engleski

Probing reactivation of tabun phosphylated cholinesterases by mutagenesis and new oximes

The copper-catalyzed azide-alkyne cycloaddition reaction enabled fast and reliable synthesis of libraries of oximes that were screened for the reactivation activity of tabun-inhibited human recombinant AChE, wild type, the AChE single mutant Y337A, and human BChE. Out of 100 oximes, 53 were able to reactivate wild type AChE, but only 14 oximes restored full activity. For the remaining oximes, the maximal reactivation was below 50 %. It appears that a distance of 8 atoms between two quaternary nitrogens is optimal to achieve high level of AChE activity. Phosphorylated choline-binding site Y337A AChE mutant was reactivated (> 80 %) with 13 oximes only. For three most efficient oximes (2PAM analogs) the observed reactivation rate was 4-times faster than for the most efficient reactivator of AChE w.t. Since all oximes were designed as reactivators of phosphorylated AChE, a limited reactivation capacity for BChE was expected. However, 37 oximes reactivated tabun-inhibited BChE more efficiently than 2PAM, and five of them reached 70 % of maximal reactivation. In conclusion, although rank order of the rates differs for reactivation of three tabun phosphorylated enzymes, our findings may provide a platform for further modifications and development of more potent antidotes in tabun poisoning.

tabun ; cholinesterase ; oxime ; probing reactivation

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