Song_2025_J.Agric.Food.Chem__2

Haloxyfop-methyl is a chiral aryloxyphenoxypropionate (AOPP) with two enantiomeric forms that is widely used throughout the globe and is associated with severe environmental issues. While relatively little remains known of haloxyfop-methyl enantiomeric resolution or the selective degradation of these enantiomers by bacteria. Here, a novel aopE gene capable of catalyzing initial haloxyfop-methyl degradation was cloned from the newly isolated Brevundimonas sp. strain YS. No significant similarity was detected when comparing AopE to other esterases that have undergone biochemical characterization to date. AopE catalyzed the hydrolysis of haloxyfop-methyl to haloxyfop-acid and exhibited enantioselectivity by preferentially processing (R)-(+)-haloxyfop-methyl over its (S)-form. This preference extended to two structural analogues, (R)-(+)-quizalofop-ethyl and (R)-(+)-diclofop-methyl, which share the 4-oxyphenoxypropanoic acid scaffold. Molecular docking, molecular dynamics simulation, and site-directed mutagenesis analyses revealed that the Phe227 residue plays an essential role in the catalytic activity of AopE toward (R)-(+)-haloxyfop-methyl by imposing the Pi-Pi T-shaped and Pi-alkyl interactions. Together, these results offer greater insight into the enantioselective catabolic processing of chiral AOPP herbicides by bacteria.