Fig. 3. The metabolism of inorganic arsenic (iAs) to methylarsenic species. Inorganic arsenic includes arsenite (As
III
) and arsenate (As
V
), which can be subsequently methylated
to produce either monomethylarsonate (MMA
V
) or dimethylarsonate (DMA
V
). The metabolism of iAs involves a two-electron reduction of pentavalent As to trivalent As,
mediated by glutathione, followed by oxidative methylation (Hughes, 2002).