Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.6 (thromboplastin)
 13,278 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The mitogenic effect of activated coagulation factor X (factor Xa) was examined in cultured aortic smooth muscle cells (VSMC) from Wistar-Kyoto rats (WKY). Factor Xa stimulated DNA synthesis and cell growth in VSMC, not through the phospholipase C-protein kinase C pathway because increase of inositol monophosphate (IP) accumulation and intracellular Ca2+ concentration was not observed, but probably via the PDGF receptor tyrosine kinase pathway since the pathway's components, Ras, Raf-1, MAPK (both 42 and 44 kD), and the transcription factors, c-Fos and c-Jun, were activated. These appeared to be effected by the serine protease activity of factor Xa, since in the presence of serine protease inhibitors such as PMSF, leupeptin, benzamidine, TAP anticoagulant, and TLCK, the latter three being specific inhibitors of the factor Xa, active site, the effects were completely blocked. Anti-factor Xa mAb, 5224, which specifically negated the activity of factor Xa, also inhibited completely the mitogenic effect of factor Xa, but not that of thrombin. Addition of PDGF did not affect the effect of factor Xa, which, however, was inhibited by anti-PDGF-AB antibody. This observation and the activation of PDGF receptor tyrosine kinase pathway suggested that the factor Xa might exert its effect via PDGF-like function. Direct measurement confirmed that factor Xa stimulated the release of PDGF from VSMC. Factor Xa, therefore, exerts serine protease activity on VSMC, causing somehow the release of PDGF, that in turn acts on the PDGF receptor tyrosine kinase; the pathway is then turned on, leading eventually to DNA synthesis and cell proliferation.
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PMID:Coagulation factor Xa stimulates platelet-derived growth factor release and mitogenesis in cultured vascular smooth muscle cells of rat. 882 16

A unique blood coagulation factor X variant has been identified in a family with a history of bleeding. Plasma from affected family members had prolonged prothrombin times and activated partial thromboplastin times, low to below normal factor X coagulant activity, and normal factor X antigen levels. Sequencing of DNA from the propositus revealed a single G to A substitution in one allele of factor X at base 964 resulting in an amino acid substitution of Asn for Asp at residue 282. This residue corresponds with the active site Asp102 of chymotrypsin. The substitution eliminates a TaqI restriction site and provided the basis for a screening assay to detect the mutation in polymerase chain reaction (PCR) amplified factor X exon VIII DNA. Fourteen additional family members were identified as having the mutation at base 964. Plasma factor X purified from the proposita using an anti-factor X monoclonal antibody immunoadsorbent exhibited an approximately 50% decrease in specific activity compared with factor X purified from a normal individual in a similar manner. Bleeding in family members with the mutation, termed factor X Stockton, appears to be due to disruption of normal hemostasis by the presence in plasma of circulating abnormal factor X. Factor X Stockton is the first naturally occurring substitution at the active site Asp of a serine protease and underscores the importance of this amino acid residue in factor Xa coagulant activity.
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PMID:Factor X Stockton: a mild bleeding diathesis associated with an active site mutation in factor X. 884 63

Activation of blood coagulation factor X to factor Xa (FXa) is inhibited by tissue factor pathway inhibitor (TFPI). The second Kunitz-type inhibitory domain (K2) of TFPI binds a catalytic domain of FXa, whereas the first domain (K1) does not. We analyzed computer models of complexes of FXa with K1 or K2, which were made using a crystal structure of FXa. Favorable hydrophobic interaction was observed in the complex of FXa with K2. Furthermore, we constructed a tertiary structure of FXa using CHIMERA to assess the accuracy of a homology modeling method. The isolated model structure of FXa agreed well with the crystal structure, but analyses of complexes of this structure with K1 or K2 revealed that the models of complexes could not provide clear evidence of greater binding ability to K2 because of the positional difference of a few side chains interacting with the inhibitor.
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PMID:A computer modeling study of the interaction between tissue factor pathway inhibitor and blood coagulation factor Xa. 926 22

A review of literature concerning cancer procoagulant (CP) has been carried out. This procoagulant directly activates coagulation factor X to factor Xa. Possibilities of utilising determinations of this activator in diagnostics and prognostics of the cancerous disease are discussed.
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PMID:Cancer procoagulant--CP. 933 29

(+)-2S-2-[4-[[(3S)-1-Acetimidoyl-3- pyrrolidinyl]oxy]phenyl]-3-[7-amidino-2-naphthyl]propanoic acid hydrochloride pentahydrate (DX-9065a) is an antithrombin III (AT III)-independent and selective inhibitor of activated blood coagulation factor X (FXa). The aim of the present study was to compare the antithrombotic and hemorrhagic effects of DX-9065a with a direct thrombin inhibitor and AT III-dependent anticoagulants in rat models of thrombosis and bleeding. Rats were administered intravenously DX-9065a (0.1-1 mg/kg/h), argatroban (0.1-1 mg/k/h), low molecular weight heparin (25-100 anti-XaU/kg/h), unfractionated heparin (25-100 anti-XaU/kg/h) or Orgaran (30-300 anti-XaU/kg/h) for 1 h. DX-9065a dose-dependently inhibited both thrombus formation and elevation in plasma thrombin-AT III complex (TAT) level in a copper wire-inserted arteriovenous (AV) shunt model in rats. The dose required for 50% inhibition of thrombus formation was 0.27 mg/kg/h. DX-9065a did not prolong transection bleeding time up to 7.78 mg/kg/h. Argatroban and AT III-dependent anticoagulants also inhibited both thrombus formation and TAT elevation, but prolonged bleeding time at a slightly higher dose than the effective dose. These results suggest that direct and selective inhibition of factor Xa by DX-9065a is preferable for the treatment of thrombosis in the aspect of lack of compromising primary hemostasis.
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PMID:Antithrombotic and hemorrhagic effects of DX-9065a, a direct and selective factor Xa inhibitor: comparison with a direct thrombin inhibitor and antithrombin III-dependent anticoagulants. 940 21

Blood coagulation factor X plays a pivotal role in the clotting cascade. When administered intravenously to mice, the majority of activated factor X (factor Xa) binds to alpha 2-macroglobulin (alpha 2M) and is rapidly cleared from the circulation into liver. We show here that the low-density lipoprotein receptor-related protein (LRP) is responsible for factor Xa catabolism in vivo. Mice overexpressing a 39-kD receptor-associated protein that binds to LRP and inhibits its ligand binding activity displayed dramatically prolonged plasma clearance of 125I-factor Xa. Preadministration of alpha 2M-proteinase complexes (alpha 2M*) also diminished the plasma clearance of 125I-factor Xa in a dose-dependent fashion. The clearance of preformed complexes of 125I-factor Xa and alpha 2M was similar to that of 125I-factor Xa alone and was also inhibited by mice overexpressing a 39-kD receptor-associated protein. These results thus suggest that, in vivo, factor Xa is metabolized via LRP after complex formation with alpha 2M.
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PMID:The low-density lipoprotein receptor-related protein (LRP) mediates clearance of coagulation factor Xa in vivo. 942 9

Electrostatic interactions during activation of coagulation factor X were analysed by comparing effects of ionic strength on reaction rates with predictions of classical electrostatic theory. Geometrical correlations were investigated using alpha-shape-based computations on the crystal structure of Ca-fragment 1 of prothrombin. The ionic strength of the reaction environment was controlled with different univalent salts including NaCl, KCl, CsCl, LiCl, NaI, NaBr and KI. Reactions were assembled in three different environments: aqueous phase, cell membranes and synthetic TF/PS/PC (tissue factor relipidated in 30% phosphatidylserine, 70% phosphatidylcholine) vesicles. Reaction rates were measured at pH 7. 2, 4 mM CaCl2 and 33 degrees C, using chromogenic substrate to follow factor Xa generation. Rates decreased with increasing concentration of univalent salt, and the magnitude of the decrease was independent of salt type. On the basis of electrostatic relationships on PS/PC vesicles, the effective charge on factor X was +1.5, and the PS/factor X stoichiometry was 2.28. Structural analysis of the gamma-carboxyglutamic acid (Gla) domain revealed three surface pockets, forming potential sites for Ca2+ binding, with distinct spatial orientations. Interpreted together, the results of the geometric analysis and the measured effective charges suggest an efficient electrostatic mechanism for capture and retention of substrates by procoagulant membranes. Non-specific and delocalized interaction between the membrane and each one of the charged facets of the Gla domain can increase the probability of substrate binding, while allowing rotational and translational mobility of substrate for specific interaction with the enzyme.
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PMID:Effective electrostatic charge of coagulation factor X in solution and on phospholipid membranes: implications for activation mechanisms and structure-function relationships of the Gla domain. 946 53

Engineering of recombinant coagulation factor X variants, which can be activated by tumor-associated proteinases may lead to the development of new therapeutic molecules. However, the evaluation of such variants requires an appropriate animal model. Therefore, we isolated the complete coding sequence of mouse coagulation factor X from mouse liver cDNA by polymerase chain reaction. The deduced amino acid sequence codes for a prepro protein of 481 amino acids homologous to factor X sequences from various species. Recombinant mouse factor X was expressed in human embryonic kidney cells and secreted into cell culture supernatant as zymogen, which could be converted to catalytically active factor Xa by Russell's viper venom. Purified recombinant mouse factor X restored coagulation in human factor X deficient plasma, demonstrating that mouse factor X is able to functionally interact with the human blood coagulation system. Recombinant mouse factor X opens the possibility to analyze therapeutically useful variants in the mouse system.
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PMID:Cloning and recombinant expression of mouse coagulation factor X. 978 72

This review describes the physicochemical and biological properties of cancer procoagulant (CP). This procoagulant is cysteine protease which directly activates coagulation factor X to factor Xa. CP is found in the tissues and blood of subjects suffering from cancer so its determination could be very useful in diagnostics and prognostics of cancer disease.
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PMID:[Cancer procoagulant (CP): the new biochemical marker in oncologic diagnosis]. 1096 23

Low molecular weight heparins (LMWH) have become the reference drugs for the prevention and treatment of venous thromboembolism. Among the newer antithrombotic agents, the pentasaccharide is the most advanced and promising alternative of low molecular weight heparins. The pentasaccharide is a synthetic and specific inhibitor of activated coagulation factor X (factor Xa). The pentasaccharide is identical to the active sequence of heparin which is present in about a third of commercially available heparin mixtures. The pentasaccharide binds specifically to antithrombin III (ATIII) thus potentiating its inhibitory activity on factor Xa. As a result, thrombin generation and the formation of fibrin and thus of thrombi is inhibited. After a large phase II dose finding clinical trial, four large clinical trials with pentasaccharide in the prevention of venous thromboembolism in hip or knee surgery have been conducted in Europe and North America. The results of these trials show that pentasaccharide prevents venous thromboembolism to a larger extent than enoxaparine with an overall risk reduction of 50% and no significant increase in bleeding. Among newer antithrombotic drugs, an oral, direct thrombin inhibitor, ximelagatran, has been developed and evaluated in the prophylaxis of venous thromboembolism in hip or knee surgery in comparison with enoxaparine with promising RESULTS. Oral direct thrombin inhibitors have the advantage of predictable dose response with the possibility of oral administration without laboratory monitoring.
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PMID:[From heparin to synthetic antithrombotic drugs]. 1177 99


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