Structural Insights of Stereospecific Inhibition of Human Acetylcholinesterase by VX and Subsequent Reactivation by HI‑6

• Published in: Chemical research in toxicology Vol. 31; no. 12; pp. 1405 - 1417
• Main Authors: Bester, Stephanie M, Guelta, Mark A, Cheung, Jonah, Winemiller, Mark D, Bae, Su Y, Myslinski, James, Pegan, Scott D, Height, Jude J
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 17-12-2018; American Chemical Society (ACS)
• Subjects: Acetylcholinesterase - chemistry; Acetylcholinesterase - genetics; Acetylcholinesterase - metabolism; Binding Sites; Biocatalysis; Catalytic Domain; Cholinesterase Reactivators - chemistry; Cholinesterase Reactivators - metabolism; Crystallography, X-Ray; Humans; Molecular Dynamics Simulation; Organothiophosphorus Compounds - chemistry; Organothiophosphorus Compounds - metabolism; Oximes - chemistry; Oximes - metabolism; Pyridinium Compounds - chemistry; Pyridinium Compounds - metabolism; Recombinant Proteins - biosynthesis; Recombinant Proteins - chemistry; Recombinant Proteins - isolation & purification; Stereoisomerism
• ISSN: 0893-228X; 1520-5010
• DOI: 10.1021/acs.chemrestox.8b00294

Over 50 years ago, the toxicity of irreversible organophosphate inhibitors targeting human acetylcholinesterase (hAChE) was observed to be stereospecific. The therapeutic reversal of hAChE inhibition by reactivators has also been shown to depend on the stereochemistry of the inhibitor. To gain clarity on the mechanism of stereospecific inhibition, the X-ray crystallographic structures of hAChE inhibited by a racemic mixture of VX (P R/S ) and its enantiomers were obtained. Beyond identifying hAChE structural features that lend themselves to stereospecific inhibition, structures of the reactivator HI-6 bound to hAChE inhibited by VX enantiomers of varying toxicity, or in its uninhibited state, were obtained. Comparison of hAChE in these pre-reactivation and post-reactivation states along with enzymatic data reveals the potential influence of unproductive reactivator poses on the efficacy of these types of therapeutics. The recognition of structural features related to hAChE’s stereospecificity toward VX shed light on the molecular influences of toxicity and their effect on reactivators. In addition to providing a better understanding of the innate issues with current reactivators, an avenue for improvement of reactivators is envisioned.