Arsenite methyltransferase (S-adenosyl-L- methionine:arsenic(III) methyltransferase, methylarsonite methyltransferase, AS3MT, CYT19)

Function

• catalyzes the transfer of a methyl group from AdoMet to trivalent arsenicals producing methylated & dimethylated arsenicals
• methylates arsenite to form methylarsonate, Me-AsO3H2, which is reduced by methylarsonate reductase to methylarsonite, Me-As(OH)2
• methylarsonite is also a substrate & t is converted into the much less toxic compound dimethylarsinate (cacodylate), Me2As(O)-OH (putative)

S-adenosyl-L-methionine + arsenite
                <-->
S-adenosyl-L-homocysteine + methylarsonate

S-adenosyl-L-methionine + methylarsonite
                <-->
S-adenosyl-L-homocysteine + dimethylarsinate

Kinetic parameters:

• KM=4.6 uM for sodium arsenite
• KM=11.8 uM for AdoMet

Structure

belongs to the methyltransferase superfamily

Compartment

cytoplasm (putative)

More general terms

• methyltransferase

Database

• UniProt: http://www.uniprot.org/uniprot/Q9HBK9.html