Does the mechanism of AChE inhibition by Isoparathion depend on chirality?
It would appear that the mechanism of inhibition of AChE by both stereoisomers of isoparathion (Or, at least, its methyl analog) proceeds through the expulsion of the 4-nitrophenoxy leaving group. Several papers have studied the inhibition kinetics of isomalathion and compared the results to those of isoparathion. All of them seem to agree that, at least for isoparathion methyl, AChE inhibition proceeds through the expulsion of the same leaving group, but the O,S-dimethyl phosphorylated AChE would be chiral, as is expected. Furthermore, the inhibition, reactivation, and aging reaction rate constants would also differ depending on the stereoisomer of isoparathion.
References:
Berkman, C. E., Quinn, D. A., &amp; Thompson, C. M. (1993). Interaction of acetylcholinesterase with the enantiomers of malaoxon and isomalathion. Chemical Research in Toxicology, 6(5), 724–730. doi:10.1021/tx00035a019
https://pubs.acs.org/doi/pdf/10.1021/tx00023a004
Jianmongkol, S., Marable, B. R., Berkman, C. E., Talley, T. T., Thompson, C. M., &amp; Richardson, R. J. (1999). Kinetic Evidence for Different Mechanisms of Acetylcholinesterase Inhibition by (1R)- and (1S)-Stereoisomers of Isomalathion. Toxicology and Applied Pharmacology, 155(1), 43–53. doi:10.1006/taap.1998.8608