Characterization of a novel glutamate decarboxylase (GAD) from Latilactobacillus curvatus K285 isolated from Gat -Kimchi

Abstract

A lactic acid bacteria (LAB) producing gamma-aminobutyric acid (GABA) was isolated from Gat-Kimchi, a Korean vegetable food. The isolate, K285, was identified as Latilactobacillus (formly Lactobacillus) curvatus. The gadB encoding glutamate decarboxylase (GAD) was cloned and an ORF encoding a protein of 451 amino acids was located. K285 GAD was smaller than other LAB GADs, and its amino acid sequence showed less than 80% homology with other LAB GADs, indicating the uniqueness of K285 GAD. The gadC encoding glutamate/GABA antiporter was located 75 bp upstream of gadB, indicating gadCB operon structure. The gadB was overexpressed in Escherichia coli and recombinant GAD was purified. Optimum pH and temperature of recombinant K285 GAD were pH 5.0 and 50 degrees C, respectively, and the activity was dependent on pyridoxal 5 '-phosphate. The Km and Vmax of GAD were 5.35 +/- 0.27 mM and 0.041 +/- 0.0008 mM/min, respectively. Lb. curvatus K285 might be useful for the production of foods enriched with GABA.