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Unformatted text preview: Biochemistry 461 FS 2009 Michigan State University Enzymes and Inhibition September 30, 2009 Lecture 11 max max 1 ] S [ 1 1 V V K V m + = The Double-Reciprocal plot (from previous lecture) ] S [ ] S [ m max + = K V V 2 1.) K m • For reactions with two steps, if k 2 is rate determining, and if E and ES reach equilibrium with each other rapidly compared to formation of products (k-1 >> k 2 ), then d K k k K = = − 1 1 m where K d is the dissociation constant for ES into E + S. • Note that these conditions are often not met (multiple steps after formation of ES, etc.), and in these cases, K m is not accurately defined as the dissociation constant. • The K m is often approximately equal to physiological [S] Interpretation of Kinetic Parameters E + S ES E + P k 1 k-1 k 2 3 2.) V max • The value of V max depends on enzyme concentration. A useful quantity is the first-order rate constant, or turnover number , k cat : ] [ max t cat E V k = • k cat describes the limiting rate at saturation • k cat has units of time-1 and is the number of S molecules converted...
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This note was uploaded on 01/17/2012 for the course NSC 461 taught by Professor Benning during the Fall '11 term at Michigan State University.
- Fall '11