Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.7 (plasmin)
 9,023 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The mechanism of the activation of plasminogen by recombinant pro-urokinase (Rec-pro-UK), obtained by expression of the human pro-urokinase gene in Escherichia coli, was investigated in purified systems. In mixtures of Rec-pro-UK and plasminogen, both active urokinase and plasmin are quickly generated. Addition of plasmin inhibitors (aprotinin or alpha 2-antiplasmin) abolishes the conversion of Rec-pro-UK to urokinase but not the activation of plasminogen to plasmin, suggesting that Rec-pro-UK activates plasminogen directly. Human plasma competitively inhibits the activation of plasminogen by pro-urokinase with a Ki of 0.2% (v/v). This explains the relative stability of Rec-pro-UK in plasma and the lack of activation of the plasma fibrinolytic system in the absence of fibrin. The competitive inhibition by plasma is abolished by the addition of CNBr-digested fibrinogen although Rec-pro-UK has no specific affinity for fibrin. These findings suggest that the fibrin specificity of the activation of plasminogen by pro-urokinase is due to neutralization by fibrin of the competitive inhibition exerted by plasma and not to fibrin-enhanced activation of plasminogen.
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PMID:Activation of plasminogen by pro-urokinase. I. Mechanism. 293 28

The effect of a new aspirin derivative, aspirin-isopropylantipyrine (AIA), with very little gastric ulcerogenic activity and very slight acute toxicity and with analgesic, antipyretic anti-inflammatory, and platelet aggregation inhibitory activities was evaluated in vitro and ex vivo and compared with those of aspirin and isopropylantipyrine (IA). In vitro, AIA, aspirin and IA (50-200 microM) caused concentration-dependent inhibition of collagen-induced aggregation in rabbit platelets although AIA was several-fold more active than the others Arachidonic acid-induced aggregation was inhibited by all three agents (200 microM) in the following magnitude; IA greater than aspirin greater than AIA. Three agents did not influence primary ADP-induced aggregation. The in vitro effects on the release-inducing aggregants were confirmed by ex vivo experiments in rats. These demonstrated that AIA and aspirin (50 mg/kg) exhibited almost identical inhibitory potencies in the extent and the rate of collagen-induced aggregation 4 h after subcutaneous injection. AIA was still effective 24 h after administration as well as aspirin. IA was less effective, differing from the results in vitro. AIA had no effect on plasmin activity and blood flow through the common carotid artery. AIA (1 mM) maintained spreading and beating of myocardial cells in a serum-free culture. As special toxicity trials on AIA mutagenecity tests were made by the Rec-assay with Bacillus subtilis, by the plate culture with Escherichia coli, and by the Ames system with Salmonella typhimurium. AIA was found to have no mutagenic effect under any of those methods and to have no effect on the mutagenic action of 3, 4-benzopyrene under the liver microsome test using the Ames system.
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PMID:Studies on aspirin derivatives with very little side effect. II. Potent platelet anti-aggregant activity and no mutagenicity of aspirin-isopropylantipyrine (AIA). 645 43

Urokinase-type plasminogen activator (uPA) binds with high affinity to a specific cell surface glycosyl phosphatidyl-inositol (GPI)-anchored receptor, the urokinase receptor (uPAR). Pro-uPA, the enzymatically inactive single-chain form of uPA after having been activated by certain proteases, converts plasminogen into plasmin. This activation of pro-uPA to enzymatically active uPA can be prevented by the action of thrombin on pro-uPA. This inactivation process is accelerated in the presence of thrombomodulin (TM). The present study investigated whether pro-uPA bound to uPAR is still susceptible to inactivation by thrombin in the presence or absence of TM. A truncated soluble form of the uPAR lacking the GPI-anchor was cloned and expressed in CHO-cells (rec-uPAR277). Rec-uPAR277 efficiently inhibited the thrombin-mediated inactivation of pro-uPA up to 90% in a concentration dependent manner. The protective effect of rec-uPAR277 was far less pronounced when thrombin was complexed with TM. Enzyme kinetic experiments with varying concentrations of pro-uPA showed that in the presence of TM the catalytic efficiency (kcat/Km) of thrombin-mediated inactivation raised from 0.010 microM-1 s-1 to 0.50 microM-1 s-1 corresponding to a fifty-fold increase. In the presence of rec-uPAR277, however, the catalytic efficiency dropped by 4.1-fold (0.5 microM-1 s-1 to 0.122 microM-1 s-1). The inactivation kinetics of pro-uPA by thrombin (no TM added) in the presence of an excess of rec-uPAR277 could not be determined since virtually no inactivation occurred. Our data suggest that pro-uPA once bound to uPAR, is significantly protected from inactivation by thrombin.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Inactivation of receptor-bound pro-urokinase-type plasminogen activator (pro-uPA) by thrombin and thrombin/thrombomodulin complex. 784 Sep 2

An experimental disseminated intravascular coagulation (DIC) was induced in female CD rats by the intravenous administration of living bacteria (9.5 x 10(7) cfu Klebsiella pneumoniae), sublethal (5 mg/kg) or lethal (50 mg/kg) lipopolysaccharide (LPS), or tissue factor (1.5 micrograms/kg i.v. bolus or 0.4 micrograms/kg x hr i.v. infusion). We used a new fibrin monomer (FM) assay to follow the course of DIC. FM were detected by their ability to stimulate the tissue-type (t-PA) plasminogen activator dependent conversion of plasminogen to plasmin by a chromogenic assay. Miniplasminogen was used instead of plasminogen to avoid interference of the assay by alpha 2-antiplasmin. As a marker of DIC, elevated levels of FM were observed with all DIC-inducing agents (plasma levels were up to 90 micrograms/ml). The kinetics of FM formation were similar to the course of thrombin-antithrombin III (TAT) levels (maximal plasma levels 70 ng/ml); however, in the bacterial infection group, both parameters rose after a lag phase of about 1 hr. A 4 hr infusion of the highly specific thrombin inhibitor recombinant (rec.) hirudin (0.125 mg/kg x hr) resulted in a decrease of FM levels from 89.2 +/- 14.4 micrograms/ml in the LPS group (n = 10) to 27.4 +/- 11.2 micrograms/ml in the rec. hirudin group (n = 10; P < 0.001). The respective values for TAT levels were 73.1 +/- 19.7 micrograms/ml in the LPS group and 52.7 +/- 15.7 ng/ml in the rec. hirudin group (P < 0.001). Other coagulation parameters, such as platelets, fibrinogen, and fibrin(ogen) degradation products, were ameliorated accordingly.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Formation of fibrin monomers in experimental disseminated intravascular coagulation and its inhibition by recombinant hirudin. 805 64

Urokinase-type plasminogen activator (uPA) activation of plasminogen is an important mediator of cell migration in many cell types. In the developing avian heart, uPA has been implicated as a mediator of atrioventricular (AV) cushion cell migration; however, the role of the plasminogen/plasmin system has not been examined. The purpose of this study was to test the hypothesis that uPA conversion of plasminogen to plasmin mediates AV cushion cell migration in vitro. Stage 17/18 chicken atrioventricular tissue lysates converted plasminogen into plasmin through uPA activity but no tissue-type plasminogen activator activity was detected. Zymograms on living cultured AV explants also activated plasminogen producing plasmin that degraded extracellular protein. The migratory capacity of cushion cells was assessed in the presence or absence of various test reagents known to alter the plasminogen/plasmin system. Addition of either human or chicken plasminogen or aprotinin (an inhibitor of plasmin) had no effect on cell migration. However, an anti-catalytic uPA antibody that blocked AV uPA activity, significantly decreased cell migration at all concentrations tested. These results showed that uPA mediated a portion of cushion cell migration in vitro. Although AV segments activated plasminogen and degraded extracellular proteins, uPA's functional role in cushion cell migration did not involve the plasminogen/plasmin system.
Anat Rec 1999 11 01
PMID:Urokinase regulates embryonic cardiac cushion cell migration without converting plasminogen. 1052 85

Although many studies have focused on blood vessel development and new blood vessel formation associated with disease processes, the question of how endothelial cells (ECs) assemble into tubes in three dimensions (i.e., EC morphogenesis) remains unanswered. EC morphogenesis is particularly dependent on a signaling axis involving the extracellular matrix (ECM), integrins, and the cytoskeleton, which regulates EC shape changes and signals the pathways necessary for tube formation. Recent studies reveal that genes regulating this matrix-integrin-cytoskeletal (MIC) signaling axis are differentially expressed during EC morphogenesis. The Rho GTPases represent an important class of molecules involved in these events. Cdc42 and Rac1 are required for the process of EC intracellular vacuole formation and coalescence that regulates EC lumen formation in three-dimensional (3D) extracellular matrices, while RhoA appears to stabilize capillary tube networks. Once EC tube networks are established, supporting cells, such as pericytes, are recruited to further stabilize these networks, perhaps by regulating EC basement membrane matrix assembly. Furthermore, we consider recent work showing that EC morphogenesis is balanced by a tendency for newly formed tubes to regress. This morphogenesis-regression balance is controlled by differential gene expression of such molecules as VEGF, angiopoietin-2, and PAI-1, as well as a plasmin- and matrix metalloproteinase-dependent mechanism that induces tube regression through degradation of ECM scaffolds that support EC-lined tubes. It is our hope that this review will stimulate increased interest and effort focused on the basic mechanisms regulating capillary tube formation and regression in 3D extracellular matrices.
Anat Rec 2002 Nov 01
PMID:Molecular basis of endothelial cell morphogenesis in three-dimensional extracellular matrices. 1238 23