Role of Bile Salts in Activity of Cholesterol Esterase

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Abstract
In vitro taurocholic acid had a distinctly greater effect on cholesterol esterase than either glycocholic or the unconjugated cholic acid. Conjugation of cholic acid with glycine appeared to inhibit the effect of cholic acid. Free taurine and glycine had no influence on the effect of cholic acid. In the series of unconjugated acids, the effect was greatest with cholic acid, which has 3 hydroxyl groups, and the effect decreased with decreasing no. of hydroxyl groups until with dehydrocholic acid, which has no hydroxyl groups, there was no effect. Apparently, the hydroxyl groups and the carboxyl group, free or conjugated, are involved in the effect of bile salts on cholesterol esterase activity. Other data on the interrelationships of cholesterol and bile salt concn. suggest some type of combination between cholesterol and bile salt. One molecule of bile salt appeared to be associated with 1 molecule of cholesterol in the esterification reaction with fatty acid. In hydrolysis expts. the results were also in accord with the hypothesis of complex formation between cholesterol or cholesterol ester and bile salt.