Lglutamate

L-glutamate, or L-glutamic acid in its protonated form, is one of the 20 standard amino acids used to build proteins. It is the L enantiomer; the D form is rare in nature. The molecule contains an α-amino group, an α-carboxyl group, and a side-chain γ-carboxyl group. At physiological pH it carries a net negative charge (-1) because both carboxyl groups are deprotonated while the amino group remains protonated.

Biologically, glutamate is non-essential as a dietary amino acid; it can be synthesized from α-ketoglutarate via transamination and from glutamine via glutaminase. It plays a central role in nitrogen and amino acid metabolism: transaminases transfer its amino group to form other amino acids, and deamination yields α-ketoglutarate, a tricarboxylic acid cycle intermediate. It is also incorporated into proteins during translation.

In the central nervous system, glutamate is the primary excitatory neurotransmitter. It activates ionotropic receptors (NMDA, AMPA, kainate) and metabotropic glutamate receptors, supporting synaptic transmission, plasticity, and learning. Excess extracellular glutamate can cause excitotoxicity and is implicated in conditions such as stroke.

Dietary sources include protein-rich foods; free glutamate is also used as monosodium glutamate (MSG), a common food additive that enhances umami flavor. Regulatory agencies generally regard glutamate and MSG as safe at typical intake, though some individuals report sensitivity.