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Selenocysteine

Selenocysteine
Names
IUPAC name
3-Selanyl-2-aminopropanoic acid
Other names
L-Selenocysteine; 3-Selanyl-L-alanine; Selenium cysteine
Identifiers
10236-58-5 N
3D model (Jmol) Interactive image
ChEBI CHEBI:16633 YesY
ChEMBL ChEMBL109962 YesY
ChemSpider 23436 YesY
DrugBank DB02345 YesY
ECHA InfoCard 100.236.386
KEGG C05688 YesY
PubChem 25076
UNII 0CH9049VIS N
Properties
C3H7NO2Se
Molar mass 168.07 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YesYN ?)
Infobox references

Selenocysteine (abbreviated as Sec or U, in older publications also as Se-Cys) is the 21st proteinogenic amino acid.

Selenocysteine exists naturally in three domains of life, but not in every lineage, as a building block of selenoproteins. Selenocysteine is a cysteine analogue with a selenium-containing selenol group in place of the sulfur-containing thiol group.

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).

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

Selenocysteine has a structure similar to that of cysteine, but with an atom of selenium taking the place of the usual sulfur, forming a selenol group which is deprotonated at physiological pH. Proteins that contain one or more selenocysteine residues are called selenoproteins. Most selenoproteins contain a single Sec residue. Selenoproteins with catalytic activities which depend on selenocysteine's biochemical activity are called selenoenzymes. The structurally characterized selenoenzymes have been found to employ catalytic triad structures that influence the nucleophilicity of the active site selenocysteine.


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