KEGG   ENZYME: 1.17.98.1Help
Entry
EC 1.17.98.1                Enzyme                                 

Name
bile-acid 7alpha-dehydroxylase;
cholate 7alpha-dehydroxylase;
7alpha-dehydroxylase;
bile acid 7-dehydroxylase;
deoxycholate:NAD+ oxidoreductase
Class
Oxidoreductases;
Acting on CH or CH2 groups;
With other, known, physiological acceptors
BRITE hierarchy
Sysname
deoxycholate:FAD oxidoreductase (7alpha-dehydroxylating)
Reaction(IUBMB)
(1) deoxycholate + FAD + H2O = cholate + FADH2 [RN:R07220];
(2) lithocholate + FAD + H2O = chenodeoxycholate + FADH2 [RN:R03978]
Reaction(KEGG)
Substrate
deoxycholate [CPD:C04483];
FAD [CPD:C00016];
H2O [CPD:C00001];
lithocholate [CPD:C03990]
Product
cholate [CPD:C00695];
FADH2 [CPD:C01352];
chenodeoxycholate [CPD:C02528]
Comment
Under physiological conditions, the reactions form deoxycholate. This enzyme is highly specific for bile-acid substrates and requires a free C-24 carboxy group and an unhindered 7alpha-hydroxy group on the B-ring of the steroid nucleus for activity, as found in cholate and chenodeoxycholate. The reaction is stimulated by the presence of NAD+ but is inhibited by excess NADH. This unusual regulation by the NAD+/NADH ratio is most likely the result of the intermediates being linked at C-24 by an anhydride bond to the 5'-diphosphate of 3'-phospho-ADP [2,5,6]. Allodeoxycholate is also formed as a side-product of the 7alpha-dehydroxylation of cholate [6]. The enzyme is present in intestinal anaerobic bacteria [6], even though its products are important in mammalian physiology.
History
EC 1.17.98.1 created 2005 as EC 1.17.1.6, transferred 2006 to EC 1.17.99.5, transferred 2014 to EC 1.17.98.1
Reference
1  [PMID:7276750]
  Authors
White BA, Cacciapuoti AF, Fricke RJ, Whitehead TR, Mosbach EH, Hylemon PB.
  Title
Cofactor requiremets for 7 alpha-dehydroxylation of cholic and chenodeoxycholic acid in cell extracts of the intestinal anaerobic bacterium, Eubacterium species V.P.I. 13708.
  Journal
J. Lipid. Res. 22 (1981) 891-8.
Reference
2  [PMID:6833878]
  Authors
White BA, Paone DA, Cacciapuoti AF, Fricke RJ, Mosbach EH, Hylemon PB.
  Title
Regulation of bile acid 7-dehydroxylase activity by NAD+ and NADH in cell extracts of Eubacterium species V.P.I. 12708.
  Journal
J. Lipid. Res. 24 (1983) 20-7.
Reference
3  [PMID:3549693]
  Authors
Coleman JP, White WB, Hylemon PB.
  Title
Molecular cloning of bile acid 7-dehydroxylase from Eubacterium sp. strain VPI 12708.
  Journal
J. Bacteriol. 169 (1987) 1516-21.
Reference
4  [PMID:12543708]
  Authors
Russell DW.
  Title
The enzymes, regulation, and genetics of bile acid synthesis.
  Journal
Annu. Rev. Biochem. 72 (2003) 137-74.
Reference
5  [PMID:3558364]
  Authors
Coleman JP, White WB, Egestad B, Sjovall J, Hylemon PB.
  Title
Biosynthesis of a novel bile acid nucleotide and mechanism of 7 alpha-dehydroxylation by an intestinal Eubacterium species.
  Journal
J. Biol. Chem. 262 (1987) 4701-7.
Reference
6  [PMID:2010697]
  Authors
Hylemon PB, Melone PD, Franklund CV, Lund E, Bjorkhem I.
  Title
Mechanism of intestinal 7 alpha-dehydroxylation of cholic acid: evidence that allo-deoxycholic acid is an inducible side-product.
  Journal
J. Lipid. Res. 32 (1991) 89-96.
Other DBs
ExplorEnz - The Enzyme Database: 
IUBMB Enzyme Nomenclature: 
ExPASy - ENZYME nomenclature database: 
BRENDA, the Enzyme Database: 
CAS: 
85130-33-2

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