lecture7&8_9_23&25_08inclass

lecture7&8_9_23&25_08inclass - 1 Homework:...

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Unformatted text preview: 1 Homework: 8.2, 8.4, 8.7, 8.11, 8.15 Lectures 7 & 8 Chapter 8: Enzymes Overview: structure/classification enzyme thermodynamics transition state stabilization enzyme kinetics Michaelis-Menton kinetic parameters enzyme inhibition Enzymes are proteins (mostly) that are capable of catalyzing covalent bond cleavage and formation. (Enzymes are biochemical catalysts). Enzymes are agents of metabolic function. (they are also good therapeutic targets) Key attributes:-alter the rate of product formation-specificity-reactivity conditions Components: enzyme (active site) substrate (reactant) product (cofactor) (coenzyme) e.g., carbonic anhydrase in red blood cells; 10 7 rate acceleration Enzymes 2 Substrate binding to the enzyme active site chymotrypsin (a protease) active site- residues that bind substrate and are involved with the catalytic mechanism Enzymes act in concert with small molecules (cofactors/coenzymes). Enzymes are regulated by small molecules (inhibitors/activators). E displays specificity for a given substrate. Enzymes are organized into six classes based on the type of chemical reaction that they catalyze substrate + -ase ending; rxn being catalyzed with -ase 3 proteolysis: hydrolysis of a peptide bond enzyme = protease substrate = peptide/protein unnatural substrate: ester Enzymes 4 Enzyme specificity trypsin cleaves on the carboxyl side of arginine and lysine residues thrombin cleaves Arg- Gly bonds in particular sequences only Cofactors: metal ions Coenzymes: organic assist enzymes in their functions Know definitions:-prosthetic group (heme)-holoenzyme (+ cofactor/coE)-apoenzyme (-cofactor/coE)-apoprotein (empty protein) they bind to a specific site on E 5 Free energy and enzyme kinetics A > B k Rate ( v ) = d[A]/dt = d[B]/dt v = rate or velocity ([A] as function of t) v = d[A]/dt = k [A] 1st order reaction units time-1 Rate ( v ) = d[A]/dt = d[B]/dt = d[C]/dt d[A]/dt = k [A][B] 2nd order reaction units conc/time-1 mA + nB > C k d[C]/dt = k [A] m [B] n m+n order reaction Most enzyme reactions are first order reactions. k = rate constant independent of [reactant], temp, pH, etc. (- disappearing/+forming) A + B > C k *diffusion limited excess A or B pseudo first order reversible reaction 6 K eq = [C][D] [A][B] G = RT ln [C][D] [A][B] 0 = G + RT ln [C][D] [A][B] A + B C + D G = G + RT ln [C][D] [A][B] standard state is pH 7, units are kJ or kcal at equilibrium G = 0 Free energy and enzyme kinetics G = RT lnK eq (1) (2) (3) (4) (5) G = 2.303 RT log 10 K eq (6) K eq = 10 G / 2.303 RT (7) G = free energy of the rxn 7...
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This note was uploaded on 08/04/2010 for the course CHM 6620 taught by Professor Dr.christinechow during the Fall '08 term at Wayne State University.

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lecture7&8_9_23&25_08inclass - 1 Homework:...

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