cytochrome P450 a microsomal enzyme is a hemoprotein, which serves as the terminal oxidase. The name cytochrome P450 (abbreted as P450 or CYP ) is derived from the spectral propeies of this hemoprotein. In its reduced (ferrous) form, it binds carbon monoxide to give a complex that absorbs light maximally at 450 nm. They are involved in the metabolism of various drugs The relative abundance of P450s, compared with that of the reductase in the liver, contributes to making P450 heme reduction a rate-limiting step in hepatic drug oxidations. CYP is vital to the formation of cholesterol, steroids and arachidonic acid metabolites Reference: Katzung 13th edition pg: 55