Effects of exogenous calcium chloride (CaCl2) and ascorbic acid (AsA) on the γ-aminobutyric acid (GABA) metabolism in shredded carrots

Abstract

CaCl2 or AsA treatment was applied to shredded carrots to explore their influences on GABA content and its metabolic pathway. The metabolites, enzyme activity and gene expression associated with GABA shunt pathway and polyamine degradation were measured. Results demonstrated that treatment with exogenous CaCl2 or AsA alone not only significantly promoted the activities of glutamate decarboxylase (GAD), GABA transaminase (GABA-T), diamine oxidase (DAO), polyamine oxidase (PAO) and aminoaldehyde dehydrogenase (AMADH), but up-regulated the expressions of DcGAD1, DcGAD2, DcGABA-T1 and DcPAO. Meanwhile, glutamate (Glu) content, a substrate for GABA shunt, was significantly reduced in both two exogenous treatments. In addition, lower putrescine (Put) and spermine (Spm) contents were observed in AsA treatment only. Taken together, our results suggested that both CaCl2 and AsA treatments could activate GABA shunt pathway and polyamine degradation. CaCl2 seemed to be more effective to GABA shunt regulation, while AsA to polyamine degradation.