Characterization of a glutamate decarboxylase (GAD) gene from Lactobacillus zymae
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Lactic acid bacteria (LAB) were isolated from Kimchi, a Korean traditional fermented vegetable food. LAB accumulating GABA (γ-aminobutyric acid) in the culture media were screened by TLC analysis. One isolate, GU240, produced the highest amount of GABA among the 3,000 isolates and identified as a Lactobacillus zymae strain. Glutamate decarboxylase (GAD) gene was cloned and over-expressed in E. coli BL21(DE3) using pET26b(+). The recombinant GAD was purified by using a Ni–NTA column. Its size was 53 kDa by SDS-PAGE. Maximum GAD activity was at pH 4.5 and 41 °C and the activity was dependent on pyridoxal 5′-phosphate. Km and Vmax of LzGAD were 1.7 mM and 0.01 mM/min, respectively, when glutamate was used as a substrate.
Keywordsγ-Aminobutyric acid gad gene cloning Glutamate decarboxylase Lactobacillus zymae
This work was supported by Geochang HanSsal and Geochang county Regional Agriculture Specialization fund. J. Y. Park and S.-J. Jeong were supported by BK21 Plus from MOE, Republic of Korea.