Lecture 11 - Lecture 11 Enzyme mechanisms and kinetics...

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Lecture 11 Enzyme mechanisms and kinetics Non-catalyzed reaction: S S* P Catalyzed reaction: E+S ES X* EP E+P (where S* is the activated or transition form) Graphically, G “reaction coordinate” G 1. Enzyme does not affect Δ G between S and P (i.e., equilibrium) 2. Enzyme reduces Δ G between ES and X* relative to S and S* (activation energy) Algebraicly, For reaction A --> B, V = k[A] k = ( κ T/h)exp(-Ea/RT) κ = Plank’s constant; h = Boltzman’s constant so k and thus V are inversely and exponentially related to Ea and directly related to T-- a 6 kJ/mol reduction in Ea gives ca 10x increase in k and V Δ k ~ exp(+6000/8.3*300) ~ 11 (reduction in Ea is an increase from –Ea) See Table 14.1, p. 420: V(catalyzed)/V(uncatalyzed) for various enzymes vary from 10 4 to 10 21 , meaning Ea is reduced by ca 23 to 126 kJ/mol
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Enzymes reduce Ea (produce X*) through “near-attack conformations” (stress from H-, Vanderwaal’s, ionic bonds), covalent bonds, acid-base catalysis, low-barrier hydrogen bonds, and metal ion catalysis X*:
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This note was uploaded on 09/29/2010 for the course VEN 101C 91861 taught by Professor Davidsmart during the Spring '09 term at UC Davis.

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Lecture 11 - Lecture 11 Enzyme mechanisms and kinetics...

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