Experimental and Applied Acarology (2001) 25, 675-698

Mahmoud A. Ibrahim, Abdel-Hady Ghazy, Tahany Maharem and Mohamed Khalil (2001)
Isolation and properties of two forms of thrombin inhibitor from the nymphs of the camel tick Hyalomma dromedarii (Acari: Ixodidae)
Experimental and Applied Acarology 25 (8), 675-698
Abstract: Two forms of the nymphal thrombin inhibitors (NTI) 3.2 kDa and 14.9 kDa were purified by chromatography on CM-cellulose, Sephacryl S-300 and Sephadex G-50 columns and designated NTI-1 and NTI-2 respectively. The NTI-2 turned out to be homogenous monomeric protein in both native-PAGE and denatured SDS-PAGE with M(r) value of 14.9 kDa approximately and its pI value ranged from 7.2 to 7.5. The NTI-1 and NTI-2 displayed anticoagulant activity since they prolonged both the activated partial thromboplastin time (APTT) and the prothrombin time (PT) of the camel plasma in a concentration-dependent manner. The potency of NTI-1 toward thrombin was 5-fold higher than that toward FXa, while NTI-2 was 3-fold active toward FXa than thrombin. However, both of them did not inhibit any of the other examined proteases. The types of inhibition of thrombin by NTI-1 and NTI-2 were non-competitive and competitive with inhibition constants (Ki) values of 11.7 µM and 211 nM respectively. One binding site was deduced on thrombin for each inhibitor.
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Research topic(s) for pests/diseases/weeds:
molecular biology - genes

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Hyalomma dromedarii		Egypt