Studies on the α-L-Iduronidase Activity of β-Glucuronidase Preparations from Bovine Liver, Rat Liver, and Rat Preputial Gland

抄録

A commercial preparation of bovine liver β-glucuronidase contained two distinct enzyme species, both of which catalyze the hydrolysis of 4-methylumbelliferyl α-L-iduronide. The species with a molecular weight of about 290, 000 was devoid of phenyl α-L-iduronidase activity and exhibited 4-methylumbelliferyl β-D-glucuronidase activity. The species with a molecular weight of about 78, 000 was active towards phenyl α-L-iduronide but lacked the latter activity. Studies of the kinetics, of inhibition and heat inactivation suggested that the hydrolysis of 4-methylumbelliferyl α-L-iduronide is due to the β-glucuronidase in the case of the 290, 000-dalton species. The highly purified β-glucuronidase preparations derived from rat preputial gland and liver lysosomes also exhibited 4-methylumbelliferyl α-L-iduronidase activity. Thesefindings support the view that β-glucuronidase can hydrolyze certain α-L-iduronide bonds and raise the possibility that β-glucuronidase may play a role in the catabolism of iduronic acid-containing glycosaminoglycans.