关键词: 肠膜明串珠菌；乳酸脱氢酶；乳酸；苯乳酸

Abstract: In this study, the lactate dehydrogenase gene (ldh) of Leuconostoc mesenteroides ATCC8293 was cloned into pETDuetTM-1 vector to construct a recombinant plasmid, which was then transformed into Escherichia coli BL21(DE3) for expression. The recombinant enzyme was purified using Ni-NTA column chromatography and its enzymatic properties were characterized. As results, the molecular mass of lactate dehydrogenase (LDH) was measured to be 37 kDa, and the optimal pH and temperature were 7.0 and 40 ℃, respectively. Under the optimized conditions, the specific activity of LDH was 67.45 U/mg. It was also confirmed that the enzyme was D-LDH, which converts pyruvic acid to D-lactic acid. Furthermore, the Km values of this enzyme for pyruvate and NADH were 1.27 mmol/L and 0.48 mmol/L, respectively, and the Kcat and Kcat/Km values for pyruvate were 421 s-1 and 3.31×105 L/(mol·s), respectively. Besides pyruvate as a substrate, it also had high activities toward oxaloacetate and phenylpyruvate. The results of this study provide a theoretical basis for the production of lactic acid and phenyllactic acid using L. mesenteroides.

Key words: Leuconostoc mensenteroides; lactate dehydrogenase; lactic acid; phenyllactic acid