Peptide methionine (S) S oxide reductase

Peptide-methionine (S)-S-oxide reductase (EC 1.8.4.11, MsrA, methionine sulphoxide reductase A, methionine S-oxide reductase (S-form oxidizing), methionine sulfoxide reductase A, peptide methionine sulfoxide reductase) is an enzyme with systematic name peptide-L-methionine:thioredoxin-disulfide S-oxidoreductase (L-methionine (S)-S-oxide-forming). This enzyme catalyses the following chemical reaction

(1) peptide-L-methionine + thioredoxin disulfide + H₂O ⇌ peptide-L-methionine (S)-S-oxide + thioredoxin(2) L-methionine + thioredoxin disulfide + H₂O ⇌ L-methionine (S)-S-oxide + thioredoxin

The reaction occurs in the reverse direction.