Glycin

Glycin, known in English as glycine, is the simplest amino acid and one of the 20 standard amino acids used to build proteins. Its chemical formula is C2H5NO2 and its structure is NH2-CH2-COOH, with a side chain consisting of a single hydrogen. Because its side chain has no stereocenter, glycine is not chiral; at physiological pH it exists mainly as the zwitterion.

Glycin is nonessential for humans, since it can be synthesized endogenously from other amino acids, particularly serine. It is highly represented in collagen, where its small size enables the tight packing of the triple helix; in proteins it often appears in flexible regions and in tight turns.

In the nervous system, glycine acts as an inhibitory neurotransmitter in the spinal cord and brainstem via glycine receptors, and it also functions as a co-agonist at NMDA-type glutamate receptors, influencing excitatory signaling.

Glycin participates in various metabolic pathways. It is produced from serine by serine hydroxymethyltransferase and is degraded by the glycine cleavage system. It serves as a precursor for the biosynthesis of purines, creatine, heme, and glutathione.

Dietary glycine is found in protein-rich foods such as meat, fish, dairy products, and legumes. Because it is nonessential, most people obtain adequate amounts from a normal diet.

Glycin is also produced industrially by fermentation or chemical synthesis and is used as a buffering agent and humectant in pharmaceuticals, foods, and cosmetics. Supplements are marketed for various purposes, but evidence for specific health benefits varies.