Mechanistic insights into nerve agent VX detoxification by engineered phosphotriesterase

Area of Science:

• Biochemistry
• Enzymology
• Computational Chemistry

Background:

• Nerve agents pose significant decontamination challenges due to their extreme toxicity.
• Phosphotriesterase (PTE) is a key enzyme for degrading V-type nerve agents, with engineered variants showing improved efficacy.
• The 10-2-C3(C59V/C227V) PTE mutant demonstrates superior activity against V-type agents.

Purpose of the Study:

• To elucidate the catalytic mechanism of the engineered PTE mutant (10-2-C3) towards chiral VX nerve agents.
• To investigate the role of loop 7 conformational changes in substrate binding, transport, and catalysis.
• To understand the basis for the enhanced stereoselectivity of the mutant enzyme.

Main Methods:

• Quantum Mechanics/Molecular Mechanics (QM/MM) calculations were employed to study the reaction pathway.
• Molecular Mechanics Molecular Dynamics (MM MD) simulations were used to analyze conformational changes and substrate interactions.
• Analysis focused on the interaction of the mutant PTE with different stereoisomers of VX.

Main Results:

• Conformational alterations in loop 7 significantly impact substrate binding, transport, and the catalytic process.
• The engineered PTE mutant exhibits enhanced activity towards the more toxic Sp stereoisomer of VX.
• A reduced energy barrier of 22.4 kcal/mol was observed for the degradation of the Sp stereoisomer.

Conclusions:

• Loop 7 reconfiguration is a critical factor contributing to the stereoselectivity of the engineered PTE mutant.
• The study provides theoretical insights for designing and optimizing PTE variants for efficient nerve agent decontamination.
• Understanding these mechanisms aids in developing advanced enzymatic biodegradation strategies for chemical warfare agents.