side chain

Cholesterol monooxygenase (side-chain-cleaving)

In enzymology, a cholesterol monooxygenase (side-chain-cleaving) is an enzyme that catalyzes the chemical reaction

cholesterol + reduced adrenal ferredoxin + O2 rightleftharpoons pregnenolone + 4-methylpentanal + oxidized adrenal ferredoxin + H2O

The 3 substrates of this enzyme are cholesterol, reduced adrenal ferredoxin, and O2, whereas its 4 products are pregnenolone, 4-methylpentanal, oxidized adrenal ferredoxin, and H2O.

This enzyme belongs to the family of oxidoreductases, specifically those 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 o one atom of oxygen into the other donor. The systematic name of this enzyme class is cholesterol,reduced-adrenal-ferredoxin:oxygen oxidoreductase (side-chain-cleaving). Other names in common use include cholesterol desmolase, cytochrome P-450scc, desmolase, steroid 20-22, C27-side chain cleavage enzyme, cholesterol 20-22-desmolase, cholesterol C20-22 desmolase, cholesterol side-chain cleavage enzyme, cholesterol side-chain-cleaving enzyme, enzymes, cholesterol side-chain-cleaving, steroid 20-22 desmolase, and steroid 20-22-lyase. This enzyme participates in c21-steroid hormone metabolism. It employs one cofactor, heme.


  • Hanukoglu I, Jefcoate CR "Mitochondrial cytochrome P-450sec. Mechanism of electron transport by adrenodoxin". J. Biol. Chem. 255 3057–61.
  • 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 4321–8.

External links

The CAS registry number for this enzyme class is .

Gene Ontology (GO) codes

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