Structure and Function of NAD/NADP Requirement Microsomal Alcohol Dehydrogensase

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1. 3-OH-β-ionone was oxidized to 3-oxo-β-ionone by hepatic microsomes of mouse and monkey. In both animals, NAD was most effective as cofactor, followed by NADP, NADPH and NADH.2. The NADPH-dependent 3-oxo-β-ionone forming activity (MALCO activity) in mouse was almost completely inhibited by antibody against Cyp3all.3-OH-β-ionone MALCO activity in monkey was inhibited by antisera against CYP2A and Cyp3all.4. The NAD- and NADP-dependent formation of 3-oxa-β-ionone in mouse was inhibited by disulfiram.5. In the case of monkey, the NADP-dependent activity was inhibited by babital, quercetin and quercitrin as well as disulfiram and HgClィイD22ィエD2, while the NAD-dependent activity was inhibited by disulfiram and HgClィイD22ィエD2.6. In the hepatic microsomes of monkey, the Km/Vmax value for NAD-dependent 3-oxo-β-ionone forming activity was about 10-fold higher than that for the NADPH-dependent activity.7. Microsomal 3-OH-β-ionone dehydrogenate (MALDH) was purified from male Japanese monkey livers. Specific activity of the enzyme was about 5 times higher than that of microsomes, and the molecular mass is about 23.5 kDa.These results indicated that not only P450(MALCO) but also microsomal alcohol dehydrogenase(s) (MALDH) required NAD and/or NADP as cofactor catalyzed the formation of 3-oxo-β-ionone from 3-OH-β-ionone in hepatic microsomes of mouse and monkey.