7 alpha-Dehydroxylation of cholic acid by cell extracts of Eubacterium species V.P.I. 12708

NADH:flavin oxidoreductase and 7 alpha-dehydroxylase were induced 5- and 90-fold, respectively, by cholic acid in cultures of Eubacterium species V.P.I. 12708. Assays of 7 alpha-dehydroxylase activity in the presence of various cofactors revealed that optimal activity was obtained in the presence of NAD+ plus FADH2. The pH optima of 7 alpha-dehydroxylase activity in whole cells and cell extracts were 7.0. The similar induction pattern of these two enzymes and the apparent cofactor requirements for 7 alpha-dehydroxylation suggest a relationship between 7 alpha-dehydroxylase and NADH:flavin oxidoreductase.