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                            CERTIFICATE OF AMENDMENT
                                     TO THE
                      RESTATED CERTIFICATE OF INCORPORATION
                                       OF
                          NORTHERN NATURAL GAS COMPANY


         NORTHERN NATURAL GAS COMPANY, a corporation organized and existing
under and by virtue of the General Corporation Law of the State of Delaware (the
"Corporation"), DOES HEREBY CERTIFY:

         1.       The name of the Corporation is Northern Natural Gas Company.
The date of filing of its Restated Certificate of Incorporation (the "Restated
Certificate of Incorporation") with the Secretary of the State of Delaware was
April 11, 1990. The Restated Certificate of Incorporation was amended by the
filing of (i) a Certificate of Change of Location of Registered Office and
Registered Agent on February 21, 2001, (ii) a Certificate of Amendment on
November 2, 2001, (iii) a Certificate of Designations of the Series A
Preferred Stock on November 8, 2001, (iv) a Certificate of Correction of
Certificate of Designations of the Series A Preferred Stock on November 9,
2001 and (v) a Certificate of Amendment on November 19, 2001.

         2.       This Certificate of Amendment sets forth an amendment to the
Restated Certificate of Incorporation, as amended, which was duly adopted by
the written consent of the directors in accordance with the provisions of
Section 141 and 242 of the Delaware General Corporation Law (the "DGCL") and
by the written consent of the stockholders of the Corporation in accordance
with the provisions of Section 228 and 242 of the DGCL.

         3.       The Restated Certificate of Incorporation, as amended, of
the Corporation is hereby amended by amending the Certificate of Designations
of the Series A Preferred Stock, as corrected, to read in its entirety as
follows:

                            SERIES A PREFERRED STOCK

                  1. DESIGNATION AND AMOUNT; NO FRACTIONAL SHARES. There shall
be a series of Preferred Stock designated as "Series A Preferred Stock" (the
"Series A Preferred Stock") and the authorized number of shares constituting
such series shall be 1,000. The Series A Preferred Stock is issuable in whole
shares only.

                  2. DIVIDENDS. Holders of shares of Series A Preferred Stock
shall be entitled to receive, when, as and if declared by the Board of Directors
or a duly authorized committee thereof out of funds of the Corporation legally
available for payment of dividends, cumulative cash dividends at the rate of 6%
per annum, compounded quarterly, per share on the initial liquidation preference
of $1,500,000 per share. Dividends on the Series A Preferred Stock shall be
payable annually in arrears on January 31 of each year (each an "Annual Dividend
Payment Date") commencing on January 31, 2003; PROVIDED, however, the
Corporation may pay accrued dividends at any time that is not an Annual Dividend
Payment Date at its election (the date of the

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first dividend payment that is not an Annual Dividend Payment Date is referred
to herein as the "Initial Dividend Payment Date"). After the Initial Dividend
Payment Date, dividends on the Series A Preferred Stock shall be payable
quarterly in arrears commencing on the last day of the calendar quarter
immediately following the Initial Dividend Payment Date (each such quarterly
dividend payment date is referred to herein as a "Quarterly Dividend Payment
Date" and, together with the Annual Dividend Payment Date, a "Dividend Payment
Date"). If any date on which dividends would otherwise be payable is a
Saturday, Sunday or a day on which banking institutions in the State of Texas
are authorized or obligated by law or executive order to close, then the
dividends otherwise payable on such date shall instead be payable on the next
succeeding business day. Dividends on shares of the Series A Preferred Stock
shall be fully cumulative and shall accumulate (whether or not declared and
whether or not the Corporation has funds legally available for the payment of
dividends), on a daily basis, without interest, from the previous Dividend
Payment Date, except that the first dividend shall accrue, without interest,
from the date of initial issuance of the Series A Preferred Stock. Dividends
shall be payable, in arrears, to holders of record as they appear in the
records of the Corporation at the close of business on the applicable record
date, which shall be the 15th day of the calendar month in which the
applicable Dividend Payment Date falls or such other date designated by the
Board of Directors of the Corporation for the payment of dividends that is not
more than 30 nor less than 10 days prior to such Dividend Payment Date. Any
dividend payable on the Series A Preferred Stock for any dividend period that
is shorter or longer than a full quarterly or annual period, as the case may
be, shall be computed on the basis of the ratio of the actual number of days
in such partial period to the actual number of days in such full quarterly or
annual period. Additional dividends shall accrue with respect to any dividends
(including dividends payable pursuant to this sentence) not paid by the
Dividend Payment Date on which such dividend accrues; such additional
dividends shall accrue whether or not declared, at a rate of 6% per annum
compounded quarterly, and shall be payable in the same manner and at such
times as provided in this Section 2 with respect to dividends on each
outstanding share of Series A Preferred Stock.

                  No dividends may be declared or paid or set apart for payment
on any stock of the Corporation ranking on a parity with the Series A Preferred
Stock with respect to the payment of dividends unless there shall also be or
have been declared and paid or set apart for payment on the Series A Preferred
Stock dividends for all dividend payment periods of the Series A Preferred Stock
ending on or before the dividend payment date of such parity stock, ratably in
proportion to the respective amounts of dividends (x) accumulated and unpaid or
payable on such parity stock, on the one hand, and (y) accumulated and unpaid
through the dividend payment period or periods of the Series A Preferred Stock
next preceding such dividend payment date, on the other hand.

                  Except as set forth in the preceding paragraph, unless full
cumulative dividends on the Series A Preferred Stock have been paid through the
most recently completed quarterly or annual dividend period, as the case may be,
for the Series A Preferred Stock, no dividends may be paid or declared and set
apart for payment or other distribution made upon the Common Stock or on any
other stock of the Corporation ranking junior to or on a parity with the Series
A Preferred Stock as to dividends, nor may any of the Corporation's common
stock, par value $1.00 per share ("Common Stock"), or any other stock of the
Corporation ranking junior to or on a parity with the Series A Preferred Stock
as to dividends be redeemed, purchased or otherwise acquired for any
consideration (or any payment be made to or available for a sinking fund for the


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redemption of any shares of such stock; provided, however, that any moneys
theretofore deposited in any sinking fund with respect to any such stock in
compliance with the provisions of such sinking fund may thereafter be applied to
the purchase or redemption of such stock in accordance with the terms of such
sinking fund, regardless of whether at the time of such application full
cumulative dividends upon shares of the Series A Preferred Stock outstanding to
the most recent Dividend Payment Date shall have been paid or declared and set
apart for payment) by the Corporation; provided that any such junior or parity
stock or Common Stock may be converted into or exchanged for stock of the
Corporation ranking junior to the Series A Preferred Stock as to dividends.
Notwithstanding anything to the contrary in this paragraph, the Corporation may
at any time pay any dividend or other distribution resulting from the
cancellation by the Corporation of Debt (as defined in Section 5) owed by Enron
Corp. ("Enron") and its Affiliates (as defined in Section 5) to the Corporation
(the "Intercompany Note Receivable") under the zero-balance cash management
program of Enron (the "Cash Management Program"); PROVIDED, that such
cancellation of Debt does not at any time reduce the amount of the Intercompany
Note Receivable to a net amount less than the sum of (a) $240 million and (b) an
amount equal to all dividends (whether or not declared) accrued and accumulated
and unpaid on the shares of Series A Preferred Stock at such time.

                  3. LIQUIDATION PREFERENCE. The shares of Series A Preferred
Stock shall rank, as to rights to distributions upon liquidation, dissolution or
winding up of the Corporation, prior to the shares of Common Stock and any other
stock of the Corporation ranking junior to the Series A Preferred Stock as to
rights upon liquidation, dissolution or winding up of the Corporation, so that
in the event of any liquidation, dissolution or winding up of the Corporation,
whether voluntary or involuntary, the holders of the Series A Preferred Stock
shall be entitled to receive out of the assets of the Corporation legally
available for distribution to its stockholders, an amount equal to $1,500,000
per share, plus an amount equal to all dividends (whether or not declared)
accrued and accumulated and unpaid on the shares of Series A Preferred Stock to
the date of payment, before any distribution of assets is made to holders of
shares of Common Stock or any other class or series of stock of the Corporation
that ranks junior to the Series A Preferred Stock as to rights to distributions
upon liquidation, dissolution or winding up. The holders of the Series A
Preferred Stock shall not be entitled to receive the preferential amounts as
aforesaid until the liquidation preference of any other stock of the Corporation
ranking senior to the Series A Preferred Stock as to rights to distributions
upon liquidation, dissolution or winding up shall have been paid (or a sum set
aside therefor sufficient to provide for payment) in full. After payment of the
full amount of the preferential amounts as aforesaid, the holders of shares of
Series A Preferred Stock will not be entitled to any further participation in
any distribution of assets by the Corporation. If, upon any liquidation,
dissolution or winding up of the Corporation, the assets of the Corporation, or
proceeds thereof, distributable among the holders of shares of Series A
Preferred Stock and any stock ranking on a parity with the Series A Preferred
Stock as to rights to distributions on liquidation, dissolution or winding up of
the Corporation shall be insufficient to pay in full the preferential amounts to
which such stock would be entitled, then such assets, or the proceeds thereof,
shall be distributable among such holders ratably in accordance with the
respective amounts which would be payable on such shares if all amounts payable
thereon were paid in full.

                  For the purposes hereof, (i) any sale of all or substantially
all of the assets of the Corporation, (ii) any consolidation or merger of the
Corporation with any other person or entity,


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(iii) any acquisition of the Corporation by any other person or entity or (iv)
any sale of outstanding shares of capital stock of the Corporation, in each
case pursuant to which the holders of the outstanding capital stock of the
Corporation immediately prior to such event fail to hold capital stock
representing 100% of the voting power of the Corporation or surviving entity
immediately following such event shall, at the option of the holders of a
majority of the shares of Series A Preferred Stock, be deemed to be a
liquidation, dissolution or winding up of the Corporation; provided, however,
that any transfer of any shares of Common Stock of the Corporation pursuant to
the terms of the Voting Trust Agreement dated as of November 19, 2001 among
the Corporation, NNGC Holding Company, Inc. and Wilmington Trust Company shall
not be deemed to be a liquidation, dissolution or winding up of the
Corporation. In the event of a deemed liquidation, dissolution or winding up
of the Corporation pursuant to this Section 3, the Corporation shall not make,
and the holders of the Corporation's outstanding capital stock shall not be
entitled to receive, any distribution or payment in respect of the
Corporation's outstanding capital stock unless and until (i) all
non-contingent obligations of the Corporation under the Credit Agreement (as
defined below) and the Loan Documents (as defined in the Credit Agreement)
have been paid in full in cash, (ii) all Commitments (as defined in the Credit
Agreement) have been terminated, and (iii) all Letters of Credit (as defined
in the Credit Agreement) have expired or terminated or, to the extent Letters
of Credit remain outstanding, the aggregate undrawn amounts thereof have been
cash collateralized or secured by a letter of credit in favor of the Issuing
Bank (as defined in the Credit Agreement) and reasonably acceptable to the
Issuing Bank. "Credit Agreement" means the Credit Agreement dated as of
November 19, 2001, among the Corporation, Citicorp North America, Inc. and
JPMorgan Chase Bank, as Co-Administrative Agents, Citicorp North America,
Inc., as Paying Agent, JPMorgan Chase Bank, as Collateral Trustee, JPMorgan
Chase Bank, as Issuing Bank, and the lenders party thereto from time to time
(the "Banks"), as amended, restated, modified and supplemented from time to
time.

                  As used in this Certificate of Amendment, "capital stock
representing voting power" and similar phrases refer to capital stock or similar
equity securities which in ordinary circumstances vote in the election of
directors of a corporation or similar body of an entity with another
organizational form.

                  4. VOTING RIGHTS. The Series A Preferred Stock, except as
provided herein or as otherwise from time to time required by law, shall have no
voting rights. Whenever, at any time or times after two dividend payments (which
may include, after quarterly dividends have become payable, quarterly
dividends), whether or not consecutive, on the outstanding shares of Series A
Preferred Stock or on any stock ranking on a parity with the Series A Preferred
Stock with respect to the payments of dividends shall be in arrears, the holders
of the Series A Preferred Stock shall vote separately as a class upon all
matters upon which holders of the Common Stock (and of any other securities
which may similarly be entitled to vote with the holders of the Common Stock)
are entitled to vote, other than with respect to the election of directors, and,
when so voting, shall be entitled to one vote for each share of Series A
Preferred Shock held, and shall be entitled, notwithstanding any provision
hereof, to notice of any stockholders' meeting in accordance with the bylaws of
the Corporation. The voting rights set forth in the previous sentence shall
continue until all dividends accumulated on such shares of Preferred Stock on
which voting rights have been conferred, including the Series A Preferred Stock,
for the past dividend periods and the then current dividend period shall have
been fully paid or declared and a sum sufficient for the payment thereof set
aside for payment, whereupon such right shall


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terminate, subject to revesting in the event of each and every subsequent
default of the character above mentioned.

                  5.  PROTECTIVE PROVISIONS.  So long as any shares of any
Series A Preferred Stock remain outstanding, the Corporation shall not, without
the affirmative vote of the holders of at least a majority of the shares of such
Series A Preferred Stock:

                  5.1      REDEMPTIONS. Except as provided in Section 6,
                           directly or indirectly redeem, purchase or otherwise
                           acquire, any of the Corporation's or any Subsidiary's
                           equity securities;

                  5.2      ISSUANCES. Authorize, issue, or enter into any
                           agreement providing for the issuance (contingent or
                           otherwise) of (x) any notes or debt securities
                           containing equity features (including, without
                           limitation, any notes or debt securities issued in
                           connection with the issuance of equity securities or
                           containing profit participation features) or (y) any
                           equity securities (or any securities convertible into
                           or exchangeable for any equity securities, including
                           any warrants or stock options);

                  5.3      MERGERS. Merge or consolidate, or enter into an
                           agreement providing for any merger or consolidation,
                           with any Person if the holders of the Corporation's
                           capital stock prior to the transaction will own
                           capital stock representing less than 100% of the
                           voting power of the surviving entity after the
                           transaction;

                  5.4      SALE OF ASSETS. Except as provided in SCHEDULE 5.4,
                           sell, lease or otherwise dispose of any assets of the
                           Corporation, other than (i) obsolete equipment or
                           inventory, (ii) assets sales in the Ordinary Course
                           of Business not to exceed an aggregate of $20 million
                           within any 12-month period and (iii) the grant of
                           Liens (as defined in the Credit Agreement) created
                           under the Loan Documents (as defined in the Credit
                           Agreement) and any sales or other dispositions with
                           respect to assets covered by such Liens pursuant to
                           the exercise by the Paying Agent, the Collateral
                           Trustee, the Co-Administrative Agents or any Bank
                           (all as defined in the Credit Agreement) of its
                           remedies in respect of the Collateral pursuant to the
                           Loan Documents, including foreclosure, sale in lieu
                           of foreclosure or the institution of litigation;

                  5.5      LIQUIDATION; DISSOLUTION; BANKRUPTCY. (i) Dissolve or
                           liquidate, in whole or in part, (ii) pursuant to or
                           within the meaning of Title 11 of the United States
                           Code or any similar federal, state or foreign law for
                           the relief of debtors, commence a voluntary case or
                           consent to the entry of an order for relief against
                           it in an involuntary case, (iii) consent to the
                           appointment of a receiver, trustee, assignee,
                           liquidator or similar official of it or for all or
                           substantially all of its property, (iv) make a
                           general assignment for the benefit of its creditors,
                           (v) admit in writing its inability to pay its debts


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                           generally as they become due, or (vi) take any
                           corporate action in furtherance of any action set
                           forth in items (i) through (v) hereof;

                  5.6      CHARTER AMENDMENTS. Make any amendment to or waive
                           any provision of the Corporation's certificate of
                           incorporation or bylaws, or file any resolution of
                           the Board with the Secretary of State of Delaware, in
                           either case which materially and adversely affects
                           the holders of the Preferred Shares and except for
                           any amendment to the certificate of incorporation of
                           the Corporation that are intended to make the
                           Corporation bankruptcy remote;

                  5.7      INVESTMENTS AND LOANS. Make, or permit any Subsidiary
                           to make, any Investment in any Person or any loans or
                           advances to, or guarantees for the benefit of, any
                           Person, other than (i) loans to any wholly owned
                           Subsidiary, (ii) loans to MCTJ Holding Co. LLC and
                           the assumption of Debt of Enron, provided that the
                           aggregate principal amount of such loans and assumed
                           Debt does not exceed $1,950 million, (iii) loans
                           pursuant to the Cash Management Program and (iv)
                           Investments, loans, advances and guarantees made in
                           the Ordinary Course of Business;

                  5.8      INDEBTEDNESS. Create, incur, assume or suffer to
                           exist, or permit any of its Subsidiaries to create,
                           incur, assume or suffer to exist, Debt, other than
                           (i) the Debt outstanding as of the date hereof, (ii)
                           Debt in an aggregate principal amount not exceeding
                           $450 million outstanding at any time pursuant to the
                           Loan Documents and (iii) Permitted Refinancing Debt;

                  5.9      CAPITAL EXPENDITURES. Make, or permit the Corporation
                           and its Subsidiaries, taken as a whole, to make
                           Capital Expenditures (including, without limitation,
                           payments with respect to capitalized leases), (i)
                           during the period from the date hereof through
                           December 31, 2001, totaling in excess of $40 million,
                           (ii) during the year ending December 31, 2002,
                           totaling in excess of $115 million and (iii)
                           thereafter, in excess of annual budgeted amounts,
                           except in each case for additional expenditures not
                           ordinarily classified as Capital Expenditures that
                           are required to be classified as Capital Expenditures
                           by applicable regulatory requirements; and

                  5.10     NOTE RECEIVABLE. Allow the Intercompany Note
                           Receivable to be less than the sum of (a) $240
                           million and (b) an amount equal to all dividends
                           (whether or not declared) accrued and accumulated and
                           unpaid on the shares of Series A Preferred Stock at
                           any time.

                  For the purposes of this Section 5,

                  (a)      "Affiliate" shall mean, with respect to any person,
any other person that directly or indirectly through one or more
intermediaries controls, is controlled by or is under common control with, the
person in question; PROVIDED, that none of Dynegy Inc. ("Dynegy")


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and its Affiliates shall be deemed to be an Affiliate of the Corporation. For
purposes of this definition of Affiliate, "control" means the possession,
direct or indirect, of the power to direct or cause the direction of the
management and policies of a person, whether through ownership of voting
securities or general partnership or member interests, by contract or
otherwise. Without limiting the generality of the foregoing, a person shall be
deemed to control any other person in which it or any of its Affiliates owns,
directly or indirectly, a majority of the ownership interests.

                  (b)      "Capital Expenditures" has the meaning ascribed to
such term under United States generally accepted accounting principles as in
effect from time to time, consistently applied.

                  (c)      "Contingent Obligation" shall mean, as applied to
any person, any direct or indirect liability, contingent or otherwise, of that
person with respect to any indebtedness, lease, dividend, letter of credit or
other similar obligation of another, including, without limitation, any such
obligation directly or indirectly guaranteed, endorsed (other than for
collection or deposit in the ordinary course of business) co-made or
discounted or sold with recourse by that person, or in respect of which that
person is otherwise directly or indirectly liable, including, without
limitation, any such obligation for which that person is in effect liable
through any agreement (contingent or otherwise) to purchase, repurchase or
otherwise acquire such obligation or any security therefor, or to provide
funds for the payment or discharge of such obligation (whether in the form of
loans, advances, stock purchases, capital contributions or otherwise), or to
maintain the solvency or any balance sheet, income or other financial
condition of the obligor of such obligation, or to make payment for any
products, materials or supplies or for any transportation, services or lease
regardless of the non-delivery or non-furnishing thereof, in any such case if
the purpose or intent of such agreement is to provide assurance that such
obligation will be paid or discharged, or that any agreements relating thereto
will be complied with, or that the holders of such obligation will be
protected (in whole or in part) against loss in respect thereof. The amount of
any Contingent Obligation shall be equal to the amount of the obligation, or
portion thereof, so guaranteed or otherwise supported.

                  (d)      "Debt" shall mean, with respect to any person, the
aggregate amount, without duplication, of (i) all obligations for borrowed
money; (ii) all obligations evidenced by bonds, debentures, notes or other
similar instruments; (iii) all obligations to pay the deferred purchase price
of property or services; (iv) all capitalized lease obligations; (v) all
obligations or liabilities of others secured by a lien on any asset owned by
such person whether or not such obligation or liability is assumed, to the
extent of the lesser of such obligation or liability or the book value of such
asset; (vi) all Contingent Obligations of such person; and (vii) any other
obligations or liabilities which are required by generally accepted accounting
principles to be shown as debt on a balance sheet, other than trade payables
and liabilities pursuant to the tax allocation agreement between Enron and the
Corporation.

                  (e)      "Investment" as applied to any Person means (a) any
direct or indirect purchase or other acquisition by such Person of any notes,
obligations, instruments, stock, securities or ownership interest of any other
Person and (b) any capital contribution by such Person to any other Person.


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                  (f)      "Ordinary Course of Business" means the ordinary
course of business consistent with past custom and practice (including with
respect to quantity, quality and frequency).

                  (g)      "Permitted Refinancing Debt" shall mean any Debt of
the Corporation or any of its Subsidiaries issued in exchange for, or the net
proceeds of which are used to extend, refinance, renew, replace, defease or
refund other Debt of the Corporation or any of its Subsidiaries (other than
intercompany Debt); PROVIDED that:

                  (1)      the principal amount of such Permitted Refinancing
                           Debt does not exceed the principal amount of, plus
                           accrued interest on, the Debt so extended,
                           refinanced, renewed, replaced, defeased or refunded
                           (plus the amount of necessary fees and expenses
                           incurred in connection therewith and any premiums
                           paid on the Debt so extended, refinanced, renewed,
                           replaced, defeased or refunded); and

                  (2)      such Permitted Refinancing Debt has a final maturity
                           date no earlier than the final maturity date of, and
                           has a Weighted Average Life to Maturity equal to or
                           greater than the Weighted Average Life to Maturity
                           of, the Debt being extended, refinanced, renewed,
                           replaced, defeased or refunded.

                  (h)      "Person" means any individual, partnership, joint
venture, corporation, limited liability company, trust, unincorporated
organization or other entity.

                  (i)      "Subsidiary," when used with respect to any person,
shall mean any corporation, limited liability company, partnership,
association or other business entity of which (a) if a corporation, a majority
of the total voting power of shares of stock entitled (without regard to the
occurrence of any contingency) to vote in the election of directors, managers
or trustees thereof is at the time owned or controlled, directly or
indirectly, by such person or (b) if a partnership, limited liability company,
association or other business entity, a majority of the partnership or other
similar ownership interest thereof is at the time owned or controlled,
directly or indirectly, by such person. For purposes hereof, a person shall be
deemed to have a majority ownership interest in a partnership, limited
liability company, association or other business entity if such person,
directly or indirectly, is allocated a majority of partnership, limited
liability company, association or other business entity gains or losses, or is
or controls the managing director or general partner of such partnership,
limited liability company, association or other business entity.

                  (j)      "Weighted Average Life to Maturity" shall mean,
when applied to any Debt at any date, the number of years obtained by dividing:

                  (1) the sum of the products obtained by multiplying (a) the
                      amount of each then remaining installment, sinking fund,
                      serial maturity or other required payments of principal,
                      including payment at final maturity, in respect thereof,
                      by (b) the number of years (calculated to the nearest
                      one-twelfth) that will elapse between such date and the
                      making of such payment; by

                  (2) the then outstanding principal amount of such Debt.


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                  6.  REDEMPTION.  The shares of Series A Preferred Stock shall
be redeemable at the option of the Corporation in accordance with this Section
6:

                  6.1      PER SHARE REDEMPTION PAYMENT. If one of the events
                           set forth in Section 6.5 gives rise to an option on
                           the part of the Corporation to redeem all, but not
                           less than all, of the outstanding shares of Series A
                           Preferred Stock, then at such time as the shares are
                           redeemed the Corporation may redeem, to the extent it
                           has legally available funds therefor, all, but not
                           less than all, shares of Series A Preferred Stock
                           outstanding at a redemption price per share equal to
                           the original liquidation preference amount of
                           $1,500,000 per share (the "Redemption Price");
                           PROVIDED, that on the date of redemption the Board of
                           Directors, or duly authorized committee thereof,
                           declares and pays accrued and accumulated and unpaid
                           dividends on all outstanding shares of Series A
                           Preferred Stock.

                  6.2      NOTICE OF REDEMPTION. If the Corporation exercises
                           its option to redeem all, but not less than all, of
                           the outstanding shares of Series A Preferred Stock,
                           pursuant to this Section 6 then at such time as the
                           Corporation shall redeem such shares, notice of such
                           redemption shall be given by certified mail, return
                           receipt requested, to each holder of record of the
                           shares to be redeemed, at such holder's address as
                           the same appears on the stock register of the
                           Corporation at least 30 days prior to the redemption
                           date. The notice shall state:

                           6.2.1.   the redemption date;

                           6.2.1    the place or places in Houston, Texas where
                           certificates for such shares are to be surrendered
                           for payment of the Redemption Price; and

                           6.2.3    that dividends on the shares to be redeemed
                           will cease to accrue on such redemption date.

                  6.3      EFFECT OF NOTICE OF REDEMPTION. If Notice of
                           Redemption is delivered as set forth above, then from
                           and after the redemption date (unless the Corporation
                           fails to pay the Redemption Price on the redemption
                           date) dividends on the Series A Preferred Stock so
                           called for redemption shall cease to accrue, and said
                           shares shall no longer be deemed to be outstanding,
                           and all rights of the holders thereof as stockholders
                           of the Corporation (except the right to receive from
                           the Corporation the Redemption Price) shall cease.
                           Upon surrender in accordance with said notice of the
                           certificates for any shares so redeemed (properly
                           endorsed or assigned for transfer, if the Board shall
                           so require and the notice shall so state), such
                           shares shall be redeemed by the Corporation at the
                           Redemption Price aforesaid.

                  6.4      AUTHORIZED BUT UNISSUED SHARES. Any shares of Series
                           A Preferred Stock that shall at any time have been
                           redeemed or purchased by the Corporation


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                           shall, after such redemption, have the status of
                           authorized but unissued shares or Preferred Stock,
                           without designation as to series until such shares
                           are once more designated as part of a particular
                           series by the Board.

                  6.5        Events giving rise to an option to redeem.

                           6.5.1    REDEMPTION OPTION LASTING SIX MONTHS. The
                           Corporation will have the option to redeem all, but
                           not less than all, of the outstanding Series A
                           Preferred Stock for a period of six months from the
                           date of any of the following events:

                                    6.5.1.1. The Merger Agreement has been
                                    terminated pursuant to Section 9.1 thereof;

                                    6.5.1.2. The Merger Agreement has been
                                    terminated pursuant to Section 9.2(a)
                                    thereof;

                                    6.5.1.3 The Merger Agreement has been
                                    terminated pursuant to Section 9.2(d)
                                    thereof; or

                                    6.5.1.4 The third anniversary of the date
                                    that the Merger Agreement has been
                                    terminated pursuant to Section 9.2(b),
                                    9.3(c), 9.4(a) or 9.4(b) thereof.

                           6.5.2    REDEMPTION OPTION LASTING ONE YEAR. The
                           Corporation will have the option to redeem all, but
                           not less than all, of the outstanding Series A
                           Preferred Stock for a period of one year from the
                           date of any of the following events:

                                    6.5.2.1. The Merger Agreement has been
                                    terminated pursuant to Section 9.2(c);

                                    6.5.2.2. Enron notifies Dynegy that it is
                                    terminating the Merger Agreement pursuant to
                                    Section 9.3(a) of the Merger Agreement;

                                    6.5.2.3. The Merger Agreement has been
                                    terminated pursuant to Section 9.3(b); or

                                    6.5.2.4 The Merger Agreement has been
                                    terminated pursuant to Section 9.4(c).

                  For the purposes of this Section 6, "Merger Agreement" shall
mean that certain Agreement and Plan of Merger among Dynegy, Stanford, Inc.,
Sorin, Inc., Badin, Inc. and Enron dated as of November 9, 2001.

         7.       RANK.  Any stock of any class or classes or series of the
Corporation shall be deemed to rank:


                                      10

<Page>

                  7.1 prior to shares of the Series A Preferred Stock, either as
                  to dividends or upon liquidation, dissolution or winding up,
                  or both, if the holders of stock of such class or classes or
                  series shall be entitled by the terms thereof to the receipt
                  of dividends or of amounts distributable upon liquidation,
                  dissolution or winding up, as the case may be, in preference
                  or priority to the holders of shares of the Series A Preferred
                  Stock;

                  7.2 on a parity with shares of the Series A Preferred Stock,
                  either as to dividends or upon liquidation, dissolution or
                  winding up, or both, whether or not the dividend rates,
                  dividend payment dates, or liquidation prices per share
                  thereof are different from those of the Series A Preferred
                  Stock, if the holders of stock of such class or classes or
                  series shall be entitled by the terms thereof to the receipt
                  of dividends or of amounts distributed upon liquidation,
                  dissolution or winding up, as the case may be, in proportion
                  to their respective dividend rates or liquidation prices,
                  without preference or priority of one over the other as
                  between the holders of such stock and the holders of shares of
                  Series A Preferred Stock; and

                  7.3 junior to shares of the Series A Preferred Stock, either
                  as to dividends or upon liquidation, dissolution or winding
                  up, or both, if such class or classes or series shall be
                  Common Stock or if the holders of the Series A Preferred Stock
                  shall be entitled to the receipt of dividends or of amounts
                  distributable upon liquidation, dissolution or winding up, as
                  the case may be, in preference or priority to the holders of
                  stock of such class or classes or series.

         8.       ALL HOLDERS BOUND BY AGREEMENT AND CONSENT. Each holder of
shares of Series A Preferred Stock, including any holder who becomes a holder
of shares of Series A Preferred Stock after the filing of this Certificate of
Amendment, shall be subject to and bound by, and shall be deemed to have
agreed and consented to, the terms of the Agreement and Consent dated as of
November 19, 2001 among Dynegy, Dynegy Holdings Inc., Enron Corp., CGNN
Holding Company, Inc., MCTJ Holding Co. LLC, NNGC Holding Company, Inc., the
Corporation and the other parties named therein (the "Agreement and Consent"),
regardless of whether such holder has executed the Agreement and Consent or
agreed in writing to be subject to and bound by the Agreement and Consent as
required by paragraph 7 thereof. A copy of the Agreement and Consent is on
file with and available for inspection at the principal executive offices of
the Company in the State of Texas. Each certificate representing shares of
Series A Preferred Stock shall bear a conspicuous legend to the effect that
(i) the shares represented thereby are subject to the Agreement and Consent
and (ii) the holder of the certificate, by accepting the certificate and the
shares represented thereby, agrees to be subject to and bound by the Agreement
and Consent.



                                      11

<Page>

                  IN WITNESS WHEREOF, said Northern Natural Gas Company has
caused this Certificate of Amendment to be signed by Drew J. Fossum, its Vice
President, General Counsel and Assistant Secretary on November 21, 2001.




                                    NORTHERN NATURAL GAS COMPANY


                                    /s/ Drew J. Fossum
                                    --------------------------------------------
                                    Name: Drew J. Fossum
                                    Title: Vice President, General Counsel and
                                           Assistant Secretary