LECTURE 4 - Enzymes Enzymes accelerate the rate of reaction...

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Enzymes p 166 - 192 activation energy = net rxn energy = Enzymes accelerate the rate of reaction without changing the equilibrium Enzymes do not appear in the stoichiometry of the reaction. Reaction coordinate energy S P Kinetics: how fast S and P interconvert Thermodynamics: how much S and P at equilibrium K eq = e −Δ G / RT rate = [ S ] e −Δ G / RT Δ G Δ G
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Enzymes bind transition states p 166 - 192 Enzymes stabilize the transition state, not the substrate
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Enzymes are amazing p 166 - 192 Function at the diffusion limit = 10 8 - 10 9 M -1 s -1 for k cat /K m Turnover numbers are often 10 3 or up to 10 6 s -1 Enzymes are highly speci±c: they don ʼ t make many mistakes Enzyme Half-time Uncatalyzed rate (s -1 ) Catalyzed rate (s -1 ) Rate accel. Carbonic anhydrase 5 s 1.3 x 10 -1 10 6 7.7 x 10 6 Chymotrypsin 20 years 1 x 10 -9 190 1.7 x 10 11 Orotidine monophosphate decarboxylase 78,000,000 years 2.8 x 10 -10 39 1.4 x 10 17
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Enzymes - mechanisms of catalysis p 166 - 192 Intrinsic binding energy; non-covalent interactions between enzyme and substrate that contribute to rate acceleration, not measureable binding energy R-NH 3 + -O 2 C-R' electrostatic R-NH 3 + O R'' R' !" ! + ion-dipole dipole-dipole O R'' R' !" ! + R O H !" ! + R O O H O R' H H-bonding R R' R R' O H hydrophobic aromatic stacking
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LECTURE 4 - Enzymes Enzymes accelerate the rate of reaction...

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