Cholesterol side-chain cleavage enzyme is commonly referred to as P450scc, where "scc" is an acronym for side-chain cleavage. P450scc is a mitochondrial enzyme that catalyzes conversion of cholesterol to pregnenolone. This is the first reaction in the process of steroidogenesis in all mammalian tissues that specialize in the production of various steroid hormones.
cholesterol + 3 NADPH + 3 H + 3 O2
⇄ pregnenolone + 4-methylpentanal + 3 NADP + 3 H2
P450scc is a member of the cytochrome P450 superfamily of enzymes (family 11, subfamily A, polypeptide 1). The gene name is CYP11A1.