Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.5 (thrombin)
 33,306 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Endogenously activated protein C is evaluated for antithrombotic activity in porcine carotid arteries subjected to mechanical trauma. Protein C is activated by intravenous administration of guanidinobenzoyl-thrombin, which binds to thrombomodulin and there deacylates to yield thrombin. The bound, transiently active thrombin yields a peak of anticoagulant activity between 5 and 10 min after infusion of the latent thrombin. Inhibition of thrombin binding in vivo by co-infusing and active-site-blocked thrombin preparation elicits acute and lethal systemic thrombosis. Nearly occlusive platelet thrombosis, which occurs within 30 min of crushing 1 cm segments of carotid arteries with a standard hemostat, is blocked by endogenous protein C activation initiated 2 min before the crush injury. It is concluded that activated protein C blocks thrombosis is deeply injured musculo-elastic arteries, and that activation of latent thrombin bound to thrombomodulin in vivo is a practical means for delivery of pharmacologically effective concentrations of activated protein C.
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PMID:Antithrombotic action of endogenous porcine protein C activated with a latent porcine thrombin preparation. 857 15

Human thrombomodulin (hTM) is a newly described endothelial cell associated protein that functions as a potent natural anticoagulant by converting thrombin from a procoagulant protease to an anticoagulant. Focusing on the establishment of the practical evaluation of hTM immobilized materials, the activity of immobilized hTM was evaluated by in vivo and ex vivo blood contacting tests. As the basis for immobilization, regenerated cellulose films and hollow fibers were used. For the in vivo test, hTM immobilized cellular hollow fibers were implanted into dog blood vessels. Using hTM immobilized cellulose hollow fibers, a small scale dialyzer was assembled and its antithrombogenic activity was studied using human blood. As a result, it was revealed that the immobilized hTM still has co-enzymatic activity for activation of Protein C and anticoagulant activity. The coagulation time of the human blood passed through the hTM immobilized small dialyzer was effectively prolonged. It is expected that hTM immobilized cellulose should be a useful antithrombogenic biomaterial.
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PMID:In vivo and ex vivo evaluation of the antithrombogenicity of human thrombomodulin immobilized biomaterials. 857 27

Measurements of the apparent affinity constant for thrombomodulin (TM) binding to human alpha-thrombin as a function of both NA+ and temperature at constant ionic strength (0.15 M) showed that TM affinity increases in the presence of Na+ and vice versa. Moreover, this experimental strategy allowed us to accurately split the free energy of sodium binding into its entropic and enthalpic components for both the TM-free and TM-bound enzyme. Namely, at 25 degrees C, the value of delta G of sodium binding was found equal to -2.4 kcal/mol in the absence of TM and -3.6 kcal/mol for the thrombin-TM complex. The enthalpic contribution to the free energy of sodium binding is equal to -27 kcal/mol and -21 kcal/mol in the TM-free and TM-bound thrombin forms, respectively. Finally, the entropy change for sodium binding was also affected by TM, being equal to -83 cal/(mol deg) and -58 cal/(mol deg) in TM-free and TM-bound thrombin species, respectively. Moreover, the thermodynamic parameters for TM binding to Na+-free thrombin species were solved. TM binding is characterized by an enthalpy and entropy change equal to -10 kcal/mol and 2 cal/(mol deg), respectively, for Na+-free thrombin. It is well known that Na+ binding to thrombin causes conformational transitions and functional activation of the enzyme molecule. The finding that binding of thrombomodulin enhances thrombin affinity for sodium and vice versa raises the question as to whether the change of Na+ ligation induced by TM binding could contribute to the change in thrombin specificity for the hydrolysis of Protein C. Therefore, the effect of sodium binding to thrombin on the hydrolysis of human Protein C was extensively investigated. At both 25 and 37 degrees C the value of kcat/Km for Protein C hydrolysis by thrombin in the absence of TM was found to be enhanced by Na+ over a concentration ranging from 0 to 150 mM. Application of thermodynamic principles demonstrated that the Na+-thrombomodulin linkage contributes, under physiological conditions of sodium activity and temperature, to reduce significantly the transition-state stabilization free energy for Protein C hydrolysis.
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PMID:Effect of sodium on the energetics of thrombin-thrombomodulin interaction and its relevance for protein C hydrolysis. 861 87

The endothelium plays an important role in the regulation of haemostasis by producing substances such as thrombomodulin (TM). The influence of long-term volume replacement with different types of fluid on the TM-protein C-protein S system was investigated in a prospective, randomized study. Thirty trauma patients and 30 patients suffering from sepsis after major surgery received either 10% low-molecular weight (LMW) hydroxyethylstarch solution (HES-trauma, n = 15; HES-sepsis, n = 15) or 20% human albumin (HA-trauma, n = 15; HA-sepsis, n = 15) for 5 days to maintain central venous pressure (CVP) between 12 and 16 mm Hg. Plasma concentrations of TM, protein C, (free) protein S and thrombin-antithrombin (TAT) were measured in arterial blood samples obtained on the day of admission to the intensive care unit or on the day of diagnosis of sepsis and over the next 5 days. There were no differences between HA- and HES-treated trauma patients. Protein C and protein S also did not differ between HA- and HES-treatments. At baseline, TM plasma concentrations were increased to > 40 micrograms litre-1 in both sepsis groups only. In the HA-sepsis group, TM increased significantly (from 48.1 (SD 13.9) to 68.4 (13.0) micrograms litre-1), whereas it remained almost unchanged in the HES-sepsis group. In HES-sepsis patients, protein C (from 51.0 (10.1) to 71.9 (8.9)%) and protein S (from 19.0 (6.0) to 40.8 (11.4)%) increased significantly during the study, whereas both remained reduced in HA-patients. TAT (indicating intravascular coagulation) did not differ between the two fluid groups. We conclude that in trauma patients, the type of volume therapy had no influence on the TM-protein C-protein S system. In sepsis patients, volume therapy with HES was beneficial, whereas infusion of HA had no substantial positive effect on endothelial-associated coagulation.
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PMID:Does the type of volume therapy influence endothelial-related coagulation in the critically ill? 3286 9

Heparin is still the most commonly used anticoagulant in cardiac surgery necessitating cardiopulmonary bypass. In recent years, endothelial-related coagulation (e.g. thrombomodulin/protein C-system) has enlarged our knowledge of the regulation of haemostasis. In a controlled randomised study, the influence of different regimens of anticoagulation on the thrombomodulin/protein C-system was studied. Sixty patients undergoing elective coronary artery bypass grafting were randomly allocated into four groups (n = 15) to receive: 300 IU.kg-1 of heparin before bypass; 600 IU.kg-1 of heparin; 300 IU.kg-1 of heparin as bolus followed by a continuous infusion of 10 000 IU.h-1 until the end of bypass; or 600 IU.kg-1 of heparin plus 'high dose' aprotinin (2 million IU of aprotinin before bypass, 500 000 IU.h-1 until the end of the operation and 2 million IU added to the bypass pump prime). Grouping was blinded for the surgeon and the anaesthetist. Plasma concentrations of thrombomodulin, protein C and (free) protein S as well as thrombin/antithrombin III were measured by enzyme-linked-immunosorbent assays after induction of anaesthesia, during and after bypass, at the end of surgery, 5 h after bypass, and on the first postoperative day. Activated clotting time was significantly longer during bypass in group 2 (566 (60)s) and group 4 (655 (59)s), whereas standard coagulation parameters showed no differences between the four groups. Blood loss and use of homologous blood and blood products were highest in groups 2 and 3. Thrombomodulin plasma levels were similar (and normal) at baseline (< 40 ng.l-1), decreased during bypass and reached baseline values postoperatively without showing significant group differences. Protein C did not show any differences among the groups within the investigation period. 'Free' protein S plasma levels were most reduced in group 1 (from 68 (8)% to 48 (9)% after bypass). Thrombin/antithrombin III plasma concentrations increased most in groups 1 (to 69 (14) micrograms.l-1 after bypass) and 2 (to 48 (7) micrograms.l-1 after bypass), whereas they remained significantly lower in groups 3 and 4. The thrombomodulin/protein C-system was not significantly influenced by the regimen of anticoagulation. Administration of 'high-dose' heparin was associated with the highest blood loss, which could not be related to endothelial-associated coagulation.
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PMID:The effect of the anticoagulation regimen on endothelial-related coagulation in cardiac surgery patients. 2648 76

We have produced recombinant human Protein C (rHPC) in the milk of transgenic swine. After purification, we have analyzed the interaction of teh zymogen with Protac, thrombin/thrombomodulin and thrombin alone. The amidolytic and anticoagulant activities of rAPC after Protac activation were approximately 80% those of its human plasma counterpart. Upon the excision of the activation peptide by thrombin/thrombomodulin complex, both the natural and recombinant activation products had similar enzymatic and biological activities. This observation can be attributed to the difference in the mechanism of action between the two activators and structural differences between HPC and rHPC.
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PMID:Activation of recombinant human protein C. 873 26

We reported on a 74 year old patients with local advanced prostatic carcinoma. Following prostatic surgery an increased bleeding tendency was observed. The patients showed clinical and laboratory evidence for consumption coagulopathy with hyperfibrinolysis. The laboratory data were: marked decrease of AT III, Protein C, increase of thrombin/AT III complex level, fibrin degradation products (FDP) and antigen of t-PA. The treatment was ended successful.
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PMID:[Disseminated intravascular coagulation syndrome with secondary fibrinolysis activation in prostatic carcinoma]. 875 45

Protein C activation on the surface of the endothelium is critical to the negative regulation of blood coagulation. We now demonstrate that monoclonal antibodies that block protein C binding to the endothelial cell protein C receptor (EPCR) reduce protein C activation rates by the thrombin-thrombomodulin complex on endothelium, but that antibodies that bind to EPCR without blocking protein C binding have no effect. The kinetic result of blocking the EPCR-protein C interaction is an increased apparent Km for the activation without altering the affinity of thrombin for thrombomodulin. Activation rates of the protein C derivative lacking the gamma-carboxyglutamic acid domain, which is required for binding to EPCR, are not altered by the anti-EPCR antibodies. These data indicate that the protein C activation complex involves protein C, thrombin, thrombomodulin, and EPCR. These observations open new questions about the control of coagulation reactions on vascular endothelium.
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PMID:The endothelial cell protein C receptor augments protein C activation by the thrombin-thrombomodulin complex. 881 78

A pathogenetic role for fibrin deposition and platelet activation in the kidney is thought to play a role in the pathogenesis of acute renal failure (ARF). Thus, some fibrinolytic parameters and platelet function have been studied in 17 patients with ARF and compared to healthy volunteers and subjects with chronic renal failure (CRF). Since serotonin may participate in pathological processes resulting from platelet/vessel wall interactions, its level in the whole blood and plasma was also assayed. In ARF and CRF platelet aggregatory responses in both whole blood and in platelet rich plasma upon stimulation with various agonists (collagen, arachidonic acid, ADP, ristocetin) were lower than those obtained in healthy volunteers. Increased levels of lipoprotein (a), von Willebrand factor (vWF) and fibronectin were found in ARF relative to controls. Protein C activity was significantly lower in patients with ARF. Euglobulin clot lysis time was prolonged in ARF and CRF, reflecting a decreased overall fibrinolytic activity. Activity of tissue plasminogen activator (tPA) inhibitor (PAI) and PAI:Ag were higher in ARF, whereas tPA:Ag, urokinase, tPA/PAI complexes, thrombin-antithrombin complexes (TAT), plasmin-antiplasmin (PAP) complexes, fibrinogen, and F1+2 did not differ between ARF and controls. In CRF elevated levels of TAT, PAP, fibrinogen and prothrombin fragments F1+2 were found, whereas concentration of fibronectin was lowered when compared to controls. In both groups of renal failure patients increased levels of fibrin monomers and d-dimer were found relative to healthy volunteers. Whole blood serotonin was significantly lower, whereas plasma serotonin was significantly higher in patients with ARF and CRF relative to controls. Serotonin uptake and its release from platelets were markedly diminished in patients with ARF and CRF. Chronic renal failure exhibit a slightly different pattern of coagulopathies that acute renal failure.
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PMID:Hemostasis, platelet function and serotonin in acute and chronic renal failure. 887 44

A viscosity perturbation method allowed to compute the second order rate constant, k+1, for the formation of thrombin-Protein C complex, both in the absence and presence of thrombomodulin (TM) at pH 8.00 and 37 degrees C. In the absence of TM the second order rate constant was found equal to 7.9 +/- 0.6 x 10(3) M-1 sec-1, whereas it was enhanced to 9.9 +/- 0.4 x 10(4) M-1 s-1 by a saturating (100 nM) TM concentration. Addition of 5 mM Ca++ to solution containing 100 nM TM induced a further increase of k+1 value up to 7.3 +/- 0.5 x 10(5) M-1 s-1. Moreover, it was demonstrated that the thrombin-PC complex undergoes the acylation reaction more rapidly than it dissociates to form free thrombin and substrate (stickiness ratio = 2.4 +/- 0.9). This tendency is even favored when thrombin is bound to TM both in the absence and presence of Ca++ (stickiness ratio = 9 +/- 6 in the absence of Ca++ and 16 +/- 10 in the presence of Ca++). Altogether these results demonstrate that TM is able to positively affect both the molecular encounter and the kinetics of the early catalytic events of the thrombin-Protein C interaction.
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PMID:Effect of thrombomodulin on the molecular recognition and early catalytic events in thrombin-protein C interaction. 890 96


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