Thrombin generation and inactivation in the presence of antithrombin III and heparin
| Autor: | Jo Franssen, Theo Lindhout, H. Coenraad Hemker, Pieter Schoen, Dominique Baruch |
|---|---|
| Přispěvatelé: | Biochemie |
| Jazyk: | angličtina |
| Rok vydání: | 1986 |
| Předmět: |
Antithrombin III
Phospholipid Phosphatidylserines Biochemistry chemistry.chemical_compound Thrombin Reaction rate constant Prothrombinase hemic and lymphatic diseases Mole medicine Animals Chemistry Heparin Factor X Antithrombin Molecular biology Enzyme Activation Kinetics Liposomes Phosphatidylcholines Cattle Prothrombin circulatory and respiratory physiology medicine.drug |
| Zdroj: | Biochemistry, 25(20), 5962-5969. American Chemical Society Scopus-Elsevier |
| ISSN: | 0006-2960 |
| DOI: | 10.1021/bi00368a019 |
| Popis: | We have determined the rate constants of inactivation of factor X, and thrombin by antithrombin "heparin during the process of prothrombin activation. The second-order rate constant of inhibition of factor X, alone by antithrombin 111 as determined by using the synthetic peptide substrate S-2337 was found to be 1.1 X lo6 M-' min-'. Factor X, in prothrombin activation mixtures that contained prothrombin, and either saturating amounts of factor V, or phospholipid (20 mol % dioleoylphosphatidylserine/80 mol % dioleoylphosphatidylcholine, 10 pM), was inhibited by antithrombin I11 with a second-order rate constant that was essentially the same: 1.2 X lo6 M-I min-'. When both factor V, and phospholipid were present during prothrombin activation, factor X, inhibition by antithrombin 111 was reduced about 10-fold, with a second-order rate constant of 1.3 X lo5 M-' min-'. Factor X, in the prothrombin activation mixture that contained both factor V, and phospholipid was even more protected from inhibition by the antithrombin 111-heparin complex. The first-order rate constants of these reactions at 200 nM antithrombin 111 and normalized to heparin at 1 pg/mL were 0.33 and 9.5 min-' in the presence and absence of factor V, and phospholipid, respectively. When the prothrombin concentration was varied widely around the K,,, for prothrombin, this had no effect on the first-order rate constants of inhibition. It is our conclusion that factor X, when acting in prothrombinase on prothrombin is profoundly protected from inhibition by antithrombin 111 in the absence as well as in the presence of heparin. The second-order rate constant (4.5 X lo5 M-I min-') of inhibition of thrombin activity generated during prothrombin activation was found to be (1) constant during the time course of prothrombin activation, (2) independent of the composition of the prothrombin converting complex, and (3) about 4-fold lower than the second-order rate constant of inhibition of purified a-thrombin (1.9 X lo6 M-' mid). Surprisingly, heparin hardly enhanced the antithrombin 111 dependent rate of inhibition of thrombin activity formed during the initial phase of the prothrombin activation. The apparent pseudo-first-order rate constant of this reaction at 200 nM antithrombin 111 and normalized to heparin at 1 pg/mL was 0.10 min-I and independent of the stage of thrombin production. The rate constant of the purified a-thrombin/antithrombin 111 reaction, performed under the same conditions, was 25 min-' . This difference between the two reactions of thrombin inactivation is mainly caused by the fact that meizothrombin (des fragment l), rather than &-thrombin, is the major product during the initial phase of prothrombin activation. |
| Databáze: | OpenAIRE |
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