Activity and Substrate Specificity of the Esterase Associated with Organophosphorus Insectivide Resistance in the Kanzawa Spider Mite, Tetranychus kanzawai KISHIDA (Acarina : Tetranychidae)

Abstract

Organophosphorus insecticide resistance in the Kanzawa spider mite is associated with an increase in esterase activity to naphthyl acetate, tributyrin, phenyl acetate and methyln-butyrate. All of these esters except phenyl acetate are hydrolyzed by esterase (aliesterase) which is resistant to eserine inhibition and heat labile in slightly alkaline media, whereas an appreciable part of phenyl acetate hydrolysis is due to cholinesterase which is sensitive to eserine inhibition. A good correlation between aliesterase activity (naphthyl acetate hydrolyzing activity) and co-toxicity coefficient of a mixture of malathion and K-1 in organophosphorus insecticide resistant strains was recognized. Tributyrin acts as a competitive inhibitor for β-naphthyl acetate hydrolysis and phenyl acetate acts as a noncompetitive inhibitor. No inhibition of β-naphthyl acetate hydrolysis was observed when methyl-n-butyrate was added.