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B6db references: 26730883

type Journal Article
authors Kanwal S, Incharoensakdi A
title Characterization of glutamate decarboxylase from Synechocystis sp. PCC6803 and its role in nitrogen metabolism
journal Plant Physiol Biochem
sel selected
ui 26730883
year (2016)
volume 99
pages 59-65
keywords GABA metabolism; Glutamate decarboxylase; Synechocystis; Transcription; Δgad strain
abstract Glutamate decarboxylase (GAD) (EC, an enzyme responsible for the synthesis of γ-aminobutyric acid (GABA), from Synechocystis sp. PCC6803 was cloned and overexpressed in Escherichia coli BL21(DE3). The purified enzyme was expressed as a monomeric protein with a molecular mass of 53 and 55 kDa as determined by SDS-PAGE and gel filtration chromatography, respectively. The enzyme activity was pyridoxal-5'-phosphate dependent with an optimal activity at pH 6.0 and 30 C. The catalytic properties of this enzyme were, Km = 19.6 mM; kcat = 100.7 s(-1); and kcat/Km = 5.1 mM(-1) s(-1). The transcription levels of genes involved in nitrogen metabolism were up-regulated in the Δgad strain. The mutant showed approximately 4- and 8-fold increases in the transcript levels of kgd and gabdh encoding a novel α-ketoglutarate decarboxylase and γ-aminobutanal dehydrogenase, respectively. Overall results suggested that in Synechocystis lacking a functional GAD, the γ-aminobutanal dehydrogenase might serve as an alternative catalytic pathway for GABA synthesis.
last changed 2017/10/10 13:50

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