Cytochrome P-450 Enzyme System

**Definition:** A superfamily of hundreds of closely related HEMEPROTEINS found throughout the phylogenetic spectrum, from animals, plants, fungi, to bacteria. They include numerous complex monooxygenases (MIXED FUNCTION OXYGENASES). In animals, these P-450 enzymes serve two major functions: (1) biosynthesis of steroids, fatty acids, and bile acids; (2) metabolism of endogenous and a wide variety of exogenous substrates, such as toxins and drugs (BIOTRANSFORMATION). They are classified, according to their sequence similarities rather than functions, into CYP gene families (>40% homology) and subfamilies (>59% homology). For example, enzymes from the CYP1, CYP2, and CYP3 gene families are responsible for most drug metabolism.

**Tree numbers:** - D08.244.453 - D08.811.682.690.708.170 - D12.776.422.220.453

**Synonyms:** - P-450 Enzyme - P450 Enzyme - Cytochrome P-450 - Cytochrome P450 - P-450 Enzymes - P450 Enzymes - Cytochrome P-450 Enzymes - Cytochrome P450 Superfamily - Cytochrome P-450 Superfamily - Cytochrome p450 Families - Cytochrome P-450 Families - CYP450 Superfamily - Cytochrome P-450 Enzyme - CYP450 Family