Comparative Abilities and Optimal Conditions for β-Glycosidase Enzymes to Hydrolyse the Glucuronide, Glucoside and N-Acetylglucosaminide Conjugates of Bile Acids

摘要

Enzymatic hydrolyses were described for three variants of glycosidic conjugated bile acids with one /?-glucuronidase (Helix pomatia), three /J-glucosidase (almonds, sweet almonds, and Escherichia coir), and four B-N-acetylglucosaminidase (jack beans, bovine kidney, human placenta, and Diplococcus pneumoniae) preparations. The substrates include the -glucuronide, p-glucoside, and -N-acetylglucosaminide conjugates of bile acids related to hyodeoxycholic, murideoxycholic, chenodeoxycholic, and ursodeoxycholic acids possessing a sugar moiety at position C-3, C-6 or C-7. The comparative abilities and optimal conditions for the p-glycosidases to catalyze the hydrolyses of the substrates were clarified by changing pHs and incubation times. Hydrolysis rates of the bile acid glycosides with B-glycosidase treatments were influenced by both the source of the enzyme preparations and the conjugated position of a sugar moiety in the substrates, and the 3-glucoside and 3-N-acetylglucosaminide conjugates were usually hydrolyzed more efficiently than their corresponding 6- and 7-analogs. Escherichia coli and jack bean enzymes were chosen to hydrolyse the glucosidic and N-acetylglucosaminidic conjugated bile acids, respectively.