Arsenic Methyltransferase and Methylation of

Overview

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Key numbers

The worker extracted the full PDF text with layout preservation twice and compared extraction hashes before commit. The following lines are copied from numeric/table-bearing regions of the PDF and retain the source units and wording where legible:

hot springs (2). Arsenic concentrations in volcanic rocks were determined to be 3.5 ppm, whereas
granites from Minnesota measured 1.0 ppm arsenic, on average. Arsenic in combination with elements
in rivers and lakes were determined to be as high as 1100 ppm (5). Furthermore, agricultural products
and associated health risks, the WHO established a drinking water standard of 10 µg/L (4).
10 µg/L (15,17). In comparison, it has been estimated that 0.5–2.0, 2.0, and >3.0 million people are
exposed to >10 µg/L arsenic in drinking water in Argentina, China, and in Vietnam and the United States,
respectively (17). Levels of arsenic in drinking water in Bangladesh, however, often exceed 50 µg/L,
their drinking water at levels as high as 290 µg/L (20).
are enzymatically capable of converting iAs to DMA. Dogs and mice excrete approximately 81% and
71% DMA, respectively. Primary rat hepatocytes have been shown to methylate arsenic better than
of iAs, 75% was shown to be excreted as methylated iAs, of which one-third was MMA and two-thirds
for several days. About 60% of the ingested arsenic was excreted every day (28), and the composition
sequence (GenBank accession number XM_008270429) was more than 90% similar to other known
their exons were also arranged entirely at the 50 end of the gene. This could be entirely by chance,
On the other hand, rabbits and hamsters excrete about 50% arsenic as DMA, but their exon–intron
methylate iAs, their exons were also arranged entirely at the 5′ end of the gene. This could be entirely
Figure 1. Exon–intron arrangements of seven coding sequences in the AS3MT genome.
Figure 1. Exon–intron arrangements of seven coding sequences in the AS3MT genome. Exons
iAs. Their genomic sequence contains one consensus and three 90% consensus AREs. The human
ARE with 90% similarity. However, in humans, more than 60% of urinary arsenic is DMA. Additionally,
rats and rabbits have a similar number of AREs, and rabbits excrete 50% DMA compared to only 20%
that they also have three other isoforms of AS3MT, Pan troglodytes X1, X2, and X3 with GenBank
Individuals with AS3MT haplotype I (16.5% of the above population) showed slower methylation
altered the ratios of MMA/DMA concentration in their urine. Wild-type homozygotes had 33% of
excess of 200 µg/L, can metabolize arsenic efficiently and can rapidly reduce arsenic burden via
metabolize and excrete 70% to 80% arsenic in the form of DMA. Even in some human populations,

Methods (brief)

by the formation of monomethylarsonic acid (MMA) and then dimethylarsinic acid (DMA) (21).
are enzymatically capable of converting iAs to DMA. Dogs and mice excrete approximately 81% and
71% DMA, respectively. Primary rat hepatocytes have been shown to methylate arsenic better than
DMA (27). In order to develop an exposure history in industrial workers, the same authors also
protein during passage through the kidney. In contrast, MMA and DMA would only have two and
MMA is often considered more toxic than DMA, and higher body burdens of MMA have been
and DMAIII were both shown to be more toxic and reactive compared to iAsIII , and were shown to
to intermediate metabolites, namely MMAIII and DMAIII .
dimethylarsinic acid (DMAV ), monomethylarsonous acid (MMAIII ), and dimethylarsinous acid
(DMAIII ) differ significantly (33). For instance, iAsIII and iAsV produced concentration-related linear
DMAIII , on the other hand, were reported to be 54 and 77 times more potent than iAsV or iAsIII ,
respectively, and DMAIII was 270 and 386 times more potent than iAsV or iAsIII , respectively (33).
MMAV and DMAV were inactive and unable to damage DNA at high concentrations, however.
trivalent As species (33). While both trivalent methylated species MMAIII and DMAIII did show DNA
MMAIII ; >DMAIII ; >dimethylarsinic glutathione, DMAGIII ; >dimethylmonothioarsinate, DMMTAV ;
AsIII ; > monomethyltrithioarsonate, MMTTAV ; >AsV ; >dimethyldithioarsinate, DMDTAV ; >DMAV ;
and DMAIII , inorganic and organic trivalent arsenic species are certainly more cytotoxic compared to
with Coomassie blue, extracted from the gel, and subjected to trypsin digestion. They sequenced

Implications

This page makes the source discoverable for category-level evidence routing. Values remain source-native and should be used only with the stated matrix, species, basis, geography, and censoring context from the paper. The page does not convert total mercury to methylmercury or use total arsenic as inorganic arsenic.

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Verification notes

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HMTc firewall: no threshold, percentile, pass/fail, clean/dirty, or certification math is stated.

Update history

The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git. When DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.

Commit	Date	Change	Description
b01ec52c	2026-08-04	major	2 sections added
d49e450f	2026-08-03	major	5 sections added; narrative text revised