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                     U.S. SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                     FORM 4

                  STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

    Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934,
       Section 17(a) of the Public Utility Holding Company Act of 1935 or
               Section 30(f) of the Investment Company Act of 1940

[_]  Check  this  box if no  longer  subject  to  Section  16.  Form 4 or Form 5
     obligations may continue. See Instruction 1(b).

(Print or Type Responses)
________________________________________________________________________________
1.   Name and Address of Reporting Person*

 MacKinnon                         A.M. "Don"
- --------------------------------------------------------------------------------
   (Last)                           (First)             (Middle)

c/o Enzon, Inc. 20 Kingsbridge Road  
- --------------------------------------------------------------------------------
                                    (Street)

Piscataway                          NJ                   08854
- --------------------------------------------------------------------------------
   (City)                           (State)              (Zip)


________________________________________________________________________________
2.   Issuer Name and Ticker or Trading Symbol

Enzon, Inc. (ENZN)

________________________________________________________________________________
3.   IRS Identification Number of Reporting Person, if an entity (Voluntary)



________________________________________________________________________________
4.   Statement for Month/Year

March 1999

________________________________________________________________________________
5.   If Amendment, Date of Original (Month/Year)


________________________________________________________________________________
6.   Relationship of Reporting Person(s) to Issuer
     (Check all applicable)

     [X]  Director                             [_]  10% Owner
     [_]  Officer (give title below)           [_]  Other (specify below)
________________________________________________________________________________
7.   Individual or Joint/Group Filing (Check Applicable Line)

     [X]  Form filed by One Reporting Person
     [_]  Form filed by More than One Reporting Person
________________________________________________________________________________


================================================================================
           Table I -- Non-Derivative Securities Acquired, Disposed of,
                             or Beneficially Owned
================================================================================


                                                                                                                6.
                                                                 4.                              5.             Owner-
                                                                 Securities Acquired (A) or      Amount of      ship
                                                    3.           Disposed of (D)                 Securities     Form:     7.
                                                    Transaction  (Instr. 3, 4 and 5)             Beneficially   Direct    Nature of
                                      2.            Code         ------------------------------- Owned at End   (D) or    Indirect
1.                                    Transaction   (Instr. 8)                   (A)             of Month       Indirect  Beneficial
Title of Security                     Date          ------------     Amount      or     Price    (Instr. 3      (I)       Ownership
(Instr. 3)                            (mm/dd/yy)     Code     V                  (D)             and 4)         (Instr.4) (Instr. 4)
- ------------------------------------------------------------------------------------------------------------------------------------
                                                                                               

Common Stock                          3/16/99        M               20,000      A      $2.0625  
- ------------------------------------------------------------------------------------------------------------------------------------
Common Stock                          3/16/99        M               40,000      A      $2.9375  
- ------------------------------------------------------------------------------------------------------------------------------------
Common Stock                          3/16/99        M               40,000      A      $5.375 
- ------------------------------------------------------------------------------------------------------------------------------------
Common Stock                          3/16/99       G(1)             50,000      D               67,816         D  
- ------------------------------------------------------------------------------------------------------------------------------------
                                                                                                 61,800         I         by wife
- ------------------------------------------------------------------------------------------------------------------------------------

- ------------------------------------------------------------------------------------------------------------------------------------

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


FORM 4 (continued) Table II -- Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities) ================================================================================ 10. 9. Owner- Number ship of Form 2. deriv- of Conver- 5. 7. ative Deriv- 11. sion Number of Title and Amount Secur- ative Nature or Derivative 6. of Underlying 8. ities Secur- of Exer- 4. Securities Date Securities Price Bene- ity: In- cise 3. Trans- Acquired (A) Exercisable and (Instr. 3 and 4) of ficially Direct direct Price Trans- action or Disposed Expiration Date ---------------- Deriv- Owned (D) or Bene- 1. of action Code of(D) (Month/Day/Year) Amount ative at End In- ficial Title of Deriv- Date (Instr. (Instr. 3, ---------------- or Secur- of direct Owner- Derivative ative (Month/ 8) 4 and 5) Date Expira- Number ity Month (I) ship Security Secur- Day/ ------ ------------ Exer- tion of (Instr. (Instr. (Instr. (Instr. (Instr. 3) ity Year) Code V (A) (D) cisable Date Title Shares 5) 4) 4) 4) - ------------------------------------------------------------------------------------------------------------------------------------ Stock Option Common (right to buy)(2) $2.0625 3/16/99 M 20,000 8/21/95 2/21/05 Stock 20,000 D - ------------------------------------------------------------------------------------------------------------------------------------ Stock Option Common (right to buy)(2) $2.9375 3/16/99 M 40,000 (3) 1/2/07 Stock 20,000 D - ------------------------------------------------------------------------------------------------------------------------------------ Stock Option Common (right to buy)(2) $5.375 3/16/99 M 40,000 (4) 12/31/03 Stock 40,000 D - ------------------------------------------------------------------------------------------------------------------------------------ - ------------------------------------------------------------------------------------------------------------------------------------ - ------------------------------------------------------------------------------------------------------------------------------------ ==================================================================================================================================== Explanation of Responses: (1) The reporting person gifted an aggregate of 50,000 shares of the registrant's common stock to his wife. (2) Options granted under the registrant's non-qualified stock option plan and qualified under Rule 16b-3. (3) Options vested in two tranches of 20,000 shares each on January 1, 1998 and January 1, 1999. (4) Options vested in two tranches of 20,000 shares each on December 31, 1994 and December 31, 1995. /s/ A.M. "DON" MACKINNON 4/8/99 - --------------------------------------------- ----------------------- **Signature of Reporting Person Date ** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a). Note: File three copies of this Form, one of which must be manually signed. If space provided is insufficient, see Instruction 6 for procedure. Potential perosns who are to respond to the colleciton of information contained in this form are not required to respond unless the form displays a currently valid OMB Number. Page 2 SEC 1474 (7-97)