Degradation of steroids by intestinal bacteria II. Enzymes catalysing the oxidoreduction of the 3α-, 7α- and 12α-hydroxyl groups in cholic acid, and the dehydroxylation of the 7-hydroxyl group

Abstract

1. 1. Enzymes catalysing the oxidoreduction of the 7α-, 3α- and 12α-hydroxyl groups in cholic acid have been studied in the cell-free state from strains of clostridia, bacteroides, bifidobacterium and enterobacteria isolated from human faecal specimens. 2. 2. Enzymes specific for the 7α-hydroxyl group were isolated from five strains; enzymes active on both the 3α- and 7α-hydroxyl groups were isolated from two further strains, and an enzyme active on both the 3α- and 12α-hydroxyl groups from another strain. The pH optimum and bile acid specificity of these enzymes have been determined and the enzyme units per cell and K m values have been calculated. 3. 3. The 7-dehydroxylase from several human intestinal strains have been investigated.