|Other names||Aminoethanoic acid
|Molar mass||75.07 g mol−1|
233 °C (decomposition)
|Solubility in water||25 g/100 mL|
|Solubility||soluble in ethanol, pyridine
insoluble in ether
|LD50||2600 mg/kg (mouse, oral)|
|Supplementary data page|
|n, εr, etc.|
Solid, liquid, gas
|Spectral data||UV, IR, NMR, MS|
(what is this?) |
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Glycine (abbreviated as Gly or G) is an organic compound with the formula NH2CH2COOH. With only a hydrogen atom as its side chain, glycine is the smallest of the 20 amino acids commonly found in proteins.
Glycine is a colourless, sweet-tasting crystalline solid. It is unique among the proteinogenic amino acids in that it is not chiral. It can fit into hydrophilic or hydrophobic environments, due to its single hydrogen atom side chain.
About 15M kg are produced annually in this way.
There are two producers of glycine in the United States. Chattem Chemicals, Inc., purchased by Sun Pharmaceutical, who is an international pharmaceutical company based in Mumbai, India and GEO Specialty Chemicals, Inc., who purchased the glycine and naphthalene sulfonate production facilities of Dow/Hampshire Chemical Corp.
Chattem's manufacturing process ("MCA" process) occurs in batches and results in a finished product with some residual chloride but no sulfate, while GEO’s manufacturing process is considered a semi-batch process and results in a finished product with some residual sulfate but no chloride.
It's pK values are 2.35 and 9.13. So above pH 9.13, most of the glycine exists as the anionic amine, H2NCH2CO2-. Below pH 2.35, its solutions contain mostly the cationic carboxylic acid H3N+CH2CO2H. It's isoelectric point (pI) is 6.06.
Glycine is not essential to the human diet, as it is biosynthesized in the body from the amino acid serine, which is in turn derived from 3-phosphoglycerate. In most organisms, the enzyme Serine hydroxymethyltransferase catalyses this transformation via the cofactor pyridoxal phosphate:
Glycine is degraded via three pathways. The predominant pathway in animals involves the catalysis of glycine cleavage enzyme, the same enzyme also involved in the biosynthesis of glycine. The degradation pathway is the reverse of this synthetic pathway:
In the second pathway, glycine is degraded in two steps. The first step is the reverse of glycine biosynthesis from serine with serine hydroxymethyl transferase. Serine is then converted to pyruvate by serine dehydratase.
In the third pathway of glycine degradation, glycine is converted to glyoxylate by D-amino acid oxidase. Glycoxylate is then oxidized by hepatic lactate dehydrogenase to oxalate in an NAD+-dependent reaction.
The principal function of glycine is as a precursor to proteins. It is also a building block to numerous natural products.
Glycine is an inhibitory neurotransmitter in the central nervous system, especially in the spinal cord, brainstem, and retina. When glycine receptors are activated, chloride enters the neuron via ionotropic receptors, causing an Inhibitory postsynaptic potential (IPSP). Strychnine is a strong antagonist at ionotropic glycine receptors, whereas bicuculline is a weak one. Glycine is a required co-agonist along with glutamate for NMDA receptors. In contrast to the inhibitory role of glycine in the spinal cord, this behaviour is facilitated at the (NMDA) glutaminergic receptors which are excitatory. The LD50 of glycine is 7930 mg/kg in rats (oral), and it usually causes death by hyperexcitability.
In the US, glycine is typically sold in two grades: United States Pharmacopeia (“USP”), and technical grade. Most glycine is manufactured as USP grade material for diverse uses. USP grade sales account for approximately 80 to 85 percent of the U.S. market for glycine.
Other markets for USP grade glycine include its use an additive in pet food and animal feed. For humans, glycine is sold as a sweetener/taste enhancer. Food supplements and protein drinks contain glycine. Certain drug formulations include glycine to improve gastric absorption of the drug.
Many miscellaneous products use glycine or its derivatives, such as the production of rubber sponge products, fertilizers, metal complexants.
Glycine is an intermediate in the synthesis of a variety of chemical products. It is used in the manufacture of the herbicide Glyphosate. Glyphosate (N-(phosphonomethyl) glycine) is a non-selective systemic herbicide used to kill weeds, especially perennials and broadcast or used in the cut-stump treatment as a forestry herbicide. Initially, Glyphosate was sold only by Monsanto under the Monsanto tradename Roundup, but is no longer under patent.
The detection of glycine in the interstellar medium has been debated. In 2008, the glycine-like molecule amino acetonitrile was discovered in the Large Molecule Heimat, a giant gas cloud near the galactic center in the constellation Sagittarius by the Max Planck Institute for Radio Astronomy. In 2009, glycine sampled in 2004 from comet Wild 2 by the NASA spacecraft Stardust was confirmed, the first discovery of extraterrestrial glycine. That mission's results bolstered the theory of panspermia, which claims that the "seeds" of life are widespread throughout the universe.
On attempts to detect glycine in interstellar medium
Classification System: APG II (down to family level)
Cladus: core eudicots
Cladus: Eurosids I
Subgenera: G. subg. Glycine - G. subg. Soya