Abstract
1. 1. Glucose-6-phosphate dehydrogenase (EC 1.1.1.49) purified from the supernatant fraction of bovine corpora lutea has been used to demonstrate that estradiol-17 α, estradiol-17 β and pregnenolone at high concentrations are uncompetitive inhibitors of this enzyme with respect to NADP +. Estradiol-17 α demonstrated greater inhibition than the 17 β-isomer. No effect of 1 μM estrone, estradiol-17 β, estriol, diethylstilbestrol, dehydroisoandrosterone sulfate, androsterone, androstenedione, testosterone and progesterone on activity was observed. 2. 2. NADP + at physiologic concentrations stabilized the enzyme while NAD + did not. Removal of bound NADP + caused inactivation which could be reversed by exposure to 5.0 μM NADP +. This reactivation was not retarded by estradiol-17 α, estradiol-17 β or dehydroisoandrosterone. 3. 3. Glucose-6-phosphate dehydrogenase activity in the crude supernatant fraction of porcine anterior pituitary was unaffected by estradiol-17 β concentrations as high as 10 −5 M. 4. 4. These observations militate against inactivation of glucose-6-phosphate dehydrogenase as an important mechanism of steroid action in vivo.
Published Version
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