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

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 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

Some synthetic dextran derivatives that mimic the action of heparin/heparan sulfate were shown to promote in vivo tissue repair when added alone to wounds. These biofunctional mimetics were therefore designated as "regenerating agents" in regard to their in vivo properties. In vitro, these biopolymers were able to protect various heparin-binding growth factors against proteolytic degradation as well as to inhibit the enzymatic activity of neutrophil elastase. In the present work, different dextran derivatives were tested for their capacity to inhibit the enzymatic activity of human plasmin. We show that dextran containing carboxymethyl, sulfate as well as benzylamide groups (RG1192 compound), was the most efficient inhibitor of plasmin amidolytic activity. The inhibition of plasmin by RG1192 can be classified as tight binding hyperbolic noncompetitive. One molecule of RG1192 bound 20 molecules of plasmin with a K(i) of 2.8 x 10(-8) m. Analysis with an optical biosensor confirmed the high affinity of RG1192 for plasmin and revealed that this polymer equally binds plasminogen with a similar affinity (K(d) = 3 x 10(-8) m). Competitive experiments carried out with 6-aminohexanoic acid and kringle proteolytic fragments identified the lysine-binding site domains of plasmin as the RG1192 binding sites. In addition, RG1192 blocked the generation of plasmin from Glu-plasminogen and inhibited the plasmin-mediated proteolysis of fibronectin and laminin. Data from the present in vitro investigation thus indicated that specific dextran derivatives can contribute to the regulation of plasmin activity by impeding the plasmin generation, as a result of their binding to plasminogen and also by directly affecting the catalytic activity of the enzyme.
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PMID:Human plasmin enzymatic activity is inhibited by chemically modified dextrans. 1088 87

Because histidine-rich glycoprotein binds to the kringle 1-3 domain of plasminogen, it may affect fibrinolysis by reducing fibrin-dependent plasmin production, and in this way it could be mechanistically analogous to 6-aminohexanoic acid. We tested this hypothesis by comparing the effects of histidine-rich glycoprotein and 6-aminohexanoic acid in an in vitro assay of fibrin-dependent plasmin production mediated by tissue plasminogen activator. Whereas 1 mM of 6-aminohexanoic acid increased the K(m) of the reaction from approximately 0.22 microM to approximately 1.7 microM, 2 microM of histidine-rich glycoprotein had no discernible effect. Similar results were obtained in an assay based upon fibrin clot lysis. Therefore, we could not document an effect of histidine-rich glycoprotein on the rate of fibrin-dependent plasmin production.
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PMID:Comparison of the effect of histidine-rich glycoprotein and 6-aminohexanoic acid on plasmin production and fibrinolysis in vitro. 1094 92

Binding of streptokinase (SK) to plasminogen (Pg) activates the zymogen conformationally and initiates its conversion into the fibrinolytic proteinase, plasmin (Pm). Equilibrium binding studies of SK interactions with a homologous series of catalytic site-labeled fluorescent Pg and Pm analogues were performed to resolve the contributions of lysine binding site interactions, associated changes between extended and compact conformations of Pg, and activation of the proteinase domain to the affinity for SK. SK bound to fluorescein-labeled [Glu]Pg(1) and [Lys]Pg(1) with dissociation constants of 624 +/- 112 and 38 +/- 5 nM, respectively, whereas labeled [Lys]Pm(1) bound with a 57000-fold tighter dissociation constant of 11 +/- 2 pM. Saturation of lysine binding sites with 6-aminohexanoic acid had no effect on SK binding to labeled [Glu]Pg(1), but weakened binding to labeled [Lys]Pg(1) and [Lys]Pm(1) 31- and 20-fold, respectively. At low Cl(-) concentrations, where [Glu]Pg assumes the extended conformation without occupation of lysine binding sites, a 23-fold increase in the affinity of SK for labeled [Glu]Pg(1) was observed, which was quantitatively accounted for by expression of new lysine binding site interactions. The results support the conclusion that the SK affinity for the fluorescent Pg and Pm analogues is enhanced 13-16-fold by conversion of labeled [Glu]Pg to the extended conformation of the [Lys]Pg derivative as a result of lysine binding site interactions, and is enhanced 3100-3500-fold further by the increased affinity of SK for the activated proteinase domain. The results imply that binding of SK to [Glu]Pg results in transition of [Glu]Pg to an extended conformation in an early event in the SK activation mechanism.
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PMID:Streptokinase binds preferentially to the extended conformation of plasminogen through lysine binding site and catalytic domain interactions. 1107 40

Studies were conducted on the effect of 6-aminohexanoic acid (6-AH) or fucoidan on the activation of glutamic plasminogen (glu-plg) by streptokinase using 0.05 mol/l Tris buffer containing a physiological concentration of NaCl. In contrast to the earlier reports where no NaCl was added to the buffer solution, addition of 6-AH enhanced the initial rate while the inhibition by fucoidan was not affected. Double reciprocal plots of the activation of glu-plg by streptokinase in the presence of 6-AH showed an increase in Vmax, but no change in Km. However, the addition of fucoidan showed a decrease in Vmax, but no change in Km. To determine whether the stimulatory effect of 6-AH was specifically directed towards glu-plg or streptokinase, the ratios of the initial rate of plasmin generation in the presence of 6-AH over the controls were plotted against the inverse of the volume fraction of glu-plg or streptokinase after serial dilutions. The results indicated that the dilutions of glu-plg, but not of streptokinase, influenced the ratios, suggesting an interaction of 6-AH with glu-plg. Similar experiments were conducted to determine the mechanism of inhibition of streptokinase by fucoidan. The results indicated that fucoidan was interacting with streptokinase, but not with glu-plg. Circular dichroism studies of glu-plg in the near-ultraviolet spectra (250-308 nm) showed that addition of 6-AH enhanced the spectra in the region around certain chromophores, which reflected conformational changes. On the contrary, the far-ultraviolet spectra were almost identical.
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PMID:The effect of 6-aminohexanoic acid and fucoidan on the activation of glutamic plasminogen by streptokinase. 1203 2


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