Glycine (symbol Gly or G; /ˈɡlaɪsiːn/ (listen)) is an amino acid that has a single hydrogen atom as its side chain. It is the simplest stable amino acid (carbamic acid is unstable), with the chemical formula NH₂‐CH₂‐COOH. Glycine is one of the proteinogenic amino acids. It is encoded by all the codons starting with GG (GGU, GGC, GGA, GGG). Glycine is integral to the formation of alpha-helices in secondary protein structure due to its compact form. For the same reason, it is the most abundant amino acid in collagen triple-helices. Glycine is also an inhibitory neurotransmitter – interference with its release within the spinal cord (such as during a Clostridium tetani infection) can cause spastic paralysis due to uninhibited muscle contraction.

Glycine

Skeletal formula of neutral glycine Skeletal formula of zwitterionic glycine
Ball-and-stick model of the gas-phase structure Ball-and-stick model of the zwitterionic solid-state structure
Space-filling model of the gas-phase structure Space-filling model of the zwitterionic solid-state structure
Names
IUPAC name Aminoacetic acid
Systematic IUPAC name 2-Aminoethanoic acid
Other names Aminoethanoic acid, Glycocol
Identifiers
CAS Number	56-40-6 Y (HCl): 6000-43-7 Y
3D model (JSmol)	Interactive image Zwitterion: Interactive image (HCl): Interactive image
Abbreviations	Gly, G
ChEBI	CHEBI:15428 Y
ChEMBL	ChEMBL773 Y
ChemSpider	730 Y (HCl): 20944
DrugBank	DB00145 Y
ECHA InfoCard	100.000.248
EC Number	200-272-2 (HCl): 227-841-8
IUPHAR/BPS	727
KEGG	D00011 Y
PubChem CID	750 (HCl): 22316
UNII	TE7660XO1C Y (HCl): 225ZLC74HX Y
CompTox Dashboard (EPA)	DTXSID9020667
InChI InChI=1S/C2H5NH2/c3-1-2(4)5/h1,3H2,(H,4,5) Y Key: DHMQDGOQFOQNFH-UHFFFAOYSA-N Y InChI=1S/C2H5NO2/c3-1-2(4)5/h1,3H2,(H,4,5) Key: DHMQDGOQFOQNFH-UHFFFAOYAW
SMILES C(C(=O)O)N Zwitterion: C(C(=O)[O-])[NH3+] (HCl): C(C(=O)O)N.Cl
Properties
Chemical formula	C2H5NO2
Molar mass	75.067 g·mol−1
Appearance	White solid
Density	1.1607 g/cm3
Melting point	233 °C (451 °F; 506 K) (decomposition)
Solubility in water	24.99 g/100 mL (25 °C)
Solubility	soluble in pyridine sparingly soluble in ethanol insoluble in ether
Acidity (pKa)	2.34 (carboxyl), 9.6 (amino)
Magnetic susceptibility (χ)	-40.3·10−6 cm3/mol
Pharmacology
ATC code	B05CX03 (WHO)
Hazards
Lethal dose or concentration (LD, LC):
LD50 (median dose)	2600 mg/kg (mouse, oral)
Supplementary data page
Glycine (data page)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

It is the only achiral proteinogenic amino acid. It can fit into hydrophilic or hydrophobic environments, due to its minimal side chain of only one hydrogen atom.