Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.73 (urokinase-type plasminogen activator)
 10,685 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Thrombotic thrombocytopenic purpura (TTP) is characterized by widespread occluding and persistent microthrombotic lesions. Evidence for both endothelial damage and primary platelet aggregation as possible pathogenetic mechanisms has been produced. Persistence of microthrombi has not been explained satisfactorily. In patients with TTP we studied plasma fibrinolysis and protein C. Tissue plasminogen activator (t-PA) activity levels, measured functionally, were low or unmeasurable in 11 of 12 patients; t-PA antigen levels, measured immunochemically, were normal in all six observed. The level of potent inhibitor of plasminogen activation directed against both t-PA and urokinase was elevated significantly in all 12, whereas the alpha 2-antiplasmin level was elevated in only two. Protein C antigen levels were low in three of six patients observed. Fibrinolysis levels in patients in remission did not differ from those in patients with acute disease. Plasma exchange resulted in temporary reversal of the abnormalities, but achievement of clinical remission was not associated with permanent normalization of fibrinolysis. Inasmuch as all 12 patients had severely depressed fibrinolytic mechanisms it is possible that a defect in the fibrin-clearing system permits thrombus formation to occur and proceed in an unchallenged fashion, thereby contributing to the complex events leading to arterial ischemia in vital organs.
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PMID:Fibrinolysis in health and disease: abnormal levels of plasminogen activator, plasminogen activator inhibitor, and protein C in thrombotic thrombocytopenic purpura. 243 36

Plasminogen activator inhibitor (PAI) was purified in active form from porcine platelets under nondenaturing conditions. The purified inhibitor (Mr 47,000) reacts with tissue-type plasminogen activator (t-PA), urokinase (UK), and activated protein C (APC) to yield both SDS-stable complexes and a modified PAI of slightly reduced molecular weight. The second-order rate constants for the inhibition of t-PA and UK by PAI are 3.5 X 10(7) and 3.4 X 10(7) M-1 s-1, respectively. Activated protein C reacts with PAI with a second-order rate constant of 1.1 X 10(4) M-1 s-1. This rate is not accelerated by protein S, phospholipid, and calcium, or heparin. It is concluded that (1) PAI can function as both inhibitor and substrate of its target proteases, (2) if APC promotes fibrinolysis via inactivation of PAI, then APC must be present in concentrations several orders of magnitude greater than t-PA, or the interaction of APC and PAI must be accelerated by presently unknown mechanisms, and (3) in the absence of heparin, platelet PAI is the most rapid inhibitor of APC yet described.
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PMID:Platelet plasminogen activator inhibitor: purification and characterization of interaction with plasminogen activators and activated protein C. 250 42

An assay system for protein C (PC) activity and PC-inhibitor in plasma was developed. The assay was based on: (1) binding of PC to wells of a microtiter plate coated with a murine monoclonal anti-PC antibody (C3) that did not interfere with the activity or activation of PC; (2) activation of immobilized PC with Protac C; (3) incubation with or without a source of activated PC inhibitor; and (4) measurement of amidolytic activity using the substrate S-2366. The activity assay was specific for PC and sensitive to less than 1 microliter of plasma or 4 ng PC. Inhibition of activated PC by plasma followed pseudo first order kinetics. Heparin caused a dose dependent increase in the inhibition rate with half maximal stimulation at approximately 3 U/ml and maximal stimulation at heparin concentrations greater than or equal to 10 U/ml. This assay is suitable not only for determination of functional plasma levels of PC and PC inhibitor activities but also for kinetic studies of inhibition of activated PC in complex systems, such as plasma. Studies showed that urokinase interfered with the inhibition of APC by plasma inhibitor(s).
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PMID:Functional assays for protein C activity and protein C inhibitor activity in plasma. 254 80

Systemic activation of the coagulation mechanism is known to exist in patients with colon cancer. The mechanism of such activation was investigated using immunohistochemical techniques applied to fresh frozen sections of resected primary colon cancer specimens. Tumor cells stained for tissue factor, factor V, and urokinase-type plasminogen activator. Perivascular and intercellular areas stained for fibrinogen and the "a" subunit of factor XIII. Staining was minimal or absent for protein C, protein S, plasminogen activator inhibitors 1-3, factor VII, factor X, and fibrin (the antigenic site on the amino-terminal portion of B beta chain that is exposed following thrombin cleavage of fibrinopeptide B was not detected). The lack of an intact thrombin-generating pathway in situ associated with viable colon cancer cells is consistent with the findings of others that coagulation activation in colon cancer may be triggered by a soluble tumor product that exerts its effect at sites distant from the tumor. These results may explain the absence of clinical responsiveness of colon cancer to antithrombotic drug therapy and may clarify therapeutic strategies for this common tumor.
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PMID:Indirect activation of blood coagulation in colon cancer. 269 22

Between August 1983 and December 1987, 23 patients received a 30-minute intraoperative, intraarterial infusion of streptokinase (seven patients) or urokinase (16 patients) because of residual thrombus or persistent ischemia or both after thromboembolectomy. Ages ranged from 21 to 77 years (mean, 58 years). In 15 patients intraoperative lytic therapy was part of the initial operation, whereas in eight patients intraoperative lytic therapy was performed during a secondary operation to treat thrombosis of a recently placed graft. Seven patients in the latter group had hypercoagulable conditions (five had heparin-induced thrombosis; one had protein C deficiency; one had polycythemia with thrombocytosis). Improvement after intraoperative lytic therapy was seen on angiography performed after infusion in 13 of 17 (76%) patients in whom angiography was performed both before and after intraoperative lytic therapy. Grafts in 12 of these patients remained patent without additional intervention, and in one graft thrombus formed again. In contrast, among four patients without angiographic evidence of improvement, thrombus formed again in four grafts (p less than 0.004). Intraoperative lytic therapy was considered successful in 74% of instances (17/23), including four of seven patients with hypercoagulable states. Three of six patients whose grafts failed had major amputations, whereas there were no amputations after successful infusions. Twelve patients were heparinized after intraoperative lytic therapy. Ten patients in this group were considered treatment successes, and two were considered treatment failures. Three of 11 patients not heparinized after intraoperative lytic therapy were considered treatment failures. Four hematomas occurred in the former group and none in the latter (p less than 0.03). No hematomas occurred in the heparin-induced thrombosis group in spite of anticoagulation with sodium warfarin (Coumadin). Only one hematoma occurred within 6 hours of intraoperative lytic therapy, and thus it was attributable to the infusion. We conclude that intraoperative lytic therapy is an effective adjunct to manage residual thrombus or persistent ischemia or both after lower extremity revascularization. Postinfusion angiography is of prognostic value. Heparinization after intraoperative lytic therapy seems beneficial but significantly increases the risk of bleeding complications.
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PMID:Intraoperative infusion of lytic drugs for thrombotic complications of revascularization. 279 66

Purified plasma and urinary protein C inhibitors (PCI) formed heparin-dependent complexes with activated protein C (APC) which were detected by immunoblotting after nondenaturing gel electrophoresis. Bands representing APC.PCI complexes were also seen on immunoblots after incubation of plasma with APC and heparin. The same immunoblot pattern of complexes was detected by three different methods: method A, monoclonal antibody to plasminogen activator inhibitor-3 (PAI-3, urinary urokinase inhibitor) + 125I-labeled anti-mouse IgG; method B, polyclonal antibodies to PCI + 125I-labeled purified plasma PCI; and method C, monoclonal antibody to protein C + 125I-protein C. Plasma depleted of PAI-3 by immunoadsorption with insolubilized monoclonal antibody to PAI-3 showed no detectable antigen or complexes with APC as visualized by methods A or B. This PAI-3-depleted plasma had less than 10% of the heparin-dependent inhibitory activity of normal plasma toward APC. Purified plasma PCI was fully reactive in an enzyme-linked immunoabsorbent assay for PAI-3, and plasma and urinary PCI inhibited urokinase activity in a heparin-dependent manner. These data indicate that heparin-dependent plasma and urinary PCI and PAI-3 are immunologically and functionally very similar if not identical. This observation identifies a new interrelation between the protein C anticoagulant and the fibrinolytic systems. In addition, plasma contains a heparin-independent inhibitor of APC which is not immunologically related to plasma PCI or to PAI-3.
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PMID:Immunological identity of heparin-dependent plasma and urinary protein C inhibitor and plasminogen activator inhibitor-3. 282 68

Human protein C-inhibitor (PCI) was isolated from human citrated plasma by combining rivanol precipitation, ammonium sulfate precipitation, ion-exchange chromatography on DEAE-Sephacel and affinity chromatography on dextran sulfate Sepharose. The purified PCI migrated with the beta-globulins and was free from protein contaminations as judged by immunoelectrophoresis. In SDS-PAGE under reducing and unreducing conditions PCI showed a single band at Mr = 57,000. The specific activity of the inhibitor was 226 units/mg. Surprisingly, the isolated PCI inhibited the amidolytic activity of urokinase (u-PA) on Glu-Gly-Arg-pNA (S-2444) in a time-dependent manner. Heparin, dextran sulfate and pentosanpolysulfate accelerated the reaction catalytically. PCI revealed itself as a non-competitive inhibitor of u-PA. The Ki-value was determined to be 7.9 x 10(-8)M. Inhibition of amidolytic activity was found to be associated with the formation of an 1:1 equimolar complex with a Mr of 110,000 as demonstrated by means of polyacrylamide gel electrophoresis and following Western blotting technique using polyclonal antibodies against u-PA and PCI. The specific activity of the isolated PCI of 226 units/mg, which approximates the theoretical value of pure PCI, indicates a highly purified preparation of PCI. The heparin-dependent inhibition of urokinase by this highly purified protein as well as comparison of the kinetic data and amino-acid composition of both PCI and the recently described plasminogen activator inhibitor (PAI) 3 give high evidence of identity of PCI and PAI-3.
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PMID:Inhibition of urokinase by protein C-inhibitor (PCI). Evidence for identity of PCI and plasminogen activator inhibitor 3. 350 Dec 95

The important role of protein C (PC) in the regulation of hemostasis has been appreciated since the description of patients who were deficient in PC and presented with severe thromboembolic events. The potentially fatal complications associated with PC-deficiency require an early and reliable identification of those patients affected with this inherited disorder. The present study introduces a test procedure for the functional assessment of PC in plasma samples. The test utilizes the thrombin/thrombomodulin complex to achieve complete and rapid formation of activated PC whose proteolytic capacity is subsequently determined with a chromogenic substrate. Homogenate obtained from rabbit lung effectively substituted the purified component thrombomodulin in the assay system. This new approach simplifies the test procedure without losing specificity and accuracy. Proteases, such as plasmin, streptokinase and urokinase did not influence the assay and the inhibitory effect of heparin on the PC-activation could easily be overcome by the addition of protamine sulphate. The PC-activity in a group of unselected patients (n = 50), who did not reveal any abnormalities in global coagulation tests, amounted to 100 +/- 12% (mean +/- SD) with a range from 54 to 143% when analyzed in comparison to a plasma pool constituted from healthy volunteers. Since the synthesis of PC depends on the availability of vitamin K, patients receiving phenprocoumon have also been analyzed. These patients (n = 103) presented 40 +/- 11% residual PC-activity accompanied by a concomitant decrease in PC-antigen levels to 43 +/- 10% (mean +/- SD). The test described is specific, sensitive, less time-consuming and can be performed on a routine basis.
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PMID:A simplified functional assay for protein C in plasma samples. 351 73

Confluent cultures of endothelial cells from human umbilical cord were used to study the effect of activated human protein C (APC) on the production of plasminogen activators, plasminogen activator-inhibitor, and factor VIII-related antigen. Addition of APC to the cells in a serum-free medium did not affect the production of tissue-type plasminogen activator (t-PA) or factor VIII-related antigen; under all measured conditions, no urokinase activity was found. However, less plasminogen activator-inhibitor activity accumulated in the conditioned medium in the presence of APC. This decrease was dose dependent and could be prevented by specific anti-protein C antibodies. No decrease was observed with the zymogen protein C or with diisopropylfluorophosphate-inactivated APC. APC also decreased the t-PA inhibitor activity in endothelial cell-conditioned medium in the absence of cells, which suggests that the effect of APC is at least partly due to a direct effect of APC on the plasminogen activator-inhibitor. High concentrations of thrombin-but not of factor Xa or IXa--had a similar effect on the t-PA inhibitor activity. The effect of APC on the plasminogen activator-inhibitor provides a new mechanism by which APC may enhance fibrinolysis. The data suggest that activation of the coagulation system may lead to a secondary increase of the fibrinolytic activity by changing the balance between plasminogen activator(s) and its (their) fast-acting inhibitor.
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PMID:Activated protein C decreases plasminogen activator-inhibitor activity in endothelial cell-conditioned medium. 391 96

The effects of various concentrations of plasmin and activated protein C on the factor VIII procoagulant activity (VIII:C) and coagulant antigen (VIII:CAg) were studied in factor VIII concentrates and normal plasma. Small amounts (0.1 CTA U/ml) of plasmin rapidly destroyed VIII:C, and affected, but did not destroy VIII:CAg, in factor VIII concentrates. In normal plasma larger amounts of plasmin (1.8 CTA U/ml) was required to inactivate VIII:C in order to exceed the neutralizing capacity of alpha 2-antiplasmin. VIII:CAg was unchanged indicating a limited proteolysis. The difference between VIII:C and VIII:CAg was found also in urokinase-activated plasma. Activated protein C (5 micrograms/ml), in the presence of Ca2+ and phospholipids, inactivated VIII:C without affecting VIII:CAg in a high purity factor VIII concentrate. Higher concentrations of activated protein C (25 micrograms/ml) caused a slight decrease of VIII:CAg, even in the absence of Ca2+ and phospholipids, but did not change VIII:CAg in normal plasma or serum.
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PMID:The effects of plasmin and protein Ca on factor VIII:C and VIII:CAg. 622 18


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