近岸海域的砷污染已对我国海洋生物的生存以及海产品的质量安全构成了严重威胁。由于砷的毒性与其赋存形态密切相关，因此开展砷的生物转化研究是揭示其毒性机制和健康风险的必要前提。迄今为止，有关海洋软体动物砷转化规律和机制的研究鲜有报道。本项目选取兼具环境指示功能和重要经济价值的菲律宾蛤仔为研究对象，围绕砷甲基转化规律及其分子机制开展研究。通过HPLC-HG-AFS技术，测定不同组织和亚细胞组分中甲基砷的赋存形态及其含量，明确菲律宾蛤仔对无机砷的甲基转化规律；获取砷甲基化关键酶GSTΩ和AS3MT的基因全长，并探讨其对无机砷胁迫的分子响应机制；实现GSTΩ和AS3MT的重组表达，体外验证其对砷的甲基化功能；结合砷超敏感菌株大肠杆菌AW3110，进一步确认关键酶的转化机制。研究结果可为海洋软体动物砷生物转化机制的阐明奠定重要基础，亦可为我国海水水质标准的制定以及海产品潜在健康风险的评估提供科学依据。

Arsenic pollution in offshore area poses a serious threat to the survival of marine organisms and seafood safety. The toxicity of arsenic mainly depends on its species. Therefore, research on arsenic biotransformation is necessary so as to elucidate the toxic mechanisms and health risk of arsenic. However, there are few reports about the mechanisms of arsenic biotransformation in marine mollusks so far. Ruditapes philippinarum, an economically important species and widely used as environmental bioindicator, is used to investigate the molecular mechanisms of arsenic methylation in this project. The methylated-arsenic species and concentration in different tissues and subcellular fractions are determined with HPLC-HG-AFS to clarify the arsenic methylation in R. philippinarum. The genes encoding GSTΩ and AS3MT involved in arsenic methylation are cloned, and their molecular responses to inorganic arsenic exposure are studied. Then the recombinant proteins of GSTΩ and AS3MT are employed to investigate their in vitro functions during arsenic methylation. Moreover, the functions of GSTΩ and AS3MT are also validated with the arsenic-hypersensitive strain Escherichia coli AW3110. The results of this proposal will lay a foundation for elucidating the mechanism of arsenic biotransformation in marine mollusks, and also provide scientific basis for the establishmemt of seawater quality standard and the evaluation of potential health risk of eating seafood.