Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.37 (neutrophil elastase)
 4,078 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To evaluate the effect of endotoxin on the fibrinolytic response, we administered Escherichia coli endotoxin (4 ng per kilogram of body weight) intravenously to 19 healthy volunteers and measured fibrinolytic proteins, protease inhibitors, neutrophil elastase, and von Willebrand factor in serial blood samples obtained over 24 hours. One hour after endotoxin administration, the level of tissue plasminogen activator (t-PA) antigen rose from 10 to 23 ng per milliliter, peaking at 52 ng per milliliter at three hours. The level of alpha 2-plasmin inhibitor-plasmin complexes increased sevenfold, peaking at three hours. Plasminogen-activator inhibitor-1 activity rose more slowly, from 7 U per milliliter to a maximum of 49 U per milliliter at five hours. The concentrations of neutrophil elastase and von Willebrand antigen were unchanged at one hour, increased approximately threefold by 3 hours, and remained elevated at 24 hours. None of these measures changed in a control group (n = 5) given intravenous saline instead of endotoxin. We studied t-PA functional activity in four subjects. The level of activity rose rapidly, from 1.2 ng per milliliter at base line to 8.3 ng per milliliter at one hour and 13.9 ng per milliliter at two hours; it was undetectable at three hours. This increase in plasminogen activator activity was abolished in vitro by incubation of t-PA with an antiserum specific for human t-PA, suggesting that t-PA may be directly responsible for plasmin generation in the response to endotoxin. We conclude from this study of healthy subjects that endotoxin activates the fibrinolytic system, beginning with release of t-PA in the blood within one hour. The early activation of plasmin by endotoxin may prevent thrombosis, and the increase in fibrinolysis is then offset by the release of plasminogen activator inhibitor.
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PMID:Promotion and subsequent inhibition of plasminogen activation after administration of intravenous endotoxin to normal subjects. 278 17

We have studied the distribution of the plasminogen activator inhibitor type 1 (PAI-1) in cultures of confluent human umbilical vein endothelial cells. Plasminogen activator inhibitor activity measured by the 125I-fibrin plate assay was detected in the cytosol (2.85 +/- 0.16 U), 100,000 g particulate fraction (1.26 +/- 0.30 U), and in the growth substratum (9.82 +/- 1.80 U). Characterization of the protein responsible for this activity by reverse fibrin autography, immunoprecipitation, and immunoblotting demonstrated that it had an Mr of 46,000 and was antigenically related to PAI-1. Only the active form of the inhibitor was found in all three fractions. Inhibitor in the cytosol and particulate fraction converted to the latent form during 37 degrees C incubation while the substratum inhibitor remained fully active. Extracellular PAI-1 was detected in the growth substratum before its appearance in conditioned medium and represented the major protein deposited beneath the cells. The inhibitor was only transiently localized in the substratum, disappearing within 6 h and concomitantly appearing in the culture medium. Incubation of isolated metabolically labeled substratum with tissue plasminogen activator (tPA) resulted in the appearance and release of an immunologically related inactive 44,000 Mr form as well as the tPA-PAI-1 complex (110,000 Mr). PAI-1 was also converted into its 44,000-Mr form and released by treatment of the substratum with human leukocyte elastase. The rapid deposition and predominance of PAI-1 in the underlying compartment of endothelial cells may explain how the basement membrane is protected from proteolytic degradation by plasmin-generating enzymes.
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PMID:Association of a plasminogen activator inhibitor (PAI-1) with the growth substratum and membrane of human endothelial cells. 312 34

The effect of tissue plasminogen activator (TPA) or urokinase on the specific binding of human Glu-plasminogen to fibrin I formed in plasma by clotting with Reptilase was studied using 125I-plasminogen and 131I-fibrinogen. In the absence of TPA, small amounts of plasminogen were bound to fibrin I. TPA induced binding of plasminogen to plasma fibrin I that was dependent upon the concentrations of TPA and plasminogen as well as upon the time of incubation. Plasminogen binding occurred in association with fibrin clot lysis and the formation in the clot supernatant of alpha 2-plasmin inhibitor-plasmin complexes. Urokinase also induced binding of plasminogen to plasma fibrin I that was concentration- and time-dependent. The molecular form of plasminogen bound to the fibrin I plasma clot was identified as Glu-plasminogen by dodecyl sulfate-polyacrylamide gel electrophoresis and by fast performance liquid chromatography. Further studies demonstrated that fibrin I formed from fibrinogen that had been progressively degraded by plasmin-bound Glu-plasminogen. The mole ratio of plasminogen bound increased with the time of plasmin digestion. Glu-plasminogen did not bind to fibrin I formed from fibrinogen progressively digested by human leukocyte elastase, thereby demonstrating the specificity of plasmin. These studies demonstrate that plasminogen activators regulate the binding of Glu-plasminogen to fibrin I by catalyzing plasmin-mediated modifications in the fibrin substrate.
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PMID:Tissue plasminogen activator and urokinase mediate the binding of Glu-plasminogen to plasma fibrin I. Evidence for new binding sites in plasmin-degraded fibrin I. 315 57

Plasminogen-binding human alpha 2-plasmin inhibitor is converted by human granulocyte elastase into its non-plasminogen-binding and finally into the inactive form of the inhibitor. This degradation of the plasmin inhibitor, described earlier as "spontaneously" occurring conversion, is shown in dodecyl sulfate polyacrylamide gel electrophoresis, in two-dimensional immunoelectrophoresis and by measuring the kinetics of plasmin inhibition. Experiments in the presence of normal human plasma required unphysiologically high concentrations of elastase to inactivate alpha 2-plasmin inhibitor, suggesting a role of elastase in this type of indirect fibrinolysis in a microenvironment only and not in systemic events.
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PMID:Alpha 2-plasmin inhibitor inactivation by human granulocyte elastase. 656 66

Human neutrophil elastase cleaves angiogenin at the Ile-29/Met-30 peptide bond to produce two major disulfide-linked fragments with apparent molecular weights of 10,000 and 4000, respectively. Elastase-cleaved angiogenin has slightly increased ribonucleolytic activity, but has lost its ability to undergo nuclear translocation in endothelial cells, a process essential for angiogenic activity. Cleavage appears to alter the cell-binding properties of angiogenin, despite the fact that it occurs some distance from the putative receptor-binding site, since the elastase-cleaved protein fails to compete with its native counterpart for nuclear translocation in endothelial cells. Plasminogen specifically accelerates elastase proteolysis of angiogenin. It does not enhance elastase activity toward ribonuclease A or the synthetic peptide substrate MeOSuc-Ala-Ala-Pro-Val-pNA. Plasminogen-accelerated inactivation of angiogenin by elastase might be a significant event in the process of angiogenin-induced angiogenesis since (i) angiogenin and plasminogen circulate in plasma at high concentrations, (ii) angiogenin, especially when bound to actin, activates tissue plasminogen activator to generate plasmin from plasminogen, and (iii) elastase cleaves plasminogen to produce angiostatin, a potent inhibitor of angiogenesis and metastasis. Interrelationships among angiogenin, plasminogen, plasminogen activators, elastase, and angiostatin may provide a sensitive regulatory system to balance angiogenesis and antiangiogenesis.
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PMID:Limited proteolysis of angiogenin by elastase is regulated by plasminogen. 933 Feb 25

Plasminogen, the pro-enzyme of plasmin, aids various processes essential for normal, acute wound healing, such as fibrinolysis and cell migration. We have investigated if plasminogen is available to perform these functions in chronic wounds such as venous leg ulcers. We report that plasminogen is degraded by fluid from venous leg ulcers to a number of fragments, including kringle domains 1-3, an angiostatin-related protein. The enzyme responsible was inhibited by the serine protease inhibitor phenyl-methylsulfonyl fluoride, but was not inhibited by alpha1-anti-trypsin, an inhibitor of neutrophil elastase, by alpha2-anti-plasmin, an inhibitor of plasmin, or by the matrix metalloprotease inhibitor 1,10 phenanthroline. Plasminogen degraded by wound fluid was a weaker substrate than intact plasminogen for plasmin generation by the keratinocyte cell line HaCaT. These results suggest that serine protease activity in leg ulcer fluid degrades plasminogen and support the hypothesis that keratinocyte migration may be impaired in leg ulcers because of a reduced availability of intact plasminogen for plasmin generation.
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PMID:Wound fluid from venous leg ulcers degrades plasminogen and reduces plasmin generation by keratinocytes. 985 30

Neutrophil elastase and cathepsin G are abundant intracellular neutrophil proteinases that have an important role in destroying ingested particles. However, when neutrophils degranulate, these proteinases are released and can cause irreparable damage by degrading host connective tissue proteins. Despite abundant endogenous inhibitors, these proteinases are protected from inhibition because of their ability to bind to anionic surfaces. Plasminogen activator inhibitor type-1 (PAI-1), which is not an inhibitor of these proteinases, possesses properties that could make it an effective inhibitor of neutrophil proteinases if its specificity could be redirected. PAI-1 efficiently inhibits surface-sequestered proteinases, and it efficiently mediates rapid cellular clearance of PAI-1-proteinase complexes. Therefore, we examined whether PAI-1 could be engineered to inhibit and clear neutrophil elastase and cathepsin G. By introducing specific mutations in the reactive center loop of wild-type PAI-1, we generated PAI-1 mutants that are effective inhibitors of both proteinases. Kinetic analysis shows that the inhibition of neutrophil proteinases by these PAI-1 mutants is not affected by the sequestration of neutrophil elastase and cathepsin G onto surfaces. In addition, complexes of these proteinases and PAI-1 mutants are endocytosed and degraded by lung epithelial cells more efficiently than either the neutrophil proteinases alone or in complex with their physiological inhibitors, alpha1-proteinase inhibitor and alpha1-antichymotrypsin. Finally, the PAI-1 mutants were more effective in reducing the neutrophil elastase and cathepsin G activities in an in vivo model of lung inflammation than were their physiological inhibitors.
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PMID:Mutants of plasminogen activator inhibitor-1 designed to inhibit neutrophil elastase and cathepsin G are more effective in vivo than their endogenous inhibitors. 1513 Nov 25

The overall conformation of plasminogen depends upon the presence of anions and molecules such as AHA (6-aminohexanoic acid) and BZ (benzamidine). The purpose of the present study was to determine the effect of conformation on the initial and secondary cleavages of plasminogen to generate active angiostatins. Plasminogen was digested with the physiologically relevant neutrophil elastase in one of the four Tris/acetate buffers: buffer alone or buffer plus NaCl, AHA or BZ. The initial cleavage of Glu1-plasminogen was much slower in the tight NaCl-induced alpha-conformation, fastest in the intermediate BZ-induced beta-conformation and intermediate both in the control and in the AHA-induced open gamma-conformation. Although the buffer system determined the relative amounts of the initial cleavage products, the same four cleavage sites were utilized under all conditions. A fifth major initial cleavage within the protease domain was observed in the presence of BZ. N-terminal peptide cleavage required for angiostatin formation occurred as either the initial or the secondary cleavage. Angiostatins were generated fastest in the presence of BZ and slowest in the presence of NaCl. Both the initial and secondary cleavages were affected by the modifying agents, indicating that they influence the conformation of both Glu-plasminogen and the initial cleavage products. The angiostatins produced under the different conditions inhibited proliferation of human umbilical-vein endothelial cells. These results suggest that plasminogen conversion into active angiostatins is dependent more on the specific conformation changes induced by the various modifying reagents rather than on the overall openness of the molecule.
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PMID:Specific conformational changes of plasminogen induced by chloride ions, 6-aminohexanoic acid and benzamidine, but not the overall openness of plasminogen regulate, production of biologically active angiostatins. 1609 50

Plasminogen activator-plasmin system is the central role for thrombus degradation. The system is finely tuned to allow healing of a blood vessel lesion without compromising the stability of the fibrin thrombus, and to localize fibrinolytic activity to the damaged area. There is a dynamic balance between fibrinolytic factors (plasminogen activators and plasmin) and inhibitory proteins (PAL-1, alpha2-plasmin inhibitor, and TAFIa). An alternative pathway for fibrinolysis that comprises leukocyte elastase and its interaction with the plasminogen activator-plasmin system has been suggested.
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PMID:[Plasminogen activation and regulation of fibrinolysis]. 2516 11