Characterization of 7-alpha-dehydroxylase in Clostridium leptum

7-alpha-Dehydroxylation of primary bile acids was demonstrated radiochromatographically in whole cells of Clostridium leptum but was not observed in intestinal Bacteroides species. Activity of 7-alpha-Dehydroxylase was detected within a pH range of 5 to 9 and was 8-fold higher in specific activity in cell cultures in the presence of 0.1 mM sodium cholate than in its absence. 7-alpha-Dehydroxylase activity in whole cells was markedly inhibitied by 2,4-dinitrophenol, carbonyl-cyanide-m-chlorophenylhydrazine, and dicyclohexylcarbodiimide. A hypothesis concerning the dietary regulation of 7-alpha-dehydroxylating intestinal anaerobic bacteria is presented.