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)

Acetyl-salicylic acid has been found to inhibit the aggregation of erythrocytes and thrombocytes stimulated by proteolytic enzymes (fibrinolysin and trypsin) and phospholipase A. It hampers their hydrolytic action on phospholipids of the blood cells membranes, prevents deformation of the latter under the effect of aggregating agents and also averts a fall of the ATP-ase activity of the erythrocytes membranes caused by parachlormercury-benzoate.
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PMID:[Mechanism of the action of acetylsalicyclic acid on formed element aggregation]. 14 11

The mechanism of stimulation of platelets by thrombin and other proteases was studied by following kinetics of secretion of Ca2+ or ATP. The progress-time curves of secretion were analyzed for rate and total amount released. The reaction of thrombin was perturbed by addition of hydroxylamine or a competitive inhibitor and by variation of pH and it was compared with the reactions of other proteases. Trypsin and papain, with specificities for arginyl residues, induced secretion with a time course that was nearly identical with that induced by thrombin when saturating levels of enzyme were used. At low levels of enzyme, trypsin and papain gave extended lags in the progress-time curves. Higher concentrations of trypsin and papain were required for saturation of the measured parameters. Human plasmin (lysly specificity) and bovine chymotrypsin (aromatic amino acid specificity) failed to induce platelet secretion. Active site inhibited thrombin was also ineffective. Both yield and kinetics depended on pH, with the pH profile for each enzyme similar to its profile for hydrolysis of synthetic substrates. Studies at low pH also showed that the early part of the reaction undergoes a change in rate-determining step from enzyme dependent at low enzyme to enzyme indepdenent at high enzyme. Hydroxylamine, a nucleophile that would be expected to accelerate hydrolytic reactions, actually decreased both the rate of initial reactions and yield. A competitive inhibitor of thrombin also decreased both rate and yield; a calculated inhibition constant was in agreement with the value for a synthetic substrate, suggesting that the interaction of thrombin with platelets is analogous to reaction with substrates. A modification of our previous model is proposed in order to accommodate the results described here and to reaoncile the apparent contradictions that enzyme was found not to turn over in the reaction (Detwiler, T. C., and Feinman, R. D. (1973), Biochemistry 12, 282), that catalytic activity is required (Davey, M. G., and Luscher, E. F. (1967), Nature (London) 216, 875; this paper), and that the reaction is characterized by an apparent equilibrium binding (Tollefsen, D. M., Feagler J. R., and Majerus, P. W. (1974), J. Biol. Chem. 249, 2646). The essential feature is a reversible catalytic step with no dissociation of enzyme from product. This is followed by irreversible, thrombin-independent platelet processes leading to secretion, with yield dependent on the equilibrium concentration of the thrombin product. The model thus has aspects of catalysis, stoichiometry, and an agonist-receptor equilibrium.
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PMID:Platelet stimulation by thrombin and other proteases. 116 69

Binding of iodine-125-labeled thrombin to fibrin clots from two siblings with juvenile stroke was 30% of normal, and abnormally high amounts of the radioligand (not adsorbed by fibrin) were found in the supernatant. In concordance with this finding, supernatants from the patients' fibrin clots caused abnormal enhancement of platelet aggregation, ATP secretion, and binding of 125I-fibrinogen to platelets exposed to subthreshold concentrations of ADP or epinephrine. Hirudin suppressed the enhancing effect of the patients' supernatants, and substitution of gamma-thrombin for alpha-thrombin led to normalization of platelet responses. Under some experimental conditions, degradation of the patients' fibrinogen by plasmin was impaired. However, the euglobulin lysis time, the rate of fibrin degradation by plasmin, and the lysis of the patients' plasma clots by human melanoma tissue-type plasminogen activator were normal. Patients' plasmas, as well as purified fibrinogen, showed a prolonged thrombin time (partially corrected by 10 mM CaCl2) and an impaired release of fibrinopeptide A in response to thrombin. However, the release in response to reptilase was normal, and the reptilase, ancrod, and thrombin coagulase times were within control (normal) values. In addition, the patients' fibrinogen showed normal polymerization of preformed fibrin monomers, normal sialic acid content, and normal binding to ADP or epinephrine-stimulated platelets. Our studies support the concept that thrombin and platelets play an important role in the occurrence of stroke in these patients and suggest a direction to be followed to identify the mechanism(s) contributing to thrombosis in subjects with abnormal fibrinopeptide release.
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PMID:A role for platelets and thrombin in the juvenile stroke of two siblings with defective thrombin-adsorbing capacity of fibrin(ogen). 182 31

Monoamine-activated alpha 2-macroglobulin (alpha 2M) has been shown to inhibit beta-nerve growth factor (NGF)-promoted neurite outgrowth and the survival of embryonic sensory and forebrain neurons, whereas normal alpha 2M has little or no such activity. The objective of this study is to elucidate the mechanism of inhibition by monoamine-activated alpha 2M. Methylamine-activated alpha 2M (MA-alpha 2M) and serotonin-activated alpha 2M (5HT-alpha 2M) dose dependently inhibit NGF-promoted neurite outgrowth of the pheochromocytoma PC12 cell and its subline PC12(6-24) which overexpresses human trk protooncogene product, but have no effect on their viability, and this inhibition can be blocked by high concentrations of NGF. The binding of MA-alpha 2M to trk, which is a part of high-affinity NGF receptor, was studied with PC12(6-24) cells and NIH-3T3 fibroblasts expressing trk (trk-3T3). In each case MA-alpha 2M readily forms stable complexes with trk in vivo, whereas normal alpha 2M does not. Both 5HT-alpha 2M and MA-alpha 2M also dose dependently block NGF-promoted autophosphorylation of trk in vivo, whereas normal alpha 2M and plasmin-reacted alpha 2M are inactive or much less active. MA-alpha 2M also blocks NGF-promoted incorporation of 32P from [32P]ATP into trk receptors in vitro. Neither MA-alpha 2M, 5HT-alpha 2M, nor normal alpha 2M, however, blocks either platelet-derived growth factor-stimulated or epidermal growth factor-stimulated tyrosine phosphorylation of the respective receptors. Tyrosine phosphorylation of two of the intracellular substrates, phospholipase C-gamma 1 and extracellular signal-regulated kinase-2, in the NGF-promoted pathways is also dose dependently blocked by MA-alpha 2M. However, by comparison MA-alpha 2M is more effective in inhibiting the activation of phospholipase C-gamma 1 than trk. We conclude that monoamine-activated alpha 2M may block neurite outgrowth and neuronal survival by its specific binding to NGF receptors, thus inhibiting the NGF-promoted activation of intracellular second messenger pathways.
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PMID:Monoamine-activated alpha 2-macroglobulin binds trk receptor and inhibits nerve growth factor-stimulated trk phosphorylation and signal transduction. 750 36

The experiments reported here were carried out to define in greater detail actin's stimulation of plasmin generation by t-PA. Actin did not alter t-PA's hydrolysis of a synthetic substrate, and thus is unlikely to have a direct effect upon t-PA's proteolytic activity. When studied in a single-stage assay, actin accelerated t-PA-mediated plasmin generation from both Glu-plasminogen and Lys-plasminogen, indicating the central role of ternary complex formation. Although actin does not appear to bind two-chain urokinase (tcu-PA), it stimulates tcu-PA's cleavage of Glu-plasminogen. This finding suggests that actin alters the conformation of Glu-plasminogen to an open form. The failure of actin to increased plasmin generation by tcu-PA acting on Lys-plasminogen, which is in an open configuration, is consistent with this interpretation. Immunoglobin G, which shares with actin the property of binding to Glu-plasminogen after nicking by plasmin, did not stimulate tcu-PA's cleavage of Glu-plasminogen, indicating the uniqueness of actin's effects and suggesting interactions between actin and plasminogen at multiple binding sites. Unlike fibrin and heparin, whose stimulation of t-PA is related to polymer length actin is able to stimulate t-PA when presented in either a monomeric or polymeric form. Denaturation of actin by exposure to urea and guanidine increased its ability to stimulate plasmin generation by t-PA. Because actin's structure is maintained by a noncovalently bound adenine nucleotide (ATP or ADP), exposure to ATP/ADPases found in plasma and on cell membranes might also result in its denaturation. Actin treated with an enzyme functionally similar to such ecto-ATP/ADPases, potato apyrase, was more potent than native actin in stimulating plasmin generation by t-PA. The effects of apyrase were blocked by the addition of the plasma actin-binding proteins, gelsolin and the vitamin D-binding protein (DBP). Thus, denaturation of actin may occur in under physiologic conditions, with potential biological consequences. Actin thus appears to be unique with regard to its interactions with the fibrinolytic system and plasma actin-binding proteins may serve to protect the host from the effects of denatured actin.
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PMID:Actin stimulates plasmin generation by tissue and urokinase-type plasminogen activators. 823 51

Several parameters of primary hemostasis and markers of activation of coagulation and fibrinolysis were measured in 48 patients with severe (creatinine clearance < 20 ml/min) chronic renal failure (CRF) without dialysis and disease or drugs affecting hemostasis. Bleeding time (BT) was prolonged in 25/48 patients, and was correlated with age of patients, severity of renal failure, hematocrit, impairment in platelet aggregation-secretion and decrease in platelet ATP content. Defects in von Willebrand factor played no role in the prolongation of the BT. Multivariate analysis showed that only platelet dysfunction and severity of renal disease were independent predictors of the BT in uremia. The platelet functional disorder was significantly correlated with a reduction in platelet ATP and ADP. High levels of plasma thrombin-antithrombin complexes (TAT), prothrombin fragment F1 + 2, fibrinogen and factor VIIc were observed in patients with CRF, as described in prethrombotic states. Plasmin-antiplasmin complexes (PAP), fibrinogen and fibrin degradation products (FgDP, FnDP) were significantly increased, and the activity of plasminogen activator inhibitor (PAI-1) was slightly reduced, denoting an activation of fibrinolysis. A negative correlation was found between platelet levels of ATP and ADP with plasma TAT, F1 + 2 and PAP. Furthermore, plasma PAI-1 activity was negatively correlated with the BT and was lower in patients with prolonged BT as compared with controls and patients with normal BT. These links between primary hemostasis and activation of coagulation and fibrinolysis suggest that increased intravascular generation of thrombin and/or plasmin is an important mediator of the defects in primary hemostasis, prolongation of the BT and, probably, bleeding in CRF.
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PMID:Hemostatic disorder of uremia: the platelet defect, main determinant of the prolonged bleeding time, is correlated with indices of activation of coagulation and fibrinolysis. 888 63

Solid tumour cells employ glycolytic enzymes including phosphoglycerate kinase (PGK) to make ATP when their supply of oxygen is limiting. PGK is also secreted by tumour cells and facilitates cleavage of disulfide bonds in plasmin, which triggers proteolytic release of the angiogenesis inhibitor, angiostatin. Although PGK production by tumour cells was enhanced by hypoxia, its secretion was inhibited. Inhibition of secretion correlated with decrease in angiostatin formation by the tumour cells. In contrast, hypoxia did not inhibit the secretion of the angiogenesis activator, vascular endothelial cell growth factor (VEGF). PGK secretion was reversed by normoxia and was under control of the oxygen-sensing protein hydroxylases, as inhibitors of this class of enzymes mimicked the effect of hypoxia on PGK secretion. Direct hydroxylation of PGK was not the mechanism by which the protein hydroxylases controlled its secretion. These findings show that production and secretion of PGK are regulated separately and indicate that oxygen and the protein hydroxylases can control not only gene expression but also protein secretion.
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PMID:Secretion of phosphoglycerate kinase from tumour cells is controlled by oxygen-sensing hydroxylases. 1505 20

To assess the etiology of influenza-associated encephalopathy(IAE), a surveillance effort was conducted during 2000-2005 in Japan. Over half of fatal and handicapped IAE patients exhibited a disorder of mitochondrial beta-oxidation and ATP generation evoked by the thermolabile phenotype of carnitine palmitoyltransferase II variations with transiently elevated serum acylcarnitine during high-grade fever. Model mice having impaired mitochondrial beta-oxidation exhibited significant accumulation of mini-plasmin and up-regulation of trypsin in the cerebral capillaries after infection with influenza A virus, resulting in the destruction of blood-brain barrier and increased brain vascular permeability. Trypsin up-regulation was also evident in the neuronal cells in the hippocampus, suggesting a severe neurologic complication of IAE.
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PMID:[Analysis of SNPs and enzymatic disorder in the patients of influenza-associated encephalopathy: disorder of fatty acid metabolism in mitochondria induced by high fever]. 1703 63

The effects of microglia-derived plasminogen (PLGn) on the neurotrophic role of astrocytes were investigated in vitro. The treatment of astrocytes with rat PLGn led to a significant increase in transforming growth factor beta3 (TGFbeta3) in the conditioned medium (CM). This response of astrocytes to PLGn was characteristic and different from that to other stimulators, including lipopolysaccharide, phorbol-12-myristate-13-acetate, interferon-gamma, and ATP. In surveying the signaling molecules that respond to PLGn in astrocytes, we found that Akt/PKB phosphorylation is promoted. The pretreatment of astrocytes with an Akt inhibitor prior to PLGn stimulation resulted in a significant decrease in TGFbeta3 amounts in the CM, suggesting an association of Akt with TGFbeta3 production/secretion. Further survey revealed that phosphatidylinositol 3 kinase (PI3K) is closely associated with TGFbeta3 production/secretion in astrocytes. In fact, PI3K inhibitor clearly depressed the phosphorylation of Akt, indicating that PI3K is localized upstream of Akt. Moreover, the effects of PLGn to increase TGFbeta3 were depressed by pretreatment with a proteinase-activated receptor-1 (PAR-1) inhibitor. Plasmin could mimic the PLGn effects to upregulate TGFbeta3, and the plasmin effects were suppressed by pretreatment with the PAR-1 inhibitor, suggesting the association of PLGn/plasmin effects with PAR-1. In addition, Akt phosphorylation caused by plasmin was inhibited in the presence of PAR-1 inhibitor. We have therefore demonstrated that PLGn/plasmin, probably plasmin, facilitates the production/secretion of TGFbeta3 in astrocytes through both PAR-1 and the subsequent signaling cascade including PI3K and Akt.
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PMID:Characteristic response of astrocytes to plasminogen/plasmin to upregulate transforming growth factor beta 3 (TGFbeta3) production/secretion through proteinase-activated receptor-1 (PAR-1) and the downstream phosphatidylinositol 3-kinase (PI3K)-Akt/PKB signaling cascade. 1976 62

Fibroblast growth factor 2 (FGF2) plays a pivotal role in cell proliferation, angiogenesis and neuroprotection. Several clinical trials using this growth factor in bone regeneration, wound healing and cardioprotection are initiated but the inadequate stability of FGF2 after application is one major problem. Binding of ATP to FGF2 and other growth factors has been demonstrated recently. Here we report that ATP, other nucleoside triphosphates and sodium triphosphate protect FGF2 from trypsin, plasmin and neutrophile elastase digestion in vitro. A molar ratio of 2:1 (ligand/FGF2) is sufficient for these protective effects. ADP shows only little, AMP no stabilizing effect on FGF2 indicating that the number of phosphate residues is important. Protection of FGF2 by ATP can be abolished by the addition of alkaline phosphatase hydrolyzing free and FGF2-bound ATP. The mutant FGF2 (K128A/R129A/K134A/K144A) with strongly reduced ATP-binding capacity revealed no detectable protease resistance after incubation with ATP. Furthermore, a stabilizing effect of ATP on FGF2 could also be demonstrated in cell culture experiments. ATP bound to FGF2 increased FGF2-dependent human umbilical vein endothelial cells proliferation when the growth factor was treated with neutrophile elastase or heat. For the first time these data demonstrate protection of FGF2 by bound ATP, other nucleoside triphosphates or sodium triphosphate from rapid protease digestion. Our data provide new evidence that nucleoside triphosphates are capable of protecting FGF2 and favours such stabilization for various, especially medical applications.
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PMID:ATP-dependent stabilization and protection of fibroblast growth factor 2. 1983 24


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