Untersuchungen über den Stoffwechsel von Steroidhormonen bei Vertebraten, V. Stoffwechsel phenolischer Steroide in der Leber des Huhnes in vitro

Abstract

After incubation of estrone, estradiol-(17[alpha]), estradiol-(17[beta]), 16-oxo-estradiol-(17[beta]) and 16[alpha]-hydroxyestrone with chicken liver slices, the following enzymes were demonstrated: 16[alpha]-, 160-, 17[alpha]- and 17[beta]-hydroxysteroid-oxidoreductases as well as 16[alpha]- and 16[beta]-hydroxylases. 16-epi-estriol was found to be the predominant metabolite, whereas estriol was of minor significance. The 160-hydroxylase is localized in the microsomal fraction and requires NADPH as cofactor. Ammonium sulfate precipitation of the 100,000 x g supernatant of chicken liver gave a partial separation of the NAD(P)-dependent 17[alpha] -hydroxysteroid oxidoreductases from the NAD(P)-dependent 17[beta]-hydroxysteroid oxidoreductases. The highest specific activities for the 17[alpha] -enzymes were found in the fractions obtained between 30 and 40% saturation with ammonium sulfate, and those for the 17[beta]-enzyme were found in the fractions between 0-20 and 60-80% saturation with ammonium sulfate. In oxidation, the 17[alpha]-hydroxysteroid:NAD(P)-oxidoreductase shows an optimum at pH 8.0, the 17[beta]-hydroxysteroid: NAD(P)-oxidoreductase at pH 8.4.