ID 2.1.1.137 DE arsenite methyltransferase. AN methylarsonite methyltransferase. CA (1) [thioredoxin]-dithiol + arsenic triglutathione + 2 H2O + S-adenosyl- CA L-methionine = [thioredoxin]-disulfide + 3 glutathione + H(+) + CA methylarsonous acid + S-adenosyl-L-homocysteine. CA (2) 2 [thioredoxin]-dithiol + arsenic triglutathione + H2O + CA 2 S-adenosyl-L-methionine = 2 [thioredoxin]-disulfide + dimethylarsinous CA acid + 3 glutathione + 2 H(+) + 2 S-adenosyl-L-homocysteine. CA (3) 3 [thioredoxin]-dithiol + arsenic triglutathione + 3 S-adenosyl-L- CA methionine = 3 [thioredoxin]-disulfide + 3 glutathione + 3 H(+) + CA 3 S-adenosyl-L-homocysteine + trimethylarsine. CC -!- An enzyme responsible for synthesis of trivalent methylarsenical CC antibiotics in microbes or detoxification of inorganic arsenous acid CC in animals. CC -!- The in vivo substrate is arsenic triglutathione or similar thiol CC (depending on the organism), from which the arsenic is transferred to CC the enzyme forming bonds with the thiol groups of three cysteine CC residues via a disulfide bond cascade pathway. CC -!- Most of the substrates undergo two methylations and are converted to CC dimethylarsinous acid. CC -!- However, a small fraction are released earlier as methylarsonous CC acid, and a smaller amount proceeds via a third methylation, CC resulting in the volatile product trimethylarsane. CC -!- Methylation involves temporary oxidation to arsenic(V) valency, CC followed by reduction back to arsenic(III) valency using electrons CC provided by thioredoxin or a similar reduction system. CC -!- The arsenic(III) products are quickly oxidized in the presence of CC oxygen to the corresponding arsenic(V) species. DR A0A0D3MJQ5, ARSM_CLOSP ; O52025, ARSM_HALSA ; Q8TJK1, ARSM_METAC ; DR U2ZU49, ARSM_PSEA4 ; Q6N3Y0, ARSM_RHOPA ; Q9HBK9, AS3MT_HUMAN; DR Q91WU5, AS3MT_MOUSE; Q8VHT6, AS3MT_RAT ; //