Inhibitors

Inhibitors are substances that decrease the rate or extent of a chemical reaction or biological process. They act by interacting with targets such as enzymes, receptors, transporters, or metal centers, altering activity, binding, or catalysis.

Enzyme inhibitors are a major category. They may be reversible or irreversible. Reversible inhibitors can be competitive, binding the active site and competing with substrate; noncompetitive inhibitors bind an allosteric site and reduce Vmax without changing Km; uncompetitive inhibitors bind only the enzyme–substrate complex, lowering both Km and Vmax. Irreversible inhibitors form covalent bonds or cause permanent inactivation, often via reactive groups.

In pharmacology, inhibitors are used as drugs to dampen overactive pathways. Examples include competitive inhibitors like statins (HMG-CoA reductase inhibitors) and HIV protease inhibitors. Receptor- or signaling pathway inhibitors include antagonists that block receptors, such as beta-blockers (adrenergic receptor antagonists) and antihistamines. Enzyme inhibitors can be used to treat cancer, infections, and metabolic diseases; kinase inhibitors, for example, target dysregulated signaling in tumors.

Measured potency is reported as inhibition constants (Ki) or half-maximal inhibitory concentration (IC50). The context, such as substrate or effector levels, affects these values.

Outside biology, inhibitors also prevent unwanted reactions in chemistry or industry, such as corrosion inhibitors or polymerization inhibitors used to control reactions.