title: Factor Xa (FXa) inhibitor from the nymphs of the camel tick Hyalomma dromedarii.
abstract: An inhibitor of factor Xa (FXa) was isolated from the nymphs of the camel tick Hyalomma dromedarii by a combination of chromatography on DEAE-cellulose and Sephacryl S-300 columns. The isolated nymphal FXa inhibitor turned out to be a homogenous preparation of a single polypeptide chain (15 kDa) as judged by both the native and denatured SDS-PAGE. Its pI value ranged from 7.7 to 7.9. The inhibitor is a potent anticoagulant since it prolonged both the activated partial thromboplastin time (APTT) and the prothrombin time (PT) of the camel plasma in a concentration-dependent manner. Its activity was threefold lower toward thrombin than FXa, but it did not inhibit any of the proteases; trypsin, alpha-chymotrypsin, papain, pepsin and subtilisin. The inhibitor binds at two sites on FXa uncompetitively with an inhibition constant (K(i)) value of 134 nM.
authors.affiliation: Molecular Biology Department, National Research Centre, El-Tahrir st., Dokki, Cairo, Egypt. ibrahimm70@hotmail.com
authors.forename: M A
authors.initials: MA
authors.lastname: Ibrahim
authors.forename: A H
authors.initials: AH
authors.lastname: Ghazy
authors.forename: T M
authors.initials: TM
authors.lastname: Maharem
authors.forename: M I
authors.initials: MI
authors.lastname: Khalil
mesh_terms: D000818:Animals; D000925:Anticoagulants / Q000737:chemistry* / Q000494:pharmacology*; D001665:Binding Sites; D001667:Binding, Competitive; D002162:Camelus; D002848:Chromatography, DEAE-Cellulose; D002918:Chymotrypsin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D065427:Factor Xa Inhibitors; D018884:Ixodes; D007700:Kinetics; D009758:Nymph; D010206:Papain / Q000494:pharmacology; D010314:Partial Thromboplastin Time; D010434:Pepsin A / Q000494:pharmacology; D011485:Protein Binding; D011516:Prothrombin / Q000378:metabolism; D020860:Subtilisin / Q000494:pharmacology; D014357:Trypsin / Q000494:pharmacology
chemical_list: D000925:Anticoagulants; D065427:Factor Xa Inhibitors; D011516:Prothrombin; D002918:Chymotrypsin; C117608:alpha-chymotrypsin; D014357:Trypsin; D020860:Subtilisin; D010206:Papain; D010434:Pepsin A