Species: Oryctolagus cuniculus
Subunit composition of
7α-hydroxycholest-4-en-3-one 12α-hydroxylase = [POR][CYP8B1]
NADPH-cytochrome P450 reductase = POR (summary available)
cytochrome P450 8B1 = CYP8B1 (summary available)
Enzymatic reaction of: 7α-hydroxycholest-4-en-3-one 12α-hydroxylase
Synonyms: 7α-hydroxy-4-cholesten-3-one 12α-hydroxylase, sterol 12α-hydroxylase, 7α-hydroxy-4-cholesten-3-one 12α-monooxygenase, 7α-hydroxycholest-4-en-3-one,NADPH:oxygen oxidoreductase (12α-hydroxylating)
EC Number: 188.8.131.527α-hydroxycholest-4-en-3-one + 2 a ferrocytochrome b5 + 2 H+ + oxygen → 7α,12α-dihydroxycholest-4-en-3-one + 2 a ferricytochrome b5 + H2O
The direction shown, i.e. which substrates are on the left and right sides, is in accordance with the direction in which it was curated.
The reaction is physiologically favored in the direction shown.
In Pathways: bile acid biosynthesis, neutral pathway
This enzyme requires NADPH-cytochrome P450 reductase for its activity. It was assayed using the reductase, phospholipid and a NADPH regenerating system. Inclusion of cytochrome b5 enhanced the activity [Ishida92a].
The level of this enzyme activity determines the relative amounts of cholate and chenodeoxycholate (or other species-specific bile acid) produced in the liver. The 12α hydroxylation leads to cholate biosynthesis (reviewed in [Russell03] and [Norlin07]).
This enzyme also catalyzes EC 184.108.40.206 ( 5β-cholestane-3α,7α-diol + NAD(P)H + oxygen + H+ → 5β-cholestane-3α,7α,12α-triol + NAD(P)+ + H2O) and has broad substrate specificity, although 7α-hydroxycholest-4-en-3-one was the more efficient substrate. Recombinant enzyme was also demonstrated to have these activities [Andersson98].
|Gene:||POR||Accession Number: G-10911 (MetaCyc)|
Molecular Weight: 76.588 kD (from nucleotide sequence)
Molecular Weight: 77.0 kD (experimental) [Black82]
Relationship Links: InterPro:IN-FAMILY:IPR001094, InterPro:IN-FAMILY:IPR001433, InterPro:IN-FAMILY:IPR001709, InterPro:IN-FAMILY:IPR003097, InterPro:IN-FAMILY:IPR008254, InterPro:IN-FAMILY:IPR017927, InterPro:IN-FAMILY:IPR017938, InterPro:IN-FAMILY:IPR023173, InterPro:IN-FAMILY:IPR023208, InterPro:IN-FAMILY:IPR029039, Pfam:IN-FAMILY:PF00175, Pfam:IN-FAMILY:PF00258, Pfam:IN-FAMILY:PF00667, Prints:IN-FAMILY:PR00369, Prints:IN-FAMILY:PR00371, Prosite:IN-FAMILY:PS50902, Prosite:IN-FAMILY:PS51384
The enzyme is believed to form a stable, 1:1 complex with cytochrome P450 (in [Black82]).
The native apparent molecular mass was determined by SDS-PAGE [Black82].
|Gene:||CYP8B1||Accession Number: G-10912 (MetaCyc)|
Locations: endoplasmic reticulum membrane
Molecular Weight: 57.494 kD (from nucleotide sequence)
Molecular Weight: 50.0 kD (experimental) [Ishida92a]
Relationship Links: InterPro:IN-FAMILY:IPR001128, InterPro:IN-FAMILY:IPR002403, InterPro:IN-FAMILY:IPR024204, InterPro:IN-FAMILY:IPR030686, Pfam:IN-FAMILY:PF00067, Prints:IN-FAMILY:PR00465, Prosite:IN-FAMILY:PS00086
The apparent molecular mass was determined by SDS-PAGE [Ishida92a].
Andersson98: Andersson U, Eggertsen G, Bjorkhem I (1998). "Rabbit liver contains one major sterol 12alpha-hydroxylase with broad substrate specificity." Biochim Biophys Acta 1389(2);150-4. PMID: 9461256
Black82: Black SD, Coon MJ (1982). "Structural features of liver microsomal NADPH-cytochrome P-450 reductase. Hydrophobic domain, hydrophilic domain, and connecting region." J Biol Chem 257(10);5929-38. PMID: 6802823
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