Enzyme Kinetics Lecture Notes PDF
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This lecture notes cover enzyme kinetics, including definitions for concepts such as Km, Vmax and kcat. The document also discusses different types of reversible inhibitors. It's intended for students taking biochemistry courses.
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BIOL or CHEM 3361 Biochemistry I Enzyme Kinetics Reading: Chapter 13 Km values for some enzymes and their substrates Summary Only one substrate is varied ES E + P is irreversible and [P]0=0 [S] > [E]total and [E]total is constant All other conditions...
BIOL or CHEM 3361 Biochemistry I Enzyme Kinetics Reading: Chapter 13 Km values for some enzymes and their substrates Summary Only one substrate is varied ES E + P is irreversible and [P]0=0 [S] > [E]total and [E]total is constant All other conditions are identical Kinetic Measures For an enzyme-catalyzed reaction: k1 k2 S + E ES E + P k-1 Steady state or rapid equilibrium? Vmax = kcat n[E]T (n is no. of substrate binding sites) The Turnover Number or kcat A measure of catalytic activity kcat, the turnover number, is the number of substrate molecules converted to product per enzyme molecule per unit of time, when E is saturated with substrate. If the model fits, k2 = kcat Values of kcat range from less than 1/sec to many millions per sec k1 k2 S + E ES E + P k-1 kcat The Ratio kcat/Km is Catalytic Efficiency The catalytic efficiency: kcat/Km An estimate of "how perfect" the enzyme is kcat/Km is an apparent second-order rate constant It measures how well the enzyme performs when S is low The upper limit for kcat/Km is the diffusion limit - the rate at which E and S diffuse together An enzyme with a catalytic efficiency around 108-109 M- 1sec-1 is a perfect enzyme kcat/Km Kinetic Measures - Review For an enzyme-catalyzed reaction: k1 k2 S + E ES E + P k-1 Ks is the dissociation constant of E and S Km is the substrate concentration at ½ Vmax Kcat is k2 when M-M applies Kcat/Km is a measure of catalytic efficiency with an upper limit of 109 M-1sec-1 When [S] >> Km v approaches Vmax When [S]