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blocking of the action of an enzyme by a compound that binds to the free enzyme, preventing the substrate from binding and thus preventing the enzyme from acting on that substrate. The competitive inhibitor is often a substrate analogue and binds at the active site; however, this is not an absolute requirement for competitive inhibition. Saturating concentrations of substrate can remove the inhibition. Compare: isostery.
Synonym(s): selective inhibition
an inhibitor of an enzyme reaction that competes with the substrate by binding at the active site.
1. A chemical that binds to or blocks another reagent from participating in a reaction.
2. A medication, hormone, or other intercellular messenger that binds and blocks the cellular receptor or target enzyme of another agent. Drugs that act by competitive inhibition may treat or prevent disease by inactivating pathogenic enzymes or by blocking the effects of hormones or precursor molecules. For example, protease inhibitors interfere with production of human immunodeficiency virus (HIV) by binding and inactivating the protease enzyme; selective estrogen-receptor modulators limit the impact of estrogen by replacing this hormone on cells sensitive to its effects.
See also: inhibitor