Transformation of bile acids into iso-bile acids by clostridium perfringens: Possible transport of 3β-hydrogen via the coenzyme
✍ Scribed by Ashok K. Batta; Gerald Salen; Sarah Shefer
- Publisher
- John Wiley and Sons
- Year
- 1985
- Tongue
- English
- Weight
- 691 KB
- Volume
- 5
- Category
- Article
- ISSN
- 0270-9139
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✦ Synopsis
We have examined the mechanism for the bacterial transformation of chenodeoxycholic acid and lithocholic acid into the corresponding 38-hydroxy epimers with the use of 3a-and 38-tritiated bile acids. The 3-ox0 bile acids were transformed into the 3a-(85%) and 38-(15%) hydroxy bile acids after 20-hr incubation with Clostridium perfringens. Approximately 75% radioactivity was recovered in the aqueous medium when [38-3H]chenodeoxycholic acid or [38-3H]lithocholic acid was incubated with the bacteria, and approximately 15% of radioactivity in the bile acid fraction was associated with the 3a-position of the iso-bile acids. When [3B-3H]chenodeoxycholic acid was incubated with unlabeled 3-0x0-58-cholanoic acid, tritiated litho-and iso-lithocholic acids were recovered. These results can be explained only when a %ox0 intermediate is postulated, and the 3B-hydrogen in the bile acids is transferred by the bacterial coenzyme (NAD+ or NADP+) to the 3a-position in the iso-bile acids during the reduction of the 3-Ox0 compounds.
During their enterohepatic circulation, a small percentage of the bile salts passes into the large intestine where they are deconjugated by colonic bacteria and transformed into secondary bile acids by 7a-dehydroxylation, oxidation and/or isomerization. These modified bile acids enter the enterohepatic circulation by passive absorption and some of these have been shown to be physiologically important. Thus, LCA is hepatotoxic, and both LCA and DCA are considered to promote intestinal