Isolation of multiple forms of indanol dehydrogenase associated with 17β-hydroxysteroid dehydrogenase activity from male rabbit liver

Abstract

Seven multiforms of indanol dehydrogenase were isolated in a highly purified state from male rabbit liver cytosol. The enzymes were monomeric proteins with similar molecular weights of 30,000–37,000 but with distinct electrophoretic mobilities. All the enzymes oxidized alicyclic alcohols including benzene dihydrodiol and hydroxysteroids at different optimal pH, but showed clear differences in cofactor specificity, steroid specificity, and reversibility of the reaction. Two NADP +-dependent enzymes exhibited both 17β-hydroxysteroid dehydrogenase activity for 5α-androstanes and 3α-hydroxysteroid dehydrogenase activity for 5β-androstan-3α-ol-17-one. Three of the other enzymes with dual cofactor specificity catalyzed predominantly 5β-androstane-3α,17β-diol dehydrogenation. The reverse reaction rates of these five enzymes were low, whereas the other two enzymes, which had 3α-hydroxysteroid dehydrogenase activity for 5α-androstanes or 3(17)β-hydroxysteroid dehydrogenase activity for 5α-androstanes, highly reduced 3-ketosteroids and nonsteroidal aromatic carbonyl compounds with NADPH as a cofactor. All the enzymes exhibited K m values lower for the hydroxysteroids than for the alicyclic alcohols. The results of kinetic analyses with a mixture of 1-indanol and hydroxysteroids, pH and heat stability, and inhibitor sensitivity suggested strongly that, in the seven enzymes, both alicyclic alcohol dehydrogenase and hydroxysteroid dehydrogenase activities reside on a single enzyme protein. On the basis of these data, we suggest that indanol dehydrogenase exists in multiple forms in rabbit liver cytosol and may function in in vivo androgen metabolism.