Purification and characterization of acid phosphatase from larvae of the camel tick Hyalomma dromedarii: inhibition kinetics by sodium fluoride

Abstract

ABSTRACTAcid phosphatases (ACPs) perform a fundamental role in the digestion of egg proteins (vitellins), ensuring the survival of ticks by providing nutrients necessary for their oogenesis. Here, acid phosphatase activity is detected during embryogenesis of the camel tick Hyalomma dromedarii and reached its highest activity level in the larval stage. The tick larvae acid phosphatase which was named TLACP is homogeneously purified using CM cellulose cation exchange chromatography followed by gel filtration on Sephacryl S-300 column. TLACP is purified to 11 times purification folds and 51.3% yield with a specific activity of 12.9 U mg−1 protein. The molecular weight of TLACP was derived from both the gel filtration column and SDS-PAGE as monomer protein of 40 kDa. The Km of TLACP for p-nitrophenyl phosphate (p-NPP) was 1.25 mM and Vmax was 6.4 Umg−1. TLACP exhibited its optimum enzymatic activity at pH 4.8. TLACP was found highly specific to p-NPP followed by ATP, ADP, glucose-6-phosphate, naphthyl phosphate, phospho-enol-pyruvate, creatine phosphate, AMP, and GMP. The ions of Ca2+, Co2+, Mg2+, Ni2+, and Zn2+ motivated TLACP activity while Mn2+, Cu2+, and Fe2+ suppressed it. TLACP is noncompetitively inhibited with sodium fluoride with Ki value 0.15 mM. Thus, the presence of TLACP in tick embryonic and larval cells classifies this enzyme as an important molecular target for evolving potential vaccines in further studies aiming to find new strategies to control ticks.