Glycine 11835 221536384 2008-06-24T23:03:55Z 203.97.96.60 {{for|the plant|Glycine (plant)}} {{NatOrganicBox | image= [[Image:Glycin - Glycine.svg|105px|Skeletal formula of glycine]]<br>[[Image:Glycine-3D-balls.png|105px|Ball-and-stick model of the glycine molecule]][[Image:Glycine-3D-vdW.png|105px|Space-filling model of the glycine molecule]] | name=aminoethanoic acid | PubChem = 750 | CAS = 56-40-6 | SMILES = NCC(O)=O | C=2 | H=5 | N=1 | O=2 | mass=75.07 g/mol }} '''Glycine''' (abbreviated as '''Gly''' or '''G''')<ref>{{cite web | author=IUPAC-IUBMB Joint Commission on Biochemical Nomenclature | title=Nomenclature and Symbolism for Amino Acids and Peptides | work=Recommendations on Organic & Biochemical Nomenclature, Symbols & Terminology etc | url=http://www.chem.qmul.ac.uk/iupac/AminoAcid/ | accessdate=2007-05-17}}</ref> is the [[organic compound]] with the [[chemical formula|formula]] NH<sub>2</sub>CH<sub>2</sub>COOH. It is the smallest of the 20 [[amino acid]]s commonly found in [[protein]]s, coded by [[codons]] GGU, GGC, GGA and GGG. Because it has specialized structural properties in protein architecture, this compact amino acid is often evolutionarily conserved. For example, [[cytochrome c]], [[myoglobin]], and [[hemoglobin]] all contain conserved glycines.{{Fact|date=September 2007}} Glycine is the unique amino acid that is not [[chiral]]. Most proteins contain only small quantities of glycine. A notable exception is [[collagen]], which contains about 35% glycine.<ref name=Nel127>Nelson, D. L. & Cox, M. M. (2005). ''Lehninger Principles of Biochemistry'', 4th Edition. New York: W. H. Freeman and Company, p. 127. ISBN 0-7167-4339-6.</ref> In its solid, i.e., crystallized, form, glycine is a free-flowing, sweet-tasting crystalline material. ==Production== Glycine is manufactured industrially, either by treating [[chloroacetic acid]] with [[ammonia]]: :ClCH<sub>2</sub>COOH + NH<sub>3</sub> → H<sub>2</sub>NCH<sub>2</sub>COOH + HCl or via the [[Strecker amino acid synthesis]]. There are two producers of glycine in the United States. Chattem Chemicals, Inc. and GEO Specialty Chemicals, Inc., who purchased the glycine production facilities of Hampshire Chemical Corp.<ref name=usitc3810>U.S. International Trade Commission, "Glycine From China." Investigation No. 731-TA-718 (Second Review), Publication No. 3810, October 2005</ref> <ref name=Ham110105>Nov. 1, 2005 Press Release [http://news.dow.com/dow_news/prodbus/2005/20051101e.htm]</ref> ==Biosynthesis== Glycine is not essential to the human diet, since 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 by removing one carbon atom; [[pyridoxal phosphate]] is also necessary:<ref name=Nel844>Nelson, D. L. & Cox, M. M. (2005). ''Lehninger Principles of Biochemistry'', 4th Edition. New York: W. H. Freeman and Company, p. 844. ISBN 0-7167-4339-6.</ref> : Serine + [[tetrahydrofolate]] → Glycine + ''N<sup>5</sup>'',''N<sup>10</sup>''-Methylene tetrahydrofolate + H<sub>2</sub>O In the liver of [[vertebrates]], glycine synthesis is catalyzed by [[glycine synthase]] (also called glycine cleavage enzyme). This conversion is readily reversible:<ref name=Nel844/> : CO<sub>2</sub> + NH<sub>4</sub><sup>+</sup> + ''N<sup>5</sup>'',''N<sup>10</sup>''-Methylene tetrahydrofolate + [[NADH]] + H<sup>+</sup> → Glycine + tetrahydrofolate + NAD<sup>+</sup> ==Degradation== 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:<ref name=Nel675>Nelson, D. L. & Cox, M. M. (2005). ''Lehninger Principles of Biochemistry'', 4th Edition. New York: W. H. Freeman and Company, pp. 675-677. ISBN 0-7167-4339-6.</ref> : Glycine + tetrahydrofolate + NAD<sup>+</sup> → CO<sub>2</sub> + NH<sub>4</sub><sup>+</sup> + ''N<sup>5</sup>'',''N<sup>10</sup>''-Methylene tetrahydrofolate + [[NADH]] + H<sup>+</sup> 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]].<ref name=Nel675/> 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<sup>+</sup>-dependent reaction.<ref name=Nel675/> ==Physiological function== ===As a biosynthetic intermediate=== Glycine is a building block to numerous natural products. In higher [[eukaryotes]], [[D-Aminolevulinic acid]], the key precursor to [[porphyrins]], is biosynthesized from glycine and [[succinyl-CoA]]. Glycine provides the central C<sub>2</sub>N subunit of all [[purine]]s.<ref name=Nel854>Nelson, D. L. & Cox, M. M. (2005). ''Lehninger Principles of Biochemistry'', 4th Edition. New York: W. H. Freeman and Company, p. 854. ISBN 0-7167-4339-6.</ref> ===As a neurotransmitter=== 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 receptor]]s. 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|LD<sub>50</sub>]] of glycine is 7930 mg/kg in rats (oral),<ref>{{cite web |url=http://physchem.ox.ac.uk/MSDS/GL/glycine.html |title=Safety (MSDS) data for glycine |date=2005 |publisher= The Physical and Theoretical Chemistry Laboratory Oxford University |accessdate=2006-11-01}}</ref> and it usually causes death by [[hyperexcitability]]. ==Industrial Uses== Glycine is used as a sweetener/taste enhancer, buffering agent, reabsorbable amino acid, chemical intermediate, metal complexing agent, and dietary supplement as well as in certain pharmaceuticals. <ref name=72FR62827>"Notice of Preliminary Determination of Sales at Less Than Fair Value: Glycine From India" Federal Register 72 (7 November 2007): 62827.</ref> ==Antidumping tariffs== Glycine imported from China to the United States has been subject to antidumping duties since March, 1995. <ref name=usitc2863> Glycine from the People’s Republic of China, Inv. No. 731-TA-718 (Final), USITC Pub. 2863 (Mar. 1995) (“Original Determination”) at 1.</ref> In 2007, a United States manufacturer of Glycine, GEO Specialty Chemicals, Inc. filed petitions requesting that antidumping duties also be imposed on Glycine imported from Japan, the Republic of Korea, and India. On September 7, 2007 the Department of Commerce announced its affirmative preliminary determinations in the antidumping duty investigations on imports of glycine from Japan and the Republic of Korea (Korea). On October 29, 2007 the Department of Commerce announced its affirmative preliminary determination in the antidumping duty investigation on imports of glycine from India. ==Presence in the interstellar medium== In 1994 a team of astronomers at the [[University of Illinois at Urbana-Champaign|University of Illinois]], led by [[Lewis Snyder]], claimed that they had found the glycine molecule in space. It turned out that, with further analysis, this claim could not be confirmed. Nine years later, in 2003, [[Yi-Jehng Kuan]] from [[National Taiwan Normal University]] and [[Steve Charnley]] claimed that they detected interstellar glycine toward three sources in the [[interstellar medium]].<ref name=Kuan>{{cite journal |author=Kuan YJ, Charnley SB, Huang HC, et al. |title=Interstellar glycine |journal=Astrophys J |volume=593 |issue=2 |pages=848–867 |year=2003 |doi=10.1086/375637}}</ref> They claimed to have identified 27 [[spectral]] lines of glycine utilizing a [[radio telescope]]. According to computer simulations and lab-based experiments, glycine was probably formed when ices containing simple organic molecules were exposed to [[ultraviolet light]].<ref>{{cite web |url=http://www.newscientist.com/news/news.jsp?id=ns99992558 |author=Rachel Nowak |title=Amino acid found in deep space - 18 July 2002 - New Scientist |accessdate=2007-07-01}}</ref> In October 2004, Snyder and collaborators reinvestigated the glycine claim in Kuan ''et al.'' (2003). In a rigorous attempt to confirm the detection, Snyder showed that glycine was not detected in any of the three claimed sources.<ref name=Snyder>{{cite journal |author=Snyder LE, Lovas FJ, Hollis JM, et al. |title=A rigorous attempt to verify interstellar glycine |journal=Astrophys J |volume=619 |issue=2 |pages=914–930 |year=2005 |doi=10.1086/426677}}</ref> Should the glycine claim be substantiated, the finding would not prove that life exists outside the [[Earth]], but certainly makes that possibility more plausible by showing that amino acids can be formed in the interstellar medium. ==References== {{reflist}} * Dawson, R.M.C., Elliott, D.C., Elliott, W.H., and Jones, K.M., ''Data for Biochemical Research'' (3rd edition), pp. 1-31 (1986) ISBN 01-985-535-87 ==External links== *[http://www.geosc.com/ GEO Specialty Chemicals, Inc.] *[http://www.pdrhealth.com/drugs/altmed/altmed-mono.aspx?contentFileName=ame0084.xml&contentName=Glycine&contentId=247 Glycine] *[http://www.compchemwiki.org/index.php?title=Glycine Computational Chemistry Wiki] *[http://www.chem.qmul.ac.uk/iubmb/enzyme/reaction/AminoAcid/GlyCleave.html Glycine cleavage system] *[http://chemsub.online.fr/chemsearch/cas_number_56-40-6.html Glycine, ChemSub Online] {{AminoAcids}} [[Category:Proteinogenic amino acids]] [[Category:Neurotransmitters]] [[Category:Glucogenic amino acids]] [[Category:Flavour enhancers]] [[bn:গ্লাইসিন]] [[ca:Glicina]] [[cs:Glycin]] [[da:Glycin]] [[de:Glycin]] [[es:Glicina]] [[eo:Glicino]] [[fr:Glycine (acide aminé)]] [[ko:글리신]] [[hr:Glicin]] [[id:Glisin]] [[it:Glicina]] [[he:גליצין]] [[lv:Glicīns]] [[lb:Glycin]] [[lt:Glicinas]] [[hu:Glicin]] [[nl:Glycine (aminozuur)]] [[ja:グリシン]] [[no:Glycin]] [[pl:Glicyna]] [[pt:Glicina]] [[ru:Глицин]] [[sr:Глицин]] [[su:Glisin]] [[fi:Glysiini]] [[sv:Glycin]] [[tr:Glisin]] [[uk:Гліцин]] [[vls:Glycine]] [[zh:甘氨酸]]