Reaction: (1) cholest-5-ene-3β,25-diol + [reduced NADPHhemoprotein reductase] + O2 = cholest-5-ene-3β,7α,25-triol + [oxidized NADPHhemoprotein reductase] + H2O
(2) (25R)-cholest-5-ene-3β,26-diol + [reduced NADPHhemoprotein reductase] + O2 = (25R)-cholest-5-ene-3β,7α,26-triol + [oxidized NADPHhemoprotein reductase] + H2O
For diagram of reaction click here.
Other name(s): 25-hydroxycholesterol 7α-monooxygenase; CYP7B1; CYP7B1 oxysterol 7α-hydroxylase; 27-hydroxycholesterol 7-monooxygenase; 27-hydroxycholesterol 7α-hydroxylase; cholest-5-ene-3β,25-diol,NADPH:oxygen oxidoreductase (7α-hydroxylating); 25-hydroxycholesterol 7α-hydroxylase
Systematic name: cholest-5-ene-3β,25/26-diol,[NADPHhemoprotein reductase]:oxygen oxidoreductase (7α-hydroxylating)
Comments: A P-450 (heme-thiolate) protein. Unlike EC 18.104.22.168, 24-hydroxycholesterol 7α-monooxygenase, which is specific for its oxysterol substrate, this enzyme can also metabolize the oxysterols 24,25-epoxycholesterol, 22-hydroxycholesterol and 24-hydroxycholesterol, but to a lesser extent . The direct electron donor to the enzyme is EC 22.214.171.124, NADPHhemoprotein reductase.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:
1. Kumiko, O.M., Budai, K. and Javitt, N.B. Cholesterol and 27-hydroxycholesterol 7α-hydroxylation: evidence for two different enzymes. J. Lipid Res. 34 (1993) 581-588.
2. Toll, A., Wikvall, K., Sudjana-Sugiaman, E., Kondo, K.H. and Björkhem, I. 7α hydroxylation of 25-hydroxycholesterol in liver microsomes. Evidence that the enzyme involved is different from cholesterol 7α-hydroxylase. Eur. J. Biochem. 224 (1994) 309-316. [PMID: 7925343]
3. Li-Hawkins, J., Lund, E.G., Bronson, A.D. and Russell, D.W. Expression cloning of an oxysterol 7α-hydroxylase selective for 24-hydroxycholesterol. J. Biol. Chem. 275 (2000) 16543-16549. [PMID: 10748047]
4. Ren, S., Marques, D., Redford, K., Hylemon, P.B., Gil, G., Vlahcevic, Z.R. and Pandak, W.M. Regulation of oxysterol 7α-hydroxylase (CYP7B1) in the rat. Metabolism 52 (2003) 636-642. [PMID: 12759897]
5. Russell, D.W. The enzymes, regulation, and genetics of bile acid synthesis. Annu. Rev. Biochem. 72 (2003) 137-174. [PMID: 12543708]