Activities and Kinetic Parameters of Carboxylesterases in Model Insects depending on a Substrate of the Enzyme

Abstract

House flies Musca domestica L. (Diptera: Muscidae) serve as a common model organism for testing of insecticides and research of insecticidal resistance mechanisms in insects. One of important stages is to assess of detoxifying enzyme activities including carboxylesterase activities (CarE). In this study, we compared specific activities and kinetic parameters (Vmax and Km) of CarE in adults M. domestica of two laboratory strains (TY, UF) depending on the enzymatic substrate used. The specific CarE activities towards α- and β-naphthyl acetate (α-NA and β-NA) were similar in both males and females of the TY strain. In males of the UF strain, the value of the specific and the maximal velocity (Vmax) of β-NA hydrolysis was 1.90- and 1.57-fold respectively less than that of α-NA; this difference was not observed in females of the same strain. Some characteristics of CarE varied depending on sex of insects when p-nitrophenyl acetate was used as an enzymatic substrate. In particular, the specific activity was 1.62-fold less in males of the UF strain compared to this value in females. The activity and main kinetic parameters of CarE towards α-NA not differed statistically significant depending on sex and the strains. Based on the results obtained we suggest that α-naphthyl acetate is the preferred substrate to evaluate the CarE enzymatic activity in the model insect M. domestica of different strains.