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)

The objective of this study was to characterize the plasmin-induced stimulation of leukotriene (LT) B4 biosynthesis in human peripheral monocytes (PM). Plasmin up to 175 x 10(-3) CTA U/ml triggers a concentration-dependent release of 5-lipoxygenase-derived LTB4 while release of the cyclooxygenase products thromboxane (TX) B2 and prostaglandin (PG) E2 remained unaffected. The stimulatory effect appeared to be specific in as much as 1) it was found in PM, but not in polymorphonuclear neutrophils (PMN), 2) it requires the lysine binding sites of plasmin molecule since it was inhibited by the lysine analogues 6-aminohexanoic acid (6-AHA) and trans-4(aminomethyl)cyclohexane-1-carboxylic acid (t-AMCA), 3) the intact catalytic center of plasmin is required since neither plasminogen nor catalytic center-blocked plasmin share the stimulatory effect of active plasmin, 4) other serine proteases such as alpha-chymotrypsin, human neutrophil elastase and cathepsin G did not stimulate release of detectable amounts of LTB4 from PM. In addition, catalytic center-blocked plasmin antagonized the stimulatory effect of active plasmin. Plasmin-mediated monocyte activation apparently proceeds via a pertussis toxin-sensitive G protein. Plasmin did not increase inositol (1,4,5) trisphosphate levels, but a time- and concentration-dependent stimulation of cyclic GMP formation was observed. The data show that plasmin is a specific stimulus for human peripheral monocytes. Plasmin may be an important link between the coagulation cascade and inflammatory reactions.
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PMID:Plasmin is a specific stimulus of the 5-lipoxygenase pathway of human peripheral monocytes. 890 97

The murine plasminogen/urokinase-type plasminogen-activator (u-PA) system was studied using purified proteins, plasma and endothelioma cells. Recombinant murine u-PA was obtained as a single-chain molecule of 45 kDa which was converted to two-chain u-PA with plasmin by cleavage of the Lys159-Ile160 peptide bond. Murine plasminogen, purified from plasma as a single-chain protein of 95 kDa, was resistant to quantitative activation with murine recombinant two-chain u-PA: only 15% activation within 1 h at 37 degrees C was obtained in mixtures of 1 microM plasminogen and 5 nM recombinant two-chain u-PA, whereas quantitative activation was observed in the autologous human system. Addition of 6-aminohexanoic acid to native murine plasminogen resulted in quantitative activation within 1 h. In murine plasma in vitro, plasminogen was also resistant to quantitative activation with u-PA (50% activation within 1 h at 37 degrees C with 50 nM recombinant two-chain u-PA, whereas in the human system nearly quantitative activation was obtained). Murine plasma clots submerged in murine plasma were resistant to lysis with u-PA; < or = 2% clot lysis in 2 h was obtained with 80 nM recombinant two-chain u-PA in the autologous murine system whereas 50% clot lysis in 2 h required only 15 nM recombinant two-chain u-PA in the autologous human system. Saturable binding of murine recombinant two-chain u-PA was observed to murine endothelioma cells that are genetically deficient in u-PA (u-PA-/- End cells). Binding was characterized by a Kd of 5.5 nM and 800000 binding sites/cell. However, u-PA-/- End cells did not significantly stimulate the activation rate of murine plasminogen by murine recombinant two-chain u-PA and did not enhance the plasmin-mediated conversion rate of murine recombinant single-chain u-PA to its two-chain derivative. Murine recombinant two-chain u-PA bound to murine endothelioma cells was quantitatively inhibited by murine plasminogen-activator inhibitor-1 (PAI-1). Thus, the interactions between murine plasminogen, u-PA and PAI-1 are qualitatively similar to those between their human counterparts. However, quantitative differences were observed both in the presence of cells and in plasma which may contribute to a reduced u-PA-mediated fibrinolytic activity in the murine systems.
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PMID:Characterization of the murine plasminogen/urokinase-type plasminogen-activator system. 894 73

The interactions between Helicobacter pylori spiral and coccoid forms, extracellular matrix (ECM) and plasma proteins were studied in an 125I-labelled protein assay. The range of binding of collagen V, plasminogen, human lactoferrin (HLf) and vitronectin to coccoid forms of H. pylori NCTC 11637 was 26-48%. In contrast, binding of radiolabelled fibronectin and collagen types I and III was low (3-8%). The coccoid forms of 14 strains of H. pylori showed significant HLf binding (median 26%). With plasminogen, no significant difference was found between binding to the coccoid (median = 13%) and spiral (median = 12%) forms, of 13 of the 14 strains of H. pylori tested; the exception was strain NCTC 11637. 125I-plasminogen showed a dose-dependent binding to both the coccoid and spiral forms. Plasminogen binding to both forms was specific; the binding was inhibited by non-labelled plasminogen, plasmin, lysine, EACA (epsilon-aminocaproic acid) but not by fetuin or various carbohydrates. Similarly, HLf binding was found to be specific and was inhibited by non-labelled HLf and BLf. The coccoid forms showed either similar or enhanced ECM binding capabilities compared with the spiral forms. As the binding of ECM proteins may be an important mechanism of tissue adhesion for various pathogenic bacteria, the coccoid differentiated form of H. pylori can be considered as an infective form in the pathogenesis of helicobacter infection and type B gastritis.
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PMID:Binding of human plasminogen and lactoferrin by Helicobacter pylori coccoid forms. 895 46

The relative importance of different proteinases, and their inhibition, in the breakdown of human endothelial basement membrane (BM) by MDA-MB-231 and MCF7ADR human breast cancer cell lines has been studied using 35S-labelled BM-coated 96-well culture plates. Basement membrane degradation (BMD) was independent of cell proliferation above the seeding density. Inhibitors of aspartic (pepstatin and PD 134678-0073) and cysteine proteinases (E64) had little effect on BMD under normal culture conditions, suggesting that cathepsins D, B and L have only a minor role. In contrast, inhibitors of urokinase-type plasminogen activator (uPA) and/or plasminogen activation to plasmin (aprotinin, amiloride, EACA, tranexamic acid, anti-uPA antibody) all reduced BMD by MDA-MB-231 cells by approximately 30-40%, but only in the presence of serum or plasminogen. BB94, an inhibitor of matrix metalloproteinases (MMPs), also reduced BMD by about 30% under these conditions but was similarly effective in serum-free medium. Combinations of BB94 with any of the uPA/plasminogen activation inhibitors in serum-containing medium had additive effects, while BB94 with pepstatin and E64 under serum-free conditions reduced BMD to 16% of control. Serum-containing conditioned medium exhibited appreciable BMD, largely due to aprotinin-inhibitable activity. Although small reductions in cell proliferation were seen with some inhibitors, the combination of BB94 with E64 or E64d reduced the cell population by about 60% under serum-containing conditions. These in vitro observations suggest that combinations of proteinase inhibitors, particularly of uPA/plasminogen activation and MMPs, may merit clinical evaluation as potential antimetastatic therapy for breast cancer.
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PMID:Proteinase inhibitors reduce basement membrane degradation by human breast cancer cell lines. 908 29

We have previously demonstrated a low-affinity (0.8 microM, non-covalent complex formation between high-molecular-mass kininogen (HK) and plasminogen (Plg) which prevented Plg interaction with glioma and endothelial cells. We have now extended our previous observations by exploring the potential complex formation between Plg and low-molecular-mass kininogen (LK) and between LK and HK with Plg cleaved with human neutrophil elastase (HNE). Plg cleavage by HNE (PlgHNE) yielded kringles 1-3, kringle 4 and mini-plasminogen. PlgHNE was subjected to SDS/PAGE under non-reducing conditions, followed by western blotting, and incubated with either 125I-HK or 125I-LK. Autoradiograms revealed that 125I-HK bound to miniplasminogen and to kringles 1-3 but not to kringle 4 and the presence of 10 mM 6-aminohexanoic acid (Ahx) disrupted only the interaction with kringles 1-3. In contrast, 125I-LK bound to miniplasminogen but not to kringles 1-3 or 4 and Ahx had no effect at all. The complex formation of either HK (0.67 microM) or LK (3 microM) with Plg (1.5 microM) did not affect its conversion to plasmin by tissue plasminogen activator (t-PA) (10 U/ml) in the presence of a tissue plasminogen stimulator (0.14 microM). However, the rate of conversion of plasminogen to plasmin by t-PA was affected when platelets were added to the reaction mixture. Since HK (0.83 microM) has been shown to inhibit plasmin-induced platelet aggregation, we investigated whether this inhibitory property is found within the heavy chain shared by HK and LK. We found that LK inhibited plasmin-induced platelet aggregation, but a 4-fold molar excess was required when compared to HK. Compared to plasmin, 3-5-fold molar excess of miniplasmin is required to induce platelet aggregation, indicating the important role of kringles 1-3 for plasmin interactions with these cells. These results indicate that HK and LK-mediated inhibition of plasmin-induced platelet aggregation is likely due to complex formation with kringle 5 without interfering with plasmin's active site. We found an additional interaction between HK and kringles 1-3 enhancing the inhibitory effect, presumably by interfering with plasmin's interaction with platelets. This HK and LK-associated modulation of plasmin-induced platelet aggregation may serve as a template to develop synthetic peptides as novel therapeutic agents to prevent some of the plasmin-associated thrombocytopenia seen during thrombolytic therapy.
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PMID:High-molecular-mass and low-molecular-mass kininogens block plasmin-induced platelet aggregation by forming a complex with kringle 5 of plasminogen/plasmin. 942 7

The native form of plasminogen is Glu-plasminogen, which by plasmin cleavage gives Lys-plasminogen. Lys-plasminogen is a considerably better substrate compared with Glu-plasminogen for plasminogenolytic enzymes. The contact activation of the intrinsic pathway of coagulation consisting of factor XII, prekallikrein and high Mr kininogen has been implicated to play a role in the intrinsic fibrinolysis. Here activation of Glu- and Lys-plasminogen by factor XIIa in the absence of prekallikrein/kallikrein and high Mr kininogen was studied in a purified system by the generation of amidolytic activity towards pyroGlu-Phe-Lys-pNA (S-2403), a chromogenic substrate of plasmin. A slow activation rate of both Glu- and Lys-plasminogen by factor XIIa was enhanced approximately 60-fold in the presence of Zn2+ and a negatively charged surface. 6-Aminohexanoic acid further enhanced the activation of Glu-plasminogen but inhibited the activation of Lys-plasminogen. The presence of a specific factor XIIa inhibitor completely prevented the generation of plasmin amidolytic activity indicating that activation was mediated by proteolytical cleavage, although this could not be proven by Western-blotting. Physiological concentration of factor XIIa was as more efficient than soluble u-PA to lyse fibrin as a result of activation of Glu-plasminogen. This did not require the presence of Zn2+ or sulfatide.
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PMID:Factor XIIa activation of plasminogen is enhanced by contact activating surfaces and Zn2+. 951 51

Plasminogen activators are known to be involved in the metastatic spread of breast cancer. In the present study we examined the effects of antiestrogens [Analog II (1,1-dichloro-cis-2,3-diphenyl cyclopropane) (AII), ICI-182,780 (ICI) and tamoxifen (TAM)], on the in vitro release of uPA from estrogen receptor (ER)-positive MCF-7 (MCF) and ER-negative MDA-MB-231 (MDA) human breast cancer cell lines. Using a solid-phase radioassay, uPA activity was found to be higher in the culture medium from MDA cells compared to MCF cells. Aminocaproic acid, a specific plasmin inhibitor, produced a 50-60% reduction in the degradation of labeled substrate, in the solid phase assay, using culture medium from both cell lines, thus indicating that most of the proteolysis observed was due to uPA-mediated plasmin generation from plasminogen. In the absence of plasminogen, the enzyme activity was not detected in either the quantitative assay or by zymography. In MDA cells, uPA release was not altered by any of the antiestrogens used alone or in the presence of estradiol. In contrast, in MCF cells, ICI alone produced maximal inhibition (40%) of enzyme release, while estradiol alone produced a 120% increase in enzyme activity. When co-administered with estradiol, in MCF cultures, each antiestrogen reduced enzyme activity to control levels. Substrate gel zymography revealed that the urokinase-type PA is the predominant form of PA released by both cell lines. Comparison of the activity of all three antiestrogens used in this study indicates that ICI is the most potent inhibitor of enzyme activity in ER-positive MCF cells.
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PMID:The influence of antiestrogens on the release of plasminogen activator (uPA) by MDA-MB-231 and MCF-7 breast cancer cells. 956 41

The binding of the zymogenic form of urokinase-type plasminogen activator (pro-uPA) to its specific cellular receptor, uPAR, leads to a large potentiation of plasmin generation. This is dependent on the concurrent cellular binding of plasminogen, and is completely abrogated by the plasminogen lysine-binding site ligand, 6-aminohexanoic acid. Previous data have provided circumstantial evidence for the formation of specific complexes to mediate the kinetically favorable reciprocal interactions between the protease and zymogen components [Ellis, V., and Dano, K. (1993) J. Biol. Chem. 268, 4806-4813]. To further investigate the formation of these putative complexes, we have studied the effect of various lysine-binding site ligands on the binding and activation of plasminogen on U937 cells. Lysine-binding site ligands resembling internal lysine residues, such as Nalpha-acetyl-L-lysine methyl ester, were found to specifically inhibit uPAR-mediated cell-surface plasminogen activation at concentrations up to 40-fold lower than those inhibiting the cellular binding of 125I-labeled plasminogen (IC50s 300 microM vs 8.5 mM). By contrast, 6-aminohexanoic acid, resembling a C-terminal lysine residue, did not display this disparity (IC50s 25 vs 30 microM). These lysine analogues were also found to compete a non-active-site interaction between uPA and plasminogen, detected by surface plasmon resonance (Kd 50 nM), at concentrations correlating with their effect on cell-surface plasminogen activation, suggesting that this interaction is part of the kinetic mechanism. Consistent with this, synthetic peptides corresponding to the sequence uPA149-158 (GQKTLRPRFK) and uPA149-157 (GQKTLRPRF) specifically abolished the amplification of cell-surface plasminogen activation. These data demonstrate that a novel non-active-site interaction between uPA and plasminogen is necessary for the assembly and efficiency of cell-surface plasminogen activation complexes.
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PMID:Assembly of urokinase receptor-mediated plasminogen activation complexes involves direct, non-active-site interactions between urokinase and plasminogen. 988 5

Human tissue factor pathway inhibitor-2 (TFPI-2)/matrix-associated serine protease inhibitor (MSPI), a Kunitz-type serine protease inhibitor, inhibits plasmin, trypsin, chymotrypsin, plasma kallikrein, cathepsin G, and factor VIIa-tissue factor complex. The mature protein has a molecular mass of 32-33 kDa, but exists in vivo as two smaller, underglycosylated species of 31 and 27 kDa. TFPI-2/MSPI triplet is synthesized and secreted by a variety of cell types that include epithelial, endothelial, and mesenchymal cells. Because the majority (75-90%) of TFPI-2/MSPI is associated with the extracellular matrix (ECM), we examined which components of the ECM bind TFPI-2/MSPI. We found that TFPI-2/MSPI bound specifically to heparin and dermatan sulfate. Interaction of these two glycosaminoglycans (GAGs) with TFPI-2/MSPI involved one or more common protein domains, as evidenced by cross-competition experiments. However, binding affinity for TFPI-2/MSPI with heparin was 250-300 times greater than that for TFPI-2/MSPI with dermatan sulfate. Binding of TFPI-2/MSPI to GAGs was inhibited by NaCl or arginine but not by glucose, mannose, galactose, 6-aminohexanoic acid, or urea, suggesting that arginine-mediated ionic interactions participate in the GAG binding of TFPI-2/MSPI. This supposition was supported by the observation that only NaCl or arginine could elute the TFPI-2/MSPI protein triplet from an ECM derived from human dermal fibroblasts. Reduced TFPI-2/MSPI did not bind to heparin, suggesting that proper disulfide pairings and conformation are essential for matrix binding. To determine whether heparin modulates the activity of TFPI-2/MSPI, we determined the rate of inhibition of plasmin by the inhibitor with and without heparin and found that TFPI-2/MSPI is more active in the presence of heparin. Collectively, our results demonstrate that conformation-dependent arginine-mediated ionic interactions are responsible for the TFPI-2/MSPI triplet binding to fibroblast ECM, heparin, and dermatan sulfate and that heparin augmented the rate of inhibition of plasmin by TFPI-2/MSPI.
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PMID:Matrix localization of tissue factor pathway inhibitor-2/matrix-associated serine protease inhibitor (TFPI-2/MSPI) involves arginine-mediated ionic interactions with heparin and dermatan sulfate: heparin accelerates the activity of TFPI-2/MSPI toward plasmin. 1049 84

We have developed a rapid, sensitive, and quantitative latex immunoturbidimetric assay for the measurement of alpha2 plasmin inhibitor-plasmin inhibitor complex (PIC) in human plasma. The method is based on the latex agglutination reaction using a suitable pair of monoclonal antibodies. One reacts with plasmin and the other reacts with alpha2 plasmin inhibitor. In this assay, we added 6-aminohexanoic acid to the reaction buffer in order to avoid the nonspecific latex agglutination caused by precursor proteins such as plasminogen. We used this method with an automatic analyzer HITACHI 7150 (Hitachi Ltd., Hitachi, Japan) and measured PIC within the range of 0.2 to about 50 mg/mL in only 15 minutes. The precision indices (CV%) of intra-assays and interassays were <4.4% and <3.4%, respectively. The influence of plasminogen or alpha2 plasmin inhibitor on plasma was negligible. Based on these results, it is considered that this method would be useful for evaluation of a broad spectrum of fibrinolytic disorders, particularly disseminated intravascular coagulation.
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PMID:Development of a latex immunoturbidimetric assay for the automated measurement of alpha2 plasmin inhibitor-plasmin complex in human plasma. 1063 77


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