Mechanistic insights into nerve agent VX detoxification by engineered phosphotriesterase

Nerve agents are extremely toxic, and their safe and efficient degradation remains a major challenge in decontamination strategies. Phosphotriesterase (PTE), with its broad substrate range, is currently the only known enzyme capable of degrading V-type nerve agents, making it a strong candidate for enzymatic biodegradation. Among engineered variants, the mutant 10-2-C3(C59V/C227V) is recognized as the most effective enzyme for degrading V-type nerve agents. This variant contains 22 mutations per monomer and exhibits a markedly altered conformation in loop 7, compared to the wild-type PTE. In this study, a comprehensive description of the catalytic process of the mutant toward various chiral VX nerve agents was obtained through Quantum Mechanics/Molecular Mechanics (QM/MM) calculations and MM MD simulations. The results reveal that conformational changes in loop7 significantly influence substrate binding, transport, and the catalytic reaction. This structural reorganization enhances the enzyme's activity toward the more toxic Sp stereoisomer of VX, with a lower energy barrier of 22.4 kcal/mol. Loop7 reconfiguration is thus proposed as a key factor in the stereoselectivity of the mutant. These findings offer valuable theoretical insights for the rational design and advanced optimization of PTE variants for effective nerve agent decontamination.