Enzyme inhibition

Enzyme inhibition is a reduction in catalytic activity caused by a molecule binding to an enzyme. Inhibitors can bind at the active site or elsewhere, reversibly or irreversibly.

Competitive inhibition: Reversible inhibition in which an inhibitor competes with substrate for an enzyme’s active site. Substrate competition is the defining active-site mechanism and can be overcome by increasing substrate concentration.
Enzyme: A biological catalyst, usually a protein, that accelerates a chemical reaction without being consumed. Inhibition is defined by its effect on an enzyme’s catalytic activity.
Drug inhibition of dihydrofolate reductase: The inhibition of dihydrofolate reductase by drugs that disrupt folate-dependent nucleotide synthesis. Methotrexate and trimethoprim illustrate selective enzyme inhibition in cancer therapy and antimicrobial treatment.
Enzyme induction: An increase in enzyme abundance caused by enhanced gene expression or reduced degradation. Induction raises enzyme quantity, whereas inhibition lowers activity through molecular binding.
Uncompetitive inhibition: Reversible inhibition in which an inhibitor binds only to the enzyme–substrate complex. Binding after substrate association distinguishes this mechanism from competition for free enzyme.
Active site: The region of an enzyme where substrates bind and catalytic chemistry occurs. Many inhibitors reduce activity by occupying or altering this site.
ACE inhibitor: A drug that inhibits angiotensin-converting enzyme and reduces formation of the vasoconstrictor angiotensin II. This drug class lowers blood pressure by blocking a defined enzyme reaction.
Enzyme activation: An increase in an enzyme’s catalytic activity caused by a regulatory change or activating molecule. Activation changes activity in the opposite direction from inhibition.
Mixed inhibition: Reversible inhibition in which an inhibitor binds both free enzyme and enzyme–substrate complex with different affinities. Unequal binding to both enzyme states changes both apparent substrate affinity and maximum velocity.
Enzyme–substrate complex: A transient molecular complex formed when a substrate binds an enzyme before product formation. Some inhibitors bind this complex rather than the free enzyme.

Linked from 11 pages