EC - Cholestanetriol 26-monooxygenase

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IntEnz Enzyme Nomenclature


Accepted name:
cholestanetriol 26-monooxygenase
Other names:
5β-cholestane-3α,7α,12α-triol 26-hydroxylase
5β-cholestane-3α,7α,12α-triol hydroxylase
cholestanetriol 26-hydroxylase
sterol 27-hydroxylase
sterol 26-hydroxylase
cholesterol 27-hydroxylase
cytochrome P450 27A1'
vitamin D3 25-hydroxylase
Systematic name:
5β-cholestane-3α,7α,12α-triol,adrenodoxin:oxygen oxidoreductase (26-hydroxylating)




This mitochondrial cytochrome P-450 enzyme requires adrenodoxin. It catalyses the first three sterol side chain oxidations in bile acid biosynthesis via the neutral (classic) pathway. Can also act on cholesterol, cholest-5-en-3β,7α-diol, 7α-hydroxycholest-4-en-3-one, and 5β-cholestane-3α,7α-diol. The enzyme can also hydroxylate cholesterol at positions 24 and 25. 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 , DIAGRAM , ExplorEnz , ENZYME@ExPASy , KEGG , MetaCyc , UniPathway
Protein domains and families: PROSITE:PDOC00081
Structural data: CSA , EC2PDB
Gene Ontology: GO:0047749
CAS Registry Number: 52227-77-7


  1. Masui, T., Herman, R., Staple, E.
    The oxidation of 5-beta-cholestane-3-alpha, 7-alpha, 12-alpha, 26-tetraol to 5-beta-cholestane-3-alpha, 7-alpha, 12-alpha-triol-26-oic acid via 5-beta-cholestane-3-alpha, 7-alpha, 12-alpha-triol-26-al by rat liver.
    Biochim. Biophys. Acta 117: 266-268 (1966). [PMID: 5914340]
  2. Okuda, K. and Hoshita, N.
    Oxidation of 5β-cholestane-3α,7α,12α-triol by rat-liver mitochondria.
    Biochim. Biophys. Acta 164: 381-388 (1968). [PMID: 4388637]
  3. Wikvall, K.
    Hydroxylations in biosynthesis of bile acids. Isolation of a cytochrome P-450 from rabbit liver mitochondria catalyzing 26-hydroxylation of C27-steroids.
    J. Biol. Chem. 259: 3800-3804 (1984). [PMID: 6423637]
  4. Andersson, S., Davis, D.L., Dahlbäck, H., Jörnvall, H. and Russell, D.W.
    Cloning, structure, and expression of the mitochondrial cytochrome P-450 sterol 26-hydroxylase, a bile acid biosynthetic enzyme.
    J. Biol. Chem. 264: 8222-8229 (1989). [PMID: 2722778]
  5. Dahlback, H., Holmberg, I.
    Oxidation of 5 beta-cholestane-3 alpha,7 alpha, 12 alpha-triol into 3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholestanoic acid by cytochrome P-450(26) from rabbit liver mitochondria.
    Biochem. Biophys. Res. Commun. 167: 391-395 (1990). [PMID: 2322231]
  6. Holmberg-Betsholtz, I., Lund, E., Björkhem, I. and Wikvall, K.
    Sterol 27-hydroxylase in bile acid biosynthesis. Mechanism of oxidation of 5β-cholestane-3α,7α,12α,27-tetrol into 3α,7α,12α-trihydroxy-5β-cholestanoic acid.
    J. Biol. Chem. 268: 11079-11085 (1993). [PMID: 8496170]
  7. Pikuleva, I. A., Babiker, A., Waterman, M. R., Bjorkhem, I.
    Activities of recombinant human cytochrome P450c27 (CYP27) which produce intermediates of alternative bile acid biosynthetic pathways.
    J. Biol. Chem. 273: 18153-18160 (1998). [PMID: 9660774]
  8. Furster, C., Bergman, T. and Wikvall, K.
    Biochemical characterization of a truncated form of CYP27A purified from rabbit liver mitochondria.
    Biochem. Biophys. Res. Commun. 273: 663-666 (1999). [PMID: 10512735]
  9. Pikuleva, I.A., Puchkaev, A. and Björkhem, I.
    Putative helix F contributes to regioselectivity of hydroxylation in mitochondrial cytochrome P450 27A1.
    Biochemistry 40: 7621-7629 (2001). [PMID: 11412116]

[EC created 1976 as EC, modified 2005, modified 2012, transferred 2016 to EC]