EC - Cholesterol monooxygenase (side-chain-cleaving)

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IntEnz Enzyme Nomenclature


Accepted name:
cholesterol monooxygenase (side-chain-cleaving)
Other names:
C27-side chain cleavage enzyme
cholesterol 20-22-desmolase
cholesterol C20-22 desmolase
cholesterol desmolase
cholesterol side-chain cleavage enzyme
cholesterol side-chain-cleaving enzyme
cytochrome P-450scc
desmolase, steroid 20-22
enzymes, cholesterol side-chain-cleaving
steroid 20-22 desmolase
steroid 20-22-lyase
cytochrome p450scc
Systematic name:
cholesterol,reduced-adrenodoxin:oxygen oxidoreductase (side-chain-cleaving)




A heme-thiolate protein (cytochrome P450). 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, adrenodoxin-NADP+ reductase.

Links to other databases

Enzymes and pathways: NC-IUBMB , BRENDA , ExplorEnz , ENZYME@ExPASy , KEGG , MetaCyc , UniPathway
Protein domains and families: PROSITE:PDOC00081
Structural data: CSA , EC2PDB
Gene Ontology: GO:0008386
CAS Registry Number: 37292-81-2
UniProtKB/Swiss-Prot: (14) [show] [UniProt]


  1. Burstein, S., Middleditch, B. S., 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 : 9028-9037 (1975). [PMID: 1238395]
  2. Hanukoglu, I., Spitsberg, V., Bumpus, J. A., Dus, K. M., Jefcoate, C. R.
    Adrenal mitochondrial cytochrome P-450scc. Cholesterol and adrenodoxin interactions at equilibrium and during turnover.
    J. Biol. Chem. 256 : 4321-4328 (1981). [PMID: 7217084]
  3. 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 : 27-31 (1986). [PMID: 3011431]
  4. Strushkevich, N., MacKenzie, F., Cherkesova, T., Grabovec, I., Usanov, S., Park, H. W.
    Structural basis for pregnenolone biosynthesis by the mitochondrial monooxygenase system.
    Proc. Natl. Acad. Sci. U.S.A. 108 : 10139-10143 (2011). [PMID: 21636783]
  5. Mast, N., Annalora, A. J., Lodowski, D. T., Palczewski, K., Stout, C. D., Pikuleva, I. A.
    Structural basis for three-step sequential catalysis by the cholesterol side chain cleavage enzyme CYP11A1.
    J. Biol. Chem. 286 : 5607-5613 (2011). [PMID: 21159775]

[EC created 1983, modified 2013, modified 2014]