CYP450entsyymijärjestelmän

Cytochrome P450 enzymes, commonly abbreviated as CYP450, are a large and diverse superfamily of heme-containing monooxygenases that catalyze the oxidation of a wide range of endogenous and exogenous substrates. In a typical monooxygenation reaction, they insert one atom of molecular oxygen into the substrate while the other oxygen atom is reduced to water, using electrons supplied by NADPH via a P450 reductase partner. The catalytic cycle involves substrate binding, reduction, oxygen activation, second reduction, and product release.

Most human CYP enzymes are localized in the endoplasmic reticulum of liver cells, with a subset found in mitochondria. The best known drug-metabolizing families are CYP1, CYP2, and CYP3A, with CYP3A4 accounting for a large portion of drug oxidation. Beyond drug metabolism, CYP enzymes process endogenous compounds such as steroids and fatty acids, and they can also activate or detoxify certain environmental chemicals.

Genetic variation across CYP genes leads to substantial interindividual differences in metabolic capacity. Individuals can be categorized as poor, intermediate, extensive, or ultra-rapid metabolizers, influencing drug clearance, efficacy, and risk of adverse effects. Enzyme activity can be induced or inhibited by various drugs, foods, or diseases, creating important drug–drug and drug–gene interactions.

Nomenclature follows a family-based system, with families designated by numbers (CYP1, CYP2, CYP3) and subfamilies by letters (CYP3A). Specific enzymes are named with a family and gene symbol (for example, CYP3A4). The study of CYP450 enzymes spans pharmacology, toxicology, and clinical pharmacogenomics due to their central role in xenobiotic metabolism and pharmacokinetics.