Methionine

Methionine
	Skeletal formula of the canonical form of methionine
Ball-and-stick model	Space-filling model
Names
	IUPAC name Methionine
	Systematic IUPAC name 2-Amino-4-(methylsulfanyl)butanoic acid
	Other names 2-amino-4-(methylthio)butanoic acid; Amino-γ-methylthiobutyric acid
Identifiers
CAS Number	L: 63-68-3 ; D/L: 59-51-8 ; D: 348-67-4 ;
3D model (JSmol)	L: Interactive image; L Zwitterion: Interactive image;
Abbreviations	Met, M
ChEBI	L: CHEBI:16643 ; D/L: CHEBI:16811 ; D: CHEBI:16867 ;
ChEMBL	L: ChEMBL42336 ;
ChemSpider	L: 5907 ; D/L: 853 ; D: 76512 ;
DrugBank	L: DB00134 ;
ECHA InfoCard	100.000.393
EC Number	L: 200-432-1;
KEGG	L: C00073 ;
PubChem CID	L: 6137; D/L: 876; D: 84815;
UNII	L: AE28F7PNPL ; D/L: 73JWT2K6T3 ; D: 868496F25R ;
CompTox Dashboard (EPA)	L: DTXSID9020821 ;
	InChI InChI=1S/C5H11NO2S/c1-9-3-2-4(6)5(7)8/h4H,2-3,6H2,1H3,(H,7,8)/t4-/m0/s1 Key: FFEARJCKVFRZRR-BYPYZUCNSA-N ; D/L: Key: FFEARJCKVFRZRR-UHFFFAOYSA-N; D: Key: FFEARJCKVFRZRR-SCSAIBSYSA-N;
	SMILES L: CSCC[C@H](N)C(=O)O; L Zwitterion: CSCC[C@H]([NH3+])C(=O)[O-];
Properties
Chemical formula	C5H11NO2S
Molar mass	149.21 g·mol−1
Appearance	White crystalline powder
Density	1.340 g/cm3
Melting point	281 °C (538 °F; 554 K) decomposes
Solubility in water	Soluble
Acidity (pKa)	2.28 (carboxyl), 9.21 (amino)
Pharmacology
ATC code	V03AB26 (WHO) QA05BA90 (WHO), QG04BA90 (WHO)
Supplementary data page
	Methionine (data page)
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Methionine (symbol Met or M) (/mɪˈθaɪəniːn/) is an essential amino acid in humans. Compared to other amino acids, methionine has particularly decisive biosynthetic roles. It is the precursor to the amino acid cysteine and the pervasive methylation agent rSAM. Methionine is required for protein synthesis, which is initiated by N-formylmethionine-sRNA.

Methionine was first isolated in 1921 by John Howard Mueller. It is encoded by the codon AUG. It was named by Satoru Odake in 1925, as an abbreviation of its structural description 2-amino-4-(methylthio)butanoic acid.