PMID: 30462502
Bester SM, Guelta MA, Cheung J, Winemiller MD, Bae SY, Myslinski J, Pegan SD, Height JJ
Structural insights of stereospecific inhibition of human acetylcholinesterase by VX and subsequent reactivation by HI-6.
Chem Res Toxicol. 2018 Nov 21. doi: 10.1021/acs.chemrestox.8b00294.
Over 50 years ago, the toxicity of irreversible organophosphate inhibitors targeting human acetylcholinesterase (hAChE) were 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 hAChE inhibited by a racemic mixture of VX (PR/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 hAChEs 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 towards 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.