Steroid N-Acetylglucosaminyl Transferase

A comparison of glucoside formation by liver preparations from the rabbit and the mouse

“…A comparison of the 3) between the pH results in Tables 1 and 2 indicates no correlation for the formation in either rabbit or mouse preparations between the efficacy of steroids as inhibitors of p-nitrophenyl glucoside formation, and their own ability to form glucosides. The inhibition of steroid glycoside formation by steroids and other compounds which themselves do not form the corresponding glycoside has been reported (Collins et al, 1968). Labow et al (1971) suggested that this effect may be due to the binding of these steroids to the enzyme without proceeding to the formation of product.…”

“…Liver homogenates and microsomal fractions were prepared as detailed by Collins et al (1968Collins et al ( , 1970. The assays were performed by the procedure using UDP-[6-3H]glucose as described by Labow & Layne (1972).…”

Transfer of xylose to steroids by rabbit liver microsomes

“…It has been shown , that there are two enzymes in rabbit liver which effect the transfer of glucose to estrogens. One of these, which may be identical with the steroid 7V-acetylglucosaminyl transferase described by Collins et al (1968), is highly specific for the 17«-hydroxyl group of 17«-estradiol, and requires the prior conjugation of the 3-hydroxyl group of the steroid with glucuronic acid. This enzyme has a pH optimum of about 8.0 for glucose transfer from UDP-glucose.…”

“…UDP-xylose was purchased from Sigma Chemical Co., St. Louis, Missouri. Steroids and other reagents were obtained and purified as previously described (Collins et al, 1968(Collins et al, , 1970Williamson et al, 1972;. All labeled steroids contained tritium in the (6,7) positions and were obtained from New England Nuclear Corp., Boston, Mass.…”

“…liver mierosomes can effect the transfer of fV-acetylglucosamine or glucose to the 17a-hydroxyl of 17a-estradiol, provided that the 3-hydroxyl group of the steroid has previously been conjugated with glucuronic acid (Collins et al, 1968(Collins et al, , 1970. Williamson et al (1971) have shown that glucose or galactose, but not N-acetylglucosamine, can be transferred by washed rabbit liver mierosomes to the phenolic 3-hydroxyl of estrone, 17a-estradiol, and 17/3-estradiol, but not of estriol.…”