TPN- and DPN-Specific 3α-Hydroxy- and Δ5-3β-Hydroxysteroid Dehydrogenases of Liver and Kidney

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Abstract
DPN- and TPN-specific 3α- and Δ5-3β-hydroxysteroid dehydrogenases have been demonstrated in the liver and kidney. The nucleotide specific enzymes were readily separated by centrifugation. They were localized in either the microsomal or soluble fractions. In some instances the same type of dehydrogenase activity was found in both cellular particulate fractions, and the DPN dehydrogenases of the mouse, rat and hamster kidney required both fractions. The activity of the enzymes varied between tissues and among animals. A pH optimum of about 9.6 was shown by all the dehydrogenases. The microsomal enzymes were precipitated by Mg++ and by treatment with RNase but those in the soluble fraction were not. The microsomal enzymes were readily solubilized by 0.15% Triton X-100 or 0.2% desoxycholate. The enzymes lost activity on storage at 4 C. The loss was partly prevented by EDTA at an optimum concentration of 0.5–1.0 mM. A DPN reductase(s) was present in the liver. It had a pH optimum of 8.5 and was stimulated by androsterone or dehydroepiandrosterone to produce 3 times the stoichiometric amount of DPNH. It required both the microsomal and soluble fractions for activity. (Endocrinology74: 521, 1964)

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