Transformation of Bile Acids Into Iso–Bile Acids By Clostridium Perfringens : Possible Transport of 3β–Hydrogen Via the Coenzyme

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Abstract
We have examined the mechanism for the bacterial transformation of chenodeoxycholic acid and lithocholic acid into the corresponding 3β–hydroxy epimers with the use of 3α– and 3β–tritiated bile acids. The 3–oxo bile acids were transformed into the 3α– (85%) and 3β– (15%) hydroxy bile acids after 20–hr incubation with Clostridium perfringens. Approximately 75% radioactivity was recovered in the aqueous medium when [3β–3]chenodeoxycholic acid or [3β–3]lithocholic acid was incubated with the bacteria, and approximately 15% of radioactivity in the bile acid fraction was associated with the 3α–position of the iso–bile acids. When [3β–3]chenodeoxycholic acid was incubated with unlabeled 3–oxo–5β–cholanoic acid, tritiated litho– and iso–lithocholic acids were recovered. These results can be explained only when a 3–oxo intermediate is postulated, and the 3β–hydrogen in the bile acids is transferred by the bacterial coenzyme (NAD+ or NADP+) to the 3α–position in the iso–bile acids during the reduction of the 3–oxo compounds.

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