Involved in the detoxification of arsenic. Oxidizes As(III)O3(3-) (arsenite) to the somewhat less toxic As(V)O4(3-) (arsenate). arsenite + H2O + 2 oxidized [azurin] = arsenate + 3 H(+) + 2 reduced [azurin] Binds 1 [2Fe-2S] cluster per subunit. Heterodimer consisting of a large and a small subunit. Predicted to be exported by the Tat system. The position of the signal peptide cleavage has not been experimentally proven. Belongs to the AOX family.