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Effects of calcium on soybean growth and gamma-aminobutyric acid (GABA) accumulation pathways in germinating soybean were investigated. The harmful effect of NaCl stress was alleviated by CaCl while was aggravated by LaCl. Glutamate decarboxylase (GAD) activity increased significantly under NaCl plus CaCl treatment, while its gene expression levels had no significant changes compared with NaCl treatment. GAD and diamine oxidase (DAO) activities and their gene expression levels significantly decreased after LaCl was applied. When treated with AG, the soybean growth was suppressed and DAO activity was inhibited completely while DAO expression had no significant changes. Meanwhile, the GABA content decreased by 17.04 and 11.76 % in cotyledon and embryo under NaCl plus CaCl treatment compared with NaCl treatment, respectively. It can be concluded that CaCl addition changed the contribution ratio of GABA shunt and polyamine degradation pathway for GABA formation, and the increment of GABA in germinating soybean was mainly synthesized via GABA shunt. [ABSTRACT FROM AUTHOR]

Effects of NaCl stress and supplemental CaCl on soybean growth and gamma-aminobutyric acid (GABA) accumulation pathways in germinating soybean were investigated. Germinating under NaCl stress, GABA accumulation was caused not only by the activation of glutamate decarboxylase (GAD), diamine oxidase (DAO) and aminoaldehyde dehydrogenase (AMADH) existing in seed but also by their gene expression up-regulation during germination. However, after CaCl (6 mM) application, the harmful effect of NaCl stress (50 mM) was removed. GAD activity significantly increased, while its gene expression levels had no significant changes with the control, indicating that the increment in GAD activity was caused by the stimulation of exogenous Ca. Meanwhile, GABA was still accumulated although DAO and AMADH activities and their gene expression levels had no significant difference compared with the control. It can be concluded that CaCl addition decreased the contribution of polyamine degradation pathway to GABA accumulation compared with NaCl stress, and the increased GABA was mainly synthesized via GABA shunt. [ABSTRACT FROM AUTHOR]

γ-Aminobutyric acid (GABA) is a non-proteinous amino acid with some functions for human health. In this study, aminoaldehyde dehydrogenase (EC 1.2.1.19, AMADH) which has been proven to be an essential enzyme responsible for the GABA bioformation via polyamine degradation pathway was purified from 2-day germinated soybeans and characterized. The partially purified enzyme showed a single major band with a relative molecular mass of approximately 53.72 kDa-subunit using sodium dodecyl sulfate gel electrophoresis. AMADH exhibited the optimal activity at pH 8.0 and at 45 °C, respectively. The activity of purified AMADH was significantly inhibited by some heavy metal ions and sulfhydryl reagents. The cDNA of AMADH was sequenced by RT-PCR, which indicated 1,677 bp long and contained a 1,515 bp open reading frame that encoded 504 amino-acid peptides (GenBank accession number: KC478661). [ABSTRACT FROM AUTHOR]

High levels of γ-aminobutyric acid (GABA) accumulate in plant tissues under various stresses and exogenous additives. The purpose of this research is to provide an effective finding that can prove a rapid accumulation of GABA in germinated soybean ( Glycine max L.) in response to different additives under hypoxia. Hypoxia-induced GABA accumulation in soybean embryo resulted in part from polyamine oxidation. Response to different concentration of glutamate (Glu), pyridoxal phosphate, arginine, CuCl, NaCl, and CaCl, a significant difference including GABA accumulation, changes of Glutamate decarboxylase (GAD), and Diamine oxidase activity (DAO) activity in germinated soybean under hypoxia occurred ( p < 0.05) and the maximum accumulation of GABA were 4.07, 3.02, 3.50, 3.26, 4.00, and 3.30 g kg DW respectively, which were significantly higher than those germinated soybean under normal culture (CK) and hypoxia culture (CK) ( p < 0.05). The GAD and DAO have different distributions in cotyledon and embryo of germinated soybean, and the enzyme activity mainly located in embryo of germinated soybean. Germinated soybean is a good resource of GABA-rich food. Different additives have significant effects on GABA production, among which Glu and NaCl are ideal material for GABA accumulation. [ABSTRACT FROM AUTHOR]

Effects of soaking temperature, soaking time, opportunity of aeration treatment, culture temperature, pH value, and air flow rate on γ-aminobutyric acid (GABA) accumulation during germination of soybean ( Glycine max (L.) Merr.) were investigated in this study. The objective of this study was to optimize the culture conditions of GABA production in germinated soybeans. Results showed that soaking at 30 °C for 4 h was found to be the most effective soaking ways that made soybean seeds have sufficient moisture, satisfactory germination, and GABA accumulation. The suitable stress opportunity was dark culture for 2 days with distilled water and then hypoxia stress in aerated culture medium for 2 days in a dark incubator at 30 °C. Under these conditions, the maximum GABA content (2.24 mg/g DW) was 3.5 times higher than the initial sample of aeration treatment (0 h) and 12.5 times higher than the raw material. Correlation analysis also revealed that GABA accumulation was significantly correlated to the corresponding physiochemical indexes ( p < 0.01). Box-Behnken experimental analysis showed that the optimal condition with aeration treatment for GABA accumulation in germinated soybean was at a temperature of 30.5 °C, a pH value of 4.1, and an air flow rate of 0.9 L/min; the predicted highest GABA yield was 2.60 mg/g DW, which was 15.2 times higher than raw seeds. Analysis of variance and confirmatory trials for the regression model suggested that the model can quite exactly predict GABA accumulation in soybean during germination. [ABSTRACT FROM AUTHOR]