Department of Microbiology, Key Lab of Microbiology for Agricultural Environment, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095, China.
Department of Biochemistry and Molecular Biology, College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095, China; Medical School, Southeast University, Nanjing, 210009, China.
Ecotoxicol Environ Saf. 2020 Jan 15;187:109848. doi: 10.1016/j.ecoenv.2019.109848. Epub 2019 Oct 25.
Dimethyl terephthalate (DMT) is a primary ingredient widely used in the manufacture of polyesters and industrial plastics; its environmental fate is of concern due to its global use. Microorganisms play key roles in the dissipation of DMT from the environment; however, the enzymes responsible for the initial transformation of DMT and the possible altered toxicity due to this biotransformation have not been extensively studied. To reduce DMT toxicity, we identified the esterase gene dmtH involved in the initial transformation of DMT from the AOPP herbicide-transforming strain Sphingobium sp. C3. DmtH shows 24-41% identity with α/β-hydrolases and belongs to subfamily V of bacterial esterases. The purified recombinant DmtH was capable of transforming DMT to mono-methyl terephthalate (MMT) and potentially transforming other p-phthalic acid esters, including diallyl terephthalate (DAT) and diethyl terephthalate (DET). Using C. elegans as an assay model, we observed the severe toxicity of DMT in inducing reactive oxygen species (ROS) production, decreasing locomotion behavior, reducing lifespan, altering molecular basis for oxidative stress, and inducing mitochondrial stress. In contrast, exposure to MMT did not cause obvious toxicity, induce oxidative stress, and activate mitochondrial stress in nematodes. Our study highlights the usefulness of Sphingobium sp. C3 and its esterase DmtH in transforming p-phthalic acid esters and reducing the toxicity of DMT to organisms.
对苯二甲酸二甲酯（DMT）是一种广泛用于制造聚酯和工业塑料的主要成分；由于其在全球范围内的使用，其环境归宿引起了人们的关注。微生物在 DMT 从环境中消散方面发挥着关键作用；然而，负责 DMT 初始转化的酶以及由于这种生物转化可能改变的毒性尚未得到广泛研究。为了降低 DMT 的毒性，我们从 AOPP 除草剂转化菌株 Sphingobium sp. C3 中鉴定出参与 DMT 初始转化的酯酶基因 dmtH。DmtH 与α/β-水解酶具有 24-41%的同源性，属于细菌酯酶的亚家族 V。纯化的重组 DmtH 能够将 DMT 转化为单甲基对苯二甲酸酯（MMT），并可能转化其他对苯二甲酸酯，包括二烯丙基对苯二甲酸酯（DAT）和二乙基对苯二甲酸酯（DET）。我们使用秀丽隐杆线虫作为检测模型，观察到 DMT 诱导活性氧（ROS）产生、降低运动行为、缩短寿命、改变氧化应激的分子基础以及诱导线粒体应激的严重毒性。相比之下，暴露于 MMT 不会引起线虫明显的毒性、氧化应激和线粒体应激。我们的研究强调了 Sphingobium sp. C3 及其酯酶 DmtH 在转化对苯二甲酸酯和降低 DMT 对生物体毒性方面的有用性。
