Apyrase is one of the essential platelet aggregation inhibitors in hematophagous arthropods due to its ability to hydrolyze ATP and ADP molecules. Here, an apyrase (TNapyrase) with antiplatelet aggregation activity was purified and characterized from the nymphs of the camel tick Hyalomma dromedarii through anion exchange and gel filtration columns. The homogeneity of TNapyrase was confirmed by native-PAGE, SDS-PAGE as well as with isoelectric focusing. Purified TNapyrase had a molecular mass of 25 kDa and a monomer structure. TNapyrase hydrolyzed various nucleotides in the order of ATP > PPi > ADP > UDP > 6GP. The K_m value was 1.25 mM ATP and its optimum activity reached at pH 8.4. The influence of various ions on TNapyrase activity showed that FeCl₂, FeCl₃ and ZnCl₂ are activators of TNapyrase. EDTA inhibited TNapyrase activity competitively with a single binding site on the molecule and K_i value of 2 mM. Finally, TNapyrase caused 70% inhibition of ADP-stimulated platelets aggregation and is a possible target for antibodies in future tick vaccine studies.

中文翻译：

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骆驼tick若虫若虫具有抗血小板凝集活性的Apyrase

磷酸化酶由于具有水解ATP和ADP分子的能力，因此是食血节肢动物中必需的血小板聚集抑制剂之一。在这里，通过阴离子交换和凝胶过滤柱，从骆驼壁透明藻Hyalomma dromedarii的若虫中纯化并鉴定了具有抗血小板聚集活性的腺苷三磷酸双磷酸酶（TNapyrase）。通过天然-PAGE，SDS-PAGE以及等电聚焦证实了TNapyrase的均一性。纯化的TNapyrase的分子量为25 kDa，具有单体结构。TNapyrase水解各种核苷酸的顺序为ATP> PPi> ADP> UDP> 6GP。所述ķ_米值为1.25毫摩尔ATP和其最佳活性在pH 8.4达到。各种离子对TNapyrase活性的影响表明FeCl ₂FeCl ₃和ZnCl ₂是TNapyrase的活化剂。EDTA具有一个分子上的单个结合位点和2 mM的K _i竞争性抑制TNapyrase活性。最终，TNapyrase导致ADP刺激的血小板聚集受到70％的抑制，并且可能成为未来壁虱疫苗研究中抗体的靶标。