Choline acetyltransferase (ChAT) is crucial for acetylcholine synthesis and regulates diverse functions in numerous biological processes. Omeprazole, an inhibitor on human ChAT, was evaluated here on insect ChAT as a potential inhibitor, as well as its insecticidal potency on Nilaparvata lugens, a major insect pest on rice. The evaluation also included omeprazole analogs and α-NETA, in order to explore a superior leading compound targeting on insect ChAT. In toxicity test, α-NETA and omeprazole exhibited insecticidal activity, among which omeprazole exhibited activity with a mortality of around 50 % on N. lugens nymphs at 0.4 mg/mL. In vitro crude enzyme assays showed that omeprazole acted as an inhibitor on insect ChAT with a high selectivity and exciting potency compared with α-NETA and control. Three residues (Tyr84, Val95, Tyr589) was critical in N. lugens ChAT for interacting with its substrate choline through molecular docking, and it also revealed that omeprazole exhibited a higher binding affinity toward ChAT catalytic tunnel compared with α-NETA. Based on this, we screened omeprazole analogs for their affinity to N. lugens ChAT, and two compounds stood out. The 5-hydroxy omeprazole had the highest binding affinity by prediction, and 5-O-desmethyl omeprazole was with the lowest binding affinity. The toxicity bioassay and enzyme activity test were then performed on these two compounds. Aligned with the docking results, 5-hydroxy omeprazole showed a strong inhibitory effect and insecticidal activity. In summary, omeprazole and 5-hydroxy omeprazole could serve as lead compounds for insecticides targeting on insect ChAT, a novel target.
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