title: Enzymatic sulfation of steroids. V. Partial purification and some properties of sulfotransferase III, the major glucocorticoid sulfotransferase of liver cytosols from male rats.
abstract: This manuscript describes purification of sulfotransferase III (STIII), the major hepatic glucocorticoid sulfontransferase of male rats, 77.8 +/- 16 fold from cytosol. This represents a probable 250--345 fold enrichment, compared with homogenates. Purified STIII has a molecular weight of 61 500 +/- 2500 from Sephadex G-100 chromatography. It is markedly activated by 5 mM divalent Ba, Ca, Co, Cr, Mg, Mn, and Ni salts; inhibited stronlgy by 5 mM divalent Zn and Cd; and unaffected by 8 mM ADP, ATP, and AMP. Comparison of the ability of purified STIII to sulfate equimolar cortisol, estradiol-17beta, testosterone, and dehydroepiandrosterone suggests that the enzyme may sulfate glucocorticoid preferentially. However, its cortisol sulfotransferase activity is inhibited by a variety of steroids. Of these, dehydroepiandrosterone, dexamethasone, and progesterone were tested extensively. They were found to be competitive inhibitors. STIII has a sharp pH optimum at pH 6.0 +/- 0.1. However, it is routinely assayed at pH 6.8, as explained in the text. It exhibits a sequential mechanism and Km values of 6.82 +/- 1.2 and 6.28 +/- 0.64 micron for cortisol and 3'-phosphoadenosine-5'-phosphosulfate, respectively. It also possesses essential sulfhydryl groups, as shown by p-hydroxymercuribenzoate inhibition studies.
mesh_terms: D000818:Animals; D002413:Cations, Divalent; D003600:Cytosol / Q000201:enzymology; D005938:Glucocorticoids; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008297:Male; D008970:Molecular Weight; D051381:Rats; D013256:Steroids / Q000494:pharmacology; D013466:Sulfurtransferases / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D002413:Cations, Divalent; D005938:Glucocorticoids; D013256:Steroids; D013466:Sulfurtransferases