Inhibiittori

Inhibiittori (Finnish for inhibitors) are substances that reduce the rate or extent of a chemical or biological process. In biochemistry, pharmacology, and related fields, inhibitors typically act by binding to a target protein and altering its activity. Inhibition can be reversible or irreversible.

Reversible inhibitors include competitive inhibitors, which bind to the enzyme’s active site and block substrate binding; noncompetitive inhibitors, which bind to a separate site and decrease maximal activity; uncompetitive inhibitors, which bind only to the enzyme–substrate complex; and mixed inhibitors, which have characteristics of both competitive and noncompetitive types.

Irreversible inhibitors form covalent bonds or very tight complexes with their targets, producing lasting inactivation. Enzyme inhibition is characterized by kinetic constants such as Ki and IC50. Competitive inhibition increases the apparent Km without changing Vmax; noncompetitive inhibition lowers Vmax with little effect on Km; uncompetitive inhibition lowers both Km and Vmax; mixed inhibition produces effects that depend on the relative binding to enzyme and enzyme–substrate complex.

Inhibitors have widespread applications. In research, they serve as tools to probe enzyme function and metabolic pathways. In medicine, inhibitors are used as drugs (for example, tyrosine kinase inhibitors in cancer, HIV protease inhibitors, acetylcholinesterase inhibitors in neurology, and ACE inhibitors for hypertension). In agriculture and toxicology, enzyme inhibitors can act as pesticides or inform toxicity testing. Irreversible inhibitors may have lasting therapeutic or toxic effects, as seen with aspirin’s COX inhibition.

Limitations include off-target effects, adverse reactions, and the development of resistance. Understanding inhibitor properties is central to drug design, enzymology, and industrial chemistry.