Enzymatic sulfation of steroids. V. Partial purification and some properties of sulfotransferase III, the major glucocorticoid sulfotransferase of liver cytosols from male rats

Publisher Website
Google Scholar
Abstract
The purification of sulfotransferase III (STIII), the major hepatic glucocorticoid sulfotransferase of male rats, 77.8 .+-. 16-fold from cytosol is described. This represents a probable 250- to 345-fold enrichment, compared with homogenates. Purified STIII has a MW 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 strongly 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-17.beta., testosterone and dehydroepiandrosterone suggests that the enzyme may sulfate glucorcorticoids preferentially. However, its cortisol sulfotransferase activity is inhibited by a variety of steroids. Of these, dehydroepiandrosterone, dexamethasone and progesterone were tested extensively. They were competitive inhibitors. STIII has a sharp pH optimum at pH 6.0 .+-. 0.1. However, it is routinely assayed at pH 6.8. It exhibits a sequential mechanism and Km values of 6.82 .+-. 1.2 and 6.28 .+-. 0.64 mM for cortisol and 3''-phosphoadenosine-5''-phosphosulfate, respectively. It also possesses essential sulfydryl groups, as shown by p-hydroxymercuribenzoate inhibition studies.

This publication has 14 references indexed in Scilit: