Abstract
17[beta]-Hydroxysteroid dehydrogenases have been found to be present in the cytoplasma fractions of normal and hyperplastic human adrenal cortex. A 10-fold purification of the enzymes was achieved by precipitation with ammonium sulphate (40-80% saturation). With testosterone as substrate both enzymes possess similar specific activities; NAD as well as NADP can act as cofactors. The 17[beta]-hydroxysteroid dehydrogenase obtained from the hyperplastic adrenal cortex shows a pH optimum at 8.4; the Michaelis-Menten constant for testosterone was found to be 9.8 x 10-4 [image]. The enzymatic activity is markedly inhibited by SH blocking agents.