Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.68 (tissue plasminogen activator)
 11,311 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Plasminogen kringle 1+2+3 (K1-3) containing lysine-binding sites inhibited the reaction of plasmin with alpha 2-plasmin inhibitor (alpha 2PI), in a rate assay using a synthetic chromogenic substrate, S-2251. However, K1-3 did not inhibit the reaction to any degree between alpha 2PI and mini-plasmin which lacked the kringle 1 to 4 portion of plasmin. These results suggest that K1-3 blocked the binding of alpha 2PI to the lysine-binding site of plasmin. In the urokinase (UK)-induced fibrinolysis, K1-3 shortened the human plasma clot lysis time at low concentration (0.5-6 microM), and prolonged the lysis time at a high concentration (20 microM). Similar results were obtained in the lysis time of a fibrin clot consisting of plasminogen, fibrinogen and alpha 2PI isolated from human plasma. The kringle 4 (K4) of human plasminogen did not accelerate human plasma clot lysis at any concentration (1.2-24.1 microM). Furthermore, in the tissue plasminogen activator (TPA)-induced fibrinolysis, K1-3 also shortened both the lysis time of human plasma clot and fibrin clot as observed in UK-induced fibrinolysis, but K4 did not. The above findings indicate that the reaction of alpha 2PI with the lysine-binding site of plasmin is involved in the inhibition of plasmin activity by alpha 2PI, and in the presence of an inhibitor of this reaction, the balance of coagulofibrinolytic activity in plasma will be shifted towards the fibrinolytic side.
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PMID:Effects of kringles derived from human plasminogen on fibrinolysis in vitro. 282 51

Plasminogen activation catalysed by tissue-type plasminogen activator (t-PA) has been examined in the course of concomitant fibrin formation and degradation. Plasmin generation has been measured by the spectrophotometric method of Petersen et al. (Biochem. J. 225 (1985) 149-158), modified so as to allow for light scattering caused by polymerized fibrin. Glu1-, Lys77- and Val442-plasminogen are activated in the presence of fibrinogen, des A- and des AB-fibrin and the rate of plasmin formation is found to be greatly enhanced by both des A- and des AB-fibrin polymer. Plasmin formation from Glu1- and Lys77-plasminogen yields a sigmoidal curve, whereas a linear increase is obtained with Val442-plasminogen. The rate of plasmin formation from Glu1- and Lys77-plasminogen declines in parallel with decreasing turbidity of the fibrin polymer effector. In order to study the effect of polymerization, this has been inhibited by the synthetic polymerization site analogue Gly-Pro-Arg-Pro, by fibrinogen fragment D1 or by prior methylene blue-dependent photooxidation of the fibrinogen used. Inhibition of polymerization by Gly-Pro-Arg-Pro reduces plasmin generation to the low rate observed in the presence of fibrinogen. Antipolymerization with fragment D1 or photooxidation has the same effect on Glu1-plasminogen activation, but only partially reduces and delays the stimulatory effect on Lys77- and Val442-plasminogen activation. The results suggest that protofibril formation (and probably also gelation) of fibrin following fibrinopeptide release is essential to its stimulatory effect. The gradual increase and subsequent decline in the rate of plasmin formation from Glu1- or Lys77-plasminogen during fibrinolysis may be explained by sequential exposure, modification and destruction of different t-PA and plasminogen binding sites in fibrin polymer.
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PMID:Fibrin and plasminogen structures essential to stimulation of plasmin formation by tissue-type plasminogen activator. 293 32

Plasminogen activation by tissue-type plasminogen activator (t-PA) is stimulated by fibrin. In a purified system maximal fibrin-enhanced plasmin formation occurs with a delay after an initial phase of slow plasmin formation (lag phase). In the present study purified stimulating CNBr-fragment FCB-2 of fibrinogen was used, and kinetics of plasminogen activation by t-PA were analyzed with respect to the lag phase. At constant FCB-2 concentration the duration of the lag phase decreased with increasing concentrations of t-PA and plasminogen. During this period the rate of plasmin formation/min increased linearly with time with a slope dependent on the initial concentrations of FCB-2, plasminogen, and t-PA. Plasmin pretreatment of FCB-2 resulted in a dose- and time-dependent shortening of the lag phase, and at plasmin concentrations greater than or equal to 1 nM and preincubation times greater than or equal to 3 min maximal plasmin formation occurred without a lag phase. Kinetics during the phase of maximal and constant plasmin formation were not influenced by plasmin pretreatment of FCB-2. We therefore conclude that maximal t-PA-dependent plasmin formation in a system stimulated by purified FCB-2 requires plasmin modification of FCB-2.
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PMID:Plasminogen activation by tissue plasminogen activator in the presence of stimulating CNBr fragment FCB-2 of fibrinogen is a two-phase reaction. Kinetic analysis of the initial phase of slow plasmin formation. 296 2

The mammalian fibrinolytic system comprises a proenzyme, plasminogen, which can be converted to the active enzyme plasmin, which will degrade fibrin. Plasminogen activation is mediated by plasminogen activators which are classified as either tissue-type plasminogen activator (t-PA) or urokinase-type plasminogen activator (u-PA). t-PA and single-chain u-PA (scu-PA) induce clot-specific thrombolysis, however via entirely different mechanisms. t-PA is relatively inactive in the absence of fibrin, but fibrin strikingly enhances the activation rate of plasminogen by t-PA. This is explained by an increased activity of fibrin-bound t-PA for plasminogen and not by alteration of the catalytic efficiency of the enzyme. scu-PA has a high affinity for plasminogen but, however, does not activate plasminogen in plasma in the absence of a fibrin clot, due to competitive inhibition. Fibrin-specific thrombolysis appears to be due to the fact that fibrin reverses the competitive inhibition, but this does not seem to occur via specific binding of scu-PA to fibrin. The thrombolytic efficacy and fibrin-specificity of natural and recombinant t-PA has been demonstrated in animal models of pulmonary embolism, venous thrombosis and coronary artery thrombosis. In all these studies thrombolysis and relative fibrinogen sparing effect of t-PA was recently confirmed in several multicenter clinical trials in patients with acute myocardial infarction. Specific thrombolysis by scu-PA has also been demonstrated in animal models of pulmonary embolism, venous thrombosis and coronary artery thrombosis.
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PMID:Fibrin-specific thrombolytic agents. 304 5

We have examined the effects of bacterial lipopolysaccharide (endotoxin) on the fibrinolytic activity of bovine pulmonary artery endothelial cells. Endotoxin suppressed the net fibrinolytic activity of cell extracts and conditioned media in a dose-dependent manner (threshold dose, 0.1 ng/ml; maximal dose, 10-100 ng/ml). The effects of endotoxin required at least 6 h for expression. Cell extracts and conditioned media contained a 44-kDa urokinase-like plasminogen activator. Media also contained multiple plasminogen activators with molecular masses of 65-75 and 80-100 kDa. Plasminogen activators in extracts and media were unchanged by treatment of cells with endotoxin. Diisopropyl fluorophosphate (DFP) abolished fibrinolytic activity of extracts and conditioned media. DFP-treated samples from endotoxin-treated but not untreated cells inhibited urokinase and tissue plasminogen activator, but not plasmin. Inhibitory activity was lost by incubation at pH 3 or heating to 56 degrees C for 10 min. These treatments did not affect inhibitory activity of fetal bovine serum. Incubation of 125I-urokinase with DFP-treated medium from endotoxin-treated cells produced an inactive complex with an apparent molecular mass of 80-85 kDa. The complex could be detected by chromatography on Sephadex G-100, but not by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. These findings suggest that low doses of endotoxin suppress fibrinolytic activity in endothelial cells by stimulating the production or expression of a fast-acting, relatively labile inhibitor of plasminogen activator.
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PMID:Endotoxin induction of an inhibitor of plasminogen activator in bovine pulmonary artery endothelial cells. 307 53

Plasminogen activators are enzymes which convert the zymogen to plasmin, the physiological enzyme for dissolving fibrin. There are two different physiological activator enzymes, urokinase (UK) and tissue plasminogen activator (t-PA, also known as vascular activator). The most striking difference in the behavior of the two activators is the ability of fibrin to augment the activity of t-PA but not of UK. Since tumor and normal tissues have been shown to contain different ratios of UK:t-PA, it can be anticipated that their comparative activator activities measured with fibrinolytic assays would yield different results from those measured with non-fibrin tests. This study was designed to test the validity of earlier conclusions that: (a) the measured activity of t-PA is augmented in fibrinolytic assays when compared with a non-fibrin assay based on azocaseinolysis; and (b) this difference could explain the failure of some laboratories using fibrinolytic assays to detect a difference in activator activity between tumor and normal tissues or to find more activity in the normal tissue. Azocaseinolytic and fibrinolytic (fibrin plate) assays were used to measure activator activity in a series of 14 normal-tumor tissue pairs. Using azocasein tests, cancer tissues were found to contain significantly higher median activities than normal tissues [Wilcoxon test, P less than 0.05; 13.8 versus 3.7 Committee on Thrombolytic Agents (CTA) units/g tissue, respectively], whereas no significant difference was found with fibrin assays (43.5 versus 69.0 CTA units/g tissue, respectively). Of total activator activity, the median percentage of UK was significantly higher in tumor (95%) than in normal tissue (58%). In addition, using azocaseinolysis it was found that the median UK activity was significantly higher in tumor (12.1 CTA units/g) relative to normal (3.51 CTA units/g) tissues, whereas no difference was found for t-PA. To explain these results in tumor and normal tissues, a mathematical model was derived to describe the difference between azocasein and fibrin assays for both purified plasminogen activator enzymes and activator enzymes in tissue extracts. The model fits the data well, confirming in a quantitative manner the hypotheses of the study. In addition, the study revealed that the azocaseinolytic assay was able to measure the full potential activator activity of purified pro-urokinase enzyme. Pro-urokinase activity could not be measured with standard fibrinolytic assays. These results show the importance of selection and interpretation of plasminogen activator assays in studies dealing with malignant transformation.
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PMID:Plasminogen activator content of human tumor and adjacent normal tissue measured with fibrin and non-fibrin assays. 308 Dec 57

Tissue-type plasminogen activator is a new thrombolytic agent that dissolves intravascular thrombi in coronary and peripheral vessels with less pronounced systemic lysis than that produced by streptokinase. Plasminogen activator was shown to induce reperfusion, and to salvage ischemic myocardium, by lysing experimentally induced coronary artery thrombi. The effect of a melanoma cell-derived tissue-type plasminogen activator was studied in cat myocardium rendered ischemic by coronary artery ligation for 2 hours and reperfused for another 4 hours. Plasminogen activator was infused at a rate of 500 IU X kg-1 X min-1 for the first 30 minutes of reperfusion. The marked increase in plasma creatine kinase activity during reperfusion was significantly lower in plasminogen activator-treated cats at 4, 5 and 6 hours, with 7.7 +/- 1.5 X 10(-3) IU X mg protein-1 (n = 8) in the plasminogen activator group versus 17.8 +/- 3.5 X 10(-3) IU X mg protein-1 (n = 7) in the vehicle group at 6 hours (mean +/- SEM). The area at risk in the two ischemic groups was not different, being 14.6 +/- 1.5 and 16.6 +/- 1.4% of total left ventricular mass for the treated and untreated groups, respectively. However, the mass of necrotic tissue determined histochemically was significantly lower in the plasminogen activator-treated group, accounting for 29.5 +/- 3.9% of the area at risk compared with 46.8 +/- 4.2% of area at risk in cats receiving only the vehicle (p less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Beneficial effects of tissue-type plasminogen activator in acute myocardial ischemia in cats. 308 17

Plasminogen activators (PA) convert the inactive proenzyme plasminogen into plasmin, which is involved in the process of fibrinolysis, tissue remodeling, and cell migration. There are two distinct forms of PA: urokinase (u-PA) and tissue-type plasminogen activator (t-PA). t-PA has higher affinity for fibrin and is the main form involved in thrombolysis. By in situ chromosomal hybridization and Southern blot analysis of somatic cell hybrid DNA, we have assigned the human t-PA gene to chromosome 8, bands 8p12----q11.2. We have detected a common EcoRI restriction fragment length polymorphism within the t-PA gene that thus provides a precisely localized highly informative marker for genetic linkage studies. The t-PA gene localization coincides with a translocation breakpoint observed in myeloproliferative disorders. Whereas leukemic cells usually secrete both types of PA, a correlation exists between acute myeloid leukemic cells that release only t-PA and failure to respond to chemotherapy.
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PMID:Human tissue-type plasminogen activator gene located near chromosomal breakpoint in myeloproliferative disorder. 309 43

Plasminogen activators (PAs) present in the plasma of BALB/c mice and produced in vitro by murine tumor cell cultures (B77-3T3, SR-BALB, AA6) have been characterized using electrophoretic-zymographic techniques. BALB/c mouse plasma contains a main PA activity with an approximate molecular weight of 88,000 and pI 6.3, inhibited by anti-human tissue-type plasminogen activator (t-PA) serum, here defined as murine t-PA. On the contrary, all tumor cells tested release a PA activity with a molecular weight of 44,500 and pI 9.2 characteristic of urokinase-type activator (murine u-PA). The injection s.c. of the different tumorigenic cells into BALB/c mice leads to tumor development and to a rapid increase of t-PA from the first day following the injection. This early enhancement of t-PA activity is not detectable in mice given injections of lethally irradiated B77-3T3 cells. Moreover the development of the tumor in the animals is related to the appearance of increasing levels of u-PA in the blood. This activity is detectable in the plasma of treated mice almost 2 wk before detection of a tumor 1 mm in diameter. During tumor development, the molecular weight of the u-PA and t-PA forms present in the plasma does not change, while there is a decrease of the isoelectric point of the u-PA leading to the appearance of distinct PA activities with pI 7.6 and 8.9. Syngenic and allogenic lymphocytes, injected in BALB/c mice, do not induce any modification in the pattern of the plasma PA. The injection of highly metastatic cells, as opposed to nonmetastatic or low-metastatic cells, does not give rise to detectable levels of u-PA in the plasma of treated mice. These data suggest that the lack of plasma u-PA activity facilitates the formation of metastates, while the increase of this activity is important in tumor development and is independent of the metastatic potential of the injected cells.
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PMID:Relationship between circulating plasminogen activators and tumor development in mice. 309 69

Plasminogen activators convert plasminogen into plasmin, a serine protease that initiates extracellular proteolysis. Two types of plasminogen activator activities have recently been demonstrated in granulosa cells, and the proteolysis-inducing enzymes are believed to be involved in ovulation. However, little attention has been paid to the presence of these enzymes in oocytes. Using sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by a fibrin overlay technique, we studied plasminogen activator activity in oocytes. Denuded oocytes collected from ovaries of hypophysectomized, estrogen-treated immature rats contained a tissue-type plasminogen activator (tPA), but not urokinase (uPA). In contrast, oocyte-free granulosa cells in these preantral follicles contained uPA, but not tPA. The tPA activity found in oocytes was plasminogen-dependent; incubation with increasing numbers (25-200) of denuded oocytes resulted in a dose-dependent increase in fibrinolysis only in the presence of plasminogen. Cellular localization of tPA was studied in the preantral follicles using an immuno-cytochemical method. Positive tPA staining was detected in the cytoplasm, but not in the germinal vesicle or zona pellucida of the oocytes. Furthermore, analysis using a reverse fibrin-overlay method did not reveal the presence of a plasminogen activator inhibitor. Culturing of denuded oocytes for 24 h increased the cellular content of tPA, but the enzyme activity was not further enhanced by treatment with FSH or forskolin. Also, no tPA activity was detected in the medium. We further studied plasminogen activator activities in the cumulus-oocyte complexes. Although only tPA activity was detected in freshly obtained cumulus-oocyte complexes, incubation for 24 h increased both tPA and uPA activity. Furthermore, tPA, but not uPA, activity was stimulated by treatment with FSH or forskolin. This was accompanied by the secretion of tPA into the medium. The identity of tPA and uPA in the cumulus-oocyte complexes was further confirmed by immunoprecipitation with specific antibodies. Isolation of denuded oocytes and cumulus cells after hormonal stimulation of the cumulus-oocyte complexes suggested that tPA activity was stimulated in both cell types and that the cumulus cells may mediate the action of FSH and forskolin on oocytes. In conclusion, the detection and regulation of tPA activity in cumulus-oocyte complexes suggest possible involvement of this enzyme in ovulation or the process of cumulus cell expansion and dispersion. Changes in oocyte tPA content may also serve as an indicator of oocyte development.
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PMID:Identification and regulation of tissue plasminogen activator activity in rat cumulus-oocyte complexes. 309 95


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