Studies on the substrate specificity of a carboxyl ester hydrolase from human pancreatic juice. II. Action on cholesterol esters and lipid-soluble vitamin esters.

Evidence is presented that human carboxyl ester hydrolase (carboxylic-ester hydrolase, EC 3.1.1.1) is able to hydrolyze cholesterol esters and lipid-soluble vitamins A, D-3 and E esters. Those activities require the presence of bile salts and the 3 alpha, 7 alpha-dihydroxylated bile salts have been found the most efficient activators. The results presented in this paper and in the preceding one suggest the existence of two sites of bile salts recognition. One site, specific of the 3 alpha, 7 alpha-hydroxyl group of cholanic acid would induce dimerization and activation of the enzyme. The other site, unspecific towards bile salts hydroxylation would be located at the active center and would be implicated in substrate recognition.