Gamma amino butyrate is synthesized from
Gamma-aminobutyric acid or GABA is formed by decarboxylation of glutamate in presence of enzyme glutamate decarboxylase.Ref: DM Vasudevan - Textbook of Biochemistry, 7th edition, page no: 224, Fig 17.2
Fumarate
Glutamate
Histidine
Glycine
Metabolism of protein and amino acid