The inhibition kinetics of dichlorvos on carboxylesterase and acetylcholinesterase (AChE) activity extracted from Liposcelis bostrychophila and L. entomophila (Psocoptera: Liposcelididae) were compared. The results showed that L. entomophila had significantly greater specific activity of carboxylesterase than L. bostrychophila (0.045 versus 0.012 µmoles /mg /min). Moreover, the carboxylexterase of L. entomophila showed higher affinity (i.e. lower Km value) to the substrate 1-naphthyl acetate than L. bostrychophila (0.29 versus 0.67 mM). The specific activity and affinity of AChE of the two species were not significantly different. The carboxylesterase of L. bostrychophila was more sensitive to the insecticide dichlorvos than that of L. entomophila. The I 50 s values of dichlorvos to carboxylesterase for L. bostrychophila and L. entomophila were 1.43 and 3.28 µM, respectively, and to AChE were 324 and 612 nM, respectively. Inhibition kinetics revealed that AChE from L. bostrychophila was 5.8-fold more sensitive to inhibition than AChE from L. entomophila.
The inhibition kinetics of dichlorvos on carboxylesterase and acetylcholinesterase (AChE) activity extracted from Liposcelis bostrychophila and L. entomophila (Psocoptera: Liposcelididae) were compared. The results showed that L. entomophila had significantly greater specific activity of carboxylesterase than L. bostrychophila (0.045 versus 0.012 µmoles /mg /min). Moreover, the carboxylexterase of L. entomophila showed higher affinity (i.e. lower Km value) to the substrate 1-naphthyl acetate than L. bostrychophila (0.29 versus 0.67 mM). The specific activity and affinity of AChE of the two species were not significantly different. The carboxylesterase of L. bostrychophila was more sensitive to the insecticide dichlorvos than that of L. entomophila. The I50s values of dichlorvos to carboxylesterase for L. bostrychophila and L. entomophila were 1.43 and 3.28 µM, respectively, and to AChE were 324 and 612 nM, respectively. Inhibition kinetics revealed that AChE from L. bostrychophila was 5.8-fold more sensitive to inhibition than AChE from L. entomophila.Abbreviation:1-NA1-naphthyl acetateAChEAcetylcholinesteraseATChIAcetylthiocholine iodideE3carboxylesterse isozyme (E.C.3.1.1)
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 lmol of a-naphthyl acetate (a-NA) hydrolysed/mg protein/min]. Moreover, L. entomophila showed higher affinity (i.e. lower K m value) to the substrate a-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 I 50 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.
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