Expression and characterization of two L-aspartate alpha-decarboxylases

Abstract:

[Objective] In this study, two L-aspartate α-decarboxylase genes (panD) from Listeria monocytogenes (panDL.m) and Corynebacterium jeikeium (panDC.j) were expressed in Escherichia coli, respectively, and the recombinant enzymes were purified and characterized. [Methods] The panD genes from L. monocytogenes and C. jeikeium were synthesized and inserted into pET28a(+) to obtain expression plasmids, which was then transformed into E. coli BL21(DE3). PanDL.m and PanDC.j were functionally expressed and the recombinant enzymes were purified by HisTrapTM affinity chromatography. Their catalytic properties were characterized and the effects of substrate concentration on enzymatic conversion were studied. [Results] Those α and β subunits were detected by Tricine-SDS-PAGE, indicating that both of the PanDs were processed by self-cleavage. The specific activities were 8.9 U/mg for PanDL.m and 11.8 U/mg for PanDC.j. They exhibited the same optimal temperature at 60 °C, while they possessed different optimal pH at 7.0 and 6.0, respectively. Both the enzymes were stable at the condition of 30?50 °C, and pH 4.0?7.0. Compared with the most studied PanD from C. glutamicum, the substrate inhibition effect of the PanDL.m was significantly less. [Conclusion] Under the high temperature and acidic conditions, PanDL.m as well as PanDC.j could specifically transform L-aspartic to β-alanine. PanDL.m could be more appropriate for industrial application because of less substrate inhibition.

Key words:L-aspartate α-decarboxylase, β-Alanine, Listeria monocytogenes, Corynebacterium jeikeium, Enzymatic properties