Elementary Reactions and Enzyme Kinetics, Study notes of Biochemistry

Download Elementary Reactions and Enzyme Kinetics and more Study notes Biochemistry in PDF only on Docsity! Elementary Reactions A → P A → I1 → I2 → P Rate equation aA + bB + ... + zZ → P rate = k[A]a[B]b ... [Z]z k is rate constant Order is the sum of the exponents For elementary reactions, order is the molecularity Rates of reaction v d dt d dt = − =[ ] [ ]A P Zero order − =d dt k [ ]A 0 [A] = [A]0 - k0t k0 = M s -1 t k1 2 0 02 / [ ]= A First order A → B − =d dt k [ ] [ ] A A1 [ ] [ ]A A= − 0 1e k t k1 = s -1 t k1 2 1 2 / ln= A ⇔ B − = − − d dt k k [ ] [ ] [ ] A A B1 1 at equilibrium, rate = 0 [ ] [ ] B A eq eq eq k k K= = − 1 1 Reversible Reactions E + S ES P + E k1 k-1 k2 k-2 v V K V K K K f m r m m m = − + max S max P S P S P 1+ [S] P [ ] [ ] [ ] where Vfmax = k2[E]T V r max = k-1[E]T K k k km S = +−1 2 1 K k k km P = +− − 1 2 2 [E]T = [E] + [ES] Haldane Relationship Kinetic parameters of a reversible enzymatically catalyzed reaction are related by the equilibrium constant set v = 0 and solve: K V K V K f m m eq max P max r S [P] [S] = = Bisubstrate Reactions A + B P + Q E Almost all are transferase (transfer of functional group) P-X + B P + B-X E where A = P-X and Q = B-X or oxidation-reduction (transfer of reducing equivalents) reactions Terminology: substrates - A, B, C in order they add to enzyme products - P, Q, R in order they leave enzyme stable enzyme forms - E, F, G Uni - one Bi - two Ter - three Quad - four Applies to naming reactions type - i.e., one S and two P Uni Bi reaction Cleland Notation Sequential - Single Displacement reaction transfer of functional group directly from A (=P-X) to B yielding P and Q (=B-X) Ordered NAD+- and NADP+-requiring dehydrogenases Random dehydrogenases and kinases Ping Pong - Double Displacement reaction transfer of functional group to enzyme and release of first product then transfer of bound functional group from enzyme to second substrate to release second product chymotrypsin, transaminases, some flavoenzymes