氯乙酰胺除草剂是一类高效、使用量世界第二的除草剂，主要品种有乙草胺和异丙甲草胺。因乙草胺有致癌性和毒性，欧美已于2012年禁用，因此低毒无致癌性的异丙甲草胺用量显著增加。然而对异丙甲草胺微生物降解的生理和遗传机制研究还未见报道。异丙甲草胺的N-侧链是甲氧乙基，含有1个手性碳和一个手性轴（而乙草胺为N-乙氧甲基，一个手性轴），结构差异导致已报道的乙草胺脱烷基酶不能降解异丙甲草胺。异丙甲草胺降解菌Paracoccus sp. FLY-8通过一个未知的脱烷基酶催化异丙甲草胺脱烷基。本项目采用插入突变和基因组学等技术从FLY-8中克隆异丙甲草胺脱烷基酶基因，研究脱烷基酶特性、动力学和功能，及脱烷基酶降解异丙甲草胺各异构体的手性选择性。本项目将揭示菌株FLY-8中异丙甲草胺脱烷基的分子机制，为深入研究氯乙酰胺除草剂N-侧链结构影响其生物可降解性的酶学机制，及异丙甲草胺的环境行为提供材料和理论依据。

Chloroacetanilide herbicides are a class of highly efficient preemergence herbicides that are widely used for the control of annual grass and broadleaf weeds. Presently, it is the second largest herbicide in the world, and acetochlor and metolachlor were the main chloroacetanilide herbicides. Due to that acetochlor was suspected to be carcinogenic and chronic toxic, it was forbidden in European Union and USA since 2013, thus the usage of metolachlor, which was relatively low toxic and non- carcinogenic, are increasing significantly. To date, the molecular bases for the microbial degradation of metolachlor are still unknown. In structure, metolachlor has a chiral carbon and a chiral axis and the N- side chain was methoxyaethyl, whereas acetochlor has only a chiral axis and the N- side chain was ethoxymethyl. The difference in molecular structure led to that the reported acetochlor dealkylases CndABC and EthB could not catalyze the dealkylation of metolachlor. Strain Paracoccus sp. FLY-8 could completely degrade and utilize metolachlor，and the degradation of metolachlor in this strain was initiated by dealkylation under the catalysis of an unknown dealkylase. This project will try to clone the metolachlor dealkylase by using genomics analysis and transposon insertion mutation technology, study the enzymatic characteristics, function and kinetics, and chiral selectivity of the enzyme to the isomers of metolachlor. This project will elucidate the molecular mechanism of metolachlor dealkylation in strain FLY-8, and provide scientific basis for the study of the environmental behavior of metolachlor, and the enzymatic mechanism for the effect of N- side chain structure on the biodegradability of chloroacetanilide herbicides.