The enzyme is part of a system for detoxifying arsenate. The substrate binds to a catalytic cysteine residue, forming a covalent thiolate---As(V) intermediate. A tertiary intermediate is then formed between the arsenic, the enzyme's cysteine, and a glutathione cysteine. This intermediate is reduced by glutaredoxin, which forms a dithiol with the glutathione, leading to the dissociation of arsenite. Thus reduction of As(V) is mediated by three cysteine residues: one in ArsC, one in glutathione, and one in glutaredoxin. Although the arsenite formed is more toxic than arsenate, it can be extruded from some bacteria by EC
7.3.2.7, arsenite-transporting ATPase; in other organisms, arsenite can be methylated by EC
2.1.1.137, arsenite methyltransferase, in a pathway that produces non-toxic organoarsenical compounds. cf. EC
1.20.4.4, arsenate reductase (thioredoxin).
