Several distinct enzymes catalyze 20α-hydroxysteroid dehydrogenase activity in mouse liver and kidney

The effects of flavonoids and quinones on NADPH- and NADH-dependent 20α-hydroxysteroid dehydrogenase (20α-HSD) activities were examined in cytosolic fractions from the liver and kidney of mice. Judging from the data for the inhibition of NADPH- and NADH-dependent 20α-HSD activities by flavonoids and quinones, enzyme catalyzing renal NADPH-dependent 20α-HSD activity was found to be distinct from enzyme(s) catalyzing hepatic NADPH- and NADH-dependent 20α-HSD activities. Sulfobromophthalein (SBP) had little ability to inhibit hepatic NADPH-dependent 20α-HSD activity and bromophenol blue (BPB) exhibited a weak activation against the enzyme activity, whereas SBP and BPB were potent and moderate inhibitors, respectively, of hepatic NADH-dependent 20α-HSD activity. Thus, enzyme catalyzing hepatic NADPH-dependent 20α-HSD activity appeared to be distinct from enzyme catalyzing hepatic NADH-dependent 20α-HSD activity. The data for the pH profiles of hepatic NADPH- and NADH-dependent 20α-HSD activities also led us to the conclusion. Based on these results, we propose the possibility that several distinct enzymes catalyze NADPH- and NADH-dependent 20α-HSD activities in cytosolic fractions from the liver and kidney of mice.