Shandong Key Laboratory of Environmental Processes and Health, School of Environmental Science and Engineering, Shandong University, Qingdao 266237, China.
State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
Environ Sci Technol. 2024 Jan 30;58(4):1934-1943. doi: 10.1021/acs.est.3c07367. Epub 2024 Jan 5.
Antimony (Sb) biomethylation is an important but uninformed process in Sb biogeochemical cycling. Methylated Sb species have been widely detected in the environment, but the gene and enzyme for Sb methylation remain unknown. Here, we found that arsenite -adenosylmethionine methyltransferase (ArsM) is able to catalyze Sb(III) methylation. The stepwise methylation by ArsM forms mono-, di-, and trimethylated Sb species. Sb(III) is readily coordinated with glutathione, forming the preferred ArsM substrate which is anchored on three conserved cysteines. Overexpressing in AW3110 conferred resistance to Sb(III) by converting intracellular Sb(III) into gaseous methylated species, serving as a detoxification process. Methylated Sb species were detected in paddy soil cultures, and phylogenetic analysis of ArsM showed its great diversity in ecosystems, suggesting a high metabolic potential for Sb(III) methylation in the environment. This study shows an undiscovered microbial process methylating aqueous Sb(III) into the gaseous phase, mobilizing Sb on a regional and even global scale as a re-emerging contaminant.
锑（Sb）的生物甲基化是 Sb 生物地球化学循环中一个重要但尚未被了解的过程。环境中已广泛检测到甲基化 Sb 物种，但 Sb 甲基化的基因和酶仍然未知。在这里，我们发现亚砷酸盐 -腺苷甲硫氨酸甲基转移酶（ArsM）能够催化 Sb(III)甲基化。ArsM 的逐步甲基化形成单、二和三甲基化 Sb 物种。Sb(III)很容易与谷胱甘肽配位，形成 ArsM 首选的底物，该底物锚定在三个保守的半胱氨酸上。在 AW3110 中过表达 赋予了对 Sb(III)的抗性，方法是将细胞内的 Sb(III)转化为气态甲基化物种，作为解毒过程。在稻田土壤培养物中检测到了甲基化 Sb 物种，并且 ArsM 的系统发育分析表明其在生态系统中具有很大的多样性，这表明 Sb(III)甲基化在环境中有很高的代谢潜力。这项研究揭示了一个未被发现的微生物过程，即将水相 Sb(III)甲基化为气相，将 Sb 作为一种重新出现的污染物在区域甚至全球范围内迁移。
