Characterization of glutaminase activity in Lactobacillus spp.

초록

Lactobacillus spp. are known as GRAS(generally regard as safe) bacteria widely usesd in food industry. In this study we screened over 100 lactobacilli isolates for their glutaminase activity. Glutaminase (glutamine amidotransferase) deaminates glutamine converting it to glutamic acid sodium salt of which is well known as a flavor substance. Among 105 lactobacilli isolates screend one isolate showing the highest activity was selected and identified as Lactobacillus plantarum by 16S rDNA sequence comparison. For enzyme assay we spectrophotometrically measured the NADH produced during the conversion of L-glutamine to 2-oxaloglutarate. The strain L.plantarum KLB 213 showed glutminase activity of 0.748 unit/mg. In order to clone the glutaminase gene from KLB 213 we employed degenerate - PCR to obtain 431bp internal fragment. Sequence comparison of this internal fragment revealed 100% identity to the reported glutaminase sequence. Presently, full gene cloning is under way by using single - primer PCR.