Acetylcholinesterases (
AChEs) from the infective juveniles (IJs) of entomopathogenic nematode (EPN) have been investigated with respect to their susceptibility to
insecticides and immunological characteristics, aiming at nominating the most compatible
insecticide(s) to be used in conjunction with the most
insecticide-tolerant EPN strain before incorporation in integrated pest management (IPM) programs. The inhibition kinetics of two purified AChE
isoenzymes, AChEAII and AChEBI isolated from Heterorhabditid bacteriophora EM2 strain, by different
insecticides revealed that the insensitivity to inhibition by such
insecticides could be arranged in a descending order as;
methomyl>
carbofuran>
acetamiprid>
oxamyl>
malathion. Except for
malathion, the
insecticides competitively inhibited
AChEs with Ki values ranging from 0.1 to 15mM and IC50 values from 1.25 to 23mM. The two AChE
isoforms are several folds less sensitive to inhibition by
methomyl and
carbofuran compared to those previously reported for other insect species. AChEBI was used as an immunogen to raise anti-AChEBI
antisera in rabbits. The prepared
antisera cross-reacted with
AChEs of five different heterorhabditid nematode strains implying the presence of common
epitopes shared along all the examined strains. Such studies could aid in the rational selection of the compatible
insecticide(s) and the prepared polyclonal anti-AChE
antisera would be a valuable immunodiagnostic tool for evaluating the most
insecticide-tolerant EPN strain(s) in IPM programs.