EC Explorer

1.17.99.5

bile-acid 7α-dehydroxylase

(1) deoxycholate + FAD + H₂O = cholate + FADH₂;;(2) lithocholate + FAD + H₂O = chenodeoxycholate + FADH₂

cholate 7α-dehydroxylase, 7α-dehydroxylase, bile acid 7-dehydroxylase, deoxycholate:NAD⁺ oxidoreductase

deoxycholate:FAD oxidoreductase (7α-dehydroxylating)

85130-33-2

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.

created 2005 as EC 1.17.1.6, transferred 2006 to EC 1.17.99.5, deleted 2014