BCHE 395-12 Enzyme Kinetics I

E es is constant michaelis menten equaon k1 k2 e

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Unformatted text preview: vs [S] curves •  ES complex explains this behavior The ES complex explains this behavior k1 ES Complex k2 •  E + S ⇌ ES ⇌ E + P k k - 1 - 2 k1 •  E + S ⇌ ES (Fast) k k2 - 1 •  ES ⇌ E + P (Slow) k - 2 •  The slower rxn limits the rate of the overall rxn •  Overall rate is propor*onal to ES Let’s derive the M- M equa*on, Rate in terms of [S] k1, k2, k- 1, & k- 2 are rate constants, NOT equilibrium constants Michaelis- Menten Equa*on k1 k2 k- 1 k- 2 E + S ⇌ ES ⇌ E + P •  General assump:ons required for the deriva*on and use of the M- M For the reac*on: •  1) [ET]=[E]+[ES] where E is free enzyme [E][S] •  2) The ES complex forms quickly such that [ES] approximates the equilibrium dissocia*on constant, and k2 is the rate limi*ng step •  3) Throughout the reac*on, the rate of ES forma*on is equal to the rate of ES breakdown, i.e. [ES] is constant Michaelis- Menten Equa*on k1 k2 E + S ⇌ ES ⇀ E + P k- 1 •  General assump*ons required for the deriva*on and use of the M- M For the reac*on: •  4) At the early stages of the reac*ons when V0 is measured, [P] is negligible...
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