Glutamic acid crystals, polarised light micrograph. Glutamic acid is an nonessential amino acid, in which it can be synthesised by the body and does not need to be obtained from food. It has an important role in nerve function and brain signalling, where it is a precursor to the molecule GABA. GABA (gammaaminobutyric acid) is an inhibitory neurotransmitter (nerve signalling chemical) that is an integral component of the central nervous system (CNS).