One of the 20 _ amino acids commonly found in proteins. Plays a central role in amino acid metabolism, acting as precursor of glutamine, proline and arginine. Also acts as amino group donor in synthesis by transamination of alanine from pyruvate and aspartic acid from oxaloacetate. Glutamate is also a neurotransmitter. The product of its decarboxylation is the inhibitory neurotransmitter aminobutyrate (GABA).