The effects of cultivar in the bioconversion of glutamate to γ-aminobutyric acid using Korean hull-less barley bran

γ-Aminobutyric acid (GABA) is a non-protein amino acid that is synthesized from glutamate by glutamate decarboxylase (GAD). In this reaction, a pyridoxal 5´-phosphate-dependent enzyme catalyzes the irreversible α-decarboxylation of l-glutamate to GABA. GABA has recently attracted research attention. However, as GABA cannot pass the blood-brain barrier and enter the central nervous system, GABA levels in the brain are not increased by oral administration alone. Thus, it is necessary to supply sufficient GABA from outside sources such as food, necessitating the development of functional foods rich in GABA.