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Purification and Properties of the Soluble 17β-Hydroxysteroid Dehydrogenase of Rabbit Uterus

Abstract 17 β-Hydroxysteroid dehydrogenase activity towards estradiol-17 β has been demonstrated in the 105,000 X g supernatant of rabbit uterus. Hydroxylapatite chromatography of the enzyme activity isolated by ammonium sulfate precipitation, gel filtration and DEAE-cellulose chromatography yielded a single 17 β-hydroxysteroid dehydrogenase activity. Further purification of the enzyme preparation by isoelectric focusing resulted in multiple peaks of activity. The molecular weight or the enzyme, calculated from mobility data on Sephadex gel, is approximately 64,000. Some properties of partially purified 17 β-hydroxysteroid dehydrogenase activity have been studied. Estradiol-17 β reacts at a faster rate than testosterone. The Km for estradiol is 4.16X 10-5 mol/1 for the NAD-linked enzyme activity and 4.37 X 10-5 mol/1 when NADP as cofactor was used. The ratio of the maximal velocity for NADP to that for NAD was 1.42. The pH-optimum for estradiol appears between 9.5 and 10.5 and for estrone between 5.5 and 6.5. The enzyme appears to be of the sulfhydryl type.