Some properties of the pyridine nucleotide-specific 17 beta-hydroxy steroid dehydrogenases of guinea pig liver.

The liver of the guinea pig was shown (1, 2) to contain two enzymes which catalyze the dehydrogenation of testosterone. One is located in the particulate fraction and specifically requires diphosphopyridine nucleotide as hydrogen acceptor; the other, present in the fraction of guinea pig homogenate not sedimented by 24,500 X g for 60 minutes, specifically requires triphosphopyridine nucleotide as hydrogen acceptor. The kidney of the guinea pig also contains these two enzymes located in the same subcellular fractions. Hurlock and Talalay (3) reported that the transfer of hydrogen from one pyridine nucleotide to another in a preparation of rat liver occurs by the action of a single 3cu-hydroxy steroid dehydrogenase with dual nucleotide specificity. Stein and Kaplan (4), however, could find no evidence in rat liver preparations of transhydrogenation mediated by 3arhydroxy steroids. It was of interest to determine whether hydrogen transfer could be mediated by the combined action of two physically separable dehydrogenases with the same substrate but different pyridine nucleotide specificities. We have confirmed Kochakin’s observations and have partially purified the two dehydrogenases. The present paper reports studies of some of their properties and of their inability at physiological concentrations of steroids and nucleotides to mimic the action of a true steroid-dependent pyridine nucleotide transhydrogenase such as the estrogen-stimulable enzyme of the placenta which has been under study in our laboratory (5-7).