cholesterol monooxygenase (side-chain-cleaving)

(P₄₅₀SCC) cho·les·ter·ol mono·oxy·gen·ase (side-chain-cleav·ing) (P₄₅₀SCC) (kə-lesґtə-rol mon″o-okґsə-jən-ās sīd chān klēvґing) [EC 1.14.15.6] an enzyme of the oxidoreductase class that catalyzes the NADPH-dependent conversion of cholesterol to pregnenolone in a series of three reactions, successive hydroxylations of the 20 and 22 positions followed by cleavage of the side chain. The enzyme is a mitochondrial cytochrome P-450 acting as a terminal oxidase in an electron transport chain that also contains adrenodoxin and a flavoprotein. The reaction is the first step in the conversion of cholesterol to steroid hormones. Deficiency of the enzyme, an autosomal recessive trait, causes lipoid adrenal hyperplasia, a type of congenital adrenal hyperplasia (type I). Called also cholesterol desmolase and 20,22-desmolase.