<PAGE>

                                                                     EXHIBIT 4.3

                              SECOND AMENDMENT TO
                               CREDIT AGREEMENT

                                 BY AND AMONG

                      ENTERPRISE PRODUCTS OPERATING L.P.,

                              DEN NORSKE BANK ASA

                                      AND

                BANK OF TOKYO-MITSUBISHI, LTD., HOUSTON AGENCY,
                               AS CO-ARRANGERS,

                           THE BANK OF NOVA SCOTIA,
                  AS CO-ARRANGER AND AS DOCUMENTATION AGENT,

                           THE CHASE MANHATTAN BANK,
                         AS CO-ARRANGER AND AS AGENT,

                                      AND

                               THE SEVERAL BANKS
                       FROM TIME TO TIME PARTIES HERETO


                       EFFECTIVE AS OF JANUARY 24, 2000



AGGREGATE $200,000,000
REVOLVING CREDIT FACILITY
<PAGE>

                              SECOND AMENDMENT TO
                               CREDIT AGREEMENT


     This SECOND AMENDMENT TO CREDIT AGREEMENT (this "Second Amendment")
executed effective as of the 24th day of January, 2000 (the "Effective Date"),
is by and among ENTERPRISE PRODUCTS OPERATING L.P., a limited partnership formed
under the laws of the State of Delaware (the "Company"); each of the banks that
is a signatory hereto or which becomes a signatory hereto and to the hereinafter
described Credit Agreement (individually, together with its successors and
assigns, a "Bank" and, collectively, the "Banks"); THE CHASE MANHATTAN BANK, DEN
NORSKE BANK ASA, THE BANK OF NOVA SCOTIA and BANK OF TOKYO-MITSUBISHI, LTD.,
HOUSTON AGENCY, as Co-Arrangers; THE BANK OF NOVA SCOTIA, as Documentation
Agent; and THE CHASE MANHATTAN BANK ("Chase"), as Agent for the Banks (in such
capacity, together with its successors in such capacity, the "Agent").

                               R E C I T A L S:

     WHEREAS, the Company, the Agent, the Documentation Agent and the Banks are
parties to that certain Credit Agreement dated as of July 27, 1998, as Amended
and Restated as of September 30, 1998 (said Credit Agreement, as amended by
First Amendment to Credit Agreement dated as of July 28, 1999, the "Credit
Agreement"), pursuant to which the Banks agreed to make loans to and extensions
of credit on behalf of the Company; and

     WHEREAS, the Company and the Banks desire to amend the Credit Agreement in
the particulars hereinafter provided;

     NOW, THEREFORE, in consideration of the premises and the mutual covenants
herein contained, the parties hereto agree as follows:


                            SECTION 1.  DEFINITIONS

      1.1 Terms Defined Above.  As used in this Second Amendment, each of the
terms "Bank", "Banks", "Company", "Credit Agreement", "Effective Date" and
"Second Amendment" shall have the meaning assigned to such term hereinabove.

      1.2 Terms Defined in Credit Agreement.  Each term defined in the Credit
Agreement and used herein without definition shall have the meaning assigned to
such term in the Credit Agreement, unless expressly provided to the contrary.

      1.3 Other Definitional Provisions.

          (a) The words "hereby", "herein", "hereinafter", "hereof", "hereto"
     and "hereunder" when used in this Second

                                    Page 1
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     Amendment shall refer to this Second Amendment as a whole and not to any
     particular Article, Section, subsection or provision of this Second
     Amendment.

          (b) Section, subsection and Exhibit references herein are to such
     Sections, subsections and Exhibits to this Second Amendment unless
     otherwise specified.


                  SECTION 2.  AMENDMENTS TO CREDIT AGREEMENT

     The Company, the Agent and the Banks agree that the Credit Agreement is
hereby amended, effective as of the Effective Date, in the following
particulars.

     2.1 Amendments and Supplements to Definitions.

         (a) The term "Agreement", which is defined in subsection 1.1 of the
     Credit Agreement, is hereby amended to mean the Credit Agreement, as
     amended by this Second Amendment, and as the same may from time to time be
     further amended, supplemented or modified.

         (b) Subsection 1.1 of the Credit Agreement is hereby further amended
     and supplemented by adding the following new definition where
     alphabetically appropriate, which reads in its entirety as follows:

             "Second Amendment": the Second Amendment to Credit Agreement
          dated as of January ___, 2000, by and among the Company, the Agent,
          the Documentation Agent and the Banks.

     2.2 Amendments to Section 7.

         (a) Subsection 7.1 of the Credit Agreement is hereby amended as
     follows:

             (i)  Clause (j) of subsection 7.1 is hereby amended in its
          entirety to read as follows:

                 "(j)  Debt arising out of or pursuant to the issuance by the
               Company of senior unsecured notes if, at the time of issuance
               thereof, the Company has a rating no lower than BBB- from
               Standard & Poor's or Baa3 from Moody's, and no Default or Event
               of Default has occurred and is continuing or would result
               therefrom, and the Net Cash Proceeds of which shall be used by
               the Company to make the mandatory prepayment required by
               subsection 4.1(a); and"

             (ii) Subsection 7.1 is hereby further amended by adding thereto a
          new clause, to be clause (k), which reads in its entirety as follows:

                                    Page 2
<PAGE>

                 "(k)  Guarantee Obligations of a series of Taxable
               Industrial Development Revenue Bonds issued by the Mississippi
               Business Finance Corporation in connection with the Pascagoula
               gas processing plant."

         (b) Subsection 7.6 of the Credit Agreement is hereby amended by adding
     thereto two (2) new clauses, to be clauses (n) and (o), which read in their
     entirety as follows:

             "(n) Capital contributions or other Investments to consummate
          the acquisition of a 33-1/3% interest in Destin Pipeline Company,
          L.L.C. from Southern Natural Gas Company.

              (o) Capital contributions or other Investments in connection with
          the construction of a proposed 270-mile (approximate) liquids pipeline
          from Breaux Bridge, Louisiana to Mt. Belvieu, Texas."

                             SECTION 3. CONDITIONS

     The enforceability of this Second Amendment against the Agent and the Banks
is subject to the satisfaction of the following conditions precedent:

     3.1 Loan Documents.  The Agent shall have received multiple original
counterparts, as requested by the Agent, of this Second Amendment executed and
delivered by a duly authorized officer of the Company, the Agent, the
Documentation Agent, and each Bank and otherwise in form and substance
satisfactory to the Agent.

     3.2 Representations and Warranties.  Except as affected by the
transactions contemplated in the Credit Agreement and this Second Amendment,
each of the representations and warranties made by the Company in or pursuant to
the Loan Documents, including the Credit Agreement, shall be true and correct in
all material respects as of the Effective Date, as if made on and as of such
date.

     3.3 No Default.  No Default or Event of Default shall have occurred and be
continuing as of the Effective Date.

     3.4 No Change.  No event shall have occurred since September 30, 1999,
which, in the reasonable opinion of the Banks, could have a material adverse
effect on the condition (financial or otherwise), business, operations or
prospects of the Company.

     3.5 Other Instruments or Documents.  The Agent or any Bank or counsel to
the Agent shall receive such other instruments or documents as they may
reasonably request.

     3.6 Events. The following events shall have occurred or shall occur
contemporaneously with the execution of this Second Amendment:

                                    Page 3
<PAGE>

         (a) execution of the First Amendment to Credit Agreement dated as of
     January ___, 2000, amending that certain Credit Agreement dated July 28,
     1999, by and among the Company, the Agent and the several banks party
     thereto;

         (b) execution of the Third Amendment to the EPCO Credit Agreement; and

         (c) receipt by the applicable Banks of the amendment fee pertaining to
     this Second Amendment.

                           SECTION 4. MISCELLANEOUS

     4.1 Adoption, Ratification and Confirmation of Credit Agreement.  Each of
the Company, the Agent and the Banks does hereby adopt, ratify and confirm the
Credit Agreement, as amended hereby, and acknowledges and agrees that the Credit
Agreement, as amended hereby, is and remains in full force and effect.

     4.2 Successors and Assigns.  This Second Amendment shall be binding upon
and inure to the benefit of the parties hereto and their respective successors
and assigns permitted pursuant to the Credit Agreement.

     4.3 Counterparts.  This Second Amendment may be executed by one or more of
the parties hereto in any number of separate counterparts, and all of such
counterparts taken together shall be deemed to constitute one and the same
instrument and shall be enforceable as of the Effective Date upon the execution
of one or more counterparts hereof by the Company, the Agent, the Documentation
Agent and the Banks. In this regard, each of the parties hereto acknowledges
that a counterpart of this Second Amendment containing a set of counterpart
execution pages reflecting the execution of each party hereto shall be
sufficient to reflect the execution of this Second Amendment by each necessary
party hereto and shall constitute one instrument.

     4.4 Number and Gender.  Whenever the context requires, reference herein
made to the single number shall be understood to include the plural; and
likewise, the plural shall be understood to include the singular.  Words
denoting sex shall be construed to include the masculine, feminine and neuter,
when such construction is appropriate; and specific enumeration shall not
exclude the general but shall be construed as cumulative.  Definitions of terms
defined in the singular or plural shall be equally applicable to the plural or
singular, as the case may be, unless otherwise indicated.

     4.5 Entire Agreement.  This Second Amendment constitutes the entire
agreement among the parties hereto with respect to the subject hereof.  All
prior understandings, statements and agreements, whether written or oral,
relating to the subject hereof are superseded by this Second Amendment.

     4.6 Invalidity.  In the event that any one or more of the provisions
contained in this Second Amendment shall for any reason be held invalid, illegal
or unenforceable in any respect, such invalidity, illegality or unenforceability
shall not affect any other provision of this Second Amendment.

                                    Page 4
<PAGE>

     4.7 Titles of Articles, Sections and Subsections.  All titles or headings
to Articles, Sections, subsections or other divisions of this Second Amendment
or the exhibits hereto, if any, are only for the convenience of the parties and
shall not be construed to have any effect or meaning with respect to the other
content of such Articles, Sections, subsections, other divisions or exhibits,
such other content being controlling as the agreement among the parties hereto.

     4.8 GOVERNING LAW.  THIS SECOND AMENDMENT SHALL BE DEEMED TO BE A CONTRACT
MADE UNDER AND SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE
INTERNAL LAWS OF THE STATE OF NEW YORK.

     THIS SECOND AMENDMENT, THE CREDIT AGREEMENT, AS AMENDED HEREBY, THE NOTES,
     AND THE OTHER LOAN DOCUMENTS REPRESENT THE FINAL AGREEMENT BETWEEN THE
     PARTIES AND MAY NOT BE CONTRADICTED BY EVIDENCE OF PRIOR, CONTEMPORANEOUS,
     OR SUBSEQUENT ORAL AGREEMENTS OF THE PARTIES.

     THERE ARE NO UNWRITTEN OR ORAL AGREEMENTS BETWEEN THE PARTIES.



                        [Signatures begin on next page]





                                    Page 5
<PAGE>

     IN WITNESS WHEREOF, the parties hereto have caused this Second Amendment to
 be duly executed and delivered by their proper and duly authorized officers as
 of the Effective Date.

                              COMPANY:

                              ENTERPRISE PRODUCTS OPERATING L.P.


                              By: Enterprise Products GP, LLC, General Partner

                              By: /s/ GARY L. MILLER
                                  --------------------------------------------
                                      Executive Vice President and Chief
                                      Financial Officer


                              BANKS AND AGENTS:

                              THE CHASE MANHATTAN BANK, Individually as
                              a Bank and as Agent

                              By: /s/ PETER LING
                                  --------------------------------------------
                                      Vice President


                              THE BANK OF NOVA SCOTIA, Individually as a
                              Bank and as Documentation Agent

                              By: /s/ F. C. H. ASHBY
                                  --------------------------------------------
                                      Senior Manager Loan Operations


                              ABN AMRO BANK, NV

                              By: /s/ GORDON CHANG
                                  --------------------------------------------
                                      Vice President

                              By: /s/ KEVIN P. COSTELLE
                                  --------------------------------------------
                                      Vice President


                      [Second Amendment Signature Page 1]
<PAGE>

                              BANK ONE, NA (formerly known as The First
                              National Bank of Chicago)

                              By: /s/ KENNETH J. FATUR
                                  --------------------------------------------
                                      Vice President


                              BANK OF TOKYO-MITSUBISHI, LTD.,
                              HOUSTON AGENCY

                              By: /s/ MICHAEL G. MEISS
                                  --------------------------------------------
                                      Vice President


                              CIBC INC.

                              By: /s/ M. BETH MILLEH
                                  --------------------------------------------
                                      Authorized Signatory


                              CREDIT LYONNAIS NEW YORK BRANCH

                              By: /s/ PHILIPPE SOUSTRA
                                  --------------------------------------------
                                      Senior Vice President


                              DEN NORSKE BANK ASA

                              By: /s/ J. MORTEN KREUTZ
                                  --------------------------------------------
                                      First Vice President


                              FIRST UNION NATIONAL BANK

                              By: /s/ ROBERT R. WETTEROFF
                                  --------------------------------------------
                                      Senior Vice President


                              GUARANTY FEDERAL BANK, F.S.B.

                              By: /s/ JIM R. HAMILTON
                                  --------------------------------------------
                                      Vice President


                      [Second Amendment Signature Page 2]
<PAGE>

                              ING (U.S.) CAPITAL CORPORATION

                              By: /s/
                                  --------------------------------------------
                              Name:
                                    ------------------------------------------
                              Title:
                                    ------------------------------------------


                              GENERAL ELECTRIC CAPITAL CORPORATION

                              By: /s/ WILLIAM S. RICHARDSON
                                  --------------------------------------------
                                    Duly Authorized Signatory



                              MEESPIERSON CAPITAL CORP.

                              By:
                                  --------------------------------------------
                              Name:
                                    ------------------------------------------
                              Title:
                                    ------------------------------------------

                              SOCIETE GENERALE, SOUTHWEST AGENCY

                              By: /s/ PAUL E. CORNELL
                                  --------------------------------------------
                                      Managing Director


                              THE FUJI BANK, LIMITED
                              NEW YORK BRANCH

                              By: /s/ JACQUES AZAGURY
                                  --------------------------------------------
                                      Senior Vice President and Manager






                      [Second Amendment Signature Page 3]