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Incoming links: Enzyme inhibition initial-rate assay
Enzyme inhibitor 2026-10-18
An enzyme inhibitor lowers an enzyme's reaction rate. In reversible enzyme inhibition, reducing free inhibitor concentration can restore activity; slow release can make this difficult to distinguish experimentally from irreversible inactivation. Competitive inhibition and mixed inhibition describe different changes in enzyme kinetics; pure noncompetitive inhibition is a special case of mixed inhibition, not a name for every inhibitor that binds away from an active site.[ref]
Symbolism and Terminology in Enzyme Kinetics (Recommendation 1981) by Nomenclature Committee of the International Union of Biochemistry. Symbolism and Terminology in Enzyme Kinetics, recommendation 1981, sections 6.1 and 6.4: reversibility and the ambiguity of non-competitive
The useful question is how adding substrate changes the inhibition. The model below connects binding to a measurable reaction rate, predicts when more substrate can overcome inhibition, and supplies examples for comparison with an enzyme inhibition initial-rate assay. Its inhibition constants are explicitly defined; neither a binding cartoon nor one reduced reaction rate by itself determines a mechanism.
Reversible enzyme inhibition: which bound states can form?
Original branching scheme for a single substrate. is free enzyme, free substrate, free inhibitor, the productive enzyme-substrate complex, and and inactive complexes. Reversible vertical arrows show inhibitor binding and release. In competitive inhibition the right-hand inhibitor-binding branch is absent. Pure noncompetitive inhibition retains both branches with equal inhibition constants; general mixed inhibition permits unequal constants. The drawing specifies populations and allowed steps, not an atomic binding-site geometry. Details.