AMADH inhibitor optimization and its effects on GABA accumulation in soybean sprouts under NaCl-CaCl2 treatment

Abstract: 1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide (EDC) was the suitable inhibitor for aminoaldehyde dehydrogenase (AMADH) compared with N-ethylmaleimide (NEE) and iodoacetamide (IAM). EDC exhibited the most obvious inhibition effect on AMADH activity, while its inhibition on glutamate decarboxylase (GAD) was insignificant. Compared with the control, AMADH activity reduced by 70.4% with 0.5 mM EDC, and γ-aminobutyric acid (GABA) content declined by 44.3% in soybean sprouts at 4 days of germination. AMADH activity reduced by 80.62, 67.61 and 72.02% in the 4-day sprouts with 1 mM EDC under NaCl, CaCl₂ and NaCl + CaCl₂ treatment, respectively, and GABA content decreased by 43.56, 38.84 and 35.53%, respectively. EDC is a proper inhibitor for AMADH and it could be used to quantify the contribution of polyamine degradation pathway on GABA formation. In soybean sprouts, the presence of CaCl₂ under NaCl stress decreased the contribution of polyamine degradation pathway on GABA accumulation.