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Biodegradation of the pyridinecarboxamide insecticide flonicamid by Microvirga flocculans and characterization of two novel amidases involved
Ecotoxicology and Environmental Safety ( IF 6.8 ) Pub Date : 2021-06-03 , DOI: 10.1016/j.ecoenv.2021.112384
Yun-Xiu Zhao 1 , Ling Guo 1 , Li Wang 1 , Neng-Dang Jiang 1 , Ke-Xin Chen 1 , Yi-Jun Dai 1
Affiliation  

Flonicamid (N-cyanomethyl-4-trifluoromethylnicotinamide, FLO) is a new type of pyridinecarboxamide insecticide that exhibits particularly good efficacy in pest control. However, the extensive use of FLO in agricultural production poses environmental risks. Hence, its environmental behavior and degradation mechanism have received increasing attention. Microvirga flocculans CGMCC 1.16731 rapidly degrades FLO to produce the intermediate N-(4-trifluoromethylnicotinoyl) glycinamide (TFNG-AM) and the end acid metabolite 4-(trifluoromethyl) nicotinol glycine (TFNG). This bioconversion is mediated by the nitrile hydratase/amidase system; however, the amidase that is responsible for the conversion of TFNG-AM to TFNG has not yet been reported. Here, gene cloning, overexpression in Escherichia coli and characterization of pure enzymes showed that two amidases—AmiA and AmiB—hydrolyzed TFNG-AM to TFNG. AmiA and AmiB showed only 20–30% identity to experimentally characterized amidase signature family members, and represent novel amidases. Compared with AmiA, AmiB was more sensitive to silver and copper ions but more resistant to organic solvents. Both enzymes demonstrated good pH tolerance and exhibited broad amide substrate specificity. Homology modeling suggested that residues Asp191 and Ser195 may strongly affect the catalytic activity of AmiA and AmiB, respectively. The present study furthers our understanding of the enzymatic mechanisms of biodegradation of nitrile-containing insecticides and may aid in the development of a bioremediation agent for FLO.



中文翻译:

Microvirga 絮凝剂对吡啶甲酰胺杀虫剂氟啶虫胺的生物降解和两种新型酰胺酶的表征

虫酰胺(N -cyanomethyl-4-trifluoromethylnicotinamide, FLO)是一种新型的吡啶甲酰胺类杀虫剂,对害虫的防治效果特别好。然而,在农业生产中广泛使用 FLO 会带来环境风险。因此,其环境行为和降解机制越来越受到关注。Microvirga flocculans CGMCC 1.16731 快速降解 FLO 以产生中间体N-(4-三氟甲基烟酰基)甘氨酰胺(TFNG-AM)和末端酸代谢物4-(三氟甲基)烟醇甘氨酸(TFNG)。这种生物转化是由腈水合酶/酰胺酶系统介导的;然而,负责将 TFNG-AM 转化为 TFNG 的酰胺酶尚未见报道。在这里,基因克隆,在大肠杆菌中表达纯酶的表征和表征表明,两种酰胺酶——AmiA 和 AmiB——将 TFNG-AM 水解为 TFNG。AmiA 和 AmiB 与实验表征的酰胺酶特征家族成员仅显示 20-30% 的同一性,并代表新的酰胺酶。与 AmiA 相比,AmiB 对银和铜离子更敏感,但对有机溶剂更耐受。两种酶均表现出良好的 pH 耐受性并表现出广泛的酰胺底物特异性。同源性建模表明残基 Asp191 和 Ser195 可能分别强烈影响 AmiA 和 AmiB 的催化活性。本研究进一步加深了我们对含腈杀虫剂生物降解酶机制的理解,并可能有助于开发 FLO 生物修复剂。

更新日期:2021-06-03
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