Biochemical differences between cytoplasmic malate dehydrogenase allozymes of Drosophila virilis

Two allozymes (MDH^f and MDH^s) of cytoplasmic malate dehydrogenase of Drosophila virilis were partially purified and their biochemical properties were compared. MDH^f has a pH optimum of 9.75 and MDH^s one of 9.25 for malate oxidation. Optimal pH for oxaloacetate reduction is 6.75 and 8.0 for MDH^f and MDH^s, respectively. The K_m value for oxaloacetate of MDH^s is approximately twice as that of MDH^f. No differences were found with respect to thermostability and K_m's for malate, NAD⁺, or NADH. These results are discussed in terms of the physiological role of cytoplasmic malate dehydrogenase of D. virilis.This work was supported in part by grants from the Ministry of Education, Japan, Nos. 134050 and 154205.