Lecture 11- Enzyme Kinetics

Lecture 11- Enzyme Kinetics - Initial rates method Initial...

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Unformatted text preview: Initial rates method: Initial rate (v 0 ) is slope of tangent at time zero. Measure initial rate at several substrate concentrations. ] [ ] [ S vs dt S d v t = ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ − = [S] E + S E + P ES k 1 k-1 k 2 Michaelis-Menten Kinetics [ ] [ ] ES k dt P d v 2 = ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ = [ ] 2 max E k V = [E] 0 = [ES] + [E] V max ] [ ] [ max S K S V v M + = ( ) 1 2 1 k k k K M + = − K M k cat = k 2 max max 1 ] [ 1 V S V K v M + = ] [ max S K v V v M − = Reciprocal Plots Help Measure K M and V max Lineweaver-Burk plot Eadie-Hofstee plot ] [ ] [ max S K S V v M + = k cat = V max /[E] o Catalytic efficiency = k cat /K M (units: M-1 s-1 ) E + S E + P ES k 1 k-1 k cat k cat = V max /[E] o ( ) 1 1 k k k K cat M + = − Catalytic turnover number = k cat (units: s-1 ) 2 1 2 1 2 k k k k k k K k M M cat + = = − ES → ES‡ → E + P Chymotrypsin Active Site NH 3 -x-Phe-Met-x-COO- + H 2 O → N-x-Phe + Met-x-C Ser195 λ max = 400 nm Colorimetric Assay of Product Formation colorless Beer’s Law: A = ε( conc)(path-length) A = log (I 0 /I) I I t V t S S t P max ) ]( [ ] [ ) ]( [ = − = max ] [ ) ]( [ S t V t S + − = k 1 k-1 k 2 k 3 [E] 0 = [E] + [ES] + [ES’] ] [ ] [ 2 1 ES...
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This note was uploaded on 04/06/2011 for the course CHEM 107B taught by Professor Jamesames during the Winter '09 term at UC Davis.

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Lecture 11- Enzyme Kinetics - Initial rates method Initial...

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