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:3.4.21.7 (plasmin)
9,023 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Using immunochemical analysis with standard antisera, leukocyte thermostable alpha-glycoprotein (LT alpha G) was shown to be distinct from lactoferrin, lysozyme, and fibronectin. The determination of peroxidase and nonspecific elastase in immune precipitates of LT alpha G gave negative results. Affinity sorption of LT alpha G onto the pus protein component was revealed. Purified LT alpha G had amidolytic activity in response to a substrate for elastase (p-nitroanilide succinyl-trialanyl). The ability of LT alpha G to cause the hydrolysis of substrates for thrombin, kallikrein, plasmin was investigated. The identity of LT alpha G and granulocyte elastase is suggested.
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PMID:[Thermostable leukocyte alpha-glycoprotein: immunochemical study and enzyme activity research]. 310 19

Enzymes of the blood coagulation and fibrinolytic cascades are prominent in both the vascular and alveolar compartments of the human lung. Important differences exist in the regulation of these enzyme activities between the vascular and the alveolar compartments, suggesting different functions of similar enzymes in the two compartments. In the vascular bed, endothelial cells provide a nonthrombogenic lining layer and release small amounts of tissue plasminogen activator into the circulation, maintaining patency of the vascular bed, whereas the alveolar epithelial surface is replete with active enzymes of the extrinsic pathway of coagulation as well as urokinase. The alveolar surface seems primed to localize and degrade any fibrin that has leaked into alveoli during hemorrhagic states. In addition, parenchymal lung cells such as resident macrophages are coated with urokinase, providing a mechanism for cellular migration and ongoing extracellular matrix metabolism. Amplification of the PA/plasmin system in the lung during chronic inflammation, eg, cigarette smoking, could accelerate connective tissue breakdown. Recent evidence indicates that in acute inflammation there is an enhancement of mediators of coagulation and suppression of fibrinolysis. These observations may partly explain prior pathologic observations regarding the deposition of hyaline membranes and persistence of alveolar fibrin/fibronectin deposits that may be stimulants for alveolar fibrosis. The assembly of clotting components on the surface of macrophages and the integral involvement of macrophages with fibrin deposits in the lung are likely mechanisms for macrophage immobilization and focal accumulation important to local clearance, host defense, effective chemotactic signalling, and possibly proliferation since thrombin has mitogenic properties for other lung cells. Newer methods focusing on the biology and biochemistry of the pulmonary architecture and its cellular components should further elucidate the importance of these pathways and suggest new therapeutic options.
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PMID:Role of enzymes mediating thrombosis and thrombolysis in lung disease. 313 Oct 71

Tissue fibronectin (TFn) was solubilized from the terminal villi of perfused human placentas by sequential chemical extractions and plasmin digestion. Alternatively, plasmin digestion of intact tissue solubilized all the TFn, which amounted to 1.8-2.9% of the dry weight of the villi. Concomitantly, 69% of the tissue was solubilized. The non-equilibrium competitive e.l.i.s.a. (enzyme-linked immunoabsorbent assay), in which the TFn was immunologically identical with plasma fibronectin (PFn), was used for the quantification of TFn. This study demonstrates that the bulk of TFn can be obtained in a form that can be quantified by e.l.i.s.a. and that TFn is immunologically identical with PFn. Thus the fibronectin molecule is not significantly altered as it is incorporated into the connective-tissue matrix and could exchange with PFn.
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PMID:Quantification of tissue fibronectin from terminal villi of placenta. 315 71

Ternary complex formation of tissue plasminogen activator (TPA) and plasminogen (Plg) with thrombospondin (TSP) or histidine-rich glycoprotein (HRGP) has been demonstrated using an enzyme-linked immunosorbent assay, an affinity bead assay, and a rocket immunoelectrophoresis assay. The formation of these complexes was specific, concentration dependent, saturable, lysine binding site-dependent, and inhibitable by fluid phase plasminogen. Apparent Kd values were approximately 12-36 nM for the interaction of TPA with TSP-Plg complexes and 15-31 nM with HRGP-Plg complexes. At saturation the relative molar stoichiometry of Plg:TPA was 3:1 within the TSP-containing complexes and 1:1 within HRGP-containing complexes. The activation of Plg to plasmin by TPA on TSP- and HRGP-coated surfaces was studied using a synthetic fluorometric plasmin substrate (D-Val-Leu-Lys-7-amino-4-trifluoromethyl coumarin). Kinetic analysis demonstrated a marked increase in the affinity of TPA for plasminogen in the presence of surface-associated TSP or HRGP. Compared to fluid phase activation or activation on fibronectin- or Factor VIII-related antigen-coated surfaces there was a 35-fold increase in efficiency of plasmin generation. A substantial amount (up to 71%) of the plasmin formed remained surface-associated and was found to be protected from inhibition by alpha 2-plasmin inhibitor. Greater than 200-fold increase in inhibitor concentration was required to effect 50% inhibition. Complex formation of locally released tissue plasminogen activator with Plg immobilized on TSP or HRGP surfaces may thus play an important role in effecting proteolytic events in nonfibrin-containing microenvironments.
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PMID:Activation of immobilized plasminogen by tissue activator. Multimolecular complex formation. 316 Jul 7

Gelfiltered unstimulated human platelets neither bound 125-I-fibrinogen nor 125-I-fibrin. Fibrin-binding was, however, stimulated by N-terminal fibronectin 30 kD-and 70 kD-fragments while fibronectin was ineffective. The 30 kD-fragment also stimulated some platelet preparations to bind fibrinogen which, however, was suppressed by minute amounts of the thrombin inhibitor PPACK. PPACK hardly influenced fibrin-binding. Fragment-promoted fibrinogen-binding was also inhibited by a monoclonal antibody recognizing the membrane glycoprotein IIb/IIIa complex known to act as fibrinogen receptor. This antibody failed to influence fragment-stimulated fibrin-binding giving evidence that fibrinogen and fibrin were retained by different receptors. In contrast to 125-I-fibrin its plasmin-derived and 125-I-labelled fragment X was not recognized by the platelets in presence of the fibronectin 30 kD-fragment. Fragment-stimulated binding of 125-I-fibrin showed a lag phase and was completely inhibited by 0.25 mM putrescine as well as by 1 mM EDTA or 0.1 mM N-ethylmaleinimide. Evidently, a cell-attached transamidase was involved in fibrin-binding possibly by forming a ternary complex with fibrin and the fibronectin fragment.
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PMID:Free N-terminal fibronectin 30-kD-domain mediates binding of soluble fibrin to gelfiltered unstimulated thrombocytes. 317 84

Protease nexin-1 (PN-1) is a protease inhibitor that is secreted by fibroblasts and several other cultured cells. PN-1 forms complexes with certain serine proteases in the extracellular environment including thrombin, urokinase, and plasmin. The complexes then bind to the cells and are rapidly internalized and degraded. This report demonstrates that PN-1 is present on the surface of fibroblasts, bound to the extracellular matrix. Immunofluorescent studies showed that PN-1 colocalized with fibronectin on both intact cells and in preparations of extracellular matrix made from these cells. In contrast, PN-1 did not colocalize with the epidermal growth factor receptor, a plasma membrane marker. An enzyme-lined immunosorbent assay was developed which showed that the extracellular matrix contained at least 60-80% of the cellular immunoreactive PN-1. Extraction of the matrix with 2 M NaCl removed PN-1 in a form which reacted with 125I-thrombin to form complexes which were immunoprecipitated by anti-PN-1 IgG and were of identical size as complexes made from soluble PN-1 and 125I-thrombin. These data indicate that in addition to its role as a soluble protease inhibitor, PN-1 is also a component of the extracellular matrix and might control its proteolysis.
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PMID:Localization of protease nexin-1 on the fibroblast extracellular matrix. 327 57

A murine monoclonal antibody (anti-C2G7), reactive with fibrinogen, was used to analyse the structure and function of the fibrinogen epitope C2G7. Anti-C2G7 was found to be reactive with fibrinogen but not with fibronectin, Factor VIII-von Willebrand Factor (FVIII-vWF), beta-thromboglobulin (beta TG), platelet factor 4 (PF4) nor with a range of normal cells and cell lines. Biochemical and plasmin digestion studies of fibrinogen revealed that C2G7 is present on the carboxy-terminal end of the alpha chain on a fragment with a Mr approximately 30-40 K. Functional studies, on the role of fibrinogen in coagulation and platelet function, demonstrated the importance of C2G7 (or a closely associated region) for thrombin-associated fibrin polymerization and collagen induced fibrinogen binding to platelets.
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PMID:Role of A alpha chain of fibrinogen in coagulation and platelet interaction investigated with a monoclonal antibody. 331 Mar 25

The nature and influence of adhesive interactions of rat hepatocytes with components of the extracellular matrix has been studied in culture. Hepatocytes interact with different kinetics to substrata composed of collagen type IV, laminin or fibronectin and adopt significantly different morphologies. The receptors mediating these various responses appear to be specific, according to the matrix, and in the case of fibronectin are complex, implicating several components of the hepatocyte surface. Collagen type IV maintains a differentiated phenotype more efficiently than fibronectin or laminin as measured by the production of adult hepatocyte markers such as albumin and repression of alpha-foetoprotein synthesis. Formation of matrix components is also influenced by the substratum: synthesis and secretion of fibronectin or collagen type IV is down-regulated when cells are cultured on the homologous substratum. Hepatocytes cultured in vitro secrete components of the coagulation cascade and also mediate fibrinolysis on addition of exogenous plasmin. The results are discussed in relation to the normal phenotype of the mature hepatocyte in vivo.
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PMID:Adhesive interactions and the metabolic activity of hepatocytes. 333 63

Guanidinobenzoatase is a proteolytic enzyme capable of degrading fibronectin and is a tumour associated enzyme. Guanidinobenzoatase has been shown to be an arginine selective protease and is distinct from trypsin, plasminogen activator, plasmin, thrombin and a newly described tumour associated enzyme specific for guanidino phenylalanine residues. These conclusions have been derived from inhibition studies employing 4-methyl-p-guanidinobenzoate as substrate. Three active site titrants for trypsin have been shown to be good substrates for guanidinobenzoatase. A new active site titrant for trypsin, rhodamine bisguanidinobenzoate, can also be used to assay guanidinobenzoatase in a stoichiometric manner. This active site titrant can be employed to label guanidinobenzoate on the surface of leukaemia cells.
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PMID:Further inhibition studies on guanidinobenzoatase, a trypsin-like enzyme associated with tumour cells. 333 44

Binding of 125-I-fibrinmonomer to peritoneal macrophages was investigated in dependence of plasma fibronectin and of its thrombin- or plasmin-derived fragments. Plasma fibronectin failed to enhance cell binding of 125-I-fibrinmonomer. In contrast, 30kD-fragments derived from the N-termini of the fibronectin subunits improved binding considerably. The association with the cell surface was completely inhibited by EDTA, 2-5 mM putrescine and to about 40 per cent by 0.1 mM dansylcadaverine suggesting that a transamidase-catalyzed cross-linking reaction was involved. Thrombin-derived 200kD-remnants of the fibronectin subunit chains failed to mediate cell binding of 125-I-fibrinmonomer provided they had been deprived of residual thrombin activity. Otherwise they were active and their activity was inhibited by the thrombin inhibitor hirudin. Plasmin-derived 200 kD-fragments were inactive as well.
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PMID:Fibrinmonomer binding to macrophages mediated by fibrin-binding fibronectin fragments. 392 11


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