Chapter 6b students - The Michaelis-Menten Model k1 k-1...

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k 1 1 MCDB310 – Chapter 6: Enzymes k -1 k cat The Michaelis-Menten Model ] S [ ] S [ M max 0 K V V ] ES [ cat 0 k V
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Michaelis-Menten Plot 2 MCDB310 – Chapter 6: Enzymes ] S [ ] S [ M max 0 K V V k 1 k -1 k cat
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What is K M K M is [S] at which V 0 = V max /2 if k -1 >> k cat M = K D of the enzyme/substrate complex 3 MCDB310 – Chapter 6: Enzymes k 1 k -1 k cat 1 1 M k k k K cat Definition of K M :
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What are V max and k cat 4 MCDB310 – Chapter 6: Enzymes k 1 k -1 k cat T max 0 ] E [ ] ES [ cat cat k V k V Definition of V max : k cat : Turn-over number of the enzyme, i.e. how many substrate molecule each enzyme molecule turns over per second under conditions of saturation
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The Lineweaver-Burk Plot y = a + b · x 5 MCDB310 – Chapter 6: Enzymes ] S [ ] S [ M max 0 K V V ] S [ 1 1 1 max M max 0 V K V V
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k cat /K M - Catalytic Efficiency Second-order reaction with k cat /K M being the second- order rate constant! 6 MCDB310 – Chapter 6: Enzymes ] S [ ] S [ ] E [ ] S [ ] S [ M T cat M max 0 K k K V V ] S [ ] E [ ] S [ ] E [ M cat T M 0 K k K k V If [S] << K M :
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k cat /K M - Catalytic Efficiency cannot be faster than frequency with which E and S collide with each other in solution upper limit for k cat /K M is diffusion (10 8 -10 9 M -1 s -1 ) enzymes with such k cat /K M values have achieved “ catalytic perfection reaction is catalyzed almost every time enzyme encounters a substrate molecule 7 MCDB310 – Chapter 6: Enzymes ] S [ ] E [ T M cat 0 K k V
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Enzyme Kinetics Overview over Parameters K M [μM]: [S], at which V 0 = V max /2 M = K D , when k 2 << k -1 V max [μM/s]: Maximal velocity of the reaction (when [S] is not rate limiting) k cat [s -1 ]: Catalytic constant or turn-over number ; how much substrate is converted by the specific enzyme per second cat /K M [M -1 s -1 ]: Catalytic (kinetic) efficiency (specificity constant); how fast an enzyme works, once it encounters its substrate 8 MCDB310 – Chapter 6: Enzymes
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optimal k cat /K M can be achieved with various combinations of K M and k cat 9 MCDB310 – Chapter 6: Enzymes
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SOD An Enzyme with Perfect Catalytic Efficiency 10 MCDB310 – Chapter 6: Enzymes
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Reactions Involving Several Substrates a) Random b) Ordered 11 MCDB310 – Chapter 6: Enzymes c) Ping-pong
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1/[S1] (mM -1 ) [S2] sequential reactions ping-pong 1/[S1] (mM -1 ) [S2] 12 MCDB310 – Chapter 6: Enzymes Lineweaver-Burk Plots of Multi-Substrate Reactions
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Enzyme Inhibition Enzymes can be inhibited by compounds that interfere with catalysis
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This note was uploaded on 04/05/2009 for the course MCDB 310 taught by Professor Walter during the Spring '09 term at University of Michigan.

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Chapter 6b students - The Michaelis-Menten Model k1 k-1...

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