OXIDIZED NADP AS A POTENTIAL ACTIVE-SITE-DIRECTED REAGENT OF PIGEON LIVER MALIC ENZYME

Pigeon liver malic enzyme (malate dehydrogenase (decarboxylating), EC 1.1.1.40) was reversibly inactivated by periodate-oxidized NADP in a biphasic manner. The reversibility could be made irreversible by treating the modified enzyme with sodium borohydride. The inactivation showed saturation kinetics and could be prevented by nucleotide (NADP or NADPH). Fully protection was afforded by the combination of NADP, Mn2+ and L-malate. Oxidized NADP was also found to be a coenzyme and noncompetitive inhibitor of L-malate in the oxidative decarboxylase reaction catalyzed by malic enzyme. © 1979.