5beta-cholestane-3alpha,7alpha-diol 12alpha-hydroxylase explained

5beta-cholestane-3alpha,7alpha-diol 12alpha-hydroxylase
Ec Number:	1.14.13.96

In enzymology, a 5beta-cholestane-3alpha,7alpha-diol 12alpha-hydroxylase is an enzyme that catalyzes the chemical reaction

5beta-cholestane-3alpha,7alpha-diol + NADPH + H⁺ + O₂

\rightleftharpoons 5beta-cholestane-3alpha,7alpha,12alpha-triol + NADP⁺ + H₂O

The 4 substrates of this enzyme are 5beta-cholestane-3alpha,7alpha-diol, NADPH, H⁺, and O₂, whereas its 3 products are 5beta-cholestane-3alpha,7alpha,12alpha-triol, NADP⁺, and H₂O.

Nomenclature

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 NADH or NADPH as one donor, and incorporation of one atom o oxygen into the other donor. The systematic name of this enzyme class is 5beta-cholestane-3alpha,7alpha-diol,NADPH:oxygen oxidoreductase (12alpha-hydroxylating). Other names in common use include 5beta-cholestane-3alpha,7alpha-diol 12alpha-monooxygenase, sterol 12alpha-hydroxylase (ambiguous), CYP8B1, and cytochrome P450 8B1.

Further reading

• Hansson R, Wikvall K . Hydroxylations in biosynthesis of bile acids. Cytochrome P-450 LM4 and 12alpha-hydroxylation of 5beta-cholestane-3alpha, 7alpha-diol . European Journal of Biochemistry . 125 . 2 . 423–9 . July 1982 . 6811268 . 10.1111/j.1432-1033.1982.tb06700.x .
• Hansson R, Wikvall K . Hydroxylations in biosynthesis and metabolism of bile acids. Catalytic properties of different forms of cytochrome P-450 . The Journal of Biological Chemistry . 255 . 4 . 1643–9 . February 1980 . 6766451 .
• Lundell K, Wikvall K . Gene structure of pig sterol 12alpha-hydroxylase (CYP8B1) and expression in fetal liver: comparison with expression of taurochenodeoxycholic acid 6alpha-hydroxylase (CYP4A21) . Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids . 1634 . 3 . 86–96 . November 2003 . 14643796 . 10.1016/j.bbalip.2003.09.002 .
• Lukacin R, Matern U, Junghanns KT, Heskamp ML, Britsch L, Forkmann G, Martens S . Purification and antigenicity of flavone synthase I from irradiated parsley cells . Archives of Biochemistry and Biophysics . 393 . 1 . 177–83 . September 2001 . 11516175 . 10.1006/abbi.2001.2491 .
• Yang Y, Zhang M, Eggertsen G, Chiang JY . On the mechanism of bile acid inhibition of rat sterol 12alpha-hydroxylase gene (CYP8B1) transcription: roles of alpha-fetoprotein transcription factor and hepatocyte nuclear factor 4alpha . Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids . 1583 . 1 . 63–73 . June 2002 . 12069850 . 10.1016/s1388-1981(02)00186-5 .
• Russell DW . The enzymes, regulation, and genetics of bile acid synthesis . Annual Review of Biochemistry . 72 . 1 . 137–74 . 2003 . 12543708 . 10.1146/annurev.biochem.72.121801.161712 .