A Novel Dihydrodiol Dehydrogenase in Bovine Liver Cytosol: Purification and Characterization of Multiple Forms of Dihydrodiol Dehydrogenase

抄録

Three enzymes (DD1, DD2, and DD3) having dihydrodiol dehydrogenase activity were purified to homogeneity from bovine liver cytosol. DD1 and DD2 were identified as 3α-hydroxysteroid dehydrogenase and high-K_m aldehyde reductase, respectively, as judged from their molecular weights, substrate specificities and inhibitor sensitivities. DD3 was a unique enzyme which could specifically catalyze the dehydrogenation of trans-benzenedihydrodiol and trans-naphthalenedihydrodiol without any activity toward the other tested alcohols, aldehydes, ketones, and quinones. The K_m value of DD3 (0.18mM) for benzenedihydrodiol was lower than those of other dihydrodiol dehydrogenases so far reported. DD3 immunologically crossreacted with DD1, but showed no crossreactivity with DD2. Additionally, DD3 was inhibited in a competitive manner, with a low K₁ value of 1μM, by androsterone, which was a good substrate for DDl. It was assumed that DD3 is a novel enzyme which is specific to dihydrodiols, exhibiting similarity to DD1 in immunological and structural properties.