Exploring and comparing activities of esterases hydrolyzing malathion and model substrates as biomarkers of insecticide resistance in field-collected populations of Culex quinquefasciatus

Esterases are a group of metabolic enzymes that have been used extensively as biomarker for insecticide resistance in many insect pests, including mosquitoes. In many of these studies, activities towards alpha-and beta-naphthyl acetates are used as model substrates. However, in most cases, the relationship between hydrolysis of these model substrates and an actual insecticide is not established. In the current study, an assay for malathion carboxylesterase, which hydrolyzes the two ester moieties in malathion, has been optimized and used to demonstrate difference between the hydrolysis of naphthyl acetates and malathion in field- collected population of Culex quinquefasciatus.

Keywords: esterase, biomarker, alpha-and beta-naphthyl acetates, malathion carboxylesterase