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)

The effect of surface-bound immune complexes on the secretion of neutral proteases by human peripheral monocytes was examined. Monocytes cultured on 125I-fibrin secreted plasminogen activator in a continuous fashion. Monocytes incubated on 125I-fibrin with surface-bound immune complexes displayed a burst of plasminogen-independent fibrinolytic activity, whereas no release of plasminogen activator was observed through 21 h. The plasminogen-independent fibrinolytic enzymes were derived from monocytes and not from lymphocytes or contaminating polymorphonuclear neutrophils. The effects of various protease inhibitors on the secretion of plasminogen-dependent and independent enzymes were determined. Chymostatin selectively inhibited the monocyte-derived plasminogen activators. Similar effects of chymostatin were observed on human urokinase in the absence of cells. The predominant protease producing plasminogen-independent fibrinolysis exhibited responses to inhibitors characteristic of leukocyte elastase. When monocytes were cultured on 125I-fibrin with adherent immune complexes approximately equal to 40% of the solubilized radioactivity represented deiodination and not proteolysis. It was concluded that culture of human monocytes on surface-bound immune complexes stimulates the secretion of plasminogen-independent fibrinolytic proteases, primarily elastase, and of deiodinating enzymes. Under these conditions, plasminogen activator secretion is inhibited. Neutral proteases secreted from newly recruited monocytes may contribute to tissue injury in human diseases characterized by the presence of adherent immune complexes.
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PMID:Neutral protease secretion by human monocytes. Effect of surface-bound immune complexes. 42 65

The subepidermal blistering skin disease bullous pemphigoid is associated with the deposition of specific autoantibodies and activated complement at the epidermal basement membrane zone of lesional skin. Subepidermal blistering is thought to depend on proteolytic enzymes, in particular on plasmin. A possible interrelation is proposed between the initiating immune reaction and the plasminogen activator system. Complement-induced chemotaxis of PMN may induce PMN infiltration. PMN-derived reactive oxygen species would interfere with the plasminogen activator inhibitors. Lysosomal elastase may degrade alpha 2-antiplasmin. At the same time, urokinase-type plasminogen activator is stimulated in tissue constituent cells and plasmin activity increases locally. The plasmin/antiplasmin equilibrium is disturbed and excess plasmin, then, may cause the degradation of extracellular proteinaceous structures of the epidermo/dermal junction. Epidermo/dermal dyshesion and subepidermal blister formation ensues. The plasminogen activator system is seen as a part within the wide array of effector systems that may be operative upon stimulation by an initial immunological event.
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PMID:Complement and plasminogen: pathways in inflammation. 152 63

Leukocyte elastase and leukocyte cathepsin G degrade porcine plasminogen primarily by hydrolysis of the A447-I448 bond between kringle4 and kringle5. The rate of formation of des-kringle1-4-plasminogen is faster with elastase (k"obs greater than 10(5) mol-1 s-1) than with cathepsin G (kobs less than 300 mol-1 s-1). In contrast to elastase, leukocyte cathepsin G does not inactivate alpha 2-antiplasmin. Consequently, plasminogen activation by urokinase in the presence of alpha 2-antiplasmin is elastase-dependent, but cathepsin G does not overcome the action of alpha 2-antiplasmin. The rate-enhancing effect of fibrin(ogen) fragments in plasminogen activation by tissue-type plasminogen activator is also disabled efficiently by these proteases. It is concluded that enhancement of plasmin expression by neutrophil proteases is accounted for primarily by the action of elastase.
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PMID:Neutrophil proteases in plasminogen activation. 171 63

Pro-Val pseudo dipeptides incorporating protio and halo enol lactones were tested for inhibitory activity against the serine proteases human leukocyte elastase (HLE), porcine pancreatic elastase, alpha-chymotrypsin, trypsin, thrombin, and urokinase. The protio enol lactones 1a-c were found to be HLE substrates but were poor alternate substrate inhibitors. The bromo enol lactone trans isomer 2a was found to be a very effective inhibitor of HLE and chymotrypsin, as shown by the binding constants (KI), acylation rates (ka), inactivation rates, and partition ratios determined for each enzyme. This inhibitor shows better specificity toward its target enzyme HLE than monosubstituted halo enol lactones; we attribute this to a pseudo dipeptide acyl enzyme whose structure is similar to that adopted by good peptide substrates of HLE. Inactivation of chymotrypsin by the bromo enol lactone 2a is permanent, but inactivation of HLE is partially recoverable upon treatment with the nucleophile hydrazine, indicating that lactone 2a produces two species of inactivated HLE. The more stable of these species could be the result of alkylation of His-57 by the electrophilic bromomethyl ketone revealed in the acyl enzyme, and the less stable, hydrazine-reactivatable species could be the result of alkylation of Asp-102 or the hydrolysis of the bromomethyl ketone group in the initially formed acyl enzyme to form a new, more stable acyl enzyme.
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PMID:Proline-valine pseudo peptide enol lactones. Effective and selective inhibitors of chymotrypsin and human leukocyte elastase. 198 87

Senile plaques, often surrounded by abnormally grown neurites, are characteristic of Alzheimer's diseased brain. The core of the plaque is mainly composed of amyloid beta protein (beta-AP), two of whose three precursors (APP) have serine proteinase inhibitor regions (APPI). APPI derivatives containing 60, 72 or 88 amino-acid fragments (APPI-60, APPI-72 and APPI-88, respectively) of the longest APP were produced in COS-1 cell culture medium, with the APPI cDNA ligated to the signal sequence of tissue plasminogen activator. The secreted APPIs were purified by sequential acetone precipitation followed by affinity chromatography using immobilized trypsin. These three APPIs and O-glycosylation-site-mutated APPI showed similar inhibitory activity against trypsin, chymotrypsin and plasmin. The purified APPI-72 was found to inhibit trypsin (Ki = 1.1 x 10(-10) M) and chymotrypsin (Ki = 5.8 x 10(-9) M) most strongly, and to inhibit leukocyte elastase (Ki = 7.9 x 10(-7) M) and several blood coagulation proteinases (Ki = 0.46-12 x 10(-7) M), but not urokinase or thrombin. The observed inhibition pattern was quite different from that of protease nexin I, one of serine proteinase inhibitors possessing neurite outgrowth activity. This suggests that the physiological roles of APPI are different from those of protease nexin I, and that APPI could not cause aberrant growth of neurite into the plaque. The presence of APPI having strong inhibitory activity in the brain might lead to the formation of amyloid deposits by preventing complete degradation of APPs.
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PMID:Enzyme specificity of proteinase inhibitor region in amyloid precursor protein of Alzheimer's disease: different properties compared with protease nexin I. 218 Apr 85

The [Arg15,Glu52]aprotinin gene has been constructed from a synthetic [Glu52]-aprotinin gene via an exchange of the appropriate DNA cassette. The gene has been fused to the N-terminal part of the bacteriophage MS-2 polymerase and expressed in a temperature inducible E. coli expression system. The produced fusion protein is deposited as inclusion bodies. Pure and functionally active [Arg15,Glu52]aprotinin has been obtained after cleavage of the purified fusion protein and renaturation of the aprotinin homologue. Recombinant [Arg15,Glu52]aprotinin shows good inhibition of human anionic and cationic trypsin (Ki less than or equal to 10(-11)M) and of human plasma kallikrein (Ki = 3.2 x 10(-10)M). The inhibition constants for human plasmin are Ki = 1.3 x 10(-10)M and for human urinary kallikrein Ki = 10(-11)M. No inhibition was found with the human proteinases thrombin, coagulation factor Xa, urokinase, tissue plasminogen activator, cathepsin G, leukocyte elastase and pancreatic elastase.
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PMID:Expression, isolation and characterization of recombinant [Arg15,Glu52]aprotinin. 246 33

In reaction mixtures containing Glu-plasminogen, alpha 2-antiplasmin, and tissue plasminogen activator or urokinase, either pancreatic or leukocyte elastase enhances the rate of plasminogen activation by 2 or more orders of magnitude. This effect is the consequence of several reactions. (a) In concentrations on the order of 100 nM, elastase degrades plasminogen within 10 min to yield des-kringle1-4-plasminogen (mini-plasminogen), which is 10-fold more efficient than Glu-plasminogen as a substrate for plasminogen activators. Des-kringle1-4-plasminogen is insensitive to cofactor activities of fibrin(ogen) fragments or an endothelial cell cofactor. (b) Des-kringle1-4-plasmin is one-tenth as sensitive as plasmin to inhibition by alpha 2-antiplasmin: k" = 10(6) M-1 s-1 versus 10(7) M-1 s-1. (c) alpha 2-Antiplasmin is disabled efficiently by elastase, with a k" of 20,000 M-1 s-1. The elastase-dependent reactions are not influenced by 6-aminohexanoate. In diluted (10-fold) blood plasma, the capacity of endogenous inhibitors to block plasmin expression is suppressed by 30 microM elastase. It is proposed that elastases provide an alternative pathway for Glu-plasminogen activation and a mechanism for controlling initiation of fibrinolysis by urokinase-type plasminogen activators.
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PMID:An elastase-dependent pathway of plasminogen activation. 250 79

Thrombospondin (TSP) is a multifunctional platelet alpha-granule and extracellular matrix glycoprotein that binds specifically to plasminogen (Plg) via that protein's lysine-binding site and modulates activation by tissue activator (TPA). In this study we report that the plasminogen activators, TPA and urokinase, greatly influence the binding of Plg to TSP. Using an enzyme-linked immunosorbent assay and a TSP-Sepharose affinity bead-binding assay we have found that Plg-TSP complex formation was markedly enhanced (up to 5-fold) when catalytic concentrations of Plg activators were included in the reaction mixtures. The enhancement was dependent upon the generation of small amounts of active plasmin and was duplicated by pretreatment of the immobilized TSP with plasmin prior to addition of the Plg. The enhancement effect was associated with selective proteolysis of the immobilized TSP. Purified Lys-Plg (the plasmin modified form of native Glu-Plg) bound to TSP to a greater extent than Glu-Plg, and binding of both forms was augmented by Plg activators. The apparent KD values of complex formation were unchanged in the presence of Plg activators suggesting that the enhancement effect was due to the generation of additional binding sites. The increased amount of bound Plg was demonstrated to result in a similar increase in the amount of plasmin generated from the complexes by TPA. Plg activators did not influence binding of Plg to histidine-rich glycoprotein or of histidine-rich glycoprotein to TSP, demonstrating specificity. In addition when TSP was treated with other proteases (human thrombin or human leukocyte elastase) no augmentation of Plg binding was seen. Thus, the initial production of small amounts of plasmin from Plg immobilized on TSP in fibrin-free microenvironments could generate a positive feedback loop by enzymatically modifying both TSP and Plg, resulting in an increase in TSP-Plg complex formation leading to the localized production of substantially more plasmin.
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PMID:Tissue plasminogen activator and urokinase enhance the binding of plasminogen to thrombospondin. 294 36

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

Human lumbar disc tissue when extracted with 4M GuHCl and subjected to dissociative CsCl density gradient ultracentrifugation yielded trypsin inhibitor activity in the low bouyant density fractions (rho less than or equal to 1.38 g/ml). Disc proteoglycans sedimented in the high bouyant density fractions (rho greater than or equal to 1.5 g/ml). Sephadex G75F gel filtration of the low bouyant density protein fractions afforded a major low molecular weight (Kav = 0.5) trypsin inhibitor pool which was further purified by trypsin affinity chromatography. This latter step facilitated separation of the trypsin inhibitors from neutral proteinase activity also present. The trypsin inhibitor fraction so isolated was shown to possess potent inhibitory activity against a range of human serine proteinases including leukocyte elastase and cathepsin G, urokinase, kallikrein, plasmin and thrombin. Significantly this serine proteinase inhibitor preparation effectively prevented degradation of proteoglycans by a neutral proteinase also isolated from the human intervertebral disc.
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PMID:Low molecular weight serine proteinase inhibitors of the human intervertebral disc. 348 24


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