Selenocysteine

Selenocysteine
Names
	IUPAC name Selenocysteine
	Systematic IUPAC name 2-Amino-3-selanylpropanoic acid
	Other names L-Selenocysteine; Selenium-cysteine
Identifiers
CAS Number	3614-08-2 ;
3D model (JSmol)	Interactive image; Zwitterion: Interactive image;
ChEBI	CHEBI:16633 ;
ChEMBL	ChEMBL109962 ;
ChemSpider	23436 ;
DrugBank	DB02345 ;
ECHA InfoCard	100.236.386
KEGG	C05688 ;
PubChem CID	25076;
UNII	0CH9049VIS ;
CompTox Dashboard (EPA)	DTXSID00881371 ;
	InChI InChI=1S/C3H7NO2Se/c4-2(1-7)3(5)6/h2,7H,1,4H2,(H,5,6)/t2-/m0/s1 Key: ZKZBPNGNEQAJSX-REOHCLBHSA-N ; InChI=1/C3H7NO2Se/c4-2(1-7)3(5)6/h2,7H,1,4H2,(H,5,6)/t2-/m0/s1 Key: ZKZBPNGNEQAJSX-REOHCLBHBZ;
	SMILES O=C(O)[C@@H](N)C[SeH]; Zwitterion: O=C([O-])[C@@H]([NH3+])C[SeH];
Properties
Chemical formula	C3H7NO2Se
Molar mass	168.065 g·mol−1
Properties
Acidity (pKa)	5.24, 5.43
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Selenocysteine (symbol Sec or U, in older publications also as Se-Cys) is the 21st proteinogenic amino acid. Selenoproteins contain selenocysteine residues. Selenocysteine is an analogue of the more common cysteine with selenium in place of the sulfur.

Selenocysteine is present in several enzymes (for example glutathione peroxidases, tetraiodothyronine 5′ deiodinases, thioredoxin reductases, formate dehydrogenases, glycine reductases, selenophosphate synthetase 2, methionine-R-sulfoxide reductase B1 (SEPX1), and some hydrogenases). It occurs in all three domains of life, including important enzymes (listed above) present in humans.

Selenocysteine was discovered in 1974 by biochemist Thressa Stadtman at the National Institutes of Health.