Specificity of oxidation of bile-salt hydroxyl groups by crude extracts of Pseudomonas testosteroni (ATCC 11996) used in determining bile salts.

Recent experimental evidence suggests that, presumably as a recent of mutation, crude extracts of Pseudomonas testosteroni (ATCC 11996) no contain amounts of 7alpha- and 12alpha-hydroxysteroid dehydrogenate activity that invalidate the results of bile-salt determinations. To confirm or deny this, we studied the specificity of hydroxysteroid dehydrogenase contained in crude extracts of currently available samples of this bacterium in the oxidation of bile-salt hydroxyl groups. The dehydrogenases in these extracts specifically oxidized 3alpha-hydroxyl groups of cholate, chenodeoxycholate, and deoxycholate anions. No significant amount of 12alpha- or 7alpha-hydroxysteriod dehydrogenase activity was detected. Currently available crude extracts of Pseudomonas testosteroni (ATCC 11996) are therefore suitable for bile-salt quantification.