title: Further evidence that there is more than one adrenal 21-hydroxylase system.
abstract: The 21-hydroxylase activity of microsomes isolated from bovine adrenal cortex have been assayed using [21-3H]17-hydroxypregnenolone and [1,2-3H]17-hydroxyprogesterone as substrates. When the assays are performed in the presence of an NADH regenerating system, to inhibit steroid 3 beta-hydroxy isomerase-dehydrogenase activity, the microsomes oxidize the 3 beta-hydroxy-5-ene steroid at a rate of 0.37 nmol/min.nmol cytochrome P-450 and the 3-keto-4-ene steroid at a rate of 6.4 nmol/min.nmol. When the microsomes are solubilized with Triton CF-54 they lose the ability to oxidize the 3-hydroxy-5-ene steroid, while the specific activity of the microsomes for the 3-keto-4-ene steroid is enhanced 3-fold. In contrast, when the microsomes are solubilized with sodium cholate, their specific activity towards the 4-ene steroid is decreased by 50% while the specific activity for a low concentration of the 5-ene steroid, 1 microM, is unchanged. In addition, when the oxidations of the labeled steroids (at 1 microM) by the microsomes, are examined in the presence of unlabeled 17-hydroxyprogesterone (at 20 microM) the oxidation of the 3-keto-4-ene steroid is inhibited by 92% while the oxidation of the 3 beta-hydroxy-5-ene steroid is only inhibited by 20%. These results all suggest that there are at least two 21-hydroxylases in bovine adrenal tissue, one of which can utilize the 3-keto-4-ene steroids only, the other of which, in addition, can utilize the 3 beta-hydroxy-5-ene steroids as substrates.
mesh_terms: D006907:17-alpha-Hydroxypregnenolone / Q000378:metabolism; D019326:17-alpha-Hydroxyprogesterone; D000311:Adrenal Glands / Q000201:enzymology*; D000818:Animals; D002417:Cattle; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics; D003902:Detergents / Q000494:pharmacology; D006908:Hydroxyprogesterones / Q000378:metabolism; D066298:In Vitro Techniques; D009243:NAD / Q000378:metabolism; D013255:Steroid 21-Hydroxylase / Q000032:analysis* / Q000235:genetics; D013250:Steroid Hydroxylases / Q000032:analysis*; D013379:Substrate Specificity; D014316:Tritium
chemical_list: D003902:Detergents; D006908:Hydroxyprogesterones; D009243:NAD; D014316:Tritium; D006907:17-alpha-Hydroxypregnenolone; D019326:17-alpha-Hydroxyprogesterone; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; D013255:Steroid 21-Hydroxylase