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Purification and biochemical characterisation of a novel glutamate decarboxylase from rice bran
Author(s) -
Wang Li,
Xu Dong Xia,
Lv Ying Guo,
Zhang Hui
Publication year - 2010
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.3912
Subject(s) - bran , glutamate decarboxylase , chemistry , enzyme , carboxy lyases , fractionation , biochemistry , ammonium sulfate , food science , chromatography , organic chemistry , raw material
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 Ca 2+ but strongly inhibited by Ag + , Hg 2+ , sodium dodecyl sulfate and CH 3 COOH. Kinetic determination of the apparent K m 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