cholesterol monooxygenase (side-chain-cleaving);
cholesterol desmolase;
cytochrome P-450scc;
C27-side chain cleavage enzyme;
cholesterol 20-22-desmolase;
cholesterol C20-22 desmolase;
cholesterol side-chain cleavage enzyme;
cholesterol side-chain-cleaving enzyme;
steroid 20-22 desmolase;
steroid 20-22-lyase;
CYP11A1 (gene name)

Oxidoreductases;
Acting on paired donors, with O2 as oxidant and incorporation or reduction of oxygen. The oxygen incorporated need not be derived from O2;
With reduced iron-sulfur protein as one donor, and incorporation of one atom of oxygen into the other donor

cholesterol,reduced-adrenodoxin:oxygen oxidoreductase (side-chain-cleaving)

cholesterol + 6 reduced adrenodoxin + 3 O2 = pregnenolone + 4-methylpentanal + 6 oxidized adrenodoxin + 4 H2O (overall reaction) [RN:R02724];
(1a) cholesterol + 2 reduced adrenodoxin + O2 = (22R)-22-hydroxycholesterol + 2 oxidized adrenodoxin + H2O;
(1b) (22R)-22-hydroxycholesterol + 2 reduced adrenodoxin + O2 = (20R,22R)-20,22-dihydroxycholesterol + 2 oxidized adrenodoxin + H2O;
(1c) (20R,22R)-20,22-dihydroxy-cholesterol + 2 reduced adrenodoxin + O2 = pregnenolone + 4-methylpentanal + 2 oxidized adrenodoxin + 2 H2O

R02724;
(other) R01454 R02723 R03933 R04676 R04854 R04855

cholesterol [CPD:C00187];
reduced adrenodoxin [CPD:C00662];
O2 [CPD:C00007];
(22R)-22-hydroxycholesterol [CPD:C05502];
(20R,22R)-20,22-dihydroxy-cholesterol

A heme-thiolate protein (cytochrome P-450). The reaction proceeds in three stages, with two hydroxylations at C-22 and C-20 preceding scission of the side-chain between carbons 20 and 22. The initial source of the electrons is NADPH, which transfers the electrons to the adrenodoxin via EC 1.18.1.6, adrenodoxin-NADP+ reductase.

1  [PMID:1238395]

Burstein S, Middleditch BS, Gut M

Mass spectrometric study of the enzymatic conversion of cholesterol to (22R)-22-hydroxycholesterol, (20R,22R)-20,22-dihydroxycholesterol, and pregnenolone, and of (22R)-22-hydroxycholesterol to the lgycol and pregnenolone in bovine adrenocortical preparations. Mode of oxygen incorporation.

J. Biol. Chem. 250 (1975) 9028-37.

2  [PMID:7217084]

Hanukoglu I, Spitsberg V, Bumpus JA, Dus KM, Jefcoate CR.

Adrenal mitochondrial cytochrome P-450scc. Cholesterol and adrenodoxin interactions at equilibrium and during turnover.

J. Biol. Chem. 256 (1981) 4321-8.

Bos taurus [GN:bta]

3  [PMID:3011431]

Hanukoglu I, Hanukoglu Z

Stoichiometry of mitochondrial cytochromes P-450, adrenodoxin and adrenodoxin reductase in adrenal cortex and corpus luteum. Implications for membrane organization and gene regulation.

Eur. J. Biochem. 157 (1986) 27-31.

4  [PMID:21636783]

Strushkevich N, MacKenzie F, Cherkesova T, Grabovec I, Usanov S, Park HW

Structural basis for pregnenolone biosynthesis by the mitochondrial monooxygenase system.

Proc. Natl. Acad. Sci. U. S. A. 108 (2011) 10139-43.

5  [PMID:21159775]

Mast N, Annalora AJ, Lodowski DT, Palczewski K, Stout CD, Pikuleva IA

Structural basis for three-step sequential catalysis by the cholesterol side chain cleavage enzyme CYP11A1.

J. Biol. Chem. 286 (2011) 5607-13.