Methionine sulfoxide

Methionine sulfoxide

Names
IUPAC name 2-Amino-4-(methylsulfinyl)butanoic acid
Identifiers
3D model (JSmol)	Interactive image
ChemSpider	824
PubChem CID	847
InChI InChI=1S/C5H11NO3S/c1-10(9)3-2-4(6)5(7)8/h4H,2-3,6H2,1H3,(H,7,8) Key: QEFRNWWLZKMPFJ-UHFFFAOYSA-N InChI=1/C5H11NO3S/c1-10(9)3-2-4(6)5(7)8/h4H,2-3,6H2,1H3,(H,7,8) Key: QEFRNWWLZKMPFJ-UHFFFAOYAN
SMILES O=C(O)C(N)CCS(=O)C
Properties
Chemical formula	C5H11NO3S
Molar mass	165.21 g·mol−1
Appearance	white solid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Methionine sulfoxide is the organic compound with the formula CH₃S(O)CH₂CH₂CH(NH₂)CO₂H. It is an amino acid that occurs naturally although it is formed post-translationally.

Oxidation of the sulfur of methionine results in methionine sulfoxide or methionine sulfone. The sulfur-containing amino acids methionine and cysteine are more easily oxidized than the other amino acids. Unlike oxidation of other amino acids, the oxidation of methionine can be reversed by enzymatic action, specifically by enzymes in the methionine sulfoxide reductase family of enzymes. The three known methionine sulfoxide reductases are MsrA, MsrB, and fRmsr. Oxidation of methionine results in a mixture of the two diastereomers methionine-S-sulfoxide and methionine-R-sulfoxide, which are reduced by MsrA and MsrB, respectively. MsrA can reduce both free and protein-based methionine-S-sulfoxide, whereas MsrB is specific for protein-based methionine-R-sulfoxide. fRmsr, however, catalyzes the reduction of free methionine-R-sulfoxide.Thioredoxin serves to recycle by reduction some of the methionine sulfoxide reductase family of enzymes, whereas others can be reduced by metallothionein.

Methionine sulfoxide (MetO), the oxidized form of the amino acid methionine (Met), increases with age in body tissues, which is believed by some to contribute to biological ageing. Oxidation of methionine residues in tissue proteins can cause them to misfold or otherwise render them dysfunctional. Uniquely, the methionine sulfoxide reductase (Msr) group of enzymes act with thioredoxin to catalyze the enzymatic reduction and repair of oxidized methionine residues. Moreover, levels of methionine sulfoxide reductase A (MsrA) decline in aging tissues in mice and in association with age-related disease in humans. There is thus a rationale for thinking that by maintaining the structureincreased levels or activity of MsrA might retard the rate of aging.