Biodegradation of Carbamate Insecticide Indoxacarb through a Lower-Risk Metabolic Pathway by a Novel Degrading Strain, Agrobacterium sp. DPX-5

Abstract Indoxacarb is considered a substitute for some highly toxic carbamate insecticides after their prohibition. However, it is easily hydrolyzed into the highly toxic N-decarbomethoxylated metabolite (DCJW) in the environment and nontarget organisms. In this study, an indoxacarb-degrading strain, Agrobacterium sp. DPX-5, was screened. It could degrade 57.8% of 10 mg/L indoxacarb within 24 h in LB medium with urea. Three degradation products M513, M469, and M455 were identified. The structures of the degradation products revealed a new low-risk hydrolysis metabolic pathway, which does not produce DCJW. Two novel functional indoxacarb-hydrolyzing enzymes InhA and InhB were found and characterized, with purified InhA showing higher degradation activity than InhB. Their key binding sites were further verified by molecular docking and point mutation. The research not only provides strain and enzyme resources but also discovers a lower-risk indoxacarb metabolic pathway to providing technical support for the bioremediation of carbamate insecticides.