Arsenic Methyltransferase is Involved in Arsenosugar Biosynthesis by Providing DMA

Area of Science:

• Environmental Science
• Biochemistry
• Microbiology

Background:

• Arsenic is a widespread environmental toxin with diverse detoxification pathways.
• Arsenic biotransformation research has primarily focused on reduction, oxidation, and methylation.
• The biosynthesis pathway of arsenosugars, key arsenic transformation products, remains largely unknown.

Purpose of the Study:

• To investigate the role of Arsenic (As(III)) S-Adenosylmethionine methyltransferase (ArsM) in arsenosugar synthesis.
• To elucidate the precursor molecule for arsenosugar biosynthesis.
• To understand the specific functions of ArsM in arsenic metabolism.

Main Methods:

• Utilizing Synechocystis sp. PCC 6803 and a constructed ΔarsM mutant strain.
• Employing high-performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC/ICP-MS) for arsenic species analysis.
• Exposing organisms to various arsenic compounds including arsenite (As(III)), monomethylarsonic acid (MMA(V)), and dimethylarsinic acid (DMA(V)).

Main Results:

• Synechocystis produced dimethylarsinic acid (DMA(V)) and arsenosugars when exposed to As(III) or MMA(V).
• Arsenosugars were detected in cells exposed to DMA(V), even in the ΔarsM mutant.
• The ΔarsM mutant showed no methylation of inorganic arsenic species but still synthesized arsenosugars from DMA(V).

Conclusions:

• ArsM is essential for methylating inorganic arsenic species but not for arsenosugar synthesis from DMA.
• Dimethylarsinic acid (DMA) is identified as the direct precursor for arsenosugar biosynthesis.
• This research advances the understanding of complex organoarsenical biosynthesis and bioavailability.