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 184.108.40.206, arsenite-transporting ATPase; in other organisms, arsenite can be methylated by EC 220.127.116.11, arsenite methyltransferase, in a pathway that produces non-toxic organoarsenical compounds. cf. EC 18.104.22.168, arsenate reductase (thioredoxin).
EC 22.214.171.124 created 2000 as EC 126.96.36.199, transferred 2001 to EC 188.8.131.52, modified 2015, modified 2019, modified 2020