Regulation and mechanism of enzyme metabolism in germinated hemp seeds by ultrasound combined with exogenous calcium chloride treatment.

γ-aminobutyric acid (GABA) plays an important role in anti-anxiety by inhibiting neurotransmitter in the central nervous system (CNS) of mammals, which is generated in the germinating seeds. The key enzymes activity of GABA metabolism pathway and nutrients content in hemp seeds during germination were studied after treated with ultrasound and CaCl. The mechanism of exogenous stress on key enzymes in GABA metabolism pathway was investigated by molecular dynamics simulation. The results showed that ultrasonic combined with 1.5 mmol·LCaCl significantly increased the activities of glutamate decarboxylase (GAD) and GABA transaminase (GABA-T) in seeds, and promoted the conversion of glutamate to GABA, resulting in the decrease of glutamate content and the accumulation of GABA. Molecular dynamics simulations revealed that Ca environment enhanced the activity of GAD and GABA-T enzymes by altering their secondary structure, exposing their hydrophobic residues. Ultrasound, germination and CaCl stress improved the nutritional value of hemp seeds.