An antibody specific for coagulation factor IX enhances the activity of the intrinsic factor X-activating complex
| Autor: | Katalin Varadi, Randolf Kerschbaumer, Jan Rosing, Martina Kral, Friedrich Dorner, Klaudia Riedrich, Friedrich Scheiflinger |
|---|---|
| Rok vydání: | 2004 |
| Předmět: |
Enzyme complex
Time Factors Biochemistry Catalysis Factor IXa Factor IX chemistry.chemical_compound Mice Thrombin Zymogen medicine Animals Humans Molecular Biology Factor VIIIa Mice Inbred BALB C Intrinsic factor Hybridomas Dose-Response Relationship Drug Chemistry Factor X Antibodies Monoclonal Cell Biology Coagulation Factor IX Recombinant Proteins Kinetics medicine.drug Protein Binding |
| Zdroj: | The Journal of biological chemistry. 279(39) |
| ISSN: | 0021-9258 |
| Popis: | During hemostasis the zymogen factor X (FX) is converted into its enzymatically active form factor Xa by the intrinsic FX-activating complex. This complex consists of the protease factor IXa (FIXa) that assembles, together with its cofactor, factor VIIIa, on a phospholipid surface. We have studied the functional properties of a FIXa-specific monoclonal antibody, 224AE3, which has the potential to enhance intrinsic FX activation. Binding of the antibody to FIXa improved the catalytic properties of the intrinsic FX-activating complex in two ways: (i) factor VIIIa bound to the FIXa-antibody complex with a more than 18-fold higher affinity than to FIXa, and (ii) the turnover number (kcat) of the enzyme complex increased 2- to 3-fold whereas the Km for FX remained unaffected. The ability of 224AE3 to increase the FXa-generation potential (called the "booster effect") was confirmed in factor VIII (FVIII)-depleted plasma, which was supplemented with different amounts of recombinant FVIII. In the presence of antibody 224AE3 the coagulant activity was increased 2-fold at physiological FVIII concentration and up to 15-fold at low FVIII concentrations. The booster effect that we describe demonstrates the ability of antibodies to function as an additional cofactor in an enzymatic reaction and might open up a new principle for improving the treatment of hemophilia. |
| Databáze: | OpenAIRE |
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