Steroid β-d-Glucosidase Activity in Rabbit Tissues

Rabbit liver, kidney, and small intestine contain glucosidase activity with a very high affinity toward the 3-β- d -glucosides of estrone, 17α-estradiol and 17β-estradiol. The liver enzyme has been purified 300- to 400-fold by chromatography on Sephadex G-150 and CM-cellulose. The K m for the hydrolysis of 17α-estradiol-3-glucoside by the purified enzyme was 5 x 10 -10 m as compared to 3.9 x 10 -5 m , 1.3 x 10 -3 m , and 2.1 x 10 -3 m for 17α-estradiol-17-glucoside, 17β-estradiol-17-glucoside, and p -nitrophenyl glucoside, respectively. Tissue distribution studies suggest that different steroid glucosidases, or else different forms of a single enzyme, may be responsible for hydrolysis of the phenolic and the alcoholic glucosides of the estrogens. The rapid hydrolysis of the estrogen-3-glucosides may explain the previous findings that these glycosides can be made by rabbit tissues in vitro , but are absent from rabbit excreta. The steroid glucosides represent novel, naturally occurring substrates for mammalian β-glucosidase, and are also very convenient substrates for its assay.