The patterns of acetylcholinesterases during developmental stages of Aedes aegypti and their susceptibility toward insecticides in egg stage

Abstract The screening of acetylcholinesterase (AChE) during developmental stages, eggs, larvae, pupa and adults of Aedes aegypti was detected. Chromatography on a Sephacryl S-200 column revealed two distinct peaks of acetylcholinesterases AChE1 and AChE2 in every developmental stage. The egg stage had the highest expression of AChE1 activity, which progressively declined throughout the larval, pupal, and adult stages. On the other hand, AChE2 activity was lowest in eggs and larvae, progressively increased in pupae, and peaked in adults. To avoid overlap with larval development, the properties of AChE1 and AChE2 from 36 h-old eggs were detected rather than 48 h-old eggs. The enzymes’ substrate specificity revealed that, in comparison to acetylthiocholine iodide (AcSChI), the relative activity percentage for butyrylthiocholine iodide was 9.4 for AChE1 and 11.6 for AChE2. Ae. aegypti AChE1 and AChE2 had Km values of 0.256 and 0.288 mM AcSChI, respectively. The optimal pH and temperature for both enzymes were 7.5 and 40˚C, respectively. Up to 40˚C and 25˚C, respectively, the activity of AChE1 and AChE2 were thermally stable. With the exception of Co + 2 , every metal tested had a partial inhibitory impact on the two enzymes. The most sensitive organophosphates and carbamates for inhibition of both enzymes were detected in eggs for the first time. For organophosphates and carbamates, the type of inhibition, bimolecular rate constant (Ki), and Ki ratio AChE1/AChE2 were detected. According to the findings, the Ki ratio AChE1/AChE2 toward methomyl, chlorpyrifos-methyl, and pirimiphos-methyl is less than 1.0, suggesting that both enzymes are more susceptible to inhibition by these insecticides. Eserine, malathion, and fenitrothion, on the other hand, have Ki ratios AChE1/AchE2 more than 1.0, indicating lower sensitivity. The study recommended using methomyl, pirimiphos-methyl, and chlorpyrifos-methyl to attack Ae. aegypti during the egg stage.