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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
Activity 4.1.1.15
Family 4.1.1.15.b
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 4.1.1.15), 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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