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EXAM 2
Term | Definition |
---|---|
Allosteric enzyme | An enzyme that has multiple and regulatory active sites.It controls the metabolic pathways through environmental signals, including the final product.Its kinetics are complex |
Reversible inhibitors | Competive, uncompetitive,and noncompetive |
Irreversible inhibitors | Group specific reagents,affinity labels,suicide inhibitors, transition state analogs |
Reversible inhibition characteristics | -rapid dissociation of the enzyme-inhibitor complex -rapid dissiciation of the inhibitor with the enzyme |
Competive inhibition | the inhibitor resembles the substrate and binds to the active site of the enzyme.An enzyme can bind substrate forming an ES complex or inhibitor EI. |
competive unhibition kinetics | increases KM No change on Vmax Can be overcome by increasing substrate concentration Graph is a V with the same Y-intercept |
Uncompetive inhibition | It is substrate-dependent inhibition in that the inhibitor binds only to the enzyme-substrate complex (ES) |
uncompetitive inhibition kinetics | lowers Vmax Lovers KM Parallel graph, different x and Y intercept |
Noncompetitive inhibition | The inhibitor and the substrate can bind simultaneously to an enzyme molecule at different binding sites. Decreases the overall number of active enzymes |
Noncompetitive inhibition kinetics | Lowers apparent Vmax KM is unchanged the graph is a V with the same x-intercept and different y-intercept |
Irreversible inhibitor characteristics | It dissociates very slowly from its target enzyme because it has become tightly bound to the enzyme, either covalently or noncovalently |
Group-specific reagents | Modify specific R groups of amino acids Ex: Nerve gas DIPF react with serine residues |
Affinity labels, also called substrate analogs | They are structurally similar to the substrate, inhibit enzymes by covalently modifying active sites residues Ex: TPCK reacts with His 57 in chymotrypsin |
Suicide Inhibitors, or mechanism-based inhibitors | They chemically modify the substrates. The enzyme starts the reaction but the inhibitor forms a reactive intermediate that inactivates the enzyme covalently modifying it. Ex: Penicillin |
Transition-state analogs |