Term
| Specific Acid-Base Catalysis |
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Definition
| Involves the constituents of water donation of a proton by the hydronium ion [H3O+], or the acceptance of a proton by the hydroxyl ion [OH-]. |
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Term
| General Acid-Base Catalysis |
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Definition
| If the donor molecule is a weak acid or the abstracting molecule a weak base (like a reactive amino acid side chain). |
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Term
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Definition
When some of the energy of binding substrate within the active site is used to generate a conformational change in the shape of the active site.
-In such a mechanism the conformational change distorts the substrate into a more reactive
shape resembling the transition state. |
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Term
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Definition
Results when a covalent enzyme-substrate intermediate is formed during the course of the reaction.
-Catalysis results if this covalent intermediate is more reactive toward the final acceptor molecule than was the original substrate.
-serine proteases cleave peptide bonds using this mechanism, distinct from carboxypeptidases. |
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Term
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Definition
| [Products]/[Reactants]=[E][S]/[ES]=k-1/k1 |
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Term
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Definition
=(k-1+k2)/k1
-[S] which gives 1/2(Vmax)
-when k-1>>k2 then Km~KD
-a measure of the affinity of the enzyme for the substrate, the lower the Km the higher the affinity |
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Term
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Definition
I binds only to E, not ES
-I increases the apparent Km for S
-as [S] becomes large, I becomes less effective as an inhibitor
-Vmax is unaffected by the inhibitor |
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Term
| Noncompetetive inhibitors |
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Definition
I binds to E & to ES
-apparent Km may be unchanged (common), or increased or decreased
-Vmax is decreased
-I interferes with conformational change, but has no effect on S binding. |
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Term
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Definition
I binds to ES
-apparent Km is decreased
-Vmax is decreased
-k2 is lowered
-the substrate binds the enzyme more readily but the catalytic site is not available to react with it. |
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Term
| Michaelis-Menton Equation |
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Definition
vo=Vmax[S]/Km+[S]
Vmax is proportional to k2 & [Et] |
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Term
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Definition
| Rate constant is determined by the free energy of activation, catalysts can reduce that |
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Term
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Definition
A protease.
-carbonyl polarization & oxyanion stabilization is accomplished by coordination of the oxygen to an active site Zn2+.
-an active site glutamate acts as the nucleophile |
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Term
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Definition
1. Initial rate assumption: [S]=the amount of S added
-there is no P & therefore no reverse reaction
2. Steady state assumption: The concentration of [ES] is nearly constant during most of the time P is being formed. |
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