Activity, Intracellular Distribution and Some Properties of 17β-Hydroxy-C19-Steroid Dehydrogenases in Liver and Kidney1

Abstract

The activity of the DPN- and TPN-specific 17β-hydroxy steroid dehydrogenases of the liver and kidney of guinea pig, rabbit, mouse, rat, hamster and dog were compared. The enzyme activities varied markedly among the species and between tissues. The DPN-enzyme activity of the liver of the guinea pig and rat was primarily in the microsomal fraction, but that of the other species was distributed in varying proportions between the microsomal and the soluble fractions. The activity of the TPN enzyme was in the soluble fraction of the liver of all species. On the other hand, both enzyme activities of the kidney were localized in the soluble fraction. The pH optimum was the same, 9.6 for the 2 enzymes in both tissues of all animals. The microsomal DPN enzyme was precipitated at approximately pH 5.2 and the enzymes of the soluble fraction of both liver and kidney at approximately pH 4.2. The microsomal DPN enzyme was sedimented by Mg⁺⁺ and by incubation with RNase. Triton X-100, Duponol-C and desoxycholate readily solubilized the microsomal DPN enzyme. Excess amounts of these agents, however, inhibited the activity of the enzyme.