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ENZYME entry: EC

Accepted Name
arsenite methyltransferase
Alternative Name(s)
methylarsonite methyltransferase
Reaction catalysed
  • [thioredoxin]-dithiol + arsenic triglutathione + 2 H2O + S-adenosyl-L-methionine <=> [thioredoxin]-disulfide + 3 glutathione + H(+) + methylarsonous acid + S-adenosyl-L-homocysteine
  • 2 [thioredoxin]-dithiol + arsenic triglutathione + H2O + 2 S-adenosyl-L-methionine <=> 2 [thioredoxin]-disulfide + dimethylarsinous acid + 3 glutathione + 2 H(+) + 2 S-adenosyl-L-homocysteine
  • 3 [thioredoxin]-dithiol + arsenic triglutathione + 3 S-adenosyl-L-methionine <=> 3 [thioredoxin]-disulfide + 3 glutathione + 3 H(+) + 3 S-adenosyl-L-homocysteine + trimethylarsine
  • An enzyme responsible for synthesis of trivalent methylarsenical antibiotics in microbes or detoxification of inorganic arsenous acid in animals.
  • The in vivo substrate is arsenic triglutathione or similar thiol (depending on the organism), from which the arsenic is transferred to the enzyme forming bonds with the thiol groups of three cysteine residues via a disulfide bond cascade pathway.
  • Most of the substrates undergo two methylations and are converted to dimethylarsinous acid.
  • However, a small fraction are released earlier as methylarsonous acid, and a smaller amount proceeds via a third methylation, resulting in the volatile product trimethylarsane.
  • Methylation involves temporary oxidation to arsenic(V) valency, followed by reduction back to arsenic(III) valency using electrons provided by thioredoxin or a similar reduction system.
  • The arsenic(III) products are quickly oxidized in the presence of oxygen to the corresponding arsenic(V) species.
PRIAM enzyme-specific profiles2.1.1.137
KEGG Ligand Database for Enzyme Nomenclature2.1.1.137
IUBMB Enzyme Nomenclature2.1.1.137
MEDLINEFind literature relating to
Rhea expert-curated reactions2.1.1.137

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