| 20355097 |
Wang L, Liu M, Guo Lv Y, Zhang H: Purification of calmodulin from rice bran and activation of glutamate decarboxylase by Ca (2+)/calmodulin. J Sci Food Agric. 2010 Mar 15;90(4):669-75.
BACKGROUND: gamma-Aminobutyric acid (GABA) is an important bioactive regulator, and its biosynthesis is primarily through the alpha-decarboxylation of glutamate by glutamate decarboxylase (GAD). In plants, it was verified that the production of GABA is regulated, in part, via Ca (2+)/calmodulin (CaM). Our preliminary studies showed that rice bran GAD is probably also a Ca (2+)/CaM dependent enzyme; hence, in the current investigation, we purified calmodulin from rice bran, and studied the effect of the Ca (2+)/calmodulin complex on the activity of rice bran GAD in vitro.RESULTS: CaM was purified to homogeneity from the rice bran by a combined protocol involving TCA precipitation, heat treatment, and hydrophobic interaction chromatography, with the purification fold and recovery of 851.7 and 55.6%, respectively. This protein had similar amino acid composition as the CaMs from other higher plants. The rice bran GAD was found to be quite sensitive to the Ca (2+)/CaM complex at pH 7.0, and addition of exogenous EGTA or TFP efficiently inhibited the stimulatory effect of Ca (2+)/CaM complex. At a separate concentration of Ca (2+) and CaM of 200 micromol L (-1) and 150 nmol L (-1), the rice bran GAD was significantly enhanced 3-fold. Moreover, upon binding Ca (2+), CaM underwent a conformational change that facilitated a more obvious emergency of phenylalanine and tyrosine residues.CONCLUSION: This investigation provided preliminary information for the development of a GABA-based, cost-effective rice bran GAD-related functional food. Copyright (c) 2010 Society of Chemical Industry. |
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