Chemical mechanism of arsenic biomethylation.

The bioconversion of inorganic arsenic to methylated metabolites affects the tissue distribution and retention of arsenic and its actions as a toxicant or carcinogen. Although enzymes that catalyze the methylation of arsenicals have been identified in all branches of the tree of life, fundamental questions persist about the chemical processes that underlie reactions that methylate this metalloid. Here, several reaction schemes for arsenic methylation are considered to encourage careful consideration of the chemical plausibility of these schemes.