IAS Uptake
Like iAs metabolism in the host, iAs uptake is dependent on its oxidation state, and iAsIII and iAsV are taken up into cells through different membrane transporter protein. Structural similarities between iAsIII and glycerol, iAs V and phosphate make it possible for iAs to be transported by related proteins. GlpF has been reported to be responsible
Methylation
Methylation has long been regarded as a detoxification process, though trivalent methylated products (e.g., MMAIII and DMAIII) are more toxic than inorganic forms (e.g., iAsIII and iAsV) [32]. The main enzyme catalyzing methylation processes in bacteria is ArsM, which was first identified from soil bacterium Rhodopseudomonas palustris [37]. ArsM in
Demethylation
Demethylation is mediated by ArsI, a gene that can lyse the C–As bond and convert MMAIII to iAsIII [43]. ArsI was first identified from an environmental MMAIII demethylating isolate, Bacillus sp. MD1. ArsI protein confers MMAIII demethylation and resistance activities, so this process has also shown to be a detoxification process [43].
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Oxidation
iAs oxidation is also referred to as a detoxification process, which converts iAsIII to less toxic iAsV. This process takes place in periplasm in bacteria. The gene encoding arsenite oxidase which catalyzes the arsenite oxidation is AioAB [44]. During this process, signal transduction system, AioXSR, can regulate expression of AioAB: AioX (AsIII-bi
Reduction
In bacteria, iAsV reduction can happen either in cytoplasm or periplasm. The first pathway in cytoplasm is mediated by ArsC. The iAsIII can then be either extruded by efflux enzymes, such as ArsAB, Acr3, and ArsK, in As resistant system or methylated by ArsM. For the second system, ArrAB facilities cytoplasmic AsV reduction. ArrAB protein can be re
Thiolation
Gut sulfate-reducing bacteria (SRB), such as Desulfovibrio desulfuricans, are involved in the thiolation process due to its ability to produce hydrogen sulfide (H2S) and convert MMAV and DMAV to MMMTAV and DMMTAV[52].
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