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: 18.104.22.168
The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the Enzyme Commission system.
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 [Ishida92].
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 22.214.171.124 (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 , 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) [Ishida92]
|Cellular Component:||GO:0005789 - endoplasmic reticulum membrane [Ishida92]|
The apparent molecular mass was determined by SDS-PAGE [Ishida92].
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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