Inhibition kinetics on carboxylesterase and acetylcholinesterase of Liposcelis bostrychophila and Liposcelis entomophila (Psocop., Liposcelididae) of two insecticides

Abstract

The inhibition kinetics on carboxylesterase (CarE) and acetylcholinesterase (AChE) of Liposcelis bostrychophila and Liposcelis entomophila of paraoxon and carbosulfan were compared. The results showed that L. entomophila exhibited significantly greater specific activity of CarE than L. bostrychophila [0.045 vs. 0.012 μmol of α-naphthyl acetate (α-NA) hydrolysed/mg protein/min]. Moreover, L. entomophila showed higher affinity (i.e. lower K m value) to the substrate α-NA than L. bostrychophila (0.29 vs. 0.67 mM). For AChE-specific activity and affinity, no significant differences between the two species were observed. Based on the I50 values, AChE of L. bostrychophila was more sensitive to paraoxon and carbosulfan than that of L. entomophila. According to inhibition kinetics, the results revealed that AChE of L. bostrychophila was 3.8-fold more sensitive to inhibition by paraoxon than that of L. entomophila, but L. entomophila was 1.5-fold more susceptible to carbosulfan.