Enzymatic sulfation of steroids. XVIII. Study of the specific estradiol-17β sulfotransferase of rat liver cytosol, that converts the estrogen to its 3-sulfate, and some elements of the endocrine control of its production

Abstract

A radioisotopic assay for cytoplasmic estradiol-17β sulfotransferase activity in rat liver was developed. Routine enzyme assays used 120 μM [3H]estradiol-17β, 240 μM 3′-phosphoadenosine-5′-phosphosulfate, and enzyme samples containing up to 0.60 mg of cytosol protein. Livers from males and females sulfated 934 ± 231 and 861 ± 266 nmol estradiol-17β∙h−1∙g−1. DEAE-Sephadex A-50 chromatography showed that most of the cytoplasmic enzyme activity eluted as one peak that was well separated from glucocorticoid and 3β-hydroxysteroid sulfotransferases. Pooled column fractions containing this estradiol-17β sulfotransferase exhibited kinetic properties similar to the enzyme activity in cytosol, but gave slightly greater activity with 180 μM estradiol-17β and 360 μM 3′-phosphoadenosine-5′-phosphosulfate. Apparent Km's for the steroid and the coenzyme were 71–85 and 80–93 μM, respectively. The pH optimum for the enzyme reaction was 7.75 ± 0.25. The enzyme sulfated estradiol-17β at all concentrations tested between 10 and 180 μM. It did not sulfate estrone, testosterone, dehydroepiandrosterone, or cortisol well at any test concentration between 10 and 120 μM. The sulfation product was estra-1,3,5-triene-17β-ol-3-sulfate. The molecular weight of the enzyme was 54 500 ± 2300 by Sephadex G-100 chromatography. The estradiol-17β sulfotransferase was inhibited strongly by phenols, but not by corticosterone, deoxycorticosterone, dehydroepiandrosterone, estrone, progesterone, or testosterone. Adrenalectomy diminished the estradiol-17β sulfotransferase activity greatly, owing to decreases of the specific estradiol-17β sulfotransferase concentration. The possible relationships between the specific estradiol-17β sulfotransferase and other sulfotransferases in rat liver are discussed.