<PAGE>

                                                                 EXHIBIT 10.57.2


                              REVOLVING CREDIT NOTE

$17,500,000.00                                             Boston, Massachusetts
                                                               December 28, 1998

1.  PROMISE TO PAY.

FOR VALUE RECEIVED, GENZYME TRANSGENICS CORPORATION, a Massachusetts
corporation, having an address at 5 Mountain Road, Framingham, Massachusetts
01701, ("Borrower") promises to pay to the order of FLEET NATIONAL BANK, a
national banking association, having an address at One Federal Street, Boston,
Massachusetts 02110 ("Lender"), the principal sum of SEVENTEEN MILLION FIVE
HUNDRED THOUSAND DOLLARS ($17,500,000.00), or so much thereof as may be advanced
as Revolving Credit Loans from time to time under the Credit Agreement, defined
below, with interest thereon, or on the amount thereof from time to time
outstanding, to be computed, as hereinafter provided, on each advance from the
date of its disbursement until such principal sum shall be fully paid. Interest
and principal shall be payable as set forth in Section 4 below. The total
principal sum, or the amount thereof outstanding, together with any accrued but
unpaid interest, shall be due and payable in full on December 28, 2001
("Maturity Date").

2.  CREDIT AGREEMENT.

This Note is issued pursuant to the terms, provisions and conditions of a
certain Credit Agreement between Borrower and Lender dated as of the date hereof
(the "Credit Agreement"), as amended from time to time, and evidences the
Revolving Credit Loans made pursuant thereto. Capitalized terms used herein
which are not otherwise specifically defined shall have the same meaning herein
as in the Credit Agreement.

3.  INTEREST RATES.

    3.1.    BORROWER'S OPTIONS. Principal amounts outstanding hereunder shall
            bear interest at the following rates, at Borrower's selection,
            subject to the conditions and limitations provided for in this Note:
            (i) Variable Rate or (ii) Libo Rate.

            3.1.1.  SELECTION TO BE MADE. Borrower shall select, and thereafter
                    may change the selection of, the applicable interest rate,
                    from the alternatives otherwise provided for in this Note,
                    by giving Lender a Notice of Rate Selection: (i) prior to
                    the end of each Interest Period applicable to a Libor
                    Advance, or (iii) on any Business Day on which Borrower
                    desires to convert an outstanding Variable Rate Advance to a
                    Libor Advance.

<PAGE>

            3.1.2.  NOTICE. A "Notice of Rate Selection" shall be a written
                    notice, given by cable, tested telex, telecopier (with
                    authorized signature), or by telephone if immediately
                    confirmed by such a written notice, from an Authorized
                    Representative of Borrower which: (i) is irrevocable with
                    respect to the interest rate, amount, and Interest Period
                    selected; (ii) is received by Lender not later than 10:00
                    o'clock A.M. Eastern Time: (a) if a Libo Rate is selected,
                    at least three (3) Business Days prior to the first day of
                    the Interest Period to which such selection is to apply, (b)
                    if a Variable Rate is selected, on the first day to which it
                    applies; and (iii) as to each selected interest rate option,
                    sets forth the aggregate principal amount(s) to which such
                    interest rate option(s) shall apply and the Interest
                    Period(s) applicable to each Libor Advance.

            3.1.3.  IF NO NOTICE. If Borrower fails to select an interest rate
                    option in accordance with the foregoing prior to the last
                    day of the applicable Interest Period of an outstanding
                    Libor Advance, on the last day of the applicable Interest
                    Period all outstanding principal amounts shall be deemed
                    converted to a Variable Rate Advance.

    3.2.    TELEPHONIC NOTICE. Without any way limiting Borrower's obligation to
            confirm in writing any telephonic notice, Lender may act without
            liability upon the basis of telephonic notice believed by Lender in
            good faith to be from Borrower prior to receipt of written
            confirmation. In each case Borrower hereby waives the right to
            dispute Lender's record of the terms of such telephonic Notice of
            Rate Selection in the absence of manifest error.

    3.3.    LIMITS ON OPTIONS. Each Libor Advance shall be in a minimum amount
            of $250,000. At no time shall there be outstanding a total of more
            than six (6) Libor Advances.

4.  PAYMENT OF INTEREST AND PRINCIPAL.

    4.1.    PAYMENT AND CALCULATION OF INTEREST. All interest shall be: (a)
            payable in arrears (i) on the first day of each month (with respect
            to Variable Rate Advances) or (ii) on the last day of each Interest
            Period and, if such Interest Period is longer than three months, at
            three-month intervals following the first day of such Interest
            Period (with respect to Libor Advances), until the principal
            together with all interest and other charges payable with respect to
            the Loan Advances shall be fully paid; and (b) calculated on the
            basis of a 360 day year and the actual number of days elapsed. Each
            change in the Prime Rate shall simultaneously change the Variable
            Rate payable under this Note. Interest at the Libo Rate shall be
            computed from and including the first day of the applicable Interest
            Period to, but excluding, the last day thereof.

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    4.2.    PRINCIPAL. The entire principal balance shall be due and payable on
            the Maturity Date.

    4.3.    PREPAYMENT. The Loan Advances or any portion thereof may be prepaid
            in full or in part at any time without premium or penalty with
            respect to Variable Rate Advances and, with respect to Libor
            Advances subject to a make-whole provision and upon payment of a
            Yield Maintenance Fee.

    4.4.    MATURITY. At maturity all accrued interest, principal and other
            charges due with respect to the Loan Advances shall be due and
            payable in full and the principal balance and such other charges,
            but not unpaid interest, shall continue to bear interest at the
            default rate specified in the Credit Agreement until so paid.

    4.5.    DEFAULT RATE; LATE CHARGES. Upon and during the continuance of an
            Event of Default at the election of the Lender, interest shall be
            payable on the unpaid principal balance from time to time
            outstanding at a rate per annum equal to the interest rate
            applicable hereunder plus four percent (4%), until fully paid. Any
            payment hereunder not paid within ten (10) days after the date such
            payment is due shall be subject to a late fee equal to five percent
            (5%) of the amount overdue.

    4.6.    MAKE WHOLE PROVISION. Borrower shall pay to Lender, immediately upon
            request and notwithstanding contrary provisions contained in any of
            the Loan Documents, such amounts as shall, in the reasonable
            judgment of Lender (in the absence of manifest error), compensate
            Lender for the loss, cost or expense which it may reasonably incur
            as a result of (i) any payment or prepayment, under any
            circumstances whatsoever, whether voluntary or involuntary, of all
            or any portion of a Libor Advance on a date other than the last day
            of the applicable Interest Period of a Libor Advance, or (ii) the
            conversion, for any reason whatsoever, whether voluntary or
            involuntary, of any Libor Advance to a Variable Rate Advance on a
            date other than the last day of the applicable Interest Period. Such
            amounts payable by Borrower shall be equal to any administrative
            costs actually incurred plus, in any event, but without duplication,
            a Yield Maintenance Fee. The "Yield Maintenance Fee" shall be an
            amount equal to the product of: (a) the amount so prepaid or
            converted, as the case may be, multiplied by (b) the difference
            between the Libo Rate then in effect, or which would have been in
            effect (computed separately for each outstanding maturity or
            installment), and the Treasury Rate in effect on the date of the
            occurrence (computed separately for each outstanding maturity or
            installment), which product shall be multiplied by (c) a fraction,
            the numerator of which is the number of days from the date of
            occurrence to the last day of the applicable Interest Period (or, if
            applicable, each Interest Period) and the denominator of which is
            360 days; HOWEVER, if or to ------- the extent that the applicable
            Libo Rate for the applicable Interest Period (computed separately
            for each maturity or installment) is equal to or less than the
            Treasury Rate, no Yield Maintenance Fee shall be payable.

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5.  CERTAIN DEFINITIONS AND PROVISIONS RELATING TO INTEREST RATE.

    5.1.    ADJUSTED LIBO RATE. The term "Adjusted Libo Rate" means for each
            Interest Period the rate per annum obtained by dividing (i) the
            Applicable Libo Rate for such Interest Period, by (ii) a percentage
            equal to one hundred PERCENT (100%) minus the maximum reserve
            percentage applicable ------- during such Interest Period under
            regulations issued from time to time by the Board of Governors of
            the Federal Reserve System for determining the maximum reserve
            requirements (including, without limitation, any basic,
            supplemental, marginal and emergency reserve requirements) for
            Lender (or of any subsequent holder of this Note which is subject to
            such reserve requirements) in respect of liabilities or assets
            consisting of or including Eurocurrency liabilities (as such term is
            defined in Regulation D of the Board of Governors of the Federal
            Reserve System) having a term equal to the Interest Period.

    5.2.    APPLICABLE LIBO RATE. The term "Applicable Libo Rate" means, with
            respect to each Interest Period, the rate of interest, expressed as
            an annual rate, equal to the simple average, rounded up to the
            nearest 1/32 of 1%, of the rates shown on the display referred to as
            the "Telerate Page 3750" (or any display substituted therefor) of
            the Dow Jones Telerate Service as being the respective rates at
            which deposits in Dollars would be offered by the principal London
            offices of each of the banks named thereon to major banks in the
            London interbank market at approximately 11:00 A.M. (London time) on
            the second London Banking Day before the first day of such Interest
            Period for a period substantially coextensive with such Interest
            Period.

    5.3.    APPLICABLE MARGIN. The "Applicable Margin" shall be determined based
            upon the financial position and results of the Guarantor based upon
            the financial statements and Compliance Certificates furnished by
            the Guarantor pursuant to the Guaranty. The term "Applicable Margin"
            means, for any period set forth below the percentage set forth below
            opposite such period:

<TABLE>
<CAPTION>
                      PERIOD                         APPLICABLE MARGIN

<S>                                                       <C>   
                  Level I Period                          0.425%
                  Level II Period                         0.550%
                  Level II Period                         0.675%
                  Level IV Period                         0.925%
</TABLE>

    5.4.    BANKING DAY. The term "Banking Day" means a day on which banks are
            not required or authorized by law to close in the city in which
            Lender's principal office is situated.

    5.5.    BUSINESS DAY; SAME CALENDAR MONTH. The term "Business Day" means any
            Banking Day and, if the applicable Business Day relates to the
            selection or 

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            determination of any Libo Rate, any London Banking Day. If any day
            on WHICH a payment is due is not a Business Day, then the payment
            shall be due on the next day following which is a Business Day,
            unless, with respect to Libor Advances, the effect would be to make
            the payment due in the next calendar month, in which event such
            payment shall be due on the next preceding day which is a Business
            Day. Further, if there is no corresponding day for a payment in the
            given calendar month (i.e., there is no "February 30th"), the
            payment shall be due on the last Business Day of the calendar month.

    5.6.    CAPITAL EXPENDITURES. The term "Capital Expenditures" means, for any
            period, expenditures (including, without limitation, the aggregate
            amount of Capital Lease Obligations incurred during such period)
            made by the Guarantor or any of its Subsidiaries to acquire or
            construct fixed assets, plant and equipment (including renewals,
            improvements and replacements, but excluding repairs) during such
            period computed in accordance with GAAP.

    5.7.    CASH EQUIVALENTS. The term "Cash Equivalents" means any interest
            bearing investment of Guarantor and its wholly owned Subsidiaries
            which meets the definition of a "cash equivalent" under GAAP (i.e.,
            purchased with a remaining maturity of 90 days or less). Such
            investments shall be at least investment grade (A1/P1 for commercial
            paper, BBB or better for bonds and similar investments).

    5.8.    "CAPITAL LEASE OBLIGATIONS" shall mean, for any Person, all
            obligations of such Person to pay rent or other amounts under a
            lease of (or other agreement conveying the right to use) property to
            the extent such obligations are required to be classified and
            accounted for as a capital lease on a balance sheet of such Person
            under GAAP, and, for purposes of this Guaranty, the amount of such
            obligations shall be the capitalized amount thereof, determined in
            accordance with GAAP.

    5.9.    CONSOLIDATED. The term "Consolidated" means, when used with
            reference to any term, that term as applied to the accounts of
            Guarantor and all of its Subsidiaries consolidated in accordance
            with GAAP.

    5.10.   CONSOLIDATED EBITDA. The term "Consolidated EBITDA" means, for any
            period, the sum, for the Guarantor, of the following: (a)
            Consolidated Operating Income for such period PLUS (b) depreciation
            and amortization, but only to the extent deducted in determining
            Consolidated Operating Income for such period.

    5.11.   CONSOLIDATED DEBT COVERAGE RATIO. The term "Consolidated Debt
            Coverage Ratio" means for the Guarantor, at any date, the ratio, for
            the Guarantor and its Consolidated Subsidiaries, of (a) the sum of
            (i) Unrestricted Cash on such date plus (ii) Marketable Investments
            on such date to (b) Consolidated Funded Debt on such date.

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    5.12.   CONSOLIDATED FIXED CHARGE COVERAGE RATIO. The term "Consolidated
            Fixed Charge Coverage Ratio" means for the Guarantor, for any
            period, the ratio of (a) the sum of (i) Consolidated EBITDA for such
            period LESS (ii) the aggregate amount of Capital Expenditures made
            during such period LESS (iii) the amount of the taxes paid during
            such period LESS (iv) the aggregate amount of all Dividend Payments
            made during such period to (b) all Interest expense for such period.

    5.13.   CONSOLIDATED FUNDED DEBT. The term "Consolidated Funded Debt" means
            for the Guarantor, at any time, the outstanding balance of all
            Indebtedness in respect of borrowed money, Capital Lease
            Obligations, letters of credit and trade acceptances for the
            Guarantor and its Consolidated Subsidiaries.

    5.14.   CONSOLIDATED NET INCOME. The term "Consolidated Net Income" shall
            mean, for any period, net income (or loss) for the Guarantor and its
            Consolidated Subsidiaries (determined in accordance with GAAP),
            PROVIDED HOWEVER, that Consolidated Net Income shall not include
            amounts included in computing net income (or loss) in respect of (a)
            the write-up of assets (other than Marketable Investments) after
            December 31, 1995 and (b) extraordinary and non-recurring gains or
            losses.

    5.15.   CONSOLIDATED OPERATING INCOME. The term "Consolidated Operating
            Income" means for the Guarantor, for any period, the Consolidated
            Net Income of the Guarantor for such period, PROVIDED, HOWEVER,
            that, to the extent the following items have been included in
            determining Consolidated Net Income, they shall NOT be considered in
            computing Consolidated Operating Income: provision for income taxes,
            interest expense, equity in the operating results of unconsolidated
            Subsidiaries (including partnerships, joint ventures and Affiliates
            but only to the extent that such results represent noncash,
            nonoperating items) and other non-operating, non-cash items
            including, but not limited to, write-off of acquired technology or
            acquired, in-process research and development which, in accordance
            with GAAP, must be charged to income. Furthermore, all charges
            arising from the acquisition by Guarantor of Neozyme II Corporation
            and/or Deknatel Snowden Pencer, Inc. which are included in the
            determination of Consolidated Net Income for any period shall be
            excluded from the computation of Consolidated Operating Income
            whether such charges be of a cash or non-cash nature.

    5.16.   DIVIDEND PAYMENT. The term "Dividend Payment" means dividends (in
            cash, Property or obligations) on, or other payments or
            distributions on account of, or the setting apart of money for a
            sinking or other analogous fund for, or the purchase, redemption,
            retirement or other acquisition of, any shares of any class of stock
            of, or any partnership or other equity interest issued by, the
            Guarantor or of any warrants, options or other rights to acquire the
            same (or to make any payments to any Person, such as "phantom stock"
            payments, where the amount thereof is calculated with reference to
            the fair market or equity value of the 

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            Guarantor or any of its Subsidiaries), but excluding dividends
            payable solely in shares of common stock of the Guarantor.

    5.17.   DOLLARS. The term "Dollars" or "$" means lawful money of the United
            States.

    5.18.   EVENT OF DEFAULT. The term "Event of Default" has meaning given such
            term in the Credit Agreement.

    5.19.   GUARANTEE. The term "Guarantee" means a guarantee, an endorsement, a
            contingent agreement to purchase or to furnish funds for the payment
            or maintenance of, or otherwise to be or become contingently liable
            under or with respect to, the Indebtedness, other obligations, net
            worth, working capital or earnings of any Person, or a guarantee of
            the payment of dividends or other distributions upon the stock or
            equity interests of any Person, or an agreement to purchase, sell or
            lease (as lessee or lessor) property, products, materials, supplies
            or services primarily for the purpose of enabling a debtor to make
            payment of such debtor's obligations or an agreement to assure a
            creditor against loss, and including, without limitation, causing a
            bank or other financial institution to issue a letter of credit or
            other similar instrument for the benefit of another Person, but
            excluding endorsements for collection or deposit in the ordinary
            course of business. The terms "Guarantee" and "Guaranteed" used as a
            verb shall have a correlative meaning.

    5.20.   INDEBTEDNESS. The term "Indebtedness" means, for the Guarantor and
            its Consolidated Subsidiaries: (a) obligations created, issued or
            incurred by such Person for borrowed money (whether by loan, the
            issuance and sale of debt securities or the sale of property to
            another Person subject to an understanding or agreement, contingent
            or otherwise, to repurchase such Property from such Person); (b)
            obligations of such Person to pay the deferred purchase or
            acquisition price of property or services, other than trade accounts
            payable (other than for borrowed money) arising, and accrued
            expenses incurred, in the ordinary course of business so long as
            such trade accounts payable are payable within 120 days of the date
            the respective goods or services are delivered or rendered; (c)
            Indebtedness of others secured by a Lien on the property of such
            Person, whether or not the respective indebtedness so secured has
            been assumed by such Person; (d) obligations of such Person,
            contingent or otherwise, in respect of letters of credit, bankers'
            acceptances or similar instruments issued or accepted by banks and
            other financial institutions for account of such person; (e) Capital
            Lease Obligations of such Person; and (f) Guarantees by such Person
            of Indebtedness of others.

    5.21.   INTEREST. The term Interest means, for any period, the sum, for the
            Guarantor and its Consolidated Subsidiaries, of the following: (a)
            all interest in respect of Indebtedness (including, without
            limitation, the interest component of any payments in respect of
            Capital Lease Obligations) accrued or capitalized during 

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            such period (whether or not actually paid during such period); and
            (b) all other amounts that would be accrued or capitalized during
            such period as "interest expense" in accordance with GAAP.

    5.22.   INTEREST PERIOD.

            5.22.1. The term "Interest Period" means with respect to each Libor
                    Advance: a period of an integral multiple of one month, but
                    no Interest Period shall be greater than three (3) months,
                    subject to availability, as selected, or deemed selected, by
                    Borrower at least three (3) Business Days prior to the end
                    of the current Interest Period or the commencement of the
                    next Interest Period. Each such Interest Period shall
                    commence on the Business Day so selected, or deemed
                    selected, by Borrower and shall end on the numerically
                    corresponding day in the month in which the Interest Period
                    ends; PROVIDED, HOWEVER: (i) if there is no such numerically
                    corresponding day, such Interest Period shall end on the
                    last Business Day of the applicable month, (ii) if the last
                    day of such an Interest Period would otherwise occur on a
                    day which is not a Business Day, such Interest Period shall
                    be extended to the next succeeding Business Day; but (iii)
                    if such extension would otherwise cause such last day to
                    occur in a new calendar month, then such last day shall
                    occur on the next preceding Business Day.

            5.22.2. Intentionally omitted.

            5.22.3. No Interest Period may be selected which would end beyond
                    the Maturity Date. If the last day of an Interest Period
                    would otherwise occur on a day which is not a Business Day,
                    such last day shall be extended to the next succeeding
                    Business Day, except as provided above in clause (A)
                    relative to a Libor Advance.

    5.23.   LEVEL I PERIOD. The term "Level I Period" means any period (a) from
            and including the Business Day immediately following the Business
            Day on which a senior financial officer of the Guarantor shall have
            delivered to the Lender a Compliance Certificate, together with the
            related financial statements referred to in Section 4 of the
            Guaranty, demonstrating in reasonable detail that the Consolidated
            Debt Coverage Ratio, as of the last day of the fiscal quarter of the
            Guarantor most recently ended, is greater than or equal to 2.0 to
            1.0 or that the Consolidated Fixed Charge Coverage Ratio for such
            period was greater than 5.5 to 1.0, to but excluding the next
            succeeding Reporting Date and (b) during which no Event of Default
            shall have occurred and be continuing.

    5.24.   LEVEL II PERIOD. The term "Level II Period" means any period, other
            than a Level I Period, (a) from and including the Business Day
            immediately following the Business Day on which a senior financial
            officer of the Guarantor shall have 

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<PAGE>

            delivered to the Lender a Compliance Certificate, together with the
            related financial statements referred to in Section 4 of the
            Guaranty, demonstrating in reasonable detail that the Consolidated
            Debt Coverage Ratio, as of the last day of the fiscal quarter of the
            Guarantor most recently ended, is less than to 2.0 to 1.0 and
            greater than or equal to 1.0 to 1.0 or that the Consolidated Fixed
            Charge Coverage Ratio for such period was greater than or equal to
            4.5 to 1.0 and less than or equal to 5.5 to 1.0, to but excluding
            the next succeeding Reporting Date and (b) during which no Event of
            Default shall have occurred and be continuing.

    5.25.   LEVEL III PERIOD. The term "Level III Period" means any period,
            other than a Level I Period or Level II Period, (a) from and
            including the Business Day immediately following the Business Day on
            which a senior financial officer of the Guarantor shall have
            delivered to the Lender a Compliance Certificate, together with the
            related financial statements referred to in Section 4 of the
            Guaranty hereof, demonstrating in reasonable detail that the
            Consolidated Debt Coverage Ratio, as of the last day of the fiscal
            quarter of the Guarantor most recently ended, is less than to 1.0 to
            1.0 and that the Consolidated Fixed Charge Coverage Ratio for such
            period was greater than or equal to 3.5 to 1.0 and less than 4.5 to
            1.0, to but excluding the next succeeding Reporting Date and (b)
            during which no Event of Default shall have occurred and be
            continuing.

    5.26.   LEVEL IV PERIOD. The term "Level IV Period" means any period, other
            than a Level I Period, Level II Period or Level III Period.

    5.27.   LIBOR ADVANCE. The term "Libor Advance" means any principal
            outstanding under this Note which pursuant to this Note bears
            interest at the Libo Rate.

    5.28.   LIBO RATE. The term "Libo Rate" means the per annum rate equal to
            the Adjusted Libo Rate plus the Applicable Margin.

    5.29.   LOAN ADVANCE. The term "Loan Advance" means any portion of principal
            outstanding under this Note.

    5.30.   LONDON BANKING DAY. The term "London Banking Day" means any day on
            which dealings in deposits in Dollars are transacted in the London
            interbank market.

    5.31.   MARKETABLE INVESTMENTS. The term "Marketable Investments" means any
            interest-bearing debt obligations owned by Guarantor and its
            wholly-owned Subsidiaries (excluding directors' qualifying shares
            and items included as Cash Equivalents) which meet the definition of
            marketable securities under GAAP. Such amounts shall exclude common
            or preferred stock. Such securities shall include obligations issued
            by the U.S. Treasury and other agencies of the U.S. government,
            corporate bonds, bank notes, mortgage and asset backed securities,
            finance company securities and auction rate preferred stocks. Such
            securities shall be rated investment grade (BBB or better for bonds
            or similar securities, 

                                       9
<PAGE>

            A1/P1 for commercial paper and notes) and shall otherwise be
            reasonably liquid investments.

    5.32.   MATURITY. The term "Maturity" means the Maturity Date, or, if
            earlier, the date of acceleration of the Loans under the Credit
            Agreement.

    5.33.   Intentionally omitted.

    5.34.   PRIME RATE. The term "Prime Rate" means the per annum rate of
            interest so designated from time to time by Lender as its prime
            rate. The Prime Rate is a reference rate and does not necessarily
            represent the lowest or best rate being charged to any customer.

    5.35.   REPORTING DATE. The term "Reporting Date" means the first to occur
            of (i) the Business Day following the Business Day that the Lender
            receives a Compliance Certificate of the Guarantor providing the
            information required to determine whether a period is a Level I
            Period, Level II Period, Level III Period or Level IV Period and
            (ii) the first Business Day after the date on which the quarterly or
            annual financial statement and Compliance Certificate is required to
            be delivered to the Lender pursuant to Section 4(a) of the Guaranty.

    5.36.   SUBSIDIARY. The term "Subsidiary" means any corporation, partnership
            trust or other organization, whether or not incorporated, the
            majority of the voting stock or voting rights of which is owned or
            controlled, directly or indirectly, by Guarantor.

    5.37.   TREASURY RATE. The term "Treasury Rate" means, as of the date of any
            calculation or determination, the latest published rate for United
            States Treasury Notes or Bills (but the rate on Bills issued on a
            discounted basis shall be converted to a bond equivalent) as
            published weekly in the Federal Reserve Statistical Release
            H.15(519) of Selected Interest Rates in an amount which approximates
            (as reasonably determined by Lender) the amount (i) approximately
            comparable to the portion of the Loan Advance to which the Treasury
            Rate applies for the Interest Period, or (ii) in the case of a
            prepayment, the amount prepaid and with a maturity closest to the
            original maturity of the installment which is prepaid in whole or in
            part.

    5.38.   UNRESTRICTED CASH. The term "Unrestricted Cash" means cash and Cash
            Equivalents of the Guarantor and its wholly owned Subsidiaries that
            are readily available to Guarantor and not subject to any limitation
            or restriction on their use by the Guarantor.

    5.39.   VARIABLE RATE. The term "Variable Rate" means a per annum rate equal
            at all times to the Prime Rate, with changes therein to be effective
            simultaneously with any change in the Prime Rate.

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<PAGE>

    5.40.   VARIABLE RATE ADVANCE. The term "Variable Rate Advance" means any
            principal amount outstanding under this Note which pursuant to this
            Note bears interest at the Variable Rate.

6.  ADDITIONAL PROVISIONS RELATED TO INTEREST RATE SELECTION.

    6.1.    INCREASED COSTS. If, due to any one or more of: (i) the introduction
            of any applicable law or regulation or any change (other than any
            change by way of imposition or increase of reserve requirements
            already referred to in the definition of Libo Rate) in the
            interpretation or application by any authority charged with the
            interpretation or application thereof of any law or regulation; or
            (ii) the compliance with any guideline or request from any
            governmental central bank or other governmental authority (whether
            or not having the force of law), there shall be an increase in the
            cost to Lender of agreeing to make or making, funding or maintaining
            Libor Advances, including without limitation changes which affect or
            would affect the amount of capital or reserves required or expected
            to be maintained by Lender, with respect to all or any portion of
            the Loan Advances, or any corporation controlling Lender, on account
            thereof, then Borrower from time to time shall, upon written demand
            by Lender made within ninety (90) days of such increase in cost, pay
            Lender additional amounts sufficient to indemnify Lender against the
            increased cost. A certificate as to the amount of the increased cost
            and the reason therefor submitted to Borrower by Lender, in the
            absence of manifest error, shall be conclusive and binding for all
            purposes.

    6.2.    ILLEGALITY. Notwithstanding any other provision of this Note, if the
            introduction of or change in or in the interpretation of any law,
            treaty, statute, regulation or interpretation thereof shall make it
            unlawful, or any central bank or government authority shall assert
            by directive, guideline or otherwise, that it is unlawful, for
            Lender to make or maintain Libor Advances or to continue to fund or
            maintain Libor Advances then, on written notice thereof and demand
            by Lender to Borrower, (a) the obligation of Lender to make Libor
            Advances and to convert or continue any Loan Advances as Libor
            Advances shall terminate and (b) Borrower shall convert all
            principal outstanding under this Note into Variable Rate Advances.

    6.3.    ADDITIONAL LIBOR CONDITIONS. The selection by Borrower of a Libo
            Rate and the maintenance of Loan Advances at such rate shall be
            subject to the following additional terms and conditions:

            6.3.1.  AVAILABILITY. If, before or after Borrower has selected to
                    take or maintain a Libor Advance, Lender notifies Borrower
                    that:

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<PAGE>

                    6.3.1.1 dollar deposits in the amount and for the maturity
                            requested are not available to Lender in the London
                            interbank market at the rate specified in the
                            definition of LIBO Rate set forth above, or

                    6.3.1.2 reasonable means do not exist for Lender to
                            determine the Libo Rate for the amounts and maturity
                            requested,

then the principal which would have been a Libor Advance shall be a Variable
Rate Advance.

            6.3.2.  PAYMENTS NET OF TAXES. All payments and prepayments of
                    principal and interest under this Note shall be made net of
                    any taxes and costs resulting from having principal
                    outstanding at or computed with reference to a Libo Rate.
                    Without limiting the generality of the preceding obligation,
                    illustrations of such taxes and costs are taxes, or the
                    withholding of amounts for taxes, of any nature whatsoever
                    including income, excise, interest equalization taxes (other
                    than United States or state income taxes) as well as all
                    levies, imposts, duties or fees whether now in existence or
                    as the result of a change in or promulgation of any treaty,
                    statute, regulation, or interpretation thereof or any
                    directive guideline or otherwise by a central bank or fiscal
                    authority (whether or not having the force of law) or a
                    change in the basis of, or the time of payment of, such
                    taxes and other amounts resulting therefrom.

    6.4.    VARIABLE RATE ADVANCES. Each Variable Rate Advance shall continue as
            a Variable Rate Advance until the Maturity Date, unless sooner
            converted or prepaid, in whole or in part, to a Libor Rate Advance,
            subject to the limitations and conditions set forth in this Note.

    6.5.    CONVERSION OF OTHER ADVANCES. At the end of each applicable Interest
            Period, the applicable Libor Advance shall be converted to a
            Variable Rate Advance unless Borrower selects another option in
            accordance with the provisions of this Note.

    6.6.    CHANGE TO APPLICABLE MARGIN IF GUARANTOR CREDIT AGREEMENT IS
            REPLACED. In the event that the Credit Agreement, dated November 14,
            1996, among the Guarantor, the Subsidiary Guarantors party thereto,
            the Lenders party thereto, Fleet National Bank, as administrative
            agent and The First National Bank of Boston, as documentation agent
            (the "Guarantor Credit Agreement") is terminated and replaced by an
            unsecured revolving credit facility in excess of $100,000,000
            providing all or substantially all of the Guarantor's working
            capital financing requirements as determined by Lender in its
            reasonable discretion, the Applicable Margin as defined in Section
            5.3 hereof shall be adjusted to be five (5) basis points in excess
            of the applicable margin used in such replacement revolving credit
            facility for libor or eurodollar type borrowings (provided that the
            interest rates assigned to such libor or eurodollar type borrowings
            are determined by reference to the same market that is utilized in
            administering the Guarantor Credit 

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<PAGE>

            Agreement), but if the Guarantor Credit Agreement is terminated and
            not so replaced the Applicable Margin as defined in Section 5.3
            hereof shall remain in effect.

7.  ACCELERATION; EVENT OF DEFAULT.

At the option of the holder, this Note and the indebtedness evidenced hereby
shall become immediately due and payable without further notice or demand, and
notwithstanding any prior waiver of any breach or default, or other indulgence,
upon the occurrence at any time of any Event of Default as defined in the Credit
Agreement.

8.  CERTAIN WAIVERS, CONSENTS AND AGREEMENTS.

Each and every party liable hereon or for the indebtedness evidenced hereby
whether as maker, endorser, guarantor, surety or otherwise hereby: (a) waives
presentment, demand, protest, suretyship defenses and defenses in the nature
thereof; (b) waives any defenses based upon and specifically assents to any and
all extensions and postponements of the time for payment, changes in terms and
conditions and all other indulgences and forbearances which may be granted by
the holder to any party now or hereafter liable hereunder or for the
indebtedness evidenced hereby; (c) agrees to any substitution, exchange,
release, surrender or other delivery of any security or collateral now or
hereafter held hereunder or in connection with the Credit Agreement, or any of
the other Loan Documents, and to the addition or release of any other party or
person primarily or secondarily liable; (d) agrees that if any security or
collateral given to secure this Note or the indebtedness evidenced hereby or to
secure any of the obligations set forth or referred to in the Credit Agreement,
or any of the other Loan Documents, shall be found to be unenforceable in full
or to any extent, or if Lender or any other party shall fail to duly perfect or
protect such collateral, the same shall not relieve or release any party liable
hereon or thereon nor vitiate any other security or collateral given for any
obligations evidenced hereby or thereby; (e) subject to the terms of the Credit
Agreement, agrees to pay all costs and expenses incurred by Lender or any other
holder of this Note in connection with the indebtedness evidenced hereby,
including, without limitation, all attorneys' fees and costs, for the
implementation of the Revolving Credit Loans evidenced hereby, the collection of
the indebtedness evidenced hereby and the enforcement of rights and remedies
hereunder or under the other Loan Documents, whether or not suit is instituted;
and (f) consents to all of the terms and conditions contained in this Note, the
Credit Agreement, and all other instruments now or hereafter executed evidencing
or governing all or any portion of the security or collateral for this Note and
for such Credit Agreement, or any one or more of the other Loan Documents.

9.  DELAY NOT A BAR.

No delay or omission on the part of the holder in exercising any right hereunder
or any right under any instrument or agreement now or hereafter executed in
connection herewith, or any agreement or instrument which is given or may be
given to secure the indebtedness evidenced hereby or by the Credit Agreement, or
any other agreement now or hereafter executed in connection herewith or
therewith shall operate as a waiver of any such right or of any other right of
such holder, nor shall any delay, omission or waiver on any one occasion be
deemed to be a bar to or waiver of the same or of any other right on any future
occasion.

10.      PARTIAL INVALIDITY.

The invalidity or unenforceability of any provision hereof, of the Credit
Agreement, of the other Loan Documents, or of any other instrument, agreement or
document now or hereafter executed in connection with the Credit Agreement made
pursuant hereto and thereto shall not impair or vitiate any other provision of
any 

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<PAGE>

of such instruments, agreements and documents, all of which provisions shall
be enforceable to the fullest extent now or hereafter permitted by law.

11. COMPLIANCE WITH USURY LAWS.

All agreements between Borrower and Lender are hereby expressly limited so that
in no contingency or event whatsoever, whether by reason of acceleration of
maturity of the indebtedness evidenced hereby or otherwise, shall the amount
paid or agreed to be paid to Lender for the use or the forbearance of the
indebtedness evidenced hereby exceed the maximum permissible under applicable
law. As used herein, the term "applicable law" shall mean the law in effect as
of the date hereof, PROVIDED, HOWEVER, that in the event there is a change in
the law which results in a higher permissible rate of interest, then this Note
shall be governed by such new law as of its effective date. In this regard, it
is expressly agreed that it is the intent of Borrower and Lender in the
execution, delivery and acceptance of this Note to contract in strict compliance
with the laws of the Commonwealth of Massachusetts from time to time in effect.
If, under or from any circumstances whatsoever, fulfillment of any provision
hereof or of any of the Loan Documents at the time performance of such provision
shall be due, shall involve transcending the limit of validity prescribed by
applicable law, then the obligation to be fulfilled shall automatically be
reduced to the limit of such validity, and if under or from any circumstances
whatsoever Lender should ever receive as interest an amount which would exceed
the highest lawful rate, such amount which would be excessive interest shall be
applied to the reduction of the principal balance evidenced hereby and not to
the payment of interest. This provision shall control every other provision of
all agreements between Borrower and Lender.

12. WAIVER OF JURY TRIAL.

BORROWER AND LENDER MUTUALLY HEREBY KNOWINGLY, VOLUNTARILY AND INTENTIONALLY
WAIVES THE RIGHT TO A TRIAL BY JURY IN RESPECT OF ANY LITIGATION BASED HEREON,
ARISING OUT OF, UNDER OR IN CONNECTION WITH THIS NOTE OR ANY OTHER LOAN
DOCUMENTS CONTEMPLATED TO BE EXECUTED IN CONNECTION HEREWITH, OR ANY COURSE OF
CONDUCT, COURSE OF DEALINGS, STATEMENTS (WHETHER VERBAL OR WRITTEN) OR ACTIONS
OF ANY PARTY. THIS WAIVER CONSTITUTES A MATERIAL INDUCEMENT FOR LENDER TO ACCEPT
THIS NOTE AND MAKE THE LOAN ADVANCES.

13. NO ORAL CHANGE.

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<PAGE>

This Note and the other Loan Documents may only be amended, terminated, extended
or otherwise modified by a writing signed by the party against which enforcement
is sought. In no event shall any oral agreements, promises, actions, inactions,
knowledge, course of conduct, course of dealing, or the like be effective to
amend, terminate, extend or otherwise modify this Note or any of the other Loan
Documents.

14. RIGHTS OF THE HOLDER.

This Note and the rights and remedies provided for herein may be enforced by
Lender or any subsequent holder hereof. Wherever the context permits each
reference to the term "holder" herein shall mean and refer to Lender or the then
subsequent holder of this Note.

15. SETOFF.

Borrower hereby grants to Lender a lien, security interest and right of set off
as security for all liabilities and obligations to Lender, whether now existing
or hereafter arising, upon and against all deposits, credits, collateral and
property, now or hereafter in the possession, custody, safekeeping or control of
Lender or any entity under the control of Fleet Financial Group, Inc., or in
transit to any of them. At any time upon and during the continuance of an Event
of Default, without demand or notice, Lender may set off the same or any part
thereof and apply the same to any liability or obligation of Borrower even
though unmatured and regardless of the adequacy of any other collateral securing
the Loans. ANY AND ALL RIGHTS TO REQUIRE LENDER TO EXERCISE ITS RIGHTS OR
REMEDIES WITH RESPECT TO ANY OTHER COLLATERAL WHICH SECURES THE LOANS, PRIOR TO
EXERCISING ITS RIGHT OF SETOFF WITH RESPECT TO SUCH DEPOSITS, CREDIT OR OTHER
PROPERTY OF THE BORROWER ARE HEREBY KNOWINGLY, VOLUNTARILY AND IRREVOCABLY
WAIVED.

                  [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]


                                       15
<PAGE>


    IN WITNESS WHEREOF, Borrower has caused this Note to be duly executed as of
the date set forth above as a sealed instrument.

Witness:                              GENZYME TRANSGENICS CORPORATION


/S/ Fredrick Stukle                   By: /s/ John B. Green     
---------------------------------        ---------------------------------
Witness                                  Name: John B. Green
                                         Title: Treasurer








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