inhibiitorid

Inhibiitorid, or inhibitors, are substances that decrease or block the activity of biological molecules or chemical processes. In biochemistry and pharmacology, inhibitors most commonly act on enzymes, receptors, transporters, or signaling pathways, but they also include inhibitors of chemical reactions such as antioxidants that prevent oxidation. Inhibitors play a central role in regulation, therapy, and industrial applications.

Enzyme inhibitors can be classified by mechanism. Competitive inhibitors compete with the substrate for the active site, lowering apparent affinity but can be overcome by high substrate concentration. Noncompetitive inhibitors bind to an allosteric site, reducing catalytic efficiency without affecting substrate binding. Uncompetitive inhibitors bind only to the enzyme–substrate complex. Irreversible inhibitors form covalent bonds or very stable interactions, permanently inactivating the enzyme.

Measures of inhibitor potency include the inhibition constant (Ki) and IC50, the concentration needed to reduce activity by 50%. Reversibility, specificity, and pharmacokinetics determine how inhibitors behave in living organisms.

Common examples include aspirin, which inhibits cyclooxygenase enzymes to reduce inflammation and clotting, and statins, which inhibit HMG-CoA reductase to lower cholesterol. Protease inhibitors, such as ritonavir, block viral proteases to inhibit replication. ACE inhibitors, beta-lactamase inhibitors, and monoamine oxidase inhibitors are others used in medicine. In industrial chemistry, inhibitors may prevent undesirable side reactions or degradation, such as antioxidants that inhibit oxidation.

In research, inhibitors are tools to dissect pathways, confirm enzyme roles, and study regulatory networks. Therapeutic use requires balancing efficacy with safety, as inhibition can affect multiple targets and cause side effects.