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)

Interaction of urokinase (UK) activated plasmin with tranexamic acid and alpha 2 plasmin inhibitor (alpha 2PI) was studied by using a chromogenic substrate (S-2251) and immunoelectrophoresis. Plasma was activated by UK (P + U) in the presence of tranexamic acid (P + U + t) or in the presence of thrombin (P + U + thr) and thrombin plus tranexamic acid (P + U + thr + t). These mixtures were incubated for 10, 20, and 30 min at 37 degrees C, then an aliquot of each mixture was added to S-2251, and incubated for 3 or 10 min at 37 degrees C. Hydrolysis of S-2251 after 3 min incubation was significant in the presence of tranexamic acid or clot formation, thus the presence of tranexamic acid or clot formation enhancing the UK activation of plasminogen in both plasma and clot. Hydrolysis of S-2251 after 10 min incubation was higher in the presence of tranexamic acid than in its absence or clot formation without tranexamic acid. Tranexamic acid seems to be more effective in enhancement of activation of plasminogen by UK than clot formation. Plasmin formed by UK was coexistent with alpha 2PI in the plasma in contrast to a purified system in which alpha 2PI formed a complex with plasmin instantaneously. In an even purified system, clot formation and the presence of tranexamic acid protected plasmin from its inactivation by alpha 2PI to some extent.
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PMID:Interaction of plasmin with tranexamic acid and alpha 2 plasmin inhibitor in the plasma and clot. 644 83

The enzymic properties of urokinase (EC 3.4.21.31) were studied. The kinetic parameters of hydrolysis of 5-oxo-Pro-Gly-Arg-NA were determined in the pH range 5-9, at 25 degrees C and 37 degrees C. The reaction is affected by only one ionizing group of urokinase with pK 7.15 (25 degrees C) and pK 6.82 (37 degrees C). The results indicate that 5-oxo-Pro-Gly-Arg-NA is a good model substrate for studies of the conversion of plasminogen to plasmin. The Km values of the urokinase-catalysed hydrolysis of plasminogen and 5-oxo-Pro-Gly-Arg-NA are of the same order of magnitude. Plasmin catalyses the hydrolysis of 5-oxo-Pro-Gly-Arg-NA, but the Km value is several hundred times that of urokinase. Urokinase is shown not to react with good plasmin substrates, such as Bz-Arg-OEt and D-Val-Leu-Lys-NA, but is linearly competitively inhibited by 6-amino-hexanoic acid and trans-4-aminomethylcyclohexane-1-carboxylic acid.
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PMID:Kinetic studies of urokinase-catalysed hydrolysis of 5-oxo-L-prolylglycyl-L-arginine 4-nitroanilide. 644 58

Plasmin, generated by the interaction of urokinase with plasminogen, degraded the apoprotein B moiety of human low density lipoprotein to yield distinct high moleculr weight intermediates under conditions where only a small fraction (less than 3%) of the protein was hydrolyzed to trichloroacetic acid-soluble products. The molecular weights of these intermediates were between 60 000 and 200 000 as estimated by SDS-polyacrylamide electrophoresis. Trypsin treatment yielded fragments of similar size to those obtained with plasmin. When enzyme-treated low density lipoproteins were added to bovine aortic smooth muscle cells in culture, the receptor-binding, and rates of internalization and degradation were no different from those obtained in the case of native low density lipoproteins.
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PMID:Plasmin-treated low density lipoproteins: polypeptide analyses and metabolism by cultured smooth muscle cells. 645 2

A urokinase-activated plasmin (UK-plasmin) preparation was assayed against the International Reference Preparation for Plasmin (IRP-plasmin) using caseinolytic, fibrinolytic, fibrinogenolytic and chromogenic assay methods. The relative potency (using multi-dose bioassays) was estimated by the fibrinolytic method to be about twice that obtained by the caseinolytic, fibrinolytic and chromogenic assay methods. It was found that the UK-plasmin binds to fibrin to a greater extent than does the IRP-plasmin and this is advanced as an explanation for the discrepancy between assay methods. This difference in the binding of the two plasmins to fibrin may mean that it will be difficult to compare the fibrinolytic activities of various plasmin preparations. It is also shown that, during thermal degradation, the IRP-plasmin loses fibrinolytic activity more rapidly than amidolytic activity.
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PMID:Plasmin potency estimates: influence of the substrate used in assay. 645 87

Plasmin-mediated extracellular proteolysis has been implicated in the degradation of bone in normal and pathological conditions. Normal and malignant osteoblasts can produce both tissue-type plasminogen activator (t-PA) and urokinase-type plasminogen activator (u-PA). We have used the osteosarcoma cell line MG63 to address the question of whether the enhanced bone turnover in osteosarcomas is mediated by t-PA or by u-PAA and to study the effect of the cytokine interleukin-1 alpha (IL-1 alpha), known to influence bone degradation, on the plasminogen activator production and extracellular matrix degradation in malignant osteoblastic cells. Furthermore, the effect of IL-1 alpha on the synthesis of matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) was analyzed. u-PA production by MG63 was high (approximately 180 ng/10(6) cells/24 h). Also t-PA and PAI-1 production was observed. u-PA production was rapidly increased in MG63 by IL-1 alpha (10 ng/ml), whereas an effect on t-PA production was only found after a prolonged incubation and hardly any effect of IL-1 alpha on PAI-1 production was observed. mRNA analysis revealed similar effects. u-PA receptor (u-PAR) mRNA was detectable in MG63 cells and could be increased by IL-1 alpha after 24 h. In MG63, u-PA-mediated extracellular matrix degradation was detectable, and IL-1 alpha increased the u-PA-mediated matrix degradation (approximately 2-fold). Under control conditions in MG63, only MMP-2, TIMP-1, and TIMP-2 mRNA could be observed. After the addition of IL-1 alpha, a very rapid increase in MMP-1 and MMP-3 mRNA could be observed as well as a moderate increase in TIMP-1 mRNA. The presence of MMP-2 was demonstrated by gelatin zymography. These results show that IL-1 alpha can stimulate u-PA production and can regulate extracellular proteolytic activity mainly via u-PA induction in the MG63 osteosarcoma cell line. Furthermore, IL-1 alpha has a strong stimulating effect on the production of MMP-1 and MMP-3. These findings suggest that u-PA and possibly MMP-1 and MMP-3 play an important role in the process of bone turnover in osteosarcomas.
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PMID:Regulation of plasminogen activation, matrix metalloproteinases and urokinase-type plasminogen activator-mediated extracellular matrix degradation in human osteosarcoma cell line MG63 by interleukin-1 alpha. 750 10

Acantholysis is a feature of disorders such as Hailey-Hailey disease and Darier's disease. Immunocytochemical studies have shown internalization of desmosomal components after acantholysis. Basal cytokeratins show suprabasal expression in lesional Darier's disease. The exact mechanisms of acantholysis are still unclear. Cantharidin induces blistering, with suprabasal keratinocyte acantholysis, possibly by protease activation. Plasmin has been implicated in the pathogenesis of acantholysis in Darier's disease and Hailey-Hailey disease. We examined the distribution of desmosomal components, proteases and cytokeratins in cantharidin blisters, to compare them with those previously found in Darier's disease and Hailey-Hailey disease. Two drops of cantharidin collodion were applied to the skin of five normal volunteers. A 4-mm punch biopsy of the blister was taken, and snap frozen. Sections were stained with antibodies to desmosomal proteins (dp) 1/2, dp 3, desmosomal glycoproteins (dg) 1, 2/3, extracellular carbohydrate residues, using the lectins peanut agglutinin (PNA) and soybean agglutinin (SBA), proteases and cytokeratins. Acantholytic cells were stained diffusely with dp1/2; there was markedly reduced or absent peripheral staining for dp3, dg1, dg2/3, PNA and SBA. There was no clumping of stain. Plasminogen, fibrinogen and urokinase were expressed in some acantholytic cells. Basal keratin markers were expressed suprabasally in acantholytic cells. These results are similar to those previously obtained in Darier's disease, but different from the staining obtained in Hailey-Hailey disease. Extracellular glycosylated portions of adhesion molecules may be lost after acantholysis, perhaps as a result of conformational changes, internalization of extracellular domains, or proteolysis. The changes in the expression of plasminogen, fibrinogen, urokinase and cytokeratins in acantholytic cells in cantharidin-induced blisters are, as in Darier's disease and Hailey-Hailey disease, probably secondary to acantholysis, and changes in the shape of cells. We conclude that cantharidin blisters may be a useful model for the study of acantholysis in Darier's disease.
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PMID:Cantharidin-induced acantholysis: adhesion molecules, proteases, and related proteins. 751 Jan 21

Plasmin (Pm) is a broad action serine protease implicated in numerous physiological functions. In bone, Pm may play a role in growth, resorption, metastasis, and the activation of growth factors. The various components of the Pm system are known to bind and function on the cell surface of various cell types, but no pertinent data are available describing membrane-bound Pm or its zymogen, plasminogen (Pg), in either normal or neoplastic bone cells. We report here that Pg binds to the surface of the human osteosarcoma cell line MG-63 and is activated to Pm by endogenous urokinase plasminogen activator (uPA). These conclusions are based on experiments utilizing radiolabeled compounds and a cell surface proteolytic assay measuring amidolytic activity of Pm. 125I-Pg binding to cells was time dependent, saturable, reversible, and specific. Binding was characterized by a relatively low affinity (Kd approximately 0.9 microM) and a high capacity (approximately 7.5 x 10(6) sites/cell). The binding of 125I-Pg was associated with lysine binding sites of the plasminogen molecule. Activation of 125I-Pg to 125I-Pm occurred on the cell surface and was dependent upon cell bound uPA, as determined by inhibitory antibodies. Binding of Pg to MG-63 monolayers represented approximately 80% bound specifically to the cell surface and the remainder to the surrounding extra-cellular matrix. Either co-incubation with uPA or pre-incubation with Pm resulted in increased 125I-Pg binding to osteosarcoma cells. Cell surface Pm proteolytic activity was confirmed by an amidolytic chromogenic assay. Both Pm and Pg bound to cells with Pg being activated by endogenous uPA. Plasmin activated on the cell surface was partially protected from inhibition by alpha 2-antiPm (requiring Pm lysine binding site interaction) but inhibited by aprotinin, (interacting directly with the Pm catalytic site). Resistance of cell bound Pm to alpha 2-antiPm inhibition suggests that cell surface proteolysis can occur in the presence of a soluble Pm inhibitor known to exist in the extracellular space. Based on these results, we speculate that the various bone physiological processes implicating Pm may occur at or near the bone cell surface.
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PMID:Binding and activation of plasminogen on the surface of osteosarcoma cells. 751 Nov 44

Endothelial cell-derived proteases can be classified according to their physiological role. The proteases involved in extracellular matrix degradation are important in endothelial cell migration and thereby in angiogenesis. They include the urokinase-type plasminogen activator (uPA) and the metalloproteases, collagenases, gelatinases and stromelysin. uPA secreted from endothelial cells remains associated with the cell membrane, on specific receptors localized in the vicinity of the receptors for plasminogen. This favours the local activation of plasminogen into plasmin. Plasmin, generated on the cell surface, is fully active as it is not inhibited by alpha 2-antiplasmin. Plasmin acts directly by degrading some components of the extracellular matrix and indirectly by activating the prometalloproteases. Secretion of PAI by migrating cells is generally stimulated by the same factors that induce uPA secretion, limiting the degradation of the matrix to the pericellular path. The degradation of the fibrin clot involves the tissue-type plasminogen activator tPA, which like the uPA activates plasminogen to plasmin. This system is also regulated by two different mechanisms. On the one hand, fibrin itself favours its own degradation by formation of a ternary complex, fibrin-plasminogen-tPA, in which the affinity of tPA for plasminogen is markedly increased, as compared to the affinity of unbound tPA. In addition, plasmin generated on the clot is protected from inhibition by alpha 2-antiplasmin. On the other hand, as for uPA, tPA is inhibited by PAI-1. The importance of the regulation of this system is illustrated by the thrombotic risk observed when there is either a decrease in tPA or an increase in PAI-1, and inversely by haemorrhages in the case of increase in tPA.
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PMID:Endothelial cell proteases: physiological role and regulation. 751 36

The activation of plasminogen by macrophage is regulated by their expression of receptors for urokinase and plasmin(ogen). In these studies we have examined plasmin(ogen) binding to adherent human THP-1 macrophage. Plasmin bound to the THP-1 cells in a time- and dose-dependent manner (Kd 15.8 +/- 6.2 nM; Bmax 1.4 +/- 0.3 x 10(6)/cell). The lysine analog epsilon-aminocaproic acid competitively inhibited plasmin binding. The fraction of membrane-bound plasmin, however, became increasingly resistant to displacement with epsilon-aminocaproic acid. Over a 24-h period, membrane-bound plasmin activity fell 80% despite the presence of catalytically active plasmin in the incubation media. The loss of receptor-bound plasmin activity was not due to proteolytic alterations of its receptor since 125I-Lys-plasminogen bound to THP-1 cells pretreated with plasmin with similar affinity as to untreated cells. Following a 24-h incubation of 125I-Lys-plasminogen or 125I-plasmin with THP-1 cells, several degradative fragments were apparent in their conditioned media. The smaller degradative fragments (28 and 36 kDa) lacked cell binding activity and were demonstrated to be active by casein-zymography. A 48-kDa fragment bound to cells in a lysine-dependent manner but was not active. In contrast, phenylmethylsulfonyl fluoride-inactivated 125I-plasmin retained its binding activity over 24 h, and degradative fragments were not present in the conditioned media. The binding of 125I-Lys-plasmin(ogen) to THP-1 cells was also examined in the presence of excess alpha 2 plasmin inhibitor. Despite the absence of fluid-phase plasmin activity, membrane-bound 125I-Lys-plasmin(ogen) decreased over 24 h. At 24 h a radiolabeled 48-kDa fragment was observed in the conditioned media and together with 125I-Lys-plasmin(ogen) was bound to cells. Unlike 125I-Lys-plasmin, the 48-kDa fragment did not form a complex with alpha 2 plasmin inhibitor. Thus, autoproteolysis of receptor-bound plasmin results in fragments with truncated physiologic properties that possess either cell binding or catalytic activities. We propose that autoproteolysis is a mechanism for regulating membrane-bound plasmin activity.
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PMID:Regulation of macrophage receptor-bound plasmin by autoproteolysis. 752 19

At cellular surfaces, urokinase-type plasminogen activator (uPA) is bound to a specific receptor (uPA-R). When bound to this receptor, uPA activates plasminogen, which is derived from plasma or the interstitial fluids. Thus, plasmin is provided for proteolysis of pericellular proteinaceous substrates. Here we demonstrate by immunocytology and laser scan microscopy that in the human keratinocyte cell line HaCaT uPA-R and uPA are localized together with the integrin alpha v beta 5 in focal contacts. Via the integrin alpha v beta 5, HaCaT cells adhere to vitronectin in a RGD-dependent manner. Plasmin interfered with the alpha v beta 5-mediated keratinocyte adhesion to vitronectin, most likely via cleavage of vitronectin and destruction of its cell binding function. Our findings demonstrate that plasmin, when generated by the uPA-dependent cell surface-associated pathway of plasminogen activation, can abrogate the cell-binding function of vitronectin and can thus disturb the adhesive interaction with this matrix molecule. In focal contacts molecules are assembled that are crucial for adhesion to vitronectin (i.e., the integrin alpha v beta 5), as well as for the generation of plasmin (i.e., uPA-R and uPA), which can negatively influence the binding interaction. We suggest that the plasmin-mediated abrogation of the interaction between the integrin alpha v beta 5 and vitronectin is a pathway of negative regulation; the codistribution of uPA-R/uPA and alpha v beta 5 in focal contacts may restrict this process to areas of cell/matrix contact.
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PMID:Plasmin abrogates alpha v beta 5-mediated adhesion of a human keratinocyte cell line (HaCaT) to vitronectin. 755 34


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