Arsenic Toxicity and Biomethylation

Organoarsenic compounds have been used as chemical warfare agents. Chief among was Lewisite, which was used as a vesicant (blister agent) and lung irritant. The main 

Surprisingly enough, BAL is still used today as an antidote for heavy-metal poisoning, particularly for As, but also for Sb, Pb, and Hg. Can you speculate about the chemistry underlying BAL s efficacy  

The discovery of arsenic biomethylation goes back some 200 years, when German physicians noted cases of poisoning attributable to arsenic-containing paints such as Scheele s Green (copper arsenite, below) that were widely used on wallpaper at the time  

Impressively, the model hypothesized a positive methyl group long before such a methyl donor had been identified. Today we know that S -adenosylmethione (SAM, also known as AdoMet) is the most important such donor, and glutathione and other cellular thiols are the key reducing agents  

Although there is broad consensus that methylation acts as a detoxification mechanism in arsenic-tolerant bacteria, the physiological role of human AS3MT is less clear, because methylated trivalent arsenic species are potent careinogens. 

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