Glu

Glu is the three-letter abbreviation for the amino acid glutamic acid, one of the 20 standard amino acids. In proteins, it is represented by the one-letter code E, and in mRNA codons by GAA and GAG. In its ionized form, it is called glutamate and functions widely in metabolism and signaling. Glutamic acid is non-essential for adults.

Chemically, Glu is acidic and polar. Its side chain is a carboxylate group that carries a negative charge at physiological pH (pKa about 4.25). As a result, glutamate is highly hydrophilic and often located on protein surfaces where it participates in ionic interactions and hydrogen bonding.

Biological roles include being a key neurotransmitter in the central nervous system, mediating fast excitatory signaling through receptors such as NMDA, AMPA, and kainate receptors. It also participates in amino acid metabolism through transamination and serves as a precursor to glutamine via glutamine synthetase. In the brain, the glutamate-glutamine cycle links neurons and astrocytes.

Dietary and practical aspects: Glutamate is abundant in many proteins and is present in a wide range of foods. The monosodium salt, MSG, is widely used as a flavor enhancer. In normal dietary amounts, glutamate is generally considered safe; some individuals report sensitivity to MSG, though evidence for widespread adverse effects remains inconclusive.