Pathways of arsenic biotransformations: The arsenic methylation cycle

B. Rosen, K. Marapakala, A. A. Abdul Salam, C. Packianathan, M. Yoshinaga

Research output: Chapter in Book/Report/Conference proceedingConference contribution

4 Citations (Scopus)


Arsenic methylation is catalyzed by the enzyme As(III)-S-adenosylmethionine methyltransferase (AS3MT or ArsM) that transfers up to three methyl groups from SAM to As(III), producing CH 3 As(III), (CH 3) 2MAs(III) and the nontoxic gaseous product (CH 3) 3MAs(III). In liver AS3MT methylates arsenic, which is excreted in urine. This biotransformation is thought to activate arsenic into a carcinogen. A thermophilic orthologue of human AS3MT was crystallized, and its x-ray crystal structure solved to 1.6 å with bound SAM or As(III). Our data support a pathway of methylation in which GSH conjugates are preferred substrates, and arsenic remains trivalent throughout the catalytic cycle. The location of polymorphisms were mapped onto a homology model of human AS3MT, giving insight into their biochemical effects. Finally, a new gene/enzyme that demethylates methylarsenicals was cloned/purified and characterized.

Original languageEnglish
Title of host publicationUnderstanding the Geological and Medical Interface of Arsenic, As 2012 - 4th International Congress
Subtitle of host publicationArsenic in the Environment
Number of pages4
Publication statusPublished - 16-08-2012
Event4th International Congress on Arsenic in the Environment, As 2012 - Cairns, QLD, Australia
Duration: 22-07-201227-07-2012


Conference4th International Congress on Arsenic in the Environment, As 2012
CityCairns, QLD

All Science Journal Classification (ASJC) codes

  • Environmental Chemistry
  • Pollution


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