Acetylcholinesterase from the camel tick Hyalomma dromedarii as a target for biocontrol: biochemical characterization, molecular docking, and immunogenic potential

ABSTRACT Ticks have developed resistance to many commonly used acaricides, several of which target acetylcholinesterase (AChE), a key enzyme in tick nervous system function. This study monitored AChE activity during Hyalomma dromedarii embryogenesis, revealing peak activity at the larval stage. A simple, reproducible two-step chromatographic protocol was developed to purify larval AChE (TLAChE). The purified enzyme exhibited a specific activity of 5430.6 U mg⁻¹, achieving 7.7-fold purification with a 49.8% yield. Gel filtration estimated a native molecular mass of 168 kDa, while SDS–PAGE revealed 42 kDa subunits, indicating a homotetrameric structure. TLAChE showed optimal activity at pH 9.0 and a strong preference for acetylthiocholine iodide (Km = 0.95 mM). Enzyme activity was enhanced by Fe²⁺ and Zn²⁺, but inhibited by Cu²⁺, Mn²⁺, and Ni²⁺. TLAChE was strongly inhibited by eserine, 1,5-Bis(4 allyldimethylammoniumphenyl) pentan-3-one dibromide (BW 284C51), and phenylmethylsulfonyl fluoride. Molecular docking confirmed stable binding of eserine to the active site of H. dromedarii TLAChE with a binding energy of −7.0 kcal/mol. Immunization with purified TLAChE induced high IgG titers in rabbits, demonstrating strong immunogenicity. These findings identify TLAChE as a promising target for sustainable tick control strategies.