Purification and biochemical characterisation of a novel glutamate decarboxylase from rice bran

Autor: Ying Lv, Li Wang, Dong Xia Xu, Hui Zhang
Rok vydání: 2010
Předmět:
Zdroj: Journal of the Science of Food and Agriculture. 90:1027-1033
ISSN: 0022-5142
DOI: 10.1002/jsfa.3912
Popis: BACKGROUND: Glutamate decarboxylase (GAD) is a useful enzyme whose main function is to catalyse the irreversible α-decarboxylation of L-glutamate to produce γ-aminobutyric acid. The cheap and abundant rice-processing by-product rice bran contains a high amount of GAD, the purification and characterisation of which have not yet been reported. In this study, research on rice bran GAD was initiated. RESULTS: Rice bran GAD was purified to homogeneity via a combined purification protocol of ammonium sulfate fractionation, ion exchange chromatography and two gel filtrations, with a purification fold of 128.6 and an activity recovery of 21.3%. The enzyme was active at pH 5.5 and 40 °C and retained 80% of its original activity in the pH range 5–9 and the temperature range 30–50 °C. GAD activity was significantly enhanced in the presence of Ca2+ but strongly inhibited by Ag+, Hg2+, sodium dodecyl sulfate and CH3COOH. Kinetic determination of the apparent Km for L-glutamate and pyridoxal 5′-phosphate gave values of 27.4 mmol L−1 and 1.16 µmol L−1 respectively. CONCLUSION: Considering that rice bran is cheap and commercially available and that rice bran GAD is relatively stable, the development of cost-effective rice bran GAD-related functional foods would seem to be feasible. Copyright © 2010 Society of Chemical Industry
Databáze: OpenAIRE
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