5gp4
Lactobacillus brevis CGMCC 1306 Glutamate decarboxylase
Structural highlights
FunctionPublication Abstract from PubMedGlutamate decarboxylase (GAD), which is a unique pyridoxal 5-phosphate (PLP)-dependent enzyme, can catalyze alpha-decarboxylation of l-glutamate (L-Glu) to gamma-aminobutyrate (GABA). The crystal structure of GAD in complex with PLP from Lactobacillus brevis CGMCC 1306 was successfully solved by molecular-replacement, and refined at 2.2A resolution to an Rwork factor of 18.76% (Rfree=23.08%). The coenzyme pyridoxal 5-phosphate (PLP) forms a Schiff base with the active-site residue Lys279 by continuous electron density map, which is critical for catalysis by PLP-dependent decarboxylase. Gel filtration showed that the active (pH 4.8) and inactive (pH 7.0) forms of GAD are all dimer. The residues (Ser126, Ser127, Cys168, Ile211, Ser276, His278 and Ser321) play important roles in anchoring PLP cofactor inside the active site and supporting its catalytic reactivity. The mutant T215A around the putative substrate pocket displayed an 1.6-fold improvement in catalytic efficiency (kcat/Km) compared to the wild-type enzyme (1.227mM(-1)S(-1) versus 0.777mM(-1)S(-1)), which was the highest activity among all variants tested. The flexible loop (Tyr308-Glu312), which is positioned near the substrate-binding site, is involved in the catalytic reaction, and the conserved residue Tyr308 plays a vital role in decarboxylation of L-Glu. Lactobacillus brevis CGMCC 1306 glutamate decarboxylase: Crystal structure and functional analysis.,Huang J, Fang H, Gai ZC, Mei JQ, Li JN, Hu S, Lv CJ, Zhao WR, Mei LH Biochem Biophys Res Commun. 2018 Sep 10;503(3):1703-1709. doi:, 10.1016/j.bbrc.2018.07.102. Epub 2018 Jul 24. PMID:30049439[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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