Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.4.21.73 (urokinase-type plasminogen activator)
10,685 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Structure-activity relationships have been established for the inhibition of urokinase by aromatic diamidines. In an assay system employing purified urokinase and human plasminogen the most potent inhibitor was found in 4',4''-diamidino-2-hydroxy-1,4-diphenoxybutane which proved 5600 times more active on a molar bases than epsilon-aminocaproic acid (E-ACA). 2. 4',4''-diamidino-2-hydroxy-1,4-diphenoxybutane behaved as a competitive inhibitor of the urokinase catalyzed hydrolysis of N-alpha-acetyl-L-lysine methyl ester. At pH 7.85 and 37 degrees C the K-1 value was determined as 3.18 times 10-6 M which compares with a value of 6.79 times 10-5 M for p-aminobenzamidine and 3.57 times 10-2 M for E-ACA. 3. In two fibrinolytic tests including urokinase as activator the superiority of diamidines over E-ACA was less marked than in the pure plasminogen activation system. This was due to the presence of certain plasma proteins in the fibrinolysis assays which augmented the inhibitory strength of E-ACA. The order of effectiveness of diamidines in the lysis tests was also different from the one in the activation test. In a human fibrin clot lysis test the most active inhibitor was 3',3''-diamidino-2-hydroxy-1,4-diphenoxybutane which was 1700 times more effective on a molar basis than E-ACA. In a human plasma clot lysis test the strongest inhibitor, 2-hydroxy-stilbamidine, was 70 times more powerful than E-ACA.
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PMID:The inhibition of urokinase by aromatic diamidines. 113 21

Evidence is presented that heparin binds rabbit plasminogen types I and II under affinity chromatographic conditions using the single stage technique earlier described (Hatton, M.W.C. and Regoeczi, E. (1974) Biochim. Biophys. Acta 359, 55-65). Thus, the affinity of types I and II for Sepharose-lysine is markedly increased in the presence of heparin and elution by epsilon-aminohexanoic acid requires a steeper gradient to recover the plasminogen types. Furthermore by adding sufficient epsilon-aminohexanoic acid to non-heparinised plasma to suppress plasminogen affinity, the presence of heparin is shown to encourage binding of plasminogen (type II more so than type I) to the gel. However, the heparin effect is quickly reversed by washing the column with 0.5 M NaCl prior to elution by epsilon-aminohexanoic acid. No evidence of a stable plasminogen-heparin complex has been found from gel filtration studies and any interaction between plasminogen and heparin probably only takes place when heparin is bound to an affinity site. Studies with 35-S-labelled heparin have shown the mucopolysaccharide to bind to the free amino group of Sepharose-lysine and Sepharose-cadaverine and to be displaced by 0.5 M NaCl elution but not by 0.1 M epsilon-aminohexanoic acid. The plasminogen types produced from heparinised plasma are free from heparin and closely resemble preparations from non-heparinised plasma when compared by polyacrylamide gel electrophoresis, Sephadex gel filtration and arginine esterase activity after urokinase activation.
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PMID:The effect of heparin on the affinity chromatography of plasminogen. Demonstration of heparin-plasminogen interaction. 113 80

The two stages in the activation of human plasminogen by urokinase have been examined kinetically in order to evaluate the significance of each stage in the activation process. The cleavage of the preactivation peptide from the NH2 terminus of native plasminogen (NH2-terminal glutamic acid) is clearly catalyzed by urokinase and is the rate-limiting first step in activation (Stage 1); this reaction is 20-fold slower than the conversion of the intermediate plasminogen (NH2-terminal lysine) to plasmin (Stage 2). Both lysine and its analogoue, epsilon-aminocaproic acid, exert two effects on the activation of native plasminogen. At low concentrations of these agents, activation is greatly accelerated. Analysis of activation in the presence and absence of these agents by sodium dodecyl sulfate gel electrophoresis indicates that the activation pathway is the same in both cases with the formation of a transient intermediate plasminogen; only the kinetics of proteolysis are altered. This enhancement in the rate of activation results solely from acceleration of the Stage 1 reaction; Stage 2 is essentially unaffected at low concentrations. Stage 1 is maximally enhanced (75-fold) at either 0.0025 M epsilon-aminocaproic acid or 0.025 M lysine and occurs 4 times more rapidly than Stage 2, which becomes the rate-limiting step at these concentrations. Plasmin also cleaves the preactivation peptide from native plasminogen and this reaction rate is enhanced by the same concentrations of lysine and epsilon-aminocaproic acid. These data suggest that lysine and epsilon-aminocaproic acid, which are known to bind to plasminogen and significantly alter its conformation, may thereby enhance preactivation peptide cleavage and consequently, plasminogen activation. At high concentrations, both Stages 1 and 2 are similarly inhibited by these agents, which suggests that this effect may be exerted by the direct inhibition of urokinase. The relative rates of preactivation peptide cleavage by the enzymes urokinase, plasmin, thrombin, and ancrod were also determined. Urokinase is 10 times more effective than plasmin in catalyzing this reaction and 1.8 X 10(4) times more effective than thrombin, while ancrod does not exert an effect. No plasmin is formed by either thrombin or ancrod.
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PMID:The importance of the preactivation peptide in the two-stage mechanism of human plasminogen activation. 115 Jun 67

Plasma contained two inhibitors of plasminogen activation by urokinase when fractioned by gel filtration on Sephadex G-200. The inhibitor in the lower molecular weight fractions was separate from the principal protease inhibitors of plasma: alpha1-antitrypsin, alpha2-macroglobulin, C1 inactivator and antithrombin III, and from factor XIII. This activation inhibitor was present in both plasma and serum and its recovery was not reduced by preincubating the serum for 6 h at 37 degrees C. Its inhibitory activity was stable for several days at 4 degrees C, and was enhanced in the presence of an increased saline concentration. Preparations of the inhibitor, active in a clot lysis system, failed to inhibit the esterase activity of urokinase on N-alpha-acetyl-glycyl-L-lysine methyl ester.
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PMID:Inhibitors of plasminogen activation in human blood. 125 23

To evaluate the role of plasminogen activators (PAs) in physiological angiogenesis, we have investigated the in vivo patterns of expression of urokinase-type PA (uPA) and PA-inhibitor type 1 (PAI-1) during neovascularization of ovarian follicles, the corpus luteum, and the maternal decidua. Using in situ hybridization, we detected uPA mRNA in the ovary along the route of capillary extension, originating at the existing ovarian vasculature, extending toward growing follicles, and terminating at the newly formed capillary sheaths surrounding each growing follicle. Following ovulation, uPA mRNA was expressed in capillary sprouts within the developing corpus luteum. During the process of decidual neovascularization, uPA expression was detected in endothelial cell cords traversing the maternal decidua in the direction of the newly implanted embryo. uPA mRNA was not detected in endothelial cells upon completion of neovascularization, suggesting that uPA expression is a part of the angiogenic response. During in vitro "angiogenesis" of cultured aortic explants, uPA was expressed in capillary sprouts but not in underlying endothelial cell sheets, suggesting that the expression of uPA depends on the histological context of the endothelial cell. Interestingly, during corpus luteum development and decidual neovascularization, and in aortic explants, PAI-1 expression was preferentially activated in cells in the vicinity of uPA-expressing capillary-like structures. These findings suggest a functional interplay between uPA- and PAI-1-expressing cells and support the idea that natural PA inhibitors function during angiogenesis to protect neovascularized tissues from excessive proteolysis.
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PMID:In vivo patterns of expression of urokinase and its inhibitor PAI-1 suggest a concerted role in regulating physiological angiogenesis. 127 89

20 patients (6 females, 14 males) aged between 47 and and 75 years (mean: 62.6 yrs.) with acute myocardial infarction (onset of symptoms within 6 hours) were treated intravenously with either 200,000 U urokinase (UK) and 4.5 million U pro-urokinase (pro-UK) within 60 min (group I, N = 10), or 2.5 million U UK within 5 min (group II, N = 10). Blood samples for haemostatic and fibrinolytic function tests were taken prior to and repeatedly during the 24 hours following treatment. Peak fibrinolytic activity measured by fibrin plates was equivalent in both regimens. Average decreases, with lowest levels within 60 to 120 min following thrombolytic therapy, were observed of 27% and 70% for plasminogen, of 71% and 91% for alpha-2-antiplasmin, and of 20% and 74% for fibrinogen in group I and II, respectively. The reptilase time reached maximum values of 1.5- and 4.5-fold within 60 to 180 min. Peak levels of D-dimers and thrombin-antithrombin III complexes in group II were 2.6 and 3.2 times those of group I. After 24 hours, in contrast to group I, all these parameters still remained significantly different from pretreatment values in group II. These data indicate that, contrary to high-dose UK, pro-UK in combination with low-dose UK causes minor systemic fibrinolytic effects and is, therefore, assumed to be largely clot-specific, although the fibrinolytic potential is equivalent for both regimens.
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PMID:Fibrinolytic effects of pro-urokinase combined with low-dose urokinase compared to high-dose urokinase in patients with acute myocardial infarction. 127 35

Previously, we demonstrated that the Heymann nephritis autoantigen, gp330, can serve as a receptor site for plasminogen. This binding was not significantly inhibited by the lysine analogue epsilon-amino caproic acid (EACA), indicating that plasminogen binding was not just through lysine binding sites as suggested for other plasminogen binding sites. We now report that once plasminogen is bound to gp330, it can be converted to its active form of plasmin by urokinase. This conversion of plasminogen to plasmin proceeds at a faster rate when plasminogen is first prebound to gp330. Although there is a proportional increase in the Vmax of the urokinase-catalyzed reaction with increasing gp330 concentrations, no change in Km was observed. Once activated, plasmin remains bound to gp330 in an active state capable of cleaving the chromogenic tripeptide, S-2251. The binding of plasmin to gp330 did not significantly change its enzymatic activity; however, gp330 did have a stabilizing effect on plasmin activity at 37 degrees C. While bound to gp330, plasmin is protected from inactivation by its natural inhibitor alpha 2-antiplasmin. The binding of plasmin to gp330 as analyzed by ELISA was shown to be time dependent, reversible, saturable, and specific for gp330. Inhibition of binding of both plasminogen and plasmin to gp330 by benzamidine was similar, although EACA inhibited the binding of plasmin to gp330 slightly more than the binding of plasminogen to gp330. These results indicate that the binding of plasminogen to gp330 serves as an effective means of increasing the rate of plasmin production on the glomerular and tubular epithelial cell surface while protecting the active plasmin from natural inhibitors.
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PMID:Analysis of plasmin binding and urokinase activation of plasminogen bound to the Heymann nephritis autoantigen, gp330. 128 65

Tissue and urokinase-type plasminogen activators are serine proteases with highly restricted specificity, their best characterised role being to release the broad specificity protease plasmin from inactive plasminogen. It has frequently been suggested that these, and similar proteases, are involved in axonal growth and tissue remodelling associated with neural development. To help define what this role might be, we have studied the expression of the plasminogen activators in developing rat nervous tissue. Urokinase-type plasminogen activator mRNA is strongly expressed by many classes of neurons in peripheral and central nervous system. We have analysed its appearance in spinal cord and sensory ganglia, and found the mRNA is detectable by in situ hybridisation very early in neuronal development (by embryonic day 12.5), at a stage compatible with it playing a role in axonal or dendritic growth. Tissue plasminogen activator mRNA, on the other hand, is expressed only by cells of the floor plate in the developing nervous system, from embryonic day 10.5 and thereafter. Immunohistochemical and enzymatic analysis showed that active tissue plasminogen activator is produced by, and retained within, the floor plate. A mechanism is suggested by which high levels of tissue plasminogen activator produced by the stationary cells of the floor plate could influence the direction of growth of commissural axons as they pass through this midline structure.
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PMID:The expression of tissue and urokinase-type plasminogen activators in neural development suggests different modes of proteolytic involvement in neuronal growth. 128 56

Potential approaches to improve thrombolytic agents comprise the construction of mutants and variants of tissue-type plasminogen activator (tPA) or of single chain urokinase-type plasminogen activator (scuPA, pro-urokinase), of chimeric plasminogen activators and of conjugates of plasminogen activators with monoclonal antibodies. tPA mutants have been constructed with altered pharmacokinetic properties or altered functional properties, including binding to and stimulation by fibrin, resistance to plasmin and to protease inhibitors. Mutants of tPA described to date, obtained by deletion/substitution of functional domains or of single amino acids, have markedly reduced clearances, but usually also reduced specific thrombolytic potencies. Mutants of scuPA with improved thrombolytic potencies have thus far not been reported. Chimeric molecules containing functional domains of both tPA and scuPA have intact enzymatic properties of uPA and some fibrin affinity of tPA. Surprisingly, chimeras endowed with fibrin affinity usually have unaltered or reduced thrombolytic potencies. However, a chimera consisting of amino acids 87-274 of tPA and amino acids 138-411 of scuPA, with negligible fibrin affinity, has a 10-fold higher thrombolytic potency than scuPA in animal models of venous thrombosis, as a result of a delayed in vivo clearance and a relatively maintained specific thrombolytic activity. Plasminogen activators conjugated with antifibrin or antiplatelet monoclonal antibodies, either chemically or by recombinant DNA technology, are targeted to blood clots, resulting in a 5- to 10-fold increased thrombolytic potency. Thus, it is possible to develop plasminogen activators with improved thrombolytic potency. Whether such agents will be clinically useful remains to be established.
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PMID:Remaining perspectives of mutant and chimeric plasminogen activators. 130 56

How heparin inhibits vascular smooth muscle cell proliferation and migration has not been established. We have investigated the hypothesis that heparin inhibits vascular smooth muscle cell proliferation and migration by interfering with the expression and activity of proteases such as plasminogen activators. In an in vitro mitogenesis model, tissue-type plasminogen activator (tPA) mRNA and protein increase in baboon smooth muscle cells stimulated with fetal bovine serum or phorbol esters. Heparin inhibits smooth muscle cell proliferation and suppresses the induction of tPA mRNA and protein while it has little effect on the mRNA of urokinase-type plasminogen activator, plasminogen activator inhibitor type I, and a number of genes that are also modulated by serum and phorbol esters. The inhibitory effect on tPA mRNA is specific to heparin-like molecules and does not depend on the anticoagulation activity of heparin. The increase in tPA mRNA is due to increased transcription, which is suppressed by heparin. The induction of tPA by serum and phorbol esters is diminished by protein kinase C inhibitors such as H7 or staurosporine and by protein kinase C depletion. Since heparin suppresses the induction of the tPA gene by phorbol esters, these results suggest that heparin may interfere with the protein kinase C pathway.
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PMID:Heparin selectively inhibits the transcription of tissue-type plasminogen activator in primate arterial smooth muscle cells during mitogenesis. 131 Jun 87


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