An acquired antithrombin autoantibody directed toward the catalytic center of the enzyme.
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Sie P, Bezeaud A, Dupouy D, Archipoff G, Freyssinet JM, Dugoujon JM, Serre G, Guillin MC, Boneu B
An acquired antithrombin autoantibody directed toward the catalytic center of the enzyme.
J Clin Invest. 1991 Jul;88(1):290-6.
- PubMed ID
- 1711542 [ View in PubMed]
- Abstract
Antibody inhibitors against human thrombin are rare and have remained poorly characterized. We report the case of a 40-yr-old patient who developed a potent thrombin inhibitor revealed by mild bleeding symptoms and marked prolongation of most laboratory clotting times. After two years of evolution, he died from cerebral hemorrhage. The inhibitor, a polyclonal IgG, was associated with hematological and immunological criteria of autoimmune disorder. Antithrombin IgG was isolated from the patient's plasma by protein A- and thrombin-affinity chromatography. Fab fragments inhibited amidolytic activity of alpha thrombin, and thrombin-thrombomodulin catalyzed protein C activation with a Ki of approximately 10(-8) M in a noncompetitive manner. Alpha to gamma conversion of thrombin resulted in a moderate loss of affinity for the inhibitor. Upon complex formation of thrombin with staphylocoagulase or alpha 2-macroglobulin (alpha 2M), inhibition was decreased by two orders of magnitude and acquired an apparent competitive character. In Western blot experiments, the antibody reacted with active alpha-thrombin, did not react with chloromethylketone-inhibited thrombin and reacted with a lower affinity with iPr2P-thrombin. The inhibitor did not block thrombin binding to benzamidine-, heparin-, or fibrin-Sepharose, but displaced proflavin from its complex with thrombin. Taken together, these results indicate that the patient's autoantibody recognized a conformational structure which includes, at least in part, the apolar binding site adjacent to the catalytic site of thrombin.
DrugBank Data that Cites this Article
- Drug Targets
Drug Target Kind Organism Pharmacological Action Actions Proflavine Prothrombin Protein Humans NoOther/unknownDetails