mcb450-11s07 - Lecture 11 Mechanism of Enzyme Action Lower...

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Lecture 11 Mechanism of Enzyme Action
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Lower Activation Energy Note the existence of more than one intermediate complex. This is typical.
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Rate Enhancements
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Three Factors Important in Catalysis Concentration Orientation Electron Shuffling (Acid-Base catalysis or metal ion involvement)
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The Rhodanese Reaction • S 2 O 3 2- + CN - = SO 3 2- + SCN - Enzyme abundant in liver and kidney Requires approach of negatively charged ions Enzyme has Zn 2+ at active site to withdraw electrons, favor approach of ions, and weaken S-S bond Above reaction is not the physiological one Just because an enzyme can catalyze a reaction doesn’t mean that it does catalyze the reaction.
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Acid-Base Catalysis Specific acid-base catalysis H + or 0H - accelerates reaction rate General acid-base catalysis Acid or base other than H + or 0H - accelerates reaction rate. The above can be distinguished experimentally.
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Specific vs. General Acid-Base Catalysis Specific General Both reactions are base-catalyzed, because the rates are higher at higher pH.
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Explanation In specific acid-base catalysis, directly involving H + or OH - , buffer concentration has no effect on rate because all that
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This note was uploaded on 04/07/2008 for the course MCB 450 taught by Professor Mintel during the Fall '07 term at University of Illinois at Urbana–Champaign.

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mcb450-11s07 - Lecture 11 Mechanism of Enzyme Action Lower...

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