late charge
described above, any Rent or other amounts owing hereunder which are not paid
within ten (10) days after the date they are due shall bear interest from the
date when due until paid at a rate per annum equal to the lesser of (i) the
annual "BANK PRIME LOAN" rate cited in the Federal Reserve Statistical Release
Publication G.13(415), published on the first Tuesday of each calendar month (or
such other comparable index as Landlord and Tenant shall reasonably agree upon
if such rate ceases to be published) plus four (4) percentage points, and (ii)
the highest rate permitted by applicable law.

                                   ARTICLE 26
                                   ----------

              LANDLORD'S RIGHT TO CURE DEFAULT; PAYMENTS BY TENANT
              ----------------------------------------------------

     26.1  LANDLORD'S CURE.  All covenants and agreements to be kept or
           ---------------

performed by Tenant under this Lease shall be performed by Tenant at Tenant's
sole cost and expense and without any reduction of Rent, except to the extent,
if any, otherwise expressly provided herein. If Tenant shall fail to perform any
obligation under this Lease, and such failure shall continue in excess of the
time allowed under Section 19.1.2, above, unless a specific time period is
otherwise stated in this Lease, Landlord may, but shall not be obligated to,
make any such payment or

                                      -47-
<PAGE>

perform any such act on Tenant's part without waiving its rights based upon any
default of Tenant and without releasing Tenant from any obligations hereunder.

     26.2  TENANT'S REIMBURSEMENT.  Except as may be specifically provided to
           ----------------------
the contrary in this Lease, Tenant shall pay to Landlord, upon delivery by
Landlord to Tenant of statements therefor: (i) sums equal to expenditures
reasonably made and obligations incurred by Landlord in connection with the
remedying by Landlord of Tenant's defaults pursuant to the provisions of Section
26.1; and (ii) sums equal to all expenditures made and obligations incurred by
Landlord in collecting or attempting to collect the Rent (where the same was not
paid within three days of notice that the same was not paid when due) or in
enforcing or attempting to enforce any rights of Landlord under this Lease or
pursuant to law, including, without limitation, all legal fees and other amounts
so expended. Tenant's obligations under this Section 26.2 shall survive the
expiration or sooner termination of the Lease Term.

                                   ARTICLE 27
                                   ----------

                                ENTRY BY LANDLORD
                                -----------------

     Landlord reserves the right at all reasonable times and upon reasonable
notice to Tenant (except in the case of an emergency) to enter the Premises to
(i) inspect them; (ii) show the Premises to prospective purchasers, mortgagees,
or to current or prospective mortgagees, ground or underlying lessors or
insurers, or, during the last six (6) months of the Lease Term, prospective
tenants; (iii) post notices of nonresponsibility; or (iv) for alterations,
repairs or improvements to the Building Structure. Notwithstanding anything to
the contrary contained in this Article 27, Landlord may enter the Premises at
any time to (A) perform services required of Landlord under this Lease; (B) take
possession due to any breach of this Lease in the manner provided herein; and
(C) perform any covenants of Tenant which Tenant fails to perform (after any
applicable notice and cure periods). Landlord may make any such entries without
the abatement of Rent and may take such reasonable steps as required to
accomplish the stated purposes. Tenant hereby waives any claims for damages or
for any injuries or inconvenience to or interference with Tenant's business,
lost profits, any loss of occupancy or quiet enjoyment of the Premises, and any
other loss occasioned thereby. For each of the above purposes, Landlord shall at
all times have a key with which to unlock all the doors in the Premises,
excluding Tenant's vaults, safes and special security areas designated in
advance by Tenant. In an emergency, Landlord shall have the right to use any
means that Landlord may deem proper to open the doors in and to the Premises.
Any entry into the Premises by Landlord in the manner hereinbefore described
shall not be deemed to be a forcible or unlawful entry into, or a detainer of,
the Premises, or an actual or constructive eviction of Tenant from any portion
of the Premises. No provision of this Lease shall be construed as obligating
Landlord to perform any repairs, alterations or decorations except as otherwise
expressly agreed to be performed by Landlord herein.

                                      -48-
<PAGE>

                                   ARTICLE 28
                                   ----------

                                 TENANT PARKING
                                 --------------

     Tenant shall, at all times during the Lease Term and at no additional
charge, have the exclusive use of the parking areas on Lot 5 (the legal parcel
on which the Building is located), which parking areas are indicated on Exhibit
A attached hereto. Tenant shall have the right to designate visitor, car-
pooling, executive and other parking as Tenant may reasonably require, subject
to Landlord's reasonable approval. Tenant shall be responsible for the full
amount of any taxes imposed by any governmental authority in connection with the
use of such parking areas by Tenant. Tenant's continued right to use the parking
passes is conditioned upon Tenant abiding by all reasonable rules and
regulations which are prescribed from time to time for the orderly operation and
use of such parking area, including any sticker or other identification system
established by Landlord, Tenant's cooperation in seeing that Tenant's employees
and visitors also comply with such rules and regulations and Tenant not being in
default under this Lease. The parking areas to be used by Tenant pursuant to
this Article 28 are provided exclusively to Tenant solely for use by Tenant's
own personnel and such area (and the right to use such area) may not be
transferred, assigned, subleased or otherwise alienated by Tenant without
Landlord's prior approval; provided, however, Landlord shall be deemed to have
granted such approval with regard to Non-Transfers and Transfers approved
pursuant to the TCC's of Article 14.

                                   ARTICLE 29
                                   ----------

                            MISCELLANEOUS PROVISIONS
                            ------------------------

     29.1  TERMS; CAPTIONS.  The words "Landlord" and "Tenant" as used herein
           ---------------
shall include the plural as well as the singular. The necessary grammatical
changes required to make the provisions hereof apply either to corporations or
partnerships or individuals, men or women, as the case may require, shall in all
cases be assumed as though in each case fully expressed. The captions of
Articles and Sections are for convenience only and shall not be deemed to limit,
construe, affect or alter the meaning of such Articles and Sections.

     29.2  BINDING EFFECT.  Subject to all other provisions of this Lease, each
           --------------
of the covenants, conditions and provisions of this Lease shall extend to and
shall, as the case may require, bind or inure to the benefit not only of
Landlord and of Tenant, but also of their respective heirs, personal
representatives, successors or assigns, provided this clause shall not permit
any assignment by Tenant contrary to the provisions of Article 14 of this Lease.

     29.3  NO AIR RIGHTS.  No rights to any view or to light or air over any
           -------------
property, whether belonging to Landlord or any other person, are granted to
Tenant by this Lease. If at any time any windows of the Premises are temporarily
darkened or the light or view therefrom is obstructed by reason of any repairs,
improvements, maintenance or cleaning in or about the Project, the same shall be
without liability to Landlord and without any reduction or diminution of
Tenant's obligations under this Lease.

     29.4  MODIFICATION OF LEASE.  Should any current or prospective mortgagee
           ---------------------
or ground lessor for the Building or Project require a modification of this
Lease, which modification will not cause an increased cost or expense to Tenant
or in any other way materially and adversely change the rights and obligations
of Tenant hereunder, then and in such event, Tenant agrees that this Lease may
be so modified and agrees to execute whatever documents are reasonably

                                      -49-
<PAGE>

required therefor and to deliver the same to Landlord within ten (10) days
following a request therefor. At the request of Landlord or any mortgagee or
ground lessor, Tenant agrees to execute a short form of Lease and deliver the
same to Landlord within ten (10) days following the request therefor.

     29.5  TRANSFER OF LANDLORD'S INTEREST.  Tenant acknowledges that Landlord
           -------------------------------
has the right to transfer all or any portion of its interest in the Project or
Building and in this Lease, and Tenant agrees that in the event of any such
transfer, Landlord shall automatically be released from all liability under this
Lease and Tenant agrees to look solely to such transferee for the performance of
Landlord's obligations hereunder after the date of transfer and such transferee
shall be deemed to have fully assumed and be liable for all obligations of this
Lease to be performed by Landlord, including the return of any Security Deposit,
and Tenant shall attorn to such transferee. Tenant further acknowledges that
Landlord may assign its interest in this Lease to a mortgage lender as
additional security and agrees that such an assignment shall not release
Landlord from its obligations hereunder and that Tenant shall continue to look
to Landlord for the performance of its obligations hereunder.

     29.6  PROHIBITION AGAINST RECORDING.  Except as set forth hereinbelow
           -----------------------------
and/or provided in Section 29.4 of this Lease, neither this Lease, nor any
memorandum, affidavit or other writing with respect thereto, shall be recorded
by Tenant or by anyone acting through, under or on behalf of Tenant.
Concurrently with the execution of this Lease, Landlord and Tenant shall deliver
recordable counterparts of a Short Form of Lease, in the form attached hereto as
Exhibit H, which may be recorded in the Official Records of the County Recorder
of San Diego, by either Landlord or Tenant. The recordation of any such document
shall be at the sole cost and expense of the party conducting such recordation,
and where requested by Landlord, such cost shall not be included as an Operating
Expense.

     29.7  LANDLORD'S TITLE.  Landlord's title is and always shall be paramount
           ----------------
to the title of Tenant. Nothing herein contained shall empower Tenant to do any
act which can, shall or may encumber the title of Landlord.

     29.8  RELATIONSHIP OF PARTIES.  Nothing contained in this Lease shall be
           -----------------------
deemed or construed by the parties hereto or by any third party to create the
relationship of principal and agent, partnership, joint venturer or any
association between Landlord and Tenant.

     29.9  APPLICATION OF PAYMENTS.  Landlord shall have the right to apply
           -----------------------
payments received from Tenant pursuant to this Lease, regardless of Tenant's
designation of such payments, to satisfy any obligations of Tenant hereunder, in
such order and amounts as Landlord, in its sole discretion, may elect.

     29.10  TIME OF ESSENCE.  Time is of the essence with respect to the
            ---------------
performance of every provision of this Lease in which time of performance is a
factor.

     29.11  PARTIAL INVALIDITY.  If any term, provision or condition contained
            ------------------
in this Lease shall, to any extent, be invalid or unenforceable, the remainder
of this Lease, or the application of such term, provision or condition to
persons or circumstances other than those with respect to which it is invalid or
unenforceable, shall not be affected thereby, and each and every other term,

                                      -50-
<PAGE>

provision and condition of this Lease shall be valid and enforceable to the
fullest extent possible permitted by law.

     29.12  NO WARRANTY.  In executing and delivering this Lease, Tenant has not
            -----------
relied on any representations, including, but not limited to, any representation
as to the amount of any item comprising Additional Rent or the amount of the
Additional Rent in the aggregate or that Landlord is furnishing the same
services to other tenants, at all, on the same level or on the same basis, or
any warranty or any statement of Landlord which is not set forth herein or in
one or more of the exhibits attached hereto.

     29.13  LANDLORD EXCULPATION.  The liability of Landlord or the Landlord
            --------------------
Parties to Tenant for any default by Landlord under this Lease or arising in
connection herewith or with Landlord's operation, management, leasing, repair,
renovation, alteration or any other matter relating to the Project or the
Premises shall be limited solely and exclusively to an amount which is equal to
(1) to the extent such liability arises prior to the Lease Commencement Date,
the interest of Landlord in the Building (including any insurance proceeds which
Landlord receives); provided that if the Building is encumbered by third-party
debt in excess of eighty percent (80%) of the value of the Building, such value
shall be the equity interest Landlord would have in the Building if the Building
were encumbered by such third-party debt in an amount equal to eighty percent
(80%) of the value of the Building, or (2) to the extent such liability arises
after the Lease Commencement Date, the lesser of (a) the interest of Landlord in
the Building (including any insurance, condemnation or sales proceeds which
Landlord receives (which sales proceeds shall include the monetary value of any
non- monetary interests received)); provided that if the Building is encumbered
by third-party debt in excess of eighty percent (80%) of the value of the
Building, such value shall be the equity interest Landlord would have in the
Building if the Building were encumbered by such third-party debt in an amount
equal to eighty percent (80%) of the value of the Building, or (b) the equity
interest Landlord would have in the Building if the Building were encumbered by
third- party debt in an amount equal to eighty percent (80%) of the value of the
Building (as such value is determined by Landlord), provided, however, that
except as specifically stated above with regard to the calculation of Landlord's
interests, in no event shall such liability extend to any sales or insurance
proceeds received by Landlord or the Landlord Parties in connection with the
Project, Building or Premises. Neither Landlord, nor any of the Landlord Parties
shall have any personal liability therefor, and Tenant hereby expressly waives
and releases such personal liability on behalf of itself and all persons
claiming by, through or under Tenant. The limitations of liability contained in
this Section 29.13 shall inure to the benefit of Landlord's and the Landlord
Parties' present and future partners, beneficiaries, officers, directors,
trustees, shareholders, agents and employees, and their respective partners,
heirs, successors and assigns. Under no circumstances shall any present or
future partner of Landlord (if Landlord is a partnership), or trustee or
beneficiary (if Landlord or any partner of Landlord is a trust), have any
liability for the performance of Landlord's obligations under this Lease.
Notwithstanding any contrary provision herein, neither Landlord nor the Landlord
Parties shall be liable under any circumstances for injury or damage to, or
interference with, Tenant's business, including but not limited to, loss of
profits, loss of rents or other revenues, loss of business opportunity, loss of
goodwill or loss of use, in each case, however occurring.

                                      -51-
<PAGE>

     29.14  ENTIRE AGREEMENT.  It is understood and acknowledged that there are
            ----------------
no oral agreements between the parties hereto affecting this Lease and this
Lease constitutes the parties' entire agreement with respect to the leasing of
the Premises and supersedes and cancels any and all previous negotiations,
arrangements, brochures, agreements and understandings, if any, between the
parties hereto or displayed by Landlord to Tenant with respect to the subject
matter thereof, and none thereof shall be used to interpret or construe this
Lease. None of the TCC's of this Lease can be modified, deleted or added to
except in writing signed by the parties hereto.

     29.15  RIGHT TO LEASE.  Landlord reserves the absolute right to effect such
            --------------
other tenancies in the Project as Landlord in the exercise of its sole business
judgment shall determine to best promote the interests of the Building or
Project. Tenant does not rely on the fact, nor does Landlord represent, that any
specific tenant or type or number of tenants shall, during the Lease Term,
occupy any space in the Building or Project.

     29.16  FORCE MAJEURE.  Any prevention, delay or stoppage due to strikes,
            -------------
lockouts, labor disputes, acts of God, inability to obtain services, labor, or
materials or reasonable substitutes therefor, governmental actions, civil
commotions, fire or other casualty, and other causes beyond the reasonable
control of the party obligated to perform, except with respect to the
obligations imposed with regard to Rent and other charges to be paid by Tenant
pursuant to this Lease and except as to Tenant's obligations under Section 5.2
and Article 24 of this Lease (collectively, a "FORCE MAJEURE"), notwithstanding
anything to the contrary contained in this Lease, shall excuse the performance
of such party for a period equal to any such prevention, delay or stoppage and,
therefore, if this Lease specifies a time period for performance of an
obligation of either party, that time period shall be extended by the period of
any delay in such party's performance caused by a Force Majeure.

     29.17  WAIVER OF REDEMPTION BY TENANT.  Tenant hereby waives, for Tenant
            ------------------------------
and for all those claiming under Tenant, any and all rights now or hereafter
existing to redeem by order or judgment of any court or by any legal process or
writ, Tenant's right of occupancy of the Premises after any termination of this
Lease.

     29.18  NOTICES.  All notices, demands, statements, designations,
            -------
approvals or other communications (collectively, "NOTICES") given or required to
be given by either party to the other hereunder or by law shall be in writing,
shall be (A) sent by United States certified or registered mail, postage
prepaid, return receipt requested ("MAIL"), (B) transmitted by telecopy, if such
telecopy is promptly followed by a Notice sent by Mail, (C) delivered by a
nationally recognized overnight courier, or (D) delivered personally. Any Notice
shall be sent, transmitted, or delivered, as the case may be, to Tenant at the
appropriate address set forth in Section 10 of the Summary, or to such other
place as Tenant may from time to time designate in a Notice to Landlord, or to
Landlord at the addresses set forth below, or to such other places as Landlord
may from time to time designate in a Notice to Tenant. Any Notice will be deemed
given (i) three (3) days after the date it is posted if sent by Mail, (ii) the
date the telecopy is transmitted, (iii) the date the overnight courier delivery
is made, or (iv) the date personal delivery is made or attempted to be made (if
such notice is refused). If Tenant is notified of the identity and address of
Landlord's mortgagee or ground or underlying lessor, Tenant shall give to such
mortgagee or ground or underlying lessor written notice of any default by
Landlord under the TCC's of this Lease by registered or certified mail, and such
mortgagee or ground or underlying lessor shall be

                                      -52-
<PAGE>

given a reasonable opportunity to cure such default prior to Tenant's exercising
any remedy available to Tenant. As of the date of this Lease, any Notices to
Landlord must be sent, transmitted, or delivered, as the case may be, to the
following addresses:

                    Kilroy Realty Corporation
                    2250 East Imperial Highway
                    Suite 1200
                    El Segundo, California  90245
                    Attention:  Legal Department

                    with copies to:

                    Kilroy Realty Corporation
                    12348 High Bluff Drive, Suite 110
                    San Diego, California  92130
                    Attention:  Ms. Lisa Irvin

                    and

                    Allen, Matkins, Leck, Gamble & Mallory
                    1999 Avenue of the Stars, Suite 1800
                    Los Angeles, California 90067
                    Attention:  Anton N. Natsis, Esq.

     29.19  JOINT AND SEVERAL.  If there is more than one Tenant, the
            -----------------
obligations imposed upon Tenant under this Lease shall be joint and several.

     29.20  AUTHORITY.  If Tenant or Landlord is a corporation, trust or
            ---------
partnership, each individual executing this Lease on behalf of Tenant or
Landlord hereby represents and warrants that Landlord or Tenant, as appropriate,
is a duly formed and existing entity qualified to do business in California and
that Landlord or Tenant, as appropriate, has full right and authority to execute
and deliver this Lease and that each person signing on behalf of Landlord or
Tenant, as appropriate, is authorized to do so.

     29.21  ATTORNEYS' FEES.  In the event that either Landlord or Tenant should
            ---------------
bring suit for the possession of the Premises, for the recovery of any sum due
under this Lease, or because of the breach of any provision of this Lease or for
any other relief against the other, then all costs and expenses, including
reasonable attorneys' fees, incurred by the prevailing party therein shall be
paid by the other party, which obligation on the part of the other party shall
be deemed to have accrued on the date of the commencement of such action and
shall be enforceable whether or not the action is prosecuted to judgment.

     29.22  GOVERNING LAW; WAIVER OF TRIAL BY JURY.  This Lease shall be
            --------------------------------------
construed and enforced in accordance with the laws of the State of California.
IN ANY ACTION OR PROCEEDING ARISING HEREFROM, LANDLORD AND TENANT HEREBY CONSENT
TO (I) THE JURISDICTION OF ANY COMPETENT COURT WITHIN THE STATE OF CALIFORNIA,
(II) SERVICE OF PROCESS BY ANY MEANS AUTHORIZED BY CALIFORNIA LAW, AND (III) IN
THE INTEREST OF SAVING TIME AND EXPENSE,

                                      -53-
<PAGE>

TRIAL WITHOUT A JURY IN ANY ACTION, PROCEEDING OR COUNTERCLAIM BROUGHT BY EITHER
OF THE PARTIES HERETO AGAINST THE OTHER OR THEIR SUCCESSORS IN RESPECT OF ANY
MATTER ARISING OUT OF OR IN CONNECTION WITH THIS LEASE, THE RELATIONSHIP OF
LANDLORD AND TENANT, TENANT'S USE OR OCCUPANCY OF THE PREMISES, AND/OR ANY CLAIM
FOR INJURY OR DAMAGE, OR ANY EMERGENCY OR STATUTORY REMEDY.

     29.23  SUBMISSION OF LEASE.  Submission of this instrument for examination
            -------------------
or signature by Tenant does not constitute a reservation of, option for or
option to lease, and it is not effective as a lease or otherwise until execution
and delivery by both Landlord and Tenant.

     29.24  BROKERS.  Landlord and Tenant hereby warrant to each other that
            -------
they have had no dealings with any real estate broker or agent in connection
with the negotiation of this Lease, excepting only the real estate brokers or
agents specified in Section 12 of the Summary (the "BROKERS"), and that they
know of no other real estate broker or agent who is entitled to a commission in
connection with this Lease. Each party agrees to indemnify and defend the other
party against and hold the other party harmless from any and all claims,
demands, losses, liabilities, lawsuits, judgments, costs and expenses (including
without limitation reasonable attorneys' fees) with respect to any leasing
commission or equivalent compensation alleged to be owing on account of any
dealings with any real estate broker or agent, other than the Brokers, occurring
by, through, or under the indemnifying party.

     29.25  INDEPENDENT COVENANTS.  This Lease shall be construed as though the
            ---------------------
covenants herein between Landlord and Tenant are independent and not dependent
and Tenant hereby expressly waives the benefit of any statute to the contrary
and agrees that if Landlord fails to perform its obligations set forth herein,
Tenant shall not be entitled to make any repairs or perform any acts hereunder
at Landlord's expense or to any setoff of the Rent or other amounts owing
hereunder against Landlord.

     29.26  PROJECT OR BUILDING NAME AND SIGNAGE.  Landlord shall have the right
            ------------------------------------
at any time to change the name of the Project or Building. Tenant shall not use
the name of the Project or Building or use pictures or illustrations of the
Project or Building in advertising or other publicity or for any purpose other
than as the address of the business to be conducted by Tenant in the Premises,
without the prior written consent of Landlord.

     29.27  COUNTERPARTS.  This Lease may be executed in counterparts with the
            ------------
same effect as if both parties hereto had executed the same document. Both
counterparts shall be construed together and shall constitute a single lease.

     29.28  CONFIDENTIALITY.  Tenant acknowledges that the content of this Lease
            ---------------
and any related documents are confidential information. Tenant shall keep such
confidential information strictly confidential and shall not disclose such
confidential information to any person or entity other than Tenant's financial,
legal, and space planning consultants, and except as required to be disclosed by
any applicable law or regulation. Landlord and Tenant hereby acknowledge that a
copy of this Lease will be attached to Tenant's filings with the Securities and
Exchange Commission.

                                      -54-
<PAGE>

     29.29  TRANSPORTATION MANAGEMENT.  Tenant shall fully comply with all
            -------------------------
present or future governmental programs intended to manage parking,
transportation or traffic in and around the Building, and in connection
therewith, Tenant shall take responsible action for the transportation planning
and management of all employees located at the Premises by working directly with
Landlord, any governmental transportation management organization or any other
transportation- related committees or entities.

     29.30  BUILDING RENOVATIONS.  It is specifically understood and agreed that
            --------------------
Landlord has made no representation or warranty to Tenant and has no obligation
and has made no promises to alter, remodel, improve, renovate, repair or
decorate the Premises, Building, or any part thereof and that no representations
respecting the condition of the Premises or the Building have been made by
Landlord to Tenant except as specifically set forth herein or in the Tenant Work
Letter.

     29.31  NO VIOLATION.  Tenant hereby warrants and represents that neither
            ------------
its execution of nor performance under this Lease shall cause Tenant to be in
violation of any agreement, instrument, contract, law, rule or regulation by
which Tenant is bound, and Tenant shall protect, defend, indemnify and hold
Landlord harmless against any claims, demands, losses, damages, liabilities,
costs and expenses, including, without limitation, reasonable attorneys' fees
and costs, arising from Tenant's breach of this warranty and representation.

     29.32  COMMUNICATIONS AND COMPUTER LINES.  Tenant may install, maintain,
            ---------------------------------
replace, remove or use any communications or computer wires and cables
(collectively, the "LINES") at the Project in or serving the Premises, provided
that (i) Tenant shall obtain Landlord's prior written consent, use an
experienced and qualified contractor approved in writing by Landlord, and comply
with all of the other provisions of Articles 7 and 8 of this Lease, (ii) the
Lines therefor (including riser cables) shall be appropriately insulated to
prevent excessive electromagnetic fields or radiation, and shall be surrounded
by a protective conduit reasonably acceptable to Landlord, (iii) any new or
existing Lines servicing the Premises shall comply with all applicable
governmental laws and regulations, (iv) as a condition to permitting the
installation of new Lines, Landlord may require that Tenant remove existing
Lines located in or serving the Premises and repair any damage in connection
with such removal, and (v) Tenant shall pay all costs in connection therewith.
Landlord reserves the right to require that Tenant remove any Lines located in
or serving the Premises which are installed in violation of these provisions, or
which are at any time in violation of any laws or represent a dangerous or
potentially dangerous condition.

     29.33  HAZARDOUS SUBSTANCES.
            --------------------

            29.33.1  DEFINITIONS.  For purposes of this Lease, the following
                     -----------
definitions shall apply: "HAZARDOUS MATERIAL(S)" shall mean any substance or
material that is described as a toxic or hazardous substance, waste, material,
pollutant, contaminant or infectious waste, or any matter that in certain
specified quantities would be injurious to the public health or welfare, or
words of similar import, in any of the "Environmental Laws," as that term is
defined below in this Section 29.33.1, or any other words which are intended to
define, list or classify substances by reason of deleterious properties such as
ignitability, corrosivity, reactivity, carcinogenicity, toxicity or reproductive
toxicity and includes, without limitation, asbestos, petroleum (including crude
oil or any fraction thereof, natural gas, natural gas liquids, liquefied natural
gas, or

                                      -55-
<PAGE>

synthetic gas usable for fuel, or any mixture thereof), petroleum products,
polychlorinated biphenyls, urea formaldehyde, radon gas, radioactive matter,
medical waste, and chemicals which may cause cancer or reproductive toxicity.
"ENVIRONMENTAL LAWS" shall mean all federal, state, local and quasi-
governmental laws (whether under common law, statute or otherwise), ordinances,
decrees, codes, rulings, awards, rules, regulations and guidance documents now
or hereafter be enacted or promulgated as amended from time to time, in any way
relating to or regulating Hazardous Materials.

            29.33.2  COMPLIANCE WITH ENVIRONMENTAL LAWS.  Landlord covenants
                     ----------------------------------
that during the Lease Term, Landlord shall comply with all Environmental Laws in
accordance with, and as required by, the terms and conditions of Article 24 of
this Lease; provided, however, such compliance is not the responsibility of
Tenant under this Lease, and provided further that Landlord's failure to comply
therewith would prohibit Tenant from obtaining or maintaining a certificate of
occupancy for the Premises, or would unreasonably and materially affect the
safety of Tenant's Parties or create a significant health hazard for Tenant's
Parties or otherwise materially interfere with or materially affect Tenant's
Permitted Use and enjoyment of the Premises.

            29.33.3  INDEMNIFICATIONS.  Landlord agrees to indemnify, defend,
                     ----------------
protect and hold harmless Tenant and the Tenant Parties from any and all claims
of liability asserted against Tenant or any Tenant Parties by a third party,
including without limitation any agency or instrumentality of the federal, state
or local government, for bodily injury, including death, physical damage to or
loss of use of property or cleanup activities to the extent required by
applicable law (remedial or removal), arising from any Hazardous Materials
(collectively, "HAZARDOUS MATERIALS CLAIMS") to the extent placed in, on, under
or about the Project by Landlord Parties. Tenant agrees to indemnify, defend,
protect and hold harmless Landlord and the Landlord Parties from any and all
Hazardous Materials Claims arising from any Hazardous Materials to the extent
placed in, on, under or about the Premises or the Project by Tenant or Tenant
Parties.

            29.33.4  PRE-EXISTING HAZARDOUS MATERIALS.  Tenant shall be under
                     --------------------------------
no obligation to investigate or remediate any Hazardous Material located in, on,
under or about the Premises as of the Lease Commencement Date (the "EXISTING
HAZARDOUS MATERIALS") or any Hazardous Materials which have migrated onto the
Property from off-site or which are brought onto the Property by Landlord or
Landlord's agents, employees or contractors. Additionally, Landlord agrees that
it shall indemnify, defend and hold Tenant and any Tenant Party harmless from
any cost and all claims of liability asserted against Tenant/Tenant Party by a
third party, including any agency or instrumentality of the federal, state or
local government, for cleanup activities to the extent required by applicable
law (remedial or removal), or governmental fines or penalties, relating to the
Existing Hazardous Materials and those Hazardous materials which are brought
onto the Property by Landlord or Landlord's agents, employees or contractors.

     29.34  DEVELOPMENT OF THE PROJECT.
            --------------------------

            29.34.1  SUBDIVISION.  Landlord reserves the right to further
                     -----------
subdivide all or a portion of the Project. Tenant agrees to execute and deliver,
upon demand by Landlord and

                                      -56-
<PAGE>

in the form requested by Landlord, any additional documents needed to conform
this Lease to the circumstances resulting from such subdivision.

            29.34.2  THE OTHER IMPROVEMENTS.  If portions of the Project or
                     ----------------------
property adjacent to the Project (collectively, the "OTHER IMPROVEMENTS") are
owned by an entity other than Landlord, Landlord, at its option, may enter into
an agreement with the owner or owners of any or all of the Other Improvements to
provide (i) for reciprocal rights of access and/or use of the Project and the
Other Improvements, (ii) for the common management, operation, maintenance,
improvement and/or repair of all or any portion of the Project and the Other
Improvements, (iii) for the allocation of a portion of the Direct Expenses to
the Other Improvements and the operating expenses and taxes for the Other
Improvements to the Project, and (iv) for the use or improvement of the Other
Improvements and/or the Project in connection with the improvement,
construction, and/or excavation of the Other Improvements and/or the Project;
provided that none of the foregoing materially adversely interfere with Tenant's
rights under this Lease. Nothing contained herein shall be deemed or construed
to limit or otherwise affect Landlord's right to convey all or any portion of
the Project or any other of Landlord's rights described in this Lease.

            29.34.3  CONSTRUCTION OF PROJECT AND OTHER IMPROVEMENTS.  Tenant
                     ----------------------------------------------
acknowledges that portions of the Project and/or the Other Improvements may be
under construction following Tenant's occupancy of the Premises, and that such
construction may result in levels of noise, dust, obstruction of access, etc.
which are in excess of that present in a fully constructed project. Landlord
shall use its commercially reasonable efforts to minimize the disruption to
Tenant and Tenant's business from such construction and in no event shall
Landlord be entitled to use Tenant's parking areas for construction staging,
storage of equipment or other construction related activities without Tenant's
approval, which may be granted or withheld in Tenant's sole discretion. Tenant
hereby waives any and all rent offsets or claims of constructive eviction which
may arise in connection with such construction.

     29.35  TENANT RIGHT OF FIRST OFFER TO PURCHASE BUILDING.  Landlord shall
            ------------------------------------------------
grant to the Original Tenant and its Affiliates a right of first offer with
respect to purchasing the Project, but only to the extent Landlord chooses to
sell the Building on an individual, single-building basis, and provided that
Tenant is not then in Default under this Lease (beyond any applicable notice and
cure periods). Landlord shall notify Tenant (the "First Offer Notice") in the
event Landlord desires to sell the Project on such an individual,
single-building basis, and shall notify Tenant of the material price, terms
(both monetary and non-monetary) and conditions pursuant to which it is willing
to sell the Project. Tenant shall, during the fifteen (15) day period after
Tenant's receipt of such First Offer Notice (the "EXCLUSIVE NEGOTIATION
PERIOD"), have an exclusive opportunity to agree with Landlord upon such price,
terms and conditions. If Tenant does not agree to such price, terms and
conditions within the Exclusive Negotiation Period, Landlord shall have no
obligation to sell the Building to Tenant and Landlord shall be free to
negotiate and enter into a purchase agreement for the Building to anyone whom it
desires on any price, terms and conditions it may agree. In the event Landlord
thereafter consummates the sale of the Building pursuant to such a purchase
agreement identified in the preceding sentence, the rights contained in this
Section 29.35 shall terminate and be of no further force or effect. The rights
contained in this Section 29.35 shall be personal to the Original Tenant and its
Affiliates and may only be exercised by the Original Tenant or an Affiliate (and
not any assignee, subleasee or

                                      -57-
<PAGE>

other transferee of the Original Tenant's interest in this Lease) if the
Original Tenant and/or an Affiliate occupies the entire Premises.

     29.36  SUCCESSFUL IPO CONDITION PRECEDENT.  This Lease is subject to and
            ----------------------------------
expressly conditioned upon Tenant having a "Successful IPO," as that terms is
set forth below, on or before February 29, 2000. For purposes of this section
29.36, a "Successful IPO" means (A) an initial public offering of shares of
Tenant's stock on a recognized national stock market, (B) where the share price
of tendered shares is no less than $13.00, (C) resulting in a Market
Capitalization of no less than $350,000,000.00 and (D) with Tenant thereafter
having no less than $35,000,000 of Working Capital. In the event Tenant fails to
complete a Successful IPO on or before February 29, 2000, this Lease shall
immediately terminate and be of no further force or effect; provided, however,
Tenant shall reimburse Landlord for its expenditures through the date of such
termination pursuant to that certain side letter dated December 27th, 1999 and
countersigned on December 28th, 1999 by and between Landlord and Tenant.

     29.37  BUILDING B LEASE.  Landlord and Tenant hereby acknowledge that
            ----------------
Landlord and Tenant are, concurrently with the execution of this Lease, entering
into another lease (the "BUILDING B LEASE") for an approximately 60,060 rentable
square foot building to be constructed on Lot 4 of the Project and to be known
as "BUILDING B". Tenant's execution and delivery of the Building B Lease is a
material condition to Landlord's execution and delivery of this Lease. Tenant
hereby acknowledges that a default (beyond any applicable notice and cure
periods) of this Lease shall constitute a default under the Building B Lease
and, conversely, a default (beyond any applicable notice and cure periods) of
the Building B Lease shall constitute a default of Section 19.1.4 of this Lease.

                                      -58-
<PAGE>

     IN WITNESS WHEREOF, Landlord and Tenant have caused this Lease to be
executed the day and date first above written.


                                   "LANDLORD":

                                   KR-GATEWAY PARTNERS,
                                   a Delaware limited liability company

                                   By:  Kilroy Realty, L.P.,
                                        a Delaware limited partnership
                                        Managing Member

                                   By:  Kilroy Realty Corporation,
                                        a Maryland corporation
                                        General Partner

                                        By:______________________________
                                        Name:____________________________
                                               Its:______________________

                                        By:______________________________
                                        Name:____________________________
                                               Its:______________________

                                   "TENANT":

                                   DIVERSA CORPORATION,
                                   a Delaware corporation

                                       By:______________________________
                                       Name:____________________________
                                              Its:______________________

                                        By:______________________________
                                        Name:____________________________
                                               Its:______________________




                                      -59-
<PAGE>

                                   EXHIBIT A
                                   ---------

                                SORRENTO GATEWAY

                               OUTLINE OF PREMISES

                                   [ATTACHED]














                                   EXHIBIT A
                                      -1-
<PAGE>

                                   EXHIBIT B
                                   ---------

                                SORRENTO GATEWAY

                               TENANT WORK LETTER

                                   [ATTACHED]













                                   EXHIBIT B
                                      -1-
<PAGE>

                                   EXHIBIT C
                                   ---------

                                SORRENTO GATEWAY

                           NOTICE OF LEASE TERM DATES


To:
     __________________________
     __________________________
     __________________________
     __________________________


     Re:  Lease dated ____________, 19__ between ____________________, a
          __________________ ("Landlord"),and _______________________, a
         ____________________("Tenant") concerning that certain 75,520 rentable
         square foot building located at ______________________, San Diego,
         California.

Gentlemen:

     In accordance with the lease (the "Lease"), we wish to advise you and/or
confirm as follows:

     1.   The Lease Term shall commence on or has commenced on ______________
          for a term of __________________ ending on __________________.

     2.   Rent commenced to accrue on __________________, in the amount of
          ________________.

     3.   If the Lease Commencement Date is other than the first day of the
          month, the first billing will contain a pro rata adjustment. Each
          billing thereafter, with the exception of the final billing, shall be
          for the full amount of the monthly installment as provided for in the
          Lease.

     4.   Your rent checks should be made payable to __________________ at
          ___________________.

     5.   The exact number of rentable/usable square feet within the Premises is
          ____________ square feet.




                                   EXHIBIT C
                                      -1-
<PAGE>

     6.   Tenant's Share as adjusted based upon the exact number of usable
          square feet within the Premises is ________%.

                                                "Landlord":

                                                ___________________________,

                                                a _________________________


                                                By:________________________

                                                   Its:____________________





Agreed to and Accepted
as of ____________, 19___.

"Tenant":

_________________________

a _______________________


By:______________________

   Its:__________________










                                   EXHIBIT C
                                      -2-
<PAGE>

                                   EXHIBIT D
                                   ---------

                                SORRENTO GATEWAY

                              RULES AND REGULATIONS

     Tenant shall faithfully observe and comply with the following Rules and
Regulations. Landlord shall not be responsible to Tenant for the nonperformance
of any of said Rules and Regulations by or otherwise with respect to the acts or
omissions of any other tenants or occupants of the Project. In the event of any
conflict between the Rules and Regulations and the other provisions of this
Lease, the latter shall control.

     1. Landlord shall have the right to prescribe the weight, size and position
of all safes and other heavy property brought into the Building and also the
times and manner of moving the same in and out of the Building. Safes and other
heavy objects shall, if considered necessary by Landlord, stand on supports of
such thickness as is necessary to properly distribute the weight. Landlord will
not be responsible for loss of or damage to any such safe or property in any
case. Any damage to any part of the Building, its contents, occupants or
visitors by moving or maintaining any such safe or other property shall be the
sole responsibility and expense of Tenant.

     2. The requirements of Tenant will be attended to only upon application at
the management office for the Project or at such office location designated by
Landlord. Employees of Landlord shall not perform any work or do anything
outside their regular duties unless under special instructions from Landlord.

     3. No advertisement, notice or handbill shall be exhibited, distributed,
painted or affixed by Tenant on any part of the Premises or the Building without
the prior written consent of the Landlord. Tenant shall not disturb, solicit,
peddle, or canvass any occupant of the Project and shall cooperate with Landlord
and its agents of Landlord to prevent same.

     4. The toilet rooms, urinals, wash bowls and other apparatus shall not be
used for any purpose other than that for which they were constructed, and no
foreign substance of any kind whatsoever shall be thrown therein. The expense of
any breakage, stoppage or damage resulting from the violation of this rule shall
be borne by the tenant who, or whose servants, employees, agents, visitors or
licensees shall have caused same.

     5. Tenant shall not overload the floor of the Premises.

     6. Tenant shall not use or keep in or on the Premises, the Building, or the
Project any kerosene, gasoline, explosive material, corrosive material, material
capable of emitting toxic fumes, or other inflammable or combustible fluid
chemical, substitute or material, except in compliance with applicable law.
Tenant shall provide material safety data sheets for any Hazardous Material used
or kept on the Premises.

     7. Tenant shall not use, keep or permit to be used or kept, any foul or
noxious gas or substance in or on the Premises to the extent the same is
noticeable in the Common Areas of the



                                   EXHIBIT D
                                      -1-
<PAGE>

Project or which affects other tenants of the Project. Tenant shall not throw
anything out of doors, windows or skylights or down passageways.

     8.  Except with respect to an approved "Deli Operator," no cooking shall be
done or permitted on the Premises (unless Tenant receives Landlord's prior
written approval to install a cafeteria for its employees in the Premises), nor
shall the Premises be used for lodging or for any improper, objectionable or
immoral purposes. Notwithstanding the foregoing, Underwriters' laboratory-
approved equipment and microwave ovens may be used in the Premises for heating
food and brewing coffee, tea, hot chocolate and similar beverages for employees
and visitors, provided that such use is in accordance with all applicable
federal, state, county and city laws, codes, ordinances, rules and regulations.

     9.  Tenant shall not occupy or permit any portion of the Premises to be
occupied as an office for a messenger-type operation or dispatch office, public
stenographer or typist, or for the manufacture or sale of liquor, narcotics, or
tobacco in any form, or as a medical office, or as a barber or manicure shop, or
as an employment bureau without the express prior written consent of Landlord.
Tenant shall not engage or pay any employees on the Premises except those
actually working for such tenant on the Premises nor advertise for laborers
giving an address at the Premises.

     10. Tenant shall store all its trash and garbage within the interior of the
Premises or in the appropriate external trash area(s) for the Building. No
material shall be placed in the trash boxes or receptacles if such material is
of such nature that it may not be disposed of in the ordinary and customary
manner of removing and disposing of trash and garbage in San Diego, California
without violation of any law or ordinance governing such disposal. If the
Premises is or becomes infested with vermin as a result of the use or any misuse
or neglect of the Premises by Tenant, its agents, servants, employees,
contractors, visitors or licensees, Tenant shall forthwith, at Tenant's expense,
cause the Premises to be exterminated from time to time to the satisfaction of
Landlord and shall employ such licensed exterminators as shall be approved in
writing in advance by Landlord.

     11. Tenant shall comply with all safety, fire protection and evacuation
procedures and regulations established by any governmental agency.

     12. No awnings or other projection shall be attached to the outside walls
of the Building without the prior written consent of Landlord (which shall not
be unreasonably withheld or delayed), and no curtains, blinds, shades or screens
shall be attached to or hung in, or used in connection with, any window or door
of the Premises other than Landlord standard window and door coverings unless
otherwise consented to in writing by Landlord. All electrical ceiling fixtures
hung in the Premises or spaces along the perimeter of the Building must be
fluorescent and/or of a quality, type, design and a warm white bulb color
approved in advance in writing by Landlord. Neither the interior nor exterior of
any windows shall be coated or otherwise sunscreened without the prior written
consent of Landlord. Tenant shall be responsible for any damage to the window
film on the exterior windows of the Premises and shall promptly repair any such
damage at Tenant's sole cost and expense. Tenant shall keep its window coverings
closed during any period of the day when the sun is shining directly on the
windows of the Premises.





                                   EXHIBIT D
                                      -2-
<PAGE>

     13. Tenant must comply with requests by the Landlord concerning the
informing of their employees of items of importance to the Landlord.

     14. Tenant must comply with any applicable "NO-SMOKING" Ordinances. If
Tenant is required under the ordinance to adopt a written smoking policy, a copy
of said policy shall be on file in the office of the Building. Additionally,
Tenant must provide at least one area within the Premises in which its
employees, invitees and visitors may smoke, to the extent such area is required
by law.

     15. Tenant hereby acknowledges that Landlord shall have no obligation to
provide guard service or other security measures for the benefit of the
Premises, the Building or the Project. Tenant hereby assumes all responsibility
for the protection of Tenant and its agents, employees, contractors, invitees
and guests, and the property thereof, from acts of third parties, including
keeping doors locked and other means of entry to the Premises closed, whether or
not Landlord, at its option, elects to provide security protection for the
Project or any portion thereof. Tenant further assumes the risk that any safety
and security devices, services and programs which Landlord elects, in its sole
discretion, to provide may not be effective, or may malfunction or be
circumvented by an unauthorized third party, and Tenant shall, in addition to
its other insurance obligations under this Lease, obtain its own insurance
coverage to the extent Tenant desires protection against losses related to such
occurrences. Tenant shall cooperate in any reasonable safety or security program
developed by Landlord or required by law.

     16. No auction, liquidation, fire sale, going-out-of-business or bankruptcy
sale shall be conducted in the Premises without the prior written consent of
Landlord.

     17. No tenant shall use or permit the use of any portion of the Premises
for living quarters, sleeping apartments or lodging rooms.

     18. Tenant shall install and maintain, at Tenant's sole cost and expense,
an adequate, visibly marked and properly operational fire extinguisher next to
any duplicating or photocopying machines or similar heat producing equipment,
which may or may not contain combustible material, in the Premises.

     Landlord reserves the right at any time to change or rescind any one or
more of these Rules and Regulations, or to make such other and further
reasonable Rules and Regulations as in Landlord's judgment may from time to time
be necessary (relative to a building occupied solely by one tenant) for the
management, safety, care and cleanliness of the Premises, Building, the Common
Areas and the Project, and for the preservation of good order therein, as well
as for the convenience of other occupants and tenants therein. Landlord may
waive any one or more of these Rules and Regulations for the benefit of any
particular tenants, but no such waiver by Landlord shall be construed as a
waiver of such Rules and Regulations in favor of any other tenant, nor prevent
Landlord from thereafter enforcing any such Rules or Regulations against any or
all tenants of the Project. Tenant shall be deemed to have read these Rules and
Regulations and to have agreed to abide by them as a condition of its occupancy
of the Premises.





                                   EXHIBIT D
                                      -3-
<PAGE>

                                   EXHIBIT E
                                   ---------

                                SORRENTO GATEWAY

                      FORM OF TENANT'S ESTOPPEL CERTIFICATE

     The undersigned as Tenant under that certain Lease (the "Lease") made and
entered into as of ___________, 199__ by and between _______________ as
Landlord, and the undersigned as Tenant, for Premises on the ______________
floor(s) of the building located at ______________, San Diego, California
____________, certifies as follows:

     1. Attached hereto as Exhibit A is a true and correct copy of the Lease and
all amendments and modifications thereto. The documents contained in Exhibit A
represent the entire agreement between the parties as to the Premises.

     2. The undersigned currently occupies the Premises described in the Lease,
the Lease Term commenced on __________, and the Lease Term expires on
___________, and the undersigned has no option to terminate or cancel the Lease
or to purchase all or any part of the Premises, the Building and/or the Project.

     3. Base Rent became payable on ____________.

     4. The Lease is in full force and effect and has not been modified,
supplemented or amended in any way except as provided in Exhibit A.
     5. Tenant has not transferred, assigned, or sublet any portion of the
Premises nor entered into any license or concession agreements with respect
thereto except as follows:



     6. Tenant shall not modify the documents contained in Exhibit A without the
prior written consent of Landlord's mortgagee.

     7. All monthly installments of Base Rent, all Additional Rent and all
monthly installments of estimated Additional Rent have been paid when due
through ___________. The current monthly installment of Base Rent is $_________.

     8. All conditions of the Lease to be performed by Landlord necessary to the
enforceability of the Lease have been satisfied and Landlord is not in default
thereunder. In addition, the undersigned has not delivered any notice to
Landlord regarding a default by Landlord thereunder.

     9. No rental has been paid more than thirty (30) days in advance and no
security has been deposited with Landlord except as provided in the Lease.




                                   EXHIBIT E
                                      -1-
<PAGE>

     10. As of the date hereof, there are no existing defenses or offsets, or,
to the undersigned's knowledge, claims or any basis for a claim, that the
undersigned has against Landlord.

     11. If Tenant is a corporation or partnership, each individual executing
this Estoppel Certificate on behalf of Tenant hereby represents and warrants
that Tenant is a duly formed and existing entity qualified to do business in
California and that Tenant has full right and authority to execute and deliver
this Estoppel Certificate and that each person signing on behalf of Tenant is
authorized to do so.

     12. There are no actions pending against the undersigned under the
bankruptcy or similar laws of the United States or any state.

     13. Other than in compliance with the TCCs of the Lease, the undersigned
has not used or stored any hazardous substances in the Premises.

     14. To the undersigned's knowledge, all tenant improvement work to be
performed by Landlord under the Lease has been completed in accordance with the
Lease and has been accepted by the undersigned and all reimbursements and
allowances due to the undersigned under the Lease in connection with any tenant
improvement work have been paid in full.

     The undersigned acknowledges that this Estoppel Certificate may be
delivered to Landlord or to a prospective mortgagee or prospective purchaser,
and acknowledges that said prospective mortgagee or prospective purchaser will
be relying upon the statements contained herein in making the loan or acquiring
the property of which the Premises are a part and that receipt by it of this
certificate is a condition of making such loan or acquiring such property.

     Executed at ______________ on the ____ day of ___________, 19__.

                                                "Tenant":

                                                _____________________,

                                                a ___________________


                                                By:__________________


                                                    Its:_____________

                                                By:__________________

                                                    Its:_____________






                                   EXHIBIT E
                                      -2-
<PAGE>

                                   EXHIBIT F
                                   ---------

                                 KILROY REALTY
                                 -------------

RECORDING REQUESTED BY
AND WHEN RECORDED RETURN TO:

ALLEN, MATKINS, LECK, GAMBLE
  & MALLORY LLP
1999 Avenue of the Stars
18th Floor
Los Angeles, California 90067
Attention:  Anton N. Natsis, Esq.

===============================================================================

                           RECOGNITION OF COVENANTS,
                           -------------------------
                          CONDITIONS, AND RESTRICTIONS
                          ----------------------------

     This Recognition of Covenants, Conditions, and Restrictions (this
"AGREEMENT") is entered into as of the __ day of ________, 199__, by and between
__________________ ("Landlord"), and ________________ ("Tenant"), with reference
to the following facts:

     A. Landlord and Tenant entered into that certain Lease Agreement dated
_____, 199__ (the "Lease"). Pursuant to the Lease, Landlord leased to Tenant and
Tenant leased from Landlord space (the "PREMISES") located in an office building
on certain real property described in EXHIBIT "A" attached hereto and
                                      -----------
incorporated herein by this reference (the "PROPERTY").

     B. The Premises are located in an office building located on real property
which is part of an area owned by Landlord containing approximately ___(__)
acres of real property located in the City of ____________, California (the
"PROJECT"), as more particularly described in EXHIBIT "B" attached hereto and
                                              -----------
incorporated herein by this reference.

     C. Landlord, as declarant, has previously recorded, or proposes to record
concurrently with the recordation of this Agreement, a Declaration of Covenants,
Conditions, and Restrictions (the "DECLARATION"), dated ________________, 19__,
in connection with the Project.

     D.  Tenant is agreeing to recognize and be bound by the terms of the
Declaration, and the parties hereto desire to set forth their agreements
concerning the same.

     NOW, THEREFORE, in consideration of (a) the foregoing recitals and the
mutual agreements hereinafter set forth, and (b) for other good and valuable
consideration, the receipt and sufficiency of which are hereby acknowledged, the
parties hereto agree as follows,

     1.  Tenant's Recognition of Declaration.  Notwithstanding that the Lease
         -----------------------------------
has been executed prior to the recordation of the Declaration, Tenant agrees to
recognize and by bound by all of the terms and conditions of the Declaration.




                                   EXHIBIT F
                                      -1-
<PAGE>

     2.         Miscellaneous.
                -------------

                2.1     This Agreement shall be binding upon and inure to the
benefit of the parties hereto and their respective heirs, estates, personal
representatives, successors, and assigns.

                2.2     This Agreement is made in, and shall be governed,
enforced and construed under the laws of, the State of California.

                2.3     This Agreement constitutes the entire understanding and
agreements of the parties with respect to the subject matter hereof, and shall
supersede and replace all prior understandings and agreements, whether verbal or
in writing. The parties confirm and acknowledge that there are no other
promises, covenants, understandings, agreements, representations, or warranties
with respect to the subject matter of this Agreement except as expressly set
forth herein.

                2.4     This Agreement is not to be modified, terminated, or
amended in any respect, except pursuant to any instrument in writing duly
executed by both of the parties hereto.

                2.5     In the event that either party hereto shall bring any
legal action or other proceeding with respect to the breach, interpretation, or
enforcement of this Agreement, or with respect to any dispute relating to any
transaction covered by this Agreement, the losing party in such action or
proceeding shall reimburse the prevailing party therein for all reasonable costs
of litigation, including reasonable attorneys' fees, in such amount as may be
determined by the court or other tribunal having jurisdiction, including matters
on appeal.

                2.6     All captions and heading herein are for convenience and
ease of reference only, and shall not be used or referred to in any way in
connection with the interpretation or enforcement of this Agreement.

                2.7     If any provision of this Agreement, as applied to any
party or to any circumstance, shall be adjudged by a court of competent
jurisdictions to be void or unenforceable for any reason, the same shall not
affect any other provision of this Agreement, the application of such provision
under circumstances different form those adjudged by the court, or the validity
or enforceability of this Agreement as a whole.

                2.8     Time is of the essence of this Agreement.

                2.9     The Parties agree to execute any further documents, and
take any further actions, as may be reasonable and appropriate in order to carry
out the purpose and intent of this Agreement.

                2.10    As used herein, the masculine, feminine or neuter
gender, and the singular and plural numbers, shall each be deemed to include the
others whenever and whatever the context so indicates.





                                   EXHIBIT F
                                      -2-
<PAGE>

                        SIGNATURE PAGE OF RECOGNITION OF

                     COVENANTS, CONDITIONS AND RESTRICTIONS

     IN WITNESS WHEREOF, the parties hereto have duly executed this Agreement as
of the day and year first above written.

                              "Landlord":

                              -------------------------,

                              a ________________________


                              By:_______________________

                                 Its:___________________


                              "Tenant":

                              _________________________,

                              a _______________________


                              By:______________________

                                 Its:__________________

                              By:______________________

                                 Its:__________________











                                   EXHIBIT F
                                      -3-
<PAGE>

                                   EXHIBIT G
                                   ---------

                            FORM OF LETTER OF CREDIT
                            ------------------------

                       (Letterhead of a money center bank
                          acceptable to the Landlord)

                              ______________, 2000

_______________________
_______________________
_______________________
_______________________

Gentlemen:

     We hereby establish our Irrevocable Letter of Credit and authorize you to
draw on us at sight for the account of _____________________, a
_____________________, the aggregate amount of _____________________ and No/100
Dollars ($_________).

     Funds under this Letter of Credit are available to the beneficiary hereof
as follows:

     Any or all of the sums hereunder may be drawn down at any time and from
time to time from and after the date hereof by _____________________
("Beneficiary") when accompanied by this Letter of Credit and a written
statement signed by __________________________, certifying that such moneys are
due and owing to Beneficiary, together with a certificate of incumbency executed
by ___________________ certifying the position and signature of the officer
signing the statement, and a sight draft executed and endorsed by _____________,
as a ________________ of Beneficiary.

     This Letter of Credit is transferable in its entirety. Should a transfer be
desired, such transfer will be subject to the return to us of this advice,
together with written instructions.

     The amount of each draft must be endorsed on the reverse hereof by the
negotiating bank. We hereby agree that this Letter of Credit shall be duly
honored upon presentation and delivery of the certification specified above.

     This Letter of Credit shall expire on ______________, 200__.

     Notwithstanding the above expiration date of this Letter of Credit, the
term of this Letter of Credit shall be automatically renewed for successive,
additional one (1) year periods unless, at least thirty (30) days prior to any
such date of expiration, the undersigned shall give written notice to Holder, by
certified mail, return receipt requested and at the address set forth above or
at such other address as may be given to the undersigned by Holder, that this
Letter of Credit will not be renewed.






                                   EXHIBIT G
                                      -1-
<PAGE>

     This Letter of Credit is governed by the Uniform Customs and Practice for
Documentary Credits (1983 Revision), International Chamber of Commerce
Publication 400.

     This Letter of Credit is governed by the Uniform Customs and Practice for
Documentary Credits (1983 Revision).  International Chamber of Commerce
Publication 400.

                            Very truly yours.

                            (Name of Issuing Bank)

                            By:____________________________














                                   EXHIBIT G
                                      -2-
<PAGE>

                                   EXHIBIT H
                                   ---------

                           FORM OF SHORT FORM OF LEASE
                           ---------------------------


RECORDING REQUESTED BY
AND WHEN RECORDED RETURN TO:

_______________________
_______________________
_______________________
_______________________

===============================================================================

                              SHORT FORM OF LEASE
                              -------------------


     THIS SHORT FORM OF LEASE ("MEMORANDUM") is made as of February 11, 2000, by
and between KR-Gateway Partners, a Delaware limited liability company
("LANDLORD") and Diversa Corporation, a Delaware corporation ("TENANT").
Pursuant to that certain Retail Lease by and between Landlord and Tenant dated
as of November 16, 1999 (the "LEASE"), subject to and in accordance with the
terms of such Lease, Landlord hereby leases to Tenant that certain premises
contained therein within the project comprised of that certain real property
described in Schedule 1 attached hereto and incorporated herein by reference.
             ----------

     All the terms, conditions, covenants and agreements in the Lease are
incorporated into this Memorandum with the same force and effect as if they were
fully recited herein.










                                   EXHIBIT H
                                      -1-
<PAGE>

     In the event of any inconsistency between the terms of this Memorandum and
the terms of the Lease, the Lease shall control.

     IN WITNESS WHEREOF, the parties have executed this Memorandum as of the
date first set forth above.

                                         "Landlord":

                                         ____________________________,

                                         a __________________________


                                         By:_________________________

                                         Name:_______________________

                                         Its:________________________


                                         "Tenant":

                                         ____________________________,

                                         a __________________________


                                         By:_________________________

                                         Name:_______________________

                                         Its:________________________










                                   EXHIBIT H
                                      -2-
<PAGE>

                                    EXHIBIT B
                                    ---------

                                SORRENTO GATEWAY
                                ----------------

                               TENANT WORK LETTER
                               ------------------


                                    PREAMBLE
                                    --------

     This Tenant Work Letter sets forth the TCCs relating to the construction of
the Premises.  This Tenant Work Letter is essentially organized chronologically
and specifically addresses the issues of the construction of the Premises, in
sequence, as such issues will arise during the actual construction of the
Premises.  All references in this Tenant Work Letter to Articles or Sections of
"this Lease" shall mean the relevant portions of Articles 1 through 29 of the
Lease to which this Tenant Work Letter is attached as EXHIBIT B, and all
                                                      ---------
references in this Tenant Work Letter to Sections of this "Tenant Work Letter"
shall mean the relevant portions of Sections 1 through 6 of this Tenant Work
Letter.  Except as defined to the contrary, all defined terms used in the Tenant
Work Letter shall have the same meaning as the terms defined in the Lease.


                                    SECTION 1
                                    ---------

                   DELIVERY OF THE PREMISES AND BASE BUILDING
                   ------------------------------------------

     1.1  BASE BUILDING.  In accordance with the TCCs of this Lease, Landlord
          -------------
shall deliver to Tenant the Base Building, which materially shall comply with
and include the items and matters set forth on SCHEDULE 1 attached to this
                                               ----------
EXHIBIT B, at Landlord's sole cost and expense and without deduction from the
---------
Tenant and Core Improvement Allowance. The Base Building shall be in good
condition and working order and shall comply with applicable building codes and
other governmental laws, ordinances and regulations which were enacted prior to
the Lease Commencement Date and applicable to new construction for unoccupied
space to the extent required to obtain a certificate of occupancy (collectively,
the "CODE") and Tenant shall, except as otherwise set forth in this Lease or in
this Tenant Work Letter, accept the Premises and Base Building from Landlord in
their then existing, "as-is" condition as of the Commencement Date of this
Lease, subject to the terms of this Tenant Work Letter, subject only to
punchlist items and Landlord's obligations set forth in Article 7 of the Lease,
including, without limitation, Landlord's obligation to maintain in accordance
with Section 7.1 of the Lease the Building Structure.

     1.2  INTENTIONALLY OMITTED.
          ---------------------


                                    SECTION 2
                                    ---------

                          TENANT AND CORE IMPROVEMENTS
                          ----------------------------

     2.1  TENANT AND CORE IMPROVEMENT ALLOWANCE.  Tenant shall be entitled to a
          -------------------------------------
one-time tenant and core improvement allowance (the "TENANT AND CORE IMPROVEMENT
ALLOWANCE") in the amount of $110.00 per rentable square foot of the Premises
for (A) the costs relating to the
<PAGE>

initial design and construction of the additional work of Landlord regarding the
structures and systems of the Building and its core above the level of the Base
Building (the "CORE IMPROVEMENTS"), and (B) the costs relating to the initial
design and construction of Tenant's improvements and any other improvements to
the Building above the level of the Core Improvements and the Base Building,
which are permanently affixed to the Premises, specifically including, but not
limited to Tenant's office improvements, lab improvements (including built-in
lab equipment) and other related interior improvements (the "TENANT
IMPROVEMENTS"). In addition, pursuant to Sections 2.2.1(vii) and (viii) of this
Tenant Work Letter, Tenant may use a portion of the Tenant and Core Improvement
Allowance for Tenant's FF&E and Building Signage. In no event shall Landlord be
obligated to make disbursements pursuant to this Tenant Work Letter in a total
amount which exceeds the Tenant and Core Improvement Allowance. Landlord and
Tenant acknowledge that for purposes of this Lease, the Tenant and Core
Improvement Allowance shall consist of (i) the "Base Tenant Improvement
Allowance" and the "Core Allowance," which collectively equal to $40.00 per
rentable square foot of the Premises, (ii) the "Above Standard Allowance" which
equals $70.00 per rentable square foot of the Premises, and (iii) the "Optional
Above Standard Allowance" of up to $10.00 per rentable square foot of the
Premises pursuant to the terms of Section 2.2.2 of this Tenant Work Letter.
Landlord and Tenant further acknowledge that (1) the Tenant and Core Improvement
Allowance has been factored into the Base Rent of the Lease, amortized with
interest of twelve percent (12%) per annum over the initial Lease Term, and (2)
the allocations set forth in the preceding sentence shall not affect Tenant's
usage of the Tenant and Core Improvement Allowance.

     2.2  DISBURSEMENT OF THE TENANT AND CORE IMPROVEMENT ALLOWANCE.
          ---------------------------------------------------------

          2.2.1  TENANT AND CORE IMPROVEMENT ALLOWANCE ITEMS.  Except as
                 -------------------------------------------
otherwise set forth in this Tenant Work Letter, the Tenant and Core Improvement
Allowance shall be disbursed by Landlord (each of which disbursements shall be
made pursuant to Landlord's disbursement process) for costs related to the
construction of the Core Improvements and Tenant Improvements and for the
following items and costs (collectively the "TENANT AND CORE IMPROVEMENT
ALLOWANCE ITEMS"):  (i) payment of the fees of the "Architect" and the
"Engineers," as those terms are defined in Section 3.1 of this Tenant Work
                                           -----------
Letter; (ii) the payment of plan check, permit and license fees relating to
construction of the Tenant Improvements; (iii) the cost of any changes to the
Base Building when such changes are required by the Construction Drawings; (iv)
the cost of any changes to the Construction Drawings or Tenant Improvements
required by all applicable building codes (the "CODE"); (v) the cost of the
"Landlord Supervision Fee," as that term is defined in Section 4.3.2 of this
                                                       -------------
Tenant Work Letter; (vi) sales and use taxes; (vii) the cost of delivering,
installing and purchasing Tenant's security systems, telephone switch, and
communications equipment and cabling and Tenant's work stations, furniture,
fixtures and equipment (collectively, "FF&E"), provided that the reimbursement
for such costs does not, in the aggregate, exceed Seven and No/100 Dollars
($7.00) per rentable square foot of the Premises (the "FF&E ALLOWANCE CAP");
(viii) the cost of designing, permitting and constructing the Building Signage,
provided that the reimbursement for such costs does not, in the aggregate,
exceed 50/100 Dollars ($0.50) per rentable square foot of the Premises; and (ix)
all other third-party costs actually and reasonably expended by Landlord in
connection with the construction of the Tenant Improvements pursuant to the TCCs
of this Tenant Work Letter.  Notwithstanding the foregoing, the Tenant and Core
Improvement

                                      -2-
<PAGE>

Allowance shall not be used for (and Tenant shall have no responsibility for)
the following costs: (1) Property Maintenance Costs prior to the Lease
Commencement Date, (2) costs to correct construction defects to the Base
Building, (3) principal or interest on any construction loan obtained by
Landlord for the construction of the Tenant Improvements, or (4) Base Building
costs.

          2.2.2  ABOVE STANDARD ALLOWANCE ELECTION.  Tenant may, upon written
                 ---------------------------------
notice to Landlord given on or before August 1, 2000 (provided Tenant may give
notice of a final adjustment of up to $2.00 per rentable square foot of the
Premises up to and including October 1, 2000) elect to cause the Tenant and Core
Improvement Allowance to be increased by the Above Standard Allowance in an
amount (the "TIA INCREASE") set forth in such notice; provided, however, that
the amount of such TIA Increase shall (i) be an amount equal to the product of
(A) an even number of United States Dollars (as opposed to fractions of United
States Dollars) and (B) the rentable square feet in the Premises, and (ii) in no
event exceed $10.00 per rentable square foot of the Premises.  In the event
Tenant elects to increase the amount of the Tenant and Core Improvement
Allowance pursuant to the foregoing sentence, for each $1.00 per Rentable Square
Foot of such increase (up to the cumulative increase of $10.00 per Rentable
Square Foot of the Premises), the Monthly Rental Rate per Rentable Square Foot
attributable to the Premises shall be increased by $0.01 (and the corresponding
amounts of Monthly Installment of Base Rent and Annual Base Rent shall be
increased accordingly and the Base Rent for all 15 years shall be recalculated,
based on a seven percent (7%) increase every 24 months of the Lease Term).

          2.2.3  TENANT IMPROVEMENT EXCESS.  Any unused portion of the Tenant
                 -------------------------
and Core Improvement Allowance (which unused amount, when calculated on a per
rentable square foot basis, shall be the "UNUSED TIA/RSF"), shall be applied
against Rent as a reduction in the Monthly Rental Rate per Rentable Square Foot
of the Initial Premises equal to $0.01 per square foot for each $1.00 of the
Unused TIA/RSF (with the corresponding amounts of the Monthly Installment of
Base Rent and Annual Base Rent reduced accordingly) (cumulatively, the "RENT
REDUCTION").

     2.3  STANDARD TENANT IMPROVEMENT PACKAGE.  For purposes of this Lease, the
          -----------------------------------
"BUILDING STANDARD TENANT IMPROVEMENTS" shall mean any Tenant Improvements
(approved pursuant to the TCCs of this Tenant Work Letter) constructed wholly
with the Tenant and Core Improvement Allowance.

     2.4  REMOVAL OF ABOVE BUILDING STANDARD TENANT IMPROVEMENTS.  "ABOVE
          ------------------------------------------------------
STANDARD TENANT IMPROVEMENTS" shall mean any part of the Tenant Improvements
which do not constitute Building Standard Tenant Improvements, including, but
not limited to, plumbing and millwork.  If so directed by Landlord prior to the
end of the Term of this Lease, Tenant, at its sole cost and expense, shall
remove from the Premises any Above Standard Tenant Improvements designated by
Landlord, and shall replace such designated Above Standard Tenant Improvements
to be removed with Building Standard Tenant Improvements.  Such removal and
replacement of Above Standard Tenant Improvements shall be performed promptly
and shall be completed by Tenant on or before the end of the Term of this Lease
if notice of removal is given at least thirty (30) days prior to the end of the
Term, and if Tenant fails to remove and/or replace any Above Standard Tenant
Improvements, Landlord may do so and Tenant shall reimburse Landlord for the
cost of such removal and/or replacement.

                                      -3-
<PAGE>

     2.5  FAILURE TO DISBURSE TENANT AND CORE IMPROVEMENT ALLOWANCE AND OTHER
          -------------------------------------------------------------------
ALLOWANCES.  If Landlord fails to timely fulfill its obligation to fund any
----------
portion of the Tenant and Core Improvement Allowance, Tenant shall be entitled
to deliver Notice ("PAYMENT NOTICE") thereof to Landlord and to any mortgage or
trust deed holder of the Building whose identity and address have been
previously provided to Tenant.  If Landlord still fails to fulfill any such
obligation within twenty (20) days after Landlord's receipt of the Payment
Notice from Tenant and if Landlord fails to deliver Notice to Tenant within such
twenty (20) day period explaining Landlord's reasons that Landlord believes that
the amounts described in Tenant's Payment Notice are not due and payable by
Landlord ("REFUSAL NOTICE"), Tenant shall be entitled to fund such portion of
the Tenant and Core Improvement Allowance as defined above in Section 2.1 of
this Tenant Work Letter and to offset the amount so funded, together with
interest at the Interest Rate from the date of funding until the date of offset,
against Tenant's next obligations to pay Rent.  However, if Tenant is in Default
under Section 19.1.1 of this Lease at the time that such offset would otherwise
be applicable, Tenant shall not be entitled to such offset until such Default is
cured.


                                    SECTION 3
                                    ---------

                              CONSTRUCTION DRAWINGS
                              ---------------------

     3.1  SELECTION OF ARCHITECT/CONSTRUCTION DRAWINGS.  Tenant has retained (or
          --------------------------------------------
will retain) Pacific Cornerstone Architects as the architect/space planner (the
"ARCHITECT") to prepare the "Construction Drawings," as that term is defined in
this Section 3.1.  Tenant has retained Prim Structural Engineers (structural),
     -----------
McParlane and Associates (mechanical) and Michael Wall Engineering (electrical)
as the engineering consultants (collectively, the "ENGINEERS") to prepare all
plans and engineering working drawings relating to the structural, mechanical,
electrical, plumbing, HVAC, lifesafety, and sprinkler work in the Premises,
which work is not part of the Base Building.  The plans and drawings to be
prepared by Architect and the Engineers hereunder shall be known collectively as
the "CONSTRUCTION DRAWINGS."  All Construction Drawings shall comply with the
drawing format and specifications determined by Landlord, and shall be subject
to Landlord's approval, which approval shall not be unreasonably withheld.
Tenant and Architect shall verify, in the field, the dimensions and conditions
as shown on the relevant portions of the base building plans, and Tenant and
Architect shall be solely responsible for the same, and Landlord shall have no
responsibility in connection therewith.  Landlord's review of the Construction
Drawings as set forth in this Section 3, shall be for its sole purpose and shall
                              ---------
not imply Landlord's review of the same, or obligate Landlord to review the
same, for quality, design, Code compliance or other like matters.  Accordingly,
notwithstanding that any Construction Drawings are reviewed by Landlord or its
space planner, architect, engineers and consultants, and notwithstanding any
advice or assistance which may be rendered to Tenant by Landlord or Landlord's
space planner, architect, engineers, and consultants, Landlord shall have no
liability whatsoever in connection therewith and shall not be responsible for
any omissions or errors contained in the Construction Drawings, and Tenant's
waiver and indemnity set forth in this Lease shall specifically apply to the
Construction Drawings.

     3.2  FINAL SPACE PLAN.  On or before the date set forth in Schedule 2,
          ----------------                                      ----------
attached hereto, Tenant and the Architect shall prepare the final space plan for
Tenant Improvements in the Premises (collectively, the "FINAL SPACE PLAN"),
which Final Space Plan shall include a layout

                                      -4-
<PAGE>

and designation of all offices, rooms and other partitioning, their intended
use, and equipment to be contained therein, and shall deliver the Final Space
Plan to Landlord for Landlord's approval, which approval shall not be
unreasonably withheld, delayed or conditioned. Landlord shall advise Tenant
within five (5) business days after Landlord's receipt of the Final Space Plan
for the Premises if the same is unsatisfactory or incomplete in any material
respect. If Tenant is so advised, Tenant shall promptly cause the Final Space
Plan to be revised to correct any such deficiencies, and immediately thereafter
re-submitted to Landlord for its approval.

     3.3  FINAL WORKING DRAWINGS.  On or before the date set forth in Schedule
          ----------------------                                      --------
2, Tenant, the Architect and the Engineers shall complete the architectural and
-
engineering drawings for the Premises, and the final architectural working
drawings in a form which is complete to allow subcontractors to bid on the work
and to obtain all applicable permits (collectively, the "FINAL WORKING
DRAWINGS") and shall submit the same to Landlord for Landlord's approval, which
approval shall not be unreasonably withheld, delayed or conditioned.  Landlord
shall advise Tenant within five (5) business days after Landlord's receipt of
the Final Working Drawings for the Premises if the same is unsatisfactory or
incomplete in any material respect.  If Tenant is so advised, Tenant shall
promptly cause the Final Working Drawings to be revised to correct any such
deficiencies, and immediately thereafter re-submitted to Landlord for its
approval.

     3.4  PERMITS.  The Final Working Drawings shall be approved by Landlord as
          -------
set forth in Section 3.3 above (the "Approved Working Drawings") prior to the
commencement of the construction of the Tenant Improvements.  Landlord shall
immediately submit the Approved Working Drawings to the appropriate municipal
authorities for all applicable building permits necessary to allow "Contractor,"
as that term is defined in Section 4.1, below, to commence and fully complete
                           -----------
the construction of the Tenant Improvements (the "PERMITS"), it being Landlord's
responsibility for obtaining any building permit with regard to the Base
Building and the Tenant and Core Improvements, or certificate of occupancy for
the Premises (as opposed to any use or other permit required due to Tenant's
particular use of the Premises).  No changes, modifications or alterations in
the Approved Working Drawings may be made without the prior written consent of
Landlord, which consent shall not be unreasonably withheld, delayed or
conditioned, subject to such changes being deemed a "Delay" as set forth in
Section 5.2 of this Tenant Work Letter.

     3.5  TIME DEADLINES.  Tenant and Landlord shall use their best, good faith,
          --------------
efforts and all due diligence to cooperate with the Architect, the Engineers,
and each other to complete all phases of the Construction Drawings and the
permitting process and to receive the permits, and with Contractor for approval
of the "Cost Proposal," as that term is defined in Section 4.2 of this Tenant
                                                   -----------
Work Letter, as soon as possible after the execution of the Lease, and, in that
regard, shall meet with Landlord on a scheduled basis to be determined by
Landlord, to discuss Tenant's progress in connection with the same.  The
applicable dates for approval of items, plans and drawings as described in this

Section 3, Section 4, below, and in this Tenant Work Letter are set forth and
---------  ---------
further elaborated upon in Schedule 2 (the "TIME DEADLINES"), attached hereto.
                           ----------
Tenant and Landlord agree to comply with the Time Deadlines.

                                      -5-
<PAGE>

                                    SECTION 4
                                    ---------

                CONSTRUCTION OF THE TENANT AND CORE IMPROVEMENTS
                ------------------------------------------------

     4.1  CONTRACTOR.  Landlord has designated Reno Construction ("Contractor")
          ----------
to the be the contractor which shall construct the Tenant Improvements.

     4.2  COST PROPOSAL.  After the Approved Working Drawings are signed by
          -------------
Landlord and Tenant, Landlord shall provide Tenant with a cost proposal in
accordance with the Approved Working Drawings, which cost proposal shall
include, as nearly as possible, the cost of all Tenant and Core Improvement
Allowance Items to be incurred by Tenant in connection with the design and
construction of the Tenant Improvements (the "COST PROPOSAL").  Tenant shall
approve (or disapprove) the Cost Proposal to Landlord within five (5) business
days of the receipt of the same, and upon receipt of an approved Cost Proposal
by Landlord, Landlord shall be released by Tenant to purchase the items set
forth in the Cost Proposal and to commence the construction relating to such
items.  The date by which Tenant must approve and deliver the Cost Proposal to
Landlord shall be known hereafter as the "Cost Proposal Delivery Date".

     4.3  CONSTRUCTION OF TENANT AND CORE IMPROVEMENTS BY CONTRACTOR UNDER THE
          --------------------------------------------------------------------
SUPERVISION OF LANDLORD.
-----------------------

          4.3.1  OVER-ALLOWANCE AMOUNT.  On the Cost Proposal Delivery Date,
                 ---------------------
Tenant shall deliver to Landlord cash in an amount (the "OVER-ALLOWANCE AMOUNT")
equal to the difference between (i) the amount of the Cost Proposal and (ii) the
amount of the Tenant and Core Improvement Allowance (including any Above
Standard Allowance).  The Over-Allowance Amount shall be disbursed by Landlord
prior to the disbursement of any then remaining portion of the Tenant and Core
Improvement Allowance, and such disbursement shall be pursuant to the same
procedure as the Tenant and Core Improvement Allowance.  In the event that,
after the Cost Proposal Delivery Date, any revisions, changes, or substitutions
shall be made to the Construction Drawings or the Tenant Improvements, any
additional costs which arise in connection with such revisions, changes or
substitutions or any other additional costs shall be paid by Tenant to Landlord
immediately upon Landlord's request as an addition to the Over-Allowance Amount.
In addition, if the Final Working Drawings or any amendment thereof or
supplement thereto shall require alterations in the Base, Shell and Core (as
contrasted with the Tenant Improvements), and if Landlord in its reasonable
discretion agrees to any such alterations, and notifies Tenant of the need and
cost for such alterations, then Tenant shall pay the cost of such required
changes upon receipt of bills therefor.  Tenant shall pay all direct
architectural and/or engineering fees in connection therewith.

          4.3.2  LANDLORD'S RETENTION OF CONTRACTOR.  Landlord shall
                 ----------------------------------
independently retain Contractor, to construct the Tenant Improvements in
accordance with the Approved Working Drawings and the Cost Proposal (on a GMAX
("guaranteed maximum cost") basis) and Landlord shall supervise the construction
by Contractor, and Tenant shall pay a construction supervision and management
fee (the "LANDLORD SUPERVISION FEE") to Landlord in an amount equal to one
percent (1%) of that portion of the Tenant and Core Improvement Allowance
attributable to hard costs of construction of the Tenant Improvements.

                                      -6-
<PAGE>

          4.3.3  CONTRACTOR'S WARRANTIES AND GUARANTIES.  Landlord hereby
                 --------------------------------------
assigns to Tenant all warranties and guaranties by Contractor relating to the
Tenant Improvements, and Tenant hereby waives all claims against Landlord
relating to, or arising out of the construction of, the Tenant Improvements,
except to the extent resulting from the negligence or willful misconduct of
Landlord or the Landlord Parties and except as otherwise specifically set forth
in the Lease.

          4.3.4  TENANT'S COVENANTS.  Within ten (10) days after completion of
                 ------------------
construction of the Tenant Improvements, Tenant shall cause Contractor and
Architect to cause a Notice of Completion to be recorded in the office of the
County Recorder of the county in which the Building is located in accordance
with Section 3093 of the Civil Code of the State of California or any successor
statute and furnish a copy thereof to Landlord upon recordation, failing which,
Landlord may itself execute and file the same on behalf of Tenant as Tenant's
agent for such purpose.  In addition, immediately after the Substantial
Completion of the Premises, Tenant shall have prepared and delivered to the
Building a copy of the "as built" plans and specifications (including all
working drawings) for the Tenant Improvements.


                                    SECTION 5
                                    ---------

                     COMPLETION OF THE TENANT IMPROVEMENTS;
                     --------------------------------------
                            LEASE COMMENCEMENT DELAY
                            ------------------------

     5.1  READY FOR OCCUPANCY.  The Premises shall be deemed "Ready for
          -------------------
Occupancy" upon the Substantial Completion of the Premises.  For purposes of
this Lease, "Substantial Completion" of the Premises shall occur upon the last
to occur of the following, subject to Section 5.2 of this Work Letter:  (i) a
temporary certificate of occupancy having been issued for the Premises and
Tenant is legally permitted to occupy the Premises for operations of its
business (excepting any specialized permits Tenant may need for Tenant's
particular use of the Premises, such as hazardous materials permits, (ii) the
Building Systems are in good working order to reasonably support operations
within the Premises, (iii) the completion of construction of the Tenant
Improvements in the Premises pursuant to the Approved Working Drawings, with the
exception of any industry-standard punch list items and long lead time items,
and (iv) the parking and access roads are materially complete.

     5.2  DELAY OF THE SUBSTANTIAL COMPLETION OF THE PREMISES.  Except as
          ---------------------------------------------------
provided in this Section 5.2, the Lease Commencement Date shall occur as set
forth in the Lease and Section 5.1, above.  If there shall be a delay or there
are delays in the Substantial Completion of the Premises or in the occurrence of
any of the other conditions precedent to the Lease Commencement Date, as set
forth in the Lease, as a direct, indirect, partial, or total result of:

          5.2.1  Tenant's failure to comply with the Time Deadlines;

          5.2.2  Tenant's failure to approve any matter requiring Tenant's
approval within the time periods set forth in this Tenant Work Letter;

          5.2.3  A breach by Tenant of the terms of this Tenant Work Letter or
the Lease;

                                      -7-
<PAGE>

          5.2.4  Changes in any of the Construction Drawings after reasonable
disapproval of the same by Landlord;

          5.2.5  Tenant's request for changes in the Approved Working Drawings;

          5.2.6  Tenant's requirement for materials, components, finishes or
improvements which are not available in a commercially reasonable time given the
anticipated date of Substantial Completion of the Premises, as set forth in the
Lease, or which are different from, or not included in, the Standard Improvement
Package;

          5.2.7  Changes to the Base Building required by the Approved Working
Drawings; or

          5.2.8  Any other acts or omissions of Tenant, or its agents, or
employees;

then, notwithstanding anything to the contrary set forth in the Lease or this
Tenant Work Letter and regardless of the actual date of the Substantial
Completion of the Premises, the Lease Commencement Date shall be deemed to be
the date the Lease Commencement Date would have occurred if no Tenant delay or
delays, as set forth above, had occurred.

     5.3  CHANGES.  Any request by Tenant for a change in the Tenant
          -------
Improvements after approval of the Final Plans (a "CHANGE") shall be accompanied
by all information necessary to clearly identify and explain the proposed
Change.  As soon as practicable after receipt of such a request from Tenant,
Landlord shall notify Tenant of the estimated cost of such Changes as well as
the increase in construction time caused by the Change (including any delay
pursuant to Section 5.2 of this Tenant Work Letter), if any.  Tenant shall
approve in writing such estimates within two (2) business days after receipt of
Landlord's notice.  Upon receipt of such written approval, Landlord shall be
authorized to cause the Contractor to proceed with the implementation of the
requested Change.

     5.4  OUTSIDE DATE.  In the event the Premises are not Ready for Occupancy
          ------------
on or before May 15, 2001 (the "OUTSIDE DATE"), which Outside Date shall be
subject to day-for-day extension due to a delay set forth in Section 5.2 of this
Tenant Work Letter and/or a Force Majeure delay (up to a maximum of sixty (60)
days due to such Force Majeure delay), then Tenant shall receive a credit
against Base Rent for a number of days equal to the number of days in the period
commencing on the Outside Date and ending on the Commencement Date (the
"Extended Period"); provided, however, that other than the extension to the
Lease Commencement Date, Tenant's receipt of such credit shall be Tenant's sole
and exclusive remedy for such delay.


                                    SECTION 6
                                    ---------

                                  MISCELLANEOUS
                                  -------------

     6.1  TENANT'S ENTRY INTO THE PREMISES PRIOR TO SUBSTANTIAL COMPLETION.
          ----------------------------------------------------------------
Provided that Tenant and its agents do not interfere with Contractor's work in
the Building and the Premises, Contractor shall allow Tenant access to the
Premises prior to the Substantial Completion of the Premises for the purpose of
Tenant installing overstandard equipment or fixtures (including

                                      -8-
<PAGE>

Tenant's data and telephone equipment) in the Premises. Prior to Tenant's entry
into the Premises as permitted by the terms of this Section 6.1, Tenant shall
                                                    -----------
submit a schedule to Landlord and Contractor, for their approval, which schedule
shall detail the timing and purpose of Tenant's entry. Tenant shall hold
Landlord harmless from and indemnify, protect and defend Landlord against any
loss or damage to the Building or Premises or injury to any persons caused by
Tenant's entry into the Premises prior to Substantial Completion pursuant to
this Section 6.1.
     -----------

     6.2  TENANT'S REPRESENTATIVE.  Tenant has designated Mr. Shaun Burnett as
          -----------------------
its sole representative with respect to the matters set forth in this Tenant
Work Letter, who shall have full authority and responsibility to act on behalf
of the Tenant as required in this Tenant Work Letter.

     6.3  LANDLORD'S REPRESENTATIVE.  Landlord has designated Mr. James Edwards
          -------------------------
as "Project Manager" who shall be responsible for the implementation of all
Tenant Improvements to be performed by Landlord in the Premises.  With regard to
all matters involving such Tenant Improvements, Tenant shall communicate with
the Project Manager rather than with the  Contractor.  Landlord shall not be
responsible for any statement, representation or agreement made between Tenant
and the Contractor or any subcontractor.  It is hereby expressly acknowledged by
Tenant that such Contractor is not Landlord's agent and has no authority
whatsoever to enter into agreements on Landlord's behalf or otherwise bind
Landlord.  The Project Manager will furnish Tenant with notices of substantial
completion, cost estimates for Above Standard Tenant Improvements, Landlord's
approvals or disapprovals of all documents to be prepared by Tenant pursuant to
this Tenant Work Letter and changes thereto.

     6.4  INTENTIONALLY OMITTED.
          ---------------------

     6.5  TIME OF THE ESSENCE IN THIS TENANT WORK LETTER.  Unless otherwise
          ----------------------------------------------
indicated, all references herein to a "number of days" shall mean and refer to
calendar days.  If any item requiring approval is timely disapproved by
Landlord, the procedure for preparation of the document and approval thereof
shall be repeated until the document is approved by Landlord.

     6.6  TENANT'S LEASE DEFAULT.  Notwithstanding any provision to the contrary
          ----------------------
contained in this Lease, if an event of default (beyond any applicable notice
and cure period(s)) as described in the Lease or this Tenant Work Letter has
occurred at any time on or before the Substantial Completion of the Premises,
then (i) in addition to all other rights and remedies granted to Landlord
pursuant to this Lease, Landlord shall have the right to withhold payment of all
or any portion of the Tenant Improvement Allowance and/or Landlord may cause
Contractor to cease the construction of the Premises (in which case, Tenant
shall be responsible for any delay in the substantial completion of the Premises
caused by such work stoppage), and (ii) all other obligations of Landlord under
the terms of this Tenant Work Letter shall be stayed until such time as such
default is cured pursuant to the terms of this Lease (in which case, Tenant
shall be responsible for any delay in the substantial completion of the Premises
caused by such inaction by Landlord).

                                      -9-
<PAGE>

                             SCHEDULE 1 TO EXHIBIT B
                             -----------------------

                                  BASE BUILDING
                                  -------------

                                   (attached)

















                                 SCHEDULE 1 TO
                                   EXHIBIT B
                                      -1-
<PAGE>

                             SCHEDULE 2 TO EXHIBIT B
                             -----------------------

                      TIMING FOR SUBMISSIONS AND APPROVALS

                                   (attached)

















                                 SCHEDULE 2 TO
                                   EXHIBIT B
                                      -1-
<PAGE>

                            FIRST AMENDMENT TO LEASE
                            ------------------------

                                  (BUILDING A)
                                  ------------


     This FIRST AMENDMENT TO LEASE (BUILDING A) (the "AMENDMENT") is made and
entered into as of March 3, 2000 by and between KR-GATEWAY PARTNERS, a Delaware
limited partnership ("LANDLORD"), and DIVERSA CORPORATION, a Delaware
corporation ("TENANT").

                                R E C I T A L S :
                                ----------------

     A. Landlord and Tenant entered into that certain Lease dated as of February
11, 2000 (the "LEASE"), whereby Landlord leased to Tenant and Tenant leased from
Landlord all of that certain two (2) story building to be located on lot 5 of
"Sorrento Gateway" (the "PROJECT"), containing approximately 75,520 rentable
square feet of space, and commonly referred to in the Project as "BUILDING A"
(the "PREMISES") located in San Diego.

     B. Landlord and Tenant desire to amend the Lease on the terms and
conditions set forth in this Amendment.

                               A G R E E M E N T :
                               ------------------

     NOW, THEREFORE, in consideration of the foregoing recitals and the mutual
covenants contained herein, and for other good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, the parties hereto
hereby agree as follows.

     1. CAPITALIZED TERMS. All capitalized terms when used herein shall have the
        -----------------
same meaning as is given such terms in the Lease unless expressly superseded by
the terms of this Amendment.

     2. SUBORDINATION. Article 18 of the Lease is hereby amended such that the
        -------------  ----------
forth (4th) sentence of such Article 18, which sentence commences with "Any such
                             ----------
Nondisturbance Agreement . . . " is deleted and replaced as follows: "Any such
Nondisturbance Agreement shall not contain language which allows the ground
lessor, mortgage holder or lien holder, the right to terminate this Lease when
the Tenant is not in default under the terms of this Lease."

     3. CESSATION OF CONSTRUCTION; TENANT COMPLETION RIGHT. The Tenant Work
        --------------------------------------------------
Letter attached as EXHIBIT B to the Lease is hereby amended, whereby the
following Section 5.5 is inserted:
          -----------

        5.5 TENANT COMPLETION. In the event either (i) Landlord discontinues the
            -----------------
     construction of the Building for a period of time which would render it
     unreasonable for completion of such construction to occur on or before

                                      -1-
<PAGE>

     the Outside Date, or (ii) the ground lessor, mortgage holder or lien holder
     identified in Article 18 of the Lease (A) succeeds to the interests of
                   ----------
     Landlord and (B) elects not to complete the construction of the Building,
     then Tenant may, upon delivery of notice, within thirty (30) days of such
     determination, to Landlord and any such ground lessor, mortgage holder or
     lien holder (the "TENANT COMPLETION NOTICE"), elect, effective upon the
     date occurring fifteen (15) business days following receipt by Landlord
     (and/or any such ground lessor, mortgage holder or lien holder) of such
     Completion Termination Notice, without terminating this Lease, to (a)
     assume all of Landlord's obligations, right, title and interest in, to and
     under any or all of the "Construction Documents," as that term is set forth
     below, by delivering a copy of such Completion Termination Notice to all
     parties to those "Construction Documents which Tenant elects to assume. The
     effectiveness of any such Completion Termination Notice delivered by Tenant
     to Landlord shall be governed by the terms of this Section 5.5. In the
                                                        -----------
     event Tenant exercises its rights under this Section 5.5 the determination
                                                  -----------
     of the Premises being Ready for Occupancy shall remain unchanged and, with
     regard to this Tenant Work Letter, references to "Landlord" shall mean to
     Tenant, except with regard to Landlord's disbursement obligations
     hereunder. The Outside Date shall be postponed due to due to delays caused
     by Force Majeure (up to sixty (60) days) and Tenant delays pursuant to
     Section 5.2 of this Tenant Work Letter.
     -----------

     4. BROKERS. Landlord and Tenant hereby warrant to each other that they have
        -------
had no dealings with any real estate broker, agent or finder in connection with
the negotiation of this Amendment, excepting only the "Brokers," as that term is
defined in Section 12 of the Summary and Section 29.24 of the Lease, and that
           ----------                    -------------
they know of no other real estate broker, agent or finder who is entitled to a
commission in connection with this Amendment. Each party agrees to indemnify and
defend the other party against and hold the other party harmless from any and
all claims, demands, losses, liabilities, lawsuits, judgments, and costs and
expenses (including, without limitation, reasonable attorneys' fees) with
respect to any leasing commission or equivalent compensation alleged to be owing
on account of the indemnifying party's dealings with any real estate broker,
agent or finder other than the Broker. The terms of this Section 7 shall
                                                         ---------
survive the expiration or earlier termination of this Amendment.

     5. TIME OF ESSENCE. Time is of the essence with respect to the performance
        ---------------
of every provision of this Amendment, including, without limitation, the Tenant
Work Letter, in which time of performance is a factor. Unless otherwise
indicated, all references herein to a "number of days" shall mean and refer to
calendar days. In all instances where Tenant is required to approve or deliver
an item, if no written notice of approval is given or the item is not delivered
within the stated time period, at Landlord's sole option, at the end of such
period the item shall automatically be deemed approved or delivered by Tenant
and the next succeeding time period shall commence.

                                      -2-
<PAGE>

     6. NO FURTHER MODIFICATION. Except as set forth in this Amendment, all of
        -----------------------
the terms and provisions of the Lease shall apply with respect to the Expansion
Premises and shall remain unmodified and in full force and effect.

     IN WITNESS WHEREOF, this Amendment has been executed as of the day and year
first above written.



"LANDLORD"                                        "TENANT"

KR-GATEWAY PARTNERS,                              DIVERSA CORPORATION,
a Delaware limited liability company              a Delaware corporation

By:  Kilroy Realty, L.P.,                         By:
     a Delaware limited partnership                  ---------------------------
     Managing Member                                   Its:
                                                           ---------------------
     By:  Kilroy Realty Corporation,              By:
          a Maryland corporation                     ---------------------------
          General Partner                              Its:
                                                           ---------------------
          By:
             ------------------------------
               Its:
                   ------------------------
          By:
             ------------------------------
               Its:
                   ------------------------

                                      -3-