Lecture 15 Tuesday 3/4/08 Enzymes Michealis-Menten Kinetics Lineweaver-Burk Plot Enzyme Inhibition

Last time 2/21/08

V max =k cat * E t Turnover Number: k cat Number of substrate molecules (moles) converted to product in a given time (s) on a single enzyme molecule (molecules/molecule/time) H 2 O 2 + E  H 2 O + O + E 40,000,000 molecules of H 2 O 2 converted to product per second on a single enzyme molecule.

Enzymes, Inhibition S + E → E + P 1) Mechanism and active intermediate (E·S) 2) Rates 3) Net Rates

4) Pseudo Steady-State

(Michaelis-Menten plot) V max -r s S 1/2 k m =S 1/2 therefore k m is the concentration at which the rate is half the maximum rate

Competitive Inhibition E + S E·S E + P + I E · I 1)Mechanisms 2)Rates k1k1 k2k2 k3k3 k4k4 k5k5

From before (no competition): Intercept does not change, slope increases as inhibitor concentration increases No competition Competition

Uncompetitive Inhibition E + S E·S P E · S· I I k1k1 k2k2 k3k3 k4k4 k5k5