PURIFICATION AND PROPERTIES OF MULTIPLE FORMS OF DIHYDRODIOL DEHYDROGENASE FROM HUMAN LIVER

Two acidic and three basic forms of monomeric dihydrodiol dehydrogenase with molecular weights in the range of 38,000-39,000 were purified from human liver. One acidic enzyme (pI 5.2), which was specific for NADP+ and dihydrodiols of benzene and naphthalene, was immunologically identified as aldehyde reductase. The other four enzymes oxidized alicyclic alcohols as well as the dihydrodiols using both NADP+ and NAD+ as cofactors, but showed differences in specificity for hydroxysteroids and inhibitor sensitivity. Two of the basic enzymes (pI 9.7 and 9.1) exhibited a 20α-hydroxysteroid dehydrogenase activity and sensitivity to 1,10-phenanthroline, whereas the third basic enzyme (pI 7.6) oxidized some 3a-hydroxysterolds at low rates and was inhibited by cyclopentane-1,1-diacetic acid. Another acidic enzyme, which accounted for the largest amount of enzyme activity in the tissue and appeared in two heterogenous forms with p1 values of 5.9 and 5.4, showed a high 3a-hydroxysteroid dehydrogenase activity and was the most sensitive to inhibition by medroxyprogesterone acetate. The K values of the enzymes, except the pI 5.2 enzyme, for hydroxysteroids (10-6 to 10- M) were lower than those for xenobiotic alcohols. © 1990 Copyright, 1990 by the Journal of Biochemistry.