Metabolic mechanism of a novel carboxylesterase YvaK in Priestia aryabhattai DPX-1 for carbamates insecticide indoxacarb detoxification

Carbamates, organophosphates, pyrethroids and other ester bond-containing insecticides are widely present in agricultural fields and aquatic environments, posing residue risks and threatening human health. Microbial degradation represents the primary metabolic pathway for these insecticides, yet it often generates highly toxic metabolites. In this study, we isolated a high-efficiency indoxacarb-degrading strain, Priestia aryabhattai DPX-1, which can metabolize 68% of 5mg/L indoxacarb within 24h without producing the high-toxicity N-decarbomethoxylated metabolite (DCJW). High-resolution mass spectrometry identified a novel metabolite M513, exhibiting 1-2 orders of magnitude lower acute and chronic toxicity to aquatic organisms compared to indoxacarb. The discovery of M513 reveals a new indoxacarb metabolic pathway. Concurrently, through omics analysis, we identified a novel indoxacarb-degrading key gene yvaK in strain DPX-1, encoding a carboxylesterase. The structure of enzyme YvaK was deconstructed via the AlphaFold2 AI model. Domain analysis revealed that YvaK contains a conserved nucleophilic elbow domain composed of 91Gly-92Leu-93Ser-94Leu-95Gly and an oxyanion hole domain formed by 95Gly-96Gly. Molecular docking and site-directed mutagenesis further elucidated the catalytic mechanism. Indoxacarb could stably bind to the carboxylesterase YvaK through hydrogen bonding, further enters the catalytic center via a hydrophobic channel, and ultimately hydrolysis under nucleophile attack to generate M513. These findings provide novel and safer strategies and methodologies for the bioremediation of ester bond-containing insecticides.