Oxime reactivation of erythrocyte cholinesterase inhibited by ethyl p-nitrophenyl ethylphosphonate

1. Reactivation of erythrocyte cholinesterase inhibited by ethyl p-nitrophenyl ethylphosphonate (armine) was studied with NN'-dimethylenebis-(4-hydroxy-iminomethylpyridinium bromide) (C(2)-oxime), NN'-trimethylenebis-(4-hydroxy-iminomethylpyridinium bromide) (C(3)-oxime), NN'-tetramethylene-(4-hydroxy-iminomethylpyridinium bromide) (C(4)-oxime) and NN'-pentamethylenebis-(4-hydroxyiminomethylpyridinium bromide) (C(5)-oxime) as reactivators. The kinetics of reactivation were consistent with a reaction of the type: [Formula: see text] and bimolecular rate constants for reactivation were calculated from the corresponding differential equations. 2. Of the four oximes studied C(2)-oxime was least effective and the other three oximes were about equally effective reactivators. 3. Reactivation of armine-inhibited cholinesterase by C(3)-oxime was also studied in the presence of substrate. This reaction was first-order with respect to inhibited enzyme, and slower than in the absence of substrate.