Purification and properties of two malate dehydrogenases from Candida sp N-16 grown on methanol

Two malate dehydrogenases (MDH-M1 and MDH-M2) were found in a methanol-usin g yeast, Candida sp. N-16. MDH-M2 was induced with methanol. These enzymes were purified as electrophoretically and isoelectrophoretically homogeneous proteins. The molecular weights of MDH-M1 and MDH-M2 were estimated to be about 78,000 (homodimer) and 160,000 (homotetramer). Several kinetic proper ties were significantly different between the two enzymes. The value (2.07) of V-max(oxaloacetate)/V-max(malate) and KcatS (555 s(-1) for oxaloacetate , 481 s(-1) for NADH) of MDH-M2 were higher than the ratio (1.37) of V-max and K(cat)s (241 s(-1) for oxaloacetate, 271 s(-1) for NADH) of MDH-M1, res pectively. The activity of MDH-M2 was inhibited by a high concentration of NAD(+) and the activity of MDH-M1 by oxaloacetate.