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EC 1.17.99.5 Details
EC number
1.17.99.5
Accepted name
bile-acid 7α-dehydroxylase
Reaction
(1) deoxycholate + FAD + H2O = cholate + FADH2;;(2) lithocholate + FAD + H2O = chenodeoxycholate + FADH2
Other name(s)
cholate 7α-dehydroxylase, 7α-dehydroxylase, bile acid 7-dehydroxylase, deoxycholate:NAD+ oxidoreductase
Systematic name
deoxycholate:FAD oxidoreductase (7α-dehydroxylating)
CAS registry number
85130-33-2
Comment
Under physiological conditions, the reactions occur in the reverse direction to that shown above. This enzyme is highly specific for bile-acid substrates and requires a free C-24 carboxy group and an unhindered 7α-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]. Allo-deoxycholate is also formed as a side-product of the 7α-dehydroxylation of cholate [6]. The enzyme is present in intestinal anaerobic bacteria [6], even though its products are important in mammalian physiology.
History
created 2005 as EC 1.17.1.6, transferred 2006 to EC 1.17.99.5, deleted 2014
EC Tree
1.1.1.68 created 1965, deleted 1978 [transferred to EC 1.1.99.15, deleted 1980]
1.1.1.70 created 1965, deleted 1978
1.1.1.74 created 1972, deleted 1976
1.1.1.89 created 1972, deleted 1976
1.1.1.109 created 1972, deleted 1976
1.1.1.139 created 1972, deleted 1978
1.1.1.155 created 1976, deleted 2004
1.1.1.171 created 1978, deleted 1984
1.1.1.180 created 1983, deleted 1984
1.1.1.182 created 1983, deleted 1990
1.1.1.204 created 1972 as EC 1.2.1.37, transferred 1984 to EC 1.1.1.204, modified 1989, deleted 2004
1.1.1.242 created 1992, deleted 2001
1.1.1.249 provisional version created 1999, deleted 1999 (reinstated 2001 as EC 2.5.1.46)
1.1.1.253 created 1999, deleted 2003
1.1.99.15 created 1978, deleted 1980
1.1.99.17 created 1982, deleted 2003