Organophosphorus pesticides exert their acute effects by
inhibiting acetylcholinesterase in the nervous system with
subsequent accumulation of toxic levels of acetylcholine.
They may also inhibit butylcholinesterases as well as other
esterases. The function of butylcholinesterase is unknown,
but its inhibition can provide an indication of exposure to
an organophosphate.
In many cases, the organophosphorylated enzyme is fairly
stable, so that recovery from intoxication may be slow.
Reactivation of inhibited enzyme may occur spontaneously, the
rates of reactivation depending on the tissue as well as on
the chemical group attached to the enzyme.