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EXHIBIT 3.3

               CERTIFICATE OF DESIGNATION, NUMBER, VOTING POWERS,
                 PREFERENCES AND RIGHTS OF SERIES A CONVERTIBLE
                                 PREFERRED STOCK
                                       OF
                          TRANSKARYOTIC THERAPIES, INC.

                         Pursuant to Section 151 of the
                General Corporation Law of the State of Delaware

                  The undersigned DOES HEREBY CERTIFY that the following
resolution was duly adopted by the Board of Directors of Transkaryotic
Therapies, Inc., a Delaware corporation (hereinafter called the "Corporation"),
with the preferences and rights set forth therein relating to dividends,
conversion, redemption, dissolution and distribution of assets of the
Corporation having been fixed by the Board of Directors pursuant to authority
granted to it under Article IV of the Corporation's Certificate of Incorporation
and in accordance with the provisions of Section 151 of the General Corporation
Law of the State of Delaware:

                  RESOLVED: That, pursuant to authority conferred upon the Board
of Directors by the Certificate of Incorporation of the Corporation, the Board
of Directors hereby authorizes the issuance of 10,000 shares of Series A
Convertible Preferred Stock of the Corporation, and hereby fixes the
designations, powers, preferences and relative, participating, optional or other
special rights, and the qualifications, limitations or restrictions thereof, of
such shares, in addition to those set forth in the Certificate of Incorporation
of the Corporation, as follows:

                  1. DESIGNATION AND AMOUNT. The shares of such series shall be
designated "Series A Convertible Preferred Stock" (the "Series A Preferred
Stock"), par value $0.01 per share, and the number of shares constituting such
series shall be 10,000.

                  2. DIVIDENDS. The holders of Series A Preferred Stock shall be
entitled to receive, when, as and if dividends are declared on shares of Common
Stock by the Board of Directors of the Corporation (the "Board of Directors"),
dividends per share of Series A Preferred Stock in such an amount as the holders
of the Series A Preferred Stock would have received had such holders converted
Series A Preferred Stock into Common Stock immediately prior to the record date
for such distribution. All dividends declared upon Series A Preferred Stock
shall be declared pro rata per share.

                  3. LIQUIDATION, DISSOLUTION OR WINDING UP.

                  (a) In the event of any voluntary or involuntary liquidation,
dissolution or winding up of the Corporation, the holders of shares of Series A
Preferred Stock then outstanding shall be entitled to be paid out of the assets
of the Corporation available for distribution to its stockholders, after and
subject to the payment in full of all amounts required to be distributed to the
holders of any other Preferred Stock of the Corporation ranking on liquidation
prior and in preference to the Series A Preferred Stock (such Preferred Stock
being referred to hereinafter as "Senior Preferred Stock") upon such
liquidation, dissolution or winding up, but before any payment shall be made to
the holders of Common Stock, an amount in cash equal to Ten Thousand Dollars
($10,000) per share, subject to appropriate adjustment in the event of any stock
dividend, stock split, stock distribution or combination with respect to the
Series A Preferred Stock (the "Stated Value") plus any dividends thereon
declared but unpaid (such amount being referred to hereinafter as the "Series A
Liquidation Value"). If upon any such liquidation, dissolution or winding up of
the Corporation the remaining assets of the Corporation available for the
distribution to its stockholders after payment in full of amounts required to be
paid or distributed to holders of Senior Preferred Stock shall be insufficient
to pay the holders of shares of Series A Preferred Stock the full amount to
which they shall be entitled, the holders of shares of Series A Preferred Stock,
and any class of stock ranking on liquidation on a parity with the Series A
Preferred Stock, shall share ratably in any distribution of the remaining assets
and funds of the

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Corporation in proportion to the respective amounts which would
otherwise be payable in respect to the shares held by them upon such
distribution if all amounts payable on or with respect to said shares were paid
in full.

                  (b) After the payment of all preferential amounts required to
be paid to the holders of Senior Preferred Stock and Series A Preferred Stock
and any other series of Preferred Stock upon the dissolution, liquidation or
winding up of the Corporation, the holders of shares of Common Stock then
outstanding shall be entitled to receive the remaining assets and funds of the
Corporation available for distribution to its stockholders.

                  (c) The merger or consolidation of the Corporation into or
with another corporation, the merger or consolidation of any other corporation
into or with the Corporation, or the sale, conveyance, mortgage, pledge or lease
of all or substantially all the assets of the Corporation to a person shall not
be deemed to be a liquidation, dissolution or winding up of the Corporation for
purposes of this Section 3.

                  4. VOTING.

                  (a) Each issued and outstanding share of Series A Preferred
Stock shall be entitled to the number of votes equal to the number of shares of
Common Stock into which each such share of Series A Preferred Stock is
convertible (as adjusted from time to time pursuant to Section 6 hereof), at
each meeting of stockholders of the Corporation (or pursuant to any action by
written consent) with respect to any and all matters presented to the
stockholders of the Corporation for their action or consideration. Except as
provided by law, by the provisions of Sections 4(b) and 4(c) below or by the
provisions establishing any other series of Preferred Stock, holders of Series A
Preferred Stock shall vote together with the holders of Common Stock as a single
class.

                  (b) For so long as at least 9,000 shares of the Series A
Preferred Stock remain outstanding, the holders of Series A Preferred Stock
shall have the exclusive right, voting separately as a class, to elect one
director (herein referred to as the "Series A Director"). A Series A Director
shall be elected by the affirmative vote of the holders of record of a majority
of the outstanding shares of Series A Preferred Stock either at meetings of
stockholders at which directors are elected or a special meeting of holders of
Series A Preferred Stock. A Series A Director so elected shall serve for a term
of one year and until his successor is elected and qualified. Any vacancy in the
position of a Series A Director may be filled only by the holders of the Series
A Preferred Stock. A Series A Director may, during his or her term of office, be
removed at any time, with or without cause, by and only by the affirmative vote,
at a special meeting of holders of Series A Preferred Stock called for such
purpose, or the written consent, of the holders of record of a majority of the
outstanding shares of Series A Preferred Stock. Any vacancy created by such
removal may also be filled at such meeting or by such consent.

                  (c) In addition to any other rights provided by law, the
Corporation shall not, without first obtaining the affirmative vote or written
consent of the holders of a majority of the outstanding shares of Series A
Preferred Stock, authorize any additional shares of Series A Preferred Stock or
amend, alter or repeal the preferences, special rights or other powers of the
Series A Preferred Stock so as to affect adversely the Series A Preferred Stock.
For purposes of this Section 4(c), the authorization or issuance of any series
of Senior Preferred Stock shall be deemed to affect materially and adversely the
Series A Preferred Stock.

                  5. OPTIONAL CONVERSION. Each share of Series A Preferred Stock
may be converted at any time, at the option of the holder thereof, into the
number of fully-paid and nonassessable shares of Common Stock obtained by
dividing the Stated Value by the Conversion Price then in effect (the
"Conversion Rate"), PROVIDED, HOWEVER, that on any redemption of any Series A
Preferred Stock or any liquidation of the Corporation, the right of conversion
shall terminate at the close of business on the full business day next preceding
the date fixed for such redemption or for the payment of any amounts
distributable on liquidation to the holders of Series A Preferred Stock.

                  (a) The initial conversion price, subject to adjustment as
provided herein, is equal to $28.00 (the "Conversion Price"). The initial
Conversion Rate for the Series A Preferred Stock shall be 357.142857 shares of
Common Stock for each one share of Series A Preferred Stock surrendered for
conversion. The applicable Conversion Rate and Conversion Price from time to
time in effect is subject to adjustment as hereinafter provided.

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                  (b) The Corporation shall not issue fractions of shares of
Common Stock upon conversion of Series A Preferred Stock or scrip in lieu
thereof. If any fraction of a share of Common Stock would, except for the
provisions of this Section 5(b), be issuable upon conversion of any Series A
Preferred Stock, the Corporation shall in lieu thereof pay to the person
entitled thereto an amount in cash equal to the current value of such fraction,
calculated to the nearest one-hundredth (1/100) of a share, to be computed (i)
if the Common Stock is listed on any national securities exchange, on the basis
of the last sales price of the Common Stock on such exchange (or the quoted
closing bid price if there shall have been no sales) on the date of conversion,
or (ii) if the Common Stock shall not be listed, on the basis of the mean
between the closing bid and asked prices for the Common Stock on the date of
conversion as reported by NASDAQ, or its successor, and if there are not such
closing bid and asked prices, on the basis of the fair market value per share as
determined by the Board of Directors.

                  (c) Whenever the Conversion Rate and Conversion Price shall be
adjusted as provided in Section 6 hereof, the Corporation shall forthwith file
at each office designated for the conversion of Series A Preferred Stock, a
statement, signed by the Chairman of the Board, the President, any Vice
President or Treasurer of the Corporation, showing in reasonable detail the
facts requiring such adjustment and the Conversion Rate that will be effective
after such adjustment. The Corporation shall also cause a notice setting forth
any such adjustments to be sent by mail, first class, postage prepaid, to each
record holder of Series A Preferred Stock at his or its address appearing on the
stock register. If such notice relates to an adjustment resulting from an event
referred to in Section 6(d) hereof, such notice shall be included as part of the
notice required to be mailed and published under the provisions of Section 6(d)
hereof.

                  (d) In order to exercise the conversion privilege, the holder
of any Series A Preferred Stock to be converted shall surrender his or its
certificate or certificates therefore to the principal office of the transfer
agent for the Series A Preferred Stock (or if no transfer agent be at the time
appointed, then the Corporation at its principal office), and shall give written
notice to the Corporation at such office that the holder elects to convert the
Series A Preferred Stock represented by such certificates, or any number
thereof. Such notice shall also state the name or names (with address) in which
the certificate or certificates for shares of Common Stock which shall be
issuable on such conversion shall be issued, subject to any restrictions on
transfer relating to shares of the Series A Preferred Stock or shares of Common
Stock upon conversion thereof. If so required by the Corporation, certificates
surrendered for conversion shall be endorsed or accompanied by written
instrument or instruments of transfer, in form satisfactory to the Corporation,
duly authorized in writing. The date of receipt by the transfer agent (or by the
Corporation if the Corporation serves as its own transfer agent) of the
certificates and notice shall be the conversion date. As soon as practicable
after receipt of such notice and the surrender of the certificate or
certificates for Series A Preferred Stock as aforesaid, the Corporation shall
cause to be issued and delivered at such office to such holder, or on his or its
written order, a certificate or certificates for the number of full shares of
Common Stock issuable on such conversion in accordance with the provisions
hereof, cash as provided in Section 5(b) hereof in respect of any fraction of a
share of Common Stock otherwise issuable upon such conversion and, if less than
all shares of Series A Preferred Stock represented by the certificate or
certificates so surrendered are being converted, a residual certificate or
certificates representing the shares of Series A Preferred Stock not converted.

                  (e) The Corporation shall at all times when the Series A
Preferred Stock shall be outstanding reserve and keep available out of its
authorized but unissued stock, for the purposes of effecting the conversion of
the Series A Preferred Stock, such number of its duly authorized shares of
Common Stock as shall from time to time be sufficient to effect the conversion
of all outstanding Series A Preferred Stock. Before taking any action that would
cause an adjustment reducing the Conversion Price below the then par value of
the shares of Common Stock issuable upon conversion of the Series A Preferred
Stock, the Corporation will take any corporate action that may, in the opinion
of its counsel, be necessary in order that the Corporation may validly and
legally issue fully-paid and nonassessable shares of such Common Stock at such
adjusted conversion price.

                  (f) All shares of Series A Preferred Stock which shall have
been surrendered for conversion as herein provided shall no longer be deemed to
be outstanding and all rights with respect to such shares, including the rights,
if any, to receive notices and to vote, shall forthwith cease and terminate
except only the right of the holder thereof to receive shares of Common Stock in
exchange therefor and payment of any declared and unpaid dividends thereon. Any
shares of Series A Preferred Stock so converted shall be retired and canceled
and shall not be reissued, and the Corporation may from time to time take such
appropriate action as may be necessary to reduce the authorized Series A
Preferred Stock accordingly.


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                  6. CONVERSION PRICE ADJUSTMENTS.

                  (a) In case the Corporation shall at any time (i) subdivide
the outstanding Common Stock or (ii) issue a dividend on its outstanding Common
Stock payable in shares of Common Stock, the number of shares of Common Stock
issuable upon conversion of the Series A Preferred Stock shall be
proportionately increased by the same ratio as the subdivision or dividend (with
appropriate adjustments to the Conversion Price in effect immediately prior to
such subdivision or dividend). In case the Corporation shall at any time combine
its outstanding Common Stock, the number of shares issuable upon conversion of
the Series A Preferred Stock immediately prior to such combination shall be
proportionately decreased by the same ratio as the combination (with appropriate
adjustments to the Conversion Price in effect immediately prior to such
combination).

                  (b) In the event the Corporation shall declare a dividend upon
the Common Stock (other than a dividend payable in Common Stock) payable
otherwise than out of earnings or earned surplus, determined in accordance with
generally accepted accounting principles, including the making of appropriate
deductions for minority interests, if any, in subsidiaries (herein referred to
as "Liquidating Dividends"), then, as soon as possible after the conversion of
any shares of Series A Preferred Stock, the Corporation shall pay to the person
converting such shares of Series A Preferred Stock an amount equal to the
aggregate value of all Liquidating Dividends that such person would have
received had the person converted such shares of Series A Preferred Stock
immediately prior to the record date for such Liquidating Dividend. For the
purposes of this Section 6(b), a dividend other than in cash shall be considered
payable out of earnings or earned surplus only to the extent that such earnings
or earned surplus are charged an amount equal to the fair value of such dividend
as determined in good faith by the Board of Directors.

                  (c) If any capital reorganization or reclassification of the
capital stock of the Corporation, or consolidation or merger of the Corporation
with another corporation in which the holders of Common Stock and Series A
Preferred Stock prior to such consolidation or merger hold at least 51% of the
combined voting power of the surviving person in such merger or consolidation
immediately following its effective date, shall be effected in such a way that
holders of Common Stock shall be entitled to receive stock, securities, cash or
other property with respect to or in exchange for Common Stock, then, as a
condition of such reorganization, reclassification, consolidation or merger,
lawful and adequate provision shall be made whereby the holders of the Series A
Preferred Stock shall have the right to acquire and receive upon conversion of
the Series A Preferred Stock such shares of stock, securities, cash or other
property issuable or payable (as part of such reorganization, reclassification,
consolidation or merger) with respect to or in exchange for such number of
outstanding shares of Common Stock as would have been received upon conversion
of the Series A Preferred Stock at the Conversion Price then in effect. Any
other consolidation or merger of the Corporation with another corporation or the
sale of all or substantially all of its assets to another corporation shall be
effected in such a way that the holders of the Series A Preferred Stock shall be
entitled to receive, in exchange for their shares of Series A Preferred Stock,
the stock, securities, cash or other property payable to holders of Common Stock
as if the holders of Series A Preferred Stock had converted the Series A
Preferred Stock in to Common Stock immediately prior to the effective date of
such consolidation, merger or sale. The Corporation will not effect any such
consolidation, merger or sale, unless prior to the consummation thereof the
successor corporation (if other than the Corporation) resulting from such
consolidation or merger or the corporation purchasing such assets shall assume
by written instrument mailed or delivered to the holders of the Series A
Preferred Stock at the last address of each such holder appearing on the books
of the Corporation, the obligation to deliver to each such holder such shares of
stock, securities or assets as, in accordance with the foregoing provisions,
such holder may be entitled to receive.

                  (d) In the event that:

                  (1) the Corporation shall offer for subscription pro rata to
         the holders of its Common Stock any additional shares of stock of any
         class or other rights, or

                  (2) there shall be any capital reorganization or
         reclassification of the capital stock of the Corporation, including any
         subdivision or combination of its outstanding shares of Common Stock,
         or consolidation or merger of the Corporation with, or sale of all or
         substantially all of its assets to, another corporation, or

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                  (3) there shall be a voluntary or involuntary dissolution,
         liquidation or winding up of the Corporation;

then, in connection with such event, the Corporation shall give to the holders
of the Series A Preferred Stock:

                  (i) at least twenty (20) days prior written notice of the date
                  on which the books of the Corporation shall close or a record
                  shall be taken for such dividend, distribution or subscription
                  rights or for determining rights to vote in respect of any
                  such reorganization, reclassification, consolidation, merger,
                  sale, dissolution, liquidation or winding up; and

                  (ii) in the case of any such reorganization, reclassification,
                  consolidation, merger, sale, dissolution, liquidation or
                  winding up, at least twenty (20) days prior written notice of
                  the date when the same shall take place. Such notice in
                  accordance with the foregoing clause (i) shall also specify,
                  in the case of any such dividend, distribution or subscription
                  rights, the date on which the holders of Common Stock shall be
                  entitled thereto, and such notice in accordance with the
                  foregoing clause (ii) shall also specify the date on which the
                  holders of Common Stock shall be entitled to exchange their
                  Common Stock for securities or other property deliverable upon
                  such reorganization, reclassification consolidation, merger,
                  sale, dissolution, liquidation or winding up, as the case may
                  be. Each such written notice shall be given by first class
                  mail, postage prepaid, addressed to the holders of the Series
                  A Preferred Stock at the address of each such holder as shown
                  on the books of the Corporation.

                  (e) If at any time or from time to time on or after the date
on which shares of Series A Preferred Stock are initially issued, the
Corporation shall grant, issue or sell any options, convertible securities or
rights to purchase property (the "Purchase Rights") pro rata to the record
holders of any class of Common Stock and such Purchase Rights are not issued to
the holders of Series A Preferred Stock and such grants, issuances or sales do
not result in an adjustment of the Conversion Price under this Section 6, then
each holder of Series A Preferred Stock shall be entitled to acquire (within
thirty (30) days after the later to occur of the initial exercise date of such
Purchase Rights or receipt by such holder of the notice concerning Purchase
Rights to which such holder shall be entitled under Section 6(d)) and upon the
terms applicable to such Purchase Rights either:

                  (i) the aggregate Purchase Rights which such holder could have
                  acquired if it had held the number of shares of Common Stock
                  acquirable upon conversion of the Series A Preferred Stock
                  immediately before the grant, issuance or sale of such
                  Purchase Rights; provided that if any Purchase Rights were
                  distributed to holders of Common Stock without the payment of
                  additional consideration by such holders, corresponding
                  Purchase Rights shall be distributed to the holders of the
                  Series A Preferred Stock as soon as possible and it shall not
                  be necessary for the holder of the Series A Preferred Stock
                  specifically to request delivery of such rights; or

                  (ii) in the event that any such Purchase Rights shall have
                  expired or shall expire prior to the end of said thirty (30)
                  day period, the right to acquire the number of shares of
                  Common Stock or the amount of property which such holder could
                  have acquired upon such exercise at the time or times at which
                  the Corporation granted, issued or sold such expired Purchase
                  Rights on the terms of the Purchase Rights so granted.

                  7. REDEMPTION.

                  (a) The Corporation, at its option, may redeem (to the extent
that such redemption shall not violate any applicable provisions of the General
Corporation Law of the State of Delaware) all, but not less than all, of the
shares of Series A Preferred Stock at a price equal to the then Series A
Liquidation Value (subject to adjustment in the event of any stock dividend,
stock split, stock distribution or combination with respect to such shares)
(such price is hereinafter referred to as the "Redemption Price"), at any time
after December 15, 2000 (any such date of redemption is hereafter referred to as
an "Redemption Date"), PROVIDED that no shares of Series A


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Preferred Stock may be so called for redemption unless the average of the
closing prices per share of Common Stock for any twenty (20) consecutive trading
days ending within twenty (20) business days of the date on which notice of such
redemption is given to the holders of the Series A Preferred Stock, shall have
been at least $35.00 (subject to appropriate adjustment in the event of any
stock dividend, stock split, stock distribution or combination). For purposes of
the foregoing calculation, "closing price" shall mean for any given date: (i) if
the Common Stock is listed on any national securities exchange or quoted on
Nasdaq, on the basis of the last sales price of the Common Stock on such
exchange or Nasdaq (or the quoted closing bid price if there shall have
been no sales) on such date, or (ii) if no last sales prices are then being
quoted for the Common Stock, on the basis of the mean between the closing bid
and asked prices for the Common Stock on such date as reported by Nasdaq, or its
successor, or (iii) if there are no such closing bid and asked prices, on the
basis of the fair market value per share as determined by the Board of Directors
of the Corporation.

                  (b) At least thirty (30) days prior to each Redemption Date,
written notice shall be mailed, postage prepaid, to each holder of record of
Series A Preferred Stock to be redeemed, at his or its post office address last
shown on the records of the Corporation, notifying such holder of the number of
shares so to be redeemed, specifying the Redemption Date and the date on which
such holder's conversion rights (pursuant to Section 5 hereof) as to such shares
terminate and calling upon such holder to surrender to the Corporation, in the
manner and at the place designated, his or its certificate or certificates
representing the shares to be redeemed (such notice is hereinafter referred to
as the "Redemption Notice"). On or prior to the Redemption Date, each holder of
Series A Preferred Stock to be redeemed shall surrender his or its certificate
or certificates representing such shares to the Corporation, in the manner and
at the place designated in the Redemption Notice, and thereupon the Redemption
Price of such shares shall be payable to the order of the person whose name
appears on such certificate or certificates as the owner thereof and each
surrendered certificate shall be canceled. From and after the Redemption Date,
unless there shall have been a default in payment of the Redemption Price, all
rights of the holders of the Series A Preferred Stock designated for redemption
in the Redemption Notice as holders of Series A Preferred Stock of the
Corporation (except the right to receive the Redemption Price without interest
upon surrender of their certificate or certificates) shall cease with respect to
such shares, and such shares shall not thereafter be transferred on the books of
the Corporation or be deemed to be outstanding for any purpose whatsoever.

                  (c) Except as provided in paragraph (a) above, the Corporation
shall have no right to redeem the shares of Series A Preferred Stock other than
with the consent of the holders of 66 2/3% of the then outstanding shares of
Series A Preferred Stock. Any shares of Series A Preferred Stock so redeemed
shall be permanently retired, shall no longer be deemed outstanding and shall
not under any circumstances be reissued, and the Corporation may from time to
time take such appropriate corporate action as may be necessary to reduce the
authorized Series A Preferred Stock accordingly. Nothing herein contained shall
prevent or restrict the purchase by the Corporation, from time to time either at
public or private sale, of the whole or any part of the Series A Preferred Stock
at such price or prices as the Corporation may determine, subject to the
provisions of applicable law.

                  IN WITNESS WHEREOF, Transkaryotic Therapies, Inc. has caused
this Certificate of Designation, Number, Voting Powers, Preferences and Rights
of Series A Convertible Preferred Stock to be duly executed by its VP of Finance
and CFO this 9th day of June, 2000.

                                                  TRANSKARYOTIC THERAPIES, INC.



                                                  By /s/ DANIEL E. GEFFKEN
                                                    ---------------------------
                                                  [Name:] Daniel E. Geffken
                                                  [Title:] VP of Finance and CFO

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