| Popis: |
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 Km 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. |
