Cyclic dipeptide synthetase from Leuconostoc mesenteroides LBP-K06

Abstract

This study worked with Leuconostoc mesenteroides LBP-K06, one kind of lactic acid bacteria separated from Korea traditional fermented kimchi, which had a higher antimicrobial activity than other strains, and focused on the cyclic dipeptide synthetase isolated from it. This study used ninhydrin staining method, a specific color reaction for amino acids, to determine the cyclic dipeptide synthetase in Ln. mesenteroides LBP-K06. And the activity of cyclic dipeptide synthetase was expected by the phenomenon that achromatic bands appeared on native gel after ninhydrin staining. The achromatic fragments on the native gel performed by SDS-PAGE, and the single bands on SDS gel were performed by 2D LC-MS analysis for protein identification. Analysis of the 2D LC-MS results, the ATPase family associated with various cellular activities proteins (gi: 227351295) was identified as the enzyme that synthesized cyclic dipeptides in Ln. mesenteroides LBP-K06. In this study, polymerase chain reaction was performed to clone the gene segment of cyclic dipeptide synthetase, the pET3a vector system was used to transform the target gene segment into E. coli, and isopropyl β-D-1-thiogalactopyranoside (IPTG) was used for inducing the overproduce of recombinant cyclic dipeptide synthetase. Then the overproduced proteins were purified by ammonium sulfate and DEAE-Sepharose chromatography, and the purified proteins were added to the amino acid to determine the enzyme activity. By ninhydrin staining method and HPLC analysis, the enzyme activity of cyclic dipeptide synthetase separated from Ln. mesenteroides LBP-K06 was confirmed. It was observed that the cyclic dipeptide synthetase could not only catalyze between L-leucine and L-proline, but also between L-phenylalanine and L-proline to synthesize the cyclic dipeptides.