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. 1975 Oct;30(4):530–535. doi: 10.1128/am.30.4.530-535.1975

Convenient Non-Chromatographic Assays for the Microbial Deconjugation and 7α-OH Bioconversion of Taurocholate

I A Macdonald 1, J M Bishop 1, D E Mahony 1, C N Williams 1
PMCID: PMC187225  PMID: 172011

Abstract

We described two convenient assay methods to estimate bile acid deconjugation and bile acid bioconversion at the 7α-OH position by individual microorganisms grown in media containing taurocholic acid. The methods are based on (i) a selective chemical assay for taurine conjugates previously described and (ii) the use of a cell-free preparation of 7α-hydroxysteroid dehydrogenase from Escherichia coli to directly quantify 7α-OH groups. These non-chromatographic approaches have been applied to the study of three model strains of intestinal organisms, E. coli, Bacteriodes fragilis, and Clostridium perfringens, grown in standard media in the presence of purified tritiated taurocholate. Assay results were confirmed by thin-layer chromatography solvent systems designed to separate conjugated from unconjugated bile acid and unmodified cholic acid nucleus from 7α-OH bioconversion product(s) (primarily 3α,12α dihydroxy, 7-keto-cholanoic acid). In addition, 7α-hydroxysteroid dehydrogenase activity was demonstrated in cell-free extracts of all three organisms. Of the three organisms, only C. perfringens was demonstrated to (i) deconjugate taurocholic acid, (ii) contain 3α-hydroxysteroid dehydrogenase activity, (iii) convert cholic acid into at least five labeled metabolites visible on thin-layer chromatography, and (iv) catalyze significant tritium exchange with water in the medium.

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Selected References

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