EC - 5β-cholestane-3α,7α-diol 12α-hydroxylase

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IntEnz Enzyme Nomenclature


Accepted name:
5β-cholestane-3α,7α-diol 12α-hydroxylase
Other names:
5β-cholestane-3α,7α-diol 12α-monooxygenase
sterol 12α-hydroxylase [ambiguous]
cytochrome P450 8B1
Systematic name:
5β-cholestane-3α,7α-diol,[reduced NADPH—hemoprotein reductase]:oxygen oxidoreductase (12α-hydroxylating)




A cytochrome P450 (heme-thiolate) protein found in mammals. This is the key enzyme in the biosynthesis of the bile acid cholic acid (3α,7α,12α-trihydroxy-5β-cholanoic acid). The activity of this enzyme determines the biosynthetic ratio between cholic acid and chenodeoxycholic acid [3]. The enzyme can also hydroxylate the substrate at the 25 and 26 position, but to a lesser extent [1].

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:0033779


  1. Hansson, R. and Wikvall, K.
    Hydroxylations in biosynthesis of bile acids. Cytochrome P-450 LM4 and 12α-hydroxylation of 5β-cholestane-3α,7α-diol.
    Eur. J. Biochem. 125: 423-429 (1982). [PMID: 6811268]
  2. Hansson, R. and Wikvall, K.
    Hydroxylations in biosynthesis and metabolism of bile acids. Catalytic properties of different forms of cytochrome P-450.
    J. Biol. Chem. 255: 1643-1649 (1980). [PMID: 6766451]
  3. Lundell, K. and Wikvall, K.
    Gene structure of pig sterol 12β-hydroxylase (CYP8B1) and expression in fetal liver: comparison with expression of taurochenodeoxycholic acid 6β-hydroxylase (CYP4A21).
    Biochim. Biophys. Acta 1634: 86-96 (2003). [PMID: 14643796]
  4. del Castillo-Olivares, A. and Gil, G.
    α1-fetoprotein transcription factor is required for the expression of sterol 12α-hydroxylase, the specific enzyme for cholic acid synthesis. Potential role in the bile acid-mediated regulation of gene transcription.
    J. Biol. Chem. 275: 17793-17799 (2000). [PMID: 10747975]
  5. Yang, Y., Zhang, M., Eggertsen, G. and Chiang, J.Y.L.
    On the mechanism of bile acid inhibition of rat sterol 12α-hydroxylase gene (CYP8B1) transcription: roles of α-fetoprotein transcription factor and hepatocyte nuclear factor 4α.
    Biochim. Biophys. Acta 1583: 63-73 (2002). [PMID: 12069850]
  6. Russell, D.W.
    The enzymes, regulation, and genetics of bile acid synthesis.
    Annu. Rev. Biochem. 72: 137-174 (2003). [PMID: 12543708]

[EC created 2005 as EC, transferred 2018 to EC]