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Query: UNIPROT:P00750 (PLA)
 16,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In this article we review a novel type of plasminogen activation on staphylococcal and streptococcal cells. The activation mechanism implies a specific binding of glu-plasminogen to bacterial surface via the lysine-binding sites of plasminogen. Association of plasminogen with bacterial surfaces greatly enhances the t-PA mediated activation which takes place only poorly in solution. The end product, surface-associated plasmin, is enzymatically active, protected against high molecular weight plasmin inhibitors and capable of converting itself from glu-plasmin to the lys-form. The modification is associated with an increased affinity of the bound lys-plasmin towards the binding molecules on bacterial surface. This novel way of retaining plasmin on the surface may be important for the bacteria to invade and penetrate surrounding tissues. Our data on the effect of plasmin on staphylococcal adherence indicate that plasmin is not very effective in cleaning bacteria from surfaces coated with extracellular matrix components, fibronectin and fibrinogen.
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PMID:Surface-associated activation of plasminogen on gram-positive bacteria. Effect of plasmin on the adherence of Staphylococcus aureus. 132 10

The distribution of plasminogen/plasmin, the central proteolytic component of the plasminogen activator/plasmin system was analysed in lesional skin of bullous pemphigoid by using monoclonal antibodies (MAbs) specific for distinct epitopes of the plasminogen/plasmin molecule. Four groups of MAbs were used: (i) MAbs HD-PG 1 and HD-PG 2, specific for epitopes associated with the lysine-binding sites I (kringle domain 1 + 2 + 3) and II (kringle domain 4) of plasminogen/plasmin, (ii) MAbs HD-PG 6 and HD-PG 7, specific for the lysine binding site I only, (iii) MAbs HD-PG 12 (formerly designated P 2) and HD-PG 18, specific for non-kringle domains of glu- and lys-plasminogen, and (iv) MAb HD-PG 13 which recognizes glu-plasminogen, only. The basal cell layers of normal skin consistently reacted with MAb HD-PG 12, whereas only faint staining was seen with the other MAbs in the same biopsies. In contrast, all anti-plasminogen/plasmin MAbs strongly stained lower and intermediate epidermal cell layers of fully developed bullous pemphigoid lesions.
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PMID:Enhanced association of plasminogen/plasmin with lesional epidermis of bullous pemphigoid. 139 Jan 72

alpha 2-antiplasmin (alpha 2-AP) exerts its inhibitory effect on fibrinolysis by rapidly inhibiting the plasmin evolved; in addition, it has been suggested that interference with the binding of plasminogen to fibrin, a function shared with histidine-rich glycoprotein (HRGP), may also be significant in inhibition of fibrinolysis. To elucidate if plasminogen binding by these two alpha 2-globulins may decrease the generation of plasmin by tissue-type plasminogen activator (t-PA) at the surface of fibrin, a system mimicking the fibrin/plasma interface was used. Attempts were made to differentiate the plasminogen binding from the plasmin inhibitory function of alpha 2-AP. The activation of human Glu-plasminogen (native plasminogen with NH2-terminal glutamic acid) by fibrin-bound t-PA was performed in a plasma environment using either normal plasma, alpha 2-AP- or HRGP-depleted plasmas supplemented with increasing amounts of the lacking protein, or in a reconstituted system with purified plasminogen and various concentrations of alpha 2-AP and HRGP. The activation of Glu-plasminogen in alpha 2-AP-depleted plasma containing a normal concentration of HRGP produced a time-dependent increase in the generation of plasmin. The addition of 1 microM-alpha 2-AP to this plasma prevented the formation of Lys-derivatives and produced a marked decrease (42%) in the number of plasminogen-binding sites. In contrast, the addition of 1.5 microM-HRGP to HRGP-depleted plasma containing a normal amount of alpha 2-AP produced only a modest (17%) decrease in the amount of plasmin(ogen) bound. Moreover, in a purified system the amount of plasminogen-binding sites and thereby of plasmin generated at the surface of fibrin in the presence of both alpha-2 globulins was similar to the amount generated in the presence of alpha 2-AP alone. These results indicate clearly that the formation of reversible complexes between plasminogen and alpha 2-AP does not interfere with the binding and activation of plasminogen at the fibrin surface. In contrast, the inhibition of plasmin by alpha 2-AP decreases importantly the number of plasminogen-binding sites (carboxyl-terminal lysines) and inhibits thereby the accelerated phase of fibrinolysis. It can be concluded that interference of the binding of plasminogen to fibrin by alpha 2-AP during plasminogen activation, does not play a significant role in inhibition of fibrinolysis, and that the plasminogen-binding effect of HRGP, if any, is obscured by the important inhibitory effect of alpha 2-AP.
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PMID:Plasminogen binding by alpha 2-antiplasmin and histidine-rich glycoprotein does not inhibit plasminogen activation at the surface of fibrin. 147 36

The sequence fibrinogen-A alpha-(148-160) can mimic part of the fibrin-induced rate enhancement of the activation of plasminogen by tissue-type plasminogen activator. Previously we have reported that the lysine residue at position A alpha-157 is crucial. During our further investigations on A alpha-157 we found that lysine at position A alpha-157 may be replaced by glutamic acid. This unexpected finding prompted us to re-investigate the requirements of this position. We prepared analogues of A alpha-(148-160) in which the lysine residue at position A alpha-157 was replaced by lysine derivatives (acetyl-lysine, benzyloxycarbonyl-lysine and methanesulphonylethyloxycarbonyl-lysine), acidic residues (aspartic acid and glutamic acid), basic residues (arginine and ornithine), polar residues (glutamine and methanesulphonylethyloxycarbonylornithine), apolar residues (alanine, valine, norleucine and glutamic acid 4-nitrobenzyl ester) and glycine. These analogues were tested for their stimulatory activity. When aspartic acid, glutamic acid 4-nitrobenzyl ester or norleucine is present at position A alpha-157 in A alpha-(148-160) virtually all stimulatory capacity is lost. With valine at position A alpha-157 the stimulatory activity is marginal. None of the other replacements at position A alpha-157 caused loss of rate-enhancing properties. From these results we conclude that for the rate-enhancing effect of A alpha-(148-160) the side chain of the amino acid residue at position A alpha-157 must fulfill certain requirements: there must be one (as in alanine) or no (as in glycine) carbon atom in the side chain, or at least two carbon atoms and a polar group (charged or uncharged) to which a rather bulky group (such as the benzyloxycarbonyl group) or a polar group (such as the methanesulphonylethyloxycarbonyl group) may be attached. The highest activity [even higher than native A alpha-(148-160)] was obtained with ornithine, methanesulphonylethyloxycarbonylornithine or methanesulphonylethyloxycarbonyl-lysine at position A alpha-157.
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PMID:Structural requirements of position A alpha-157 in fibrinogen for the fibrin-induced rate enhancement of the activation of plasminogen by tissue-type plasminogen activator. 190 25

Fibrinogen-NDSK complex is a model of protofibril having some features of the fibrin polymer structure. This complex has been studied for its ability to stimulate the plasminogen activation by t-PA. The fibrinogen-NDSK complex have increased the rate of plasminogen activation by t-PA as compared to fibrinogen or NDSK taken separately. This acceleration had slow and fast phases. Lys-plasminogen was activated more effectively as compared to glu-plasminogen. The kinetic parameters of glu- and lys-plasminogen activation at fast phase were: Km--0.18 and 0.015 mu/M, Kkat--0.27 and 0.06 s-1, respectively. Fibrinogen X2--fragments, deprived of alpha C-domains and NH2-end peptides of bB-chains, formed complexes with NDSK, which however did not stimulate the plasminogen activation by t-PA. These findings have shown that the fibrinogen-NDSK complex is an effective stimulator of the plasminogen activation by t-PA. The activating ability of the complex may be due to structures formed in the course of fibrinogen and NDSK polymerization as a result of alpha C-domain interaction.
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PMID:[Plasminogen activation by a tissue activator and effector properties of fibrinogen-N-terminal disulfide (N-DSK) fibrin complex]. 192 82

Modification of glutamic and aspartic acid residues of tissue-type plasminogen activator (t-PA) with 1-ethyl-3(3-dimethyl-aminopropyl)-carbodiimide leads to a decrease in affinity for lysine and fibrin, to a decrease of plasminogen activation activity in the presence of a fibrin mimic, but leaves amidolytic activity and plasminogen activation without fibrin mimic unaffected. Experiments with kringle-2 ligands and a deletion mutant of t-PA (K2P) suggests that glutamic or aspartic acid residues in K2 of t-PA are involved in stimulation of activity, lysine binding and fibrin binding. Mutant t-PA molecules were constructed by site-directed mutagenesis in which one or two of the five aspartic or glutamic acid residues in K2 were changed to asparagine or glutamine respectively. Mutation of Asp236 and/or Asp238 leads to t-PA molecules with 3- to 4-fold lower specific activity in the presence of fibrin mimic and having no detectable affinity for lysine analogs. However, fibrin binding was not influenced. Mutation of Glu254 also leads to a 3- to 4-fold lower activity, but to a much smaller reduction of lysine or fibrin binding. Residues Asp236 and Asp238 are both essential for binding to lysine derivatives, while Glu254 might be involved but is not essential. Residues Asp236, Asp238 and Glu254 are all three involved in stimulation of activity. Remarkably, mutation of residues Asp236 and/or Asp238 appears not to influence fibrin binding of t-PA whereas that of Glu254 does.
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PMID:Involvement of aspartic and glutamic residues in kringle-2 of tissue-type plasminogen activator in lysine binding, fibrin binding and stimulation of activity as revealed by chemical modification and oligonucleotide-directed mutagenesis. 196 88

The potential importance of pleural fibrin deposition in the pathogenesis of pleural injury is supported by both clinical and experimental observations. We hypothesized that the local equilibrium between procoagulant and fibrinolytic activities is disrupted to favor fibrin deposition in exudative pleuritis. To test this hypothesis, we characterized procoagulant and fibrinolytic activities in pleural exudates from patients with pneumonia, lung cancer, or empyema and transudates from patients with congestive heart failure. Procoagulant activity was generally increased in exudative processes and was due mainly to tissue factor. All effusions contained antithrombin III and inhibited factor Xa and thrombin, but endogenous prothrombinase or thrombin activities were variably detected. Pleural fluid fibrinolytic activity was increased in congestive heart failure and was due to both tissue plasminogen activator and urokinase. Depressed fibrinolytic activity was found in pleural exudates despite increased concentrations of plasminogen, mainly glu-1-plasminogen, and was due to inhibition of plasminogen activation by plasminogen activator inhibitors 1 and 2 and of plasmin, in part by alpha 2-antiplasmin. Concentrations of PAI-1 in exudative pleural fluids were increased up to 913-fold, compared with normal pooled plasma. Exudative pleural effusions are characterized by increased procoagulant and depressed fibrinolytic activity, favoring fibrin deposition in the pleural space. The balance of these activities is reversed and favors fibrin clearance in congestive heart failure.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Abnormalities of pathways of fibrin turnover in the human pleural space. 206 28

In this report, we have examined the effects of platelets on plasminogen activation by different activators. Platelets enhance activation of plasminogen by both 1- and 2-chain tissue plasminogen activator (t-PA). The primary effect of platelets is to lower the Km with a corresponding 5-8-fold increase in the kcat/Km. The effect is saturable with respect to the platelet concentration. Platelets enhance activation of both glu- and lys-plasminogen by t-PA. Platelets have no effect on plasminogen activation by streptokinase, and high and low molecular weight urokinase. Thus, there are marked differences in the effects of platelets on plasminogen activation depending on the plasminogen activator. These differences are likely to reflect differences in the interaction between platelets and the plasminogen activators.
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PMID:Differential effect of platelets on plasminogen activation by tissue plasminogen activator, urokinase, and streptokinase. 211 91

Tissue-type plasminogen activator (t-PA) catalyzes the rate-limiting step in the fibrinolytic cascade: conversion of plasminogen to plasmin. Plasma contains several inhibitors of t-PA that limit its activity and prevent systemic activation of plasminogen. The most important of these is endothelial cell plasminogen activator inhibitor (PAI-1), a member of the serine protease inhibitor (serpin) gene family. We have previously demonstrated that mutation of arginine 304 of t-PA to a glutamic acid residue drastically reduces the rate of interaction between the enzyme and its suicide substrate, PAI-1, without affecting the reactivity of the enzyme toward its normal substrate, plasminogen (Madison, E. L., Goldsmith, E. J., Gerard, R.D., Gething, M.J., and Sambrook, J.F. (1989) Nature 339, 721-724). We report here the use of protein modeling to design a compensatory mutation in PAI-1 (glutamic acid 350 to arginine) and create a molecule that rapidly inhibits this "serpin-resistant" variant of t-PA.
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PMID:Restoration of serine protease-inhibitor interaction by protein engineering. 212 70

A rapid and precise turbidimetric clot lysis assay employing a microtitre plate reader and personal computer is described in detail. The use of such widely available instrumentation, the convenience and rapid throughput suggest the assay could be developed as a reference method with which to measure the potency of tissue plasminogen activator (t-PA) in conjunction with the WHO reference preparation. The method has been used to investigate molecular parameters involved in fibrinolysis. Aggregation status of the fibrin does not appear to influence the mechanism of plasminogen activation and clot lysis by plasmin. High ratios of plasminogen to fibrin resulted in a change in clot turbidity and in a change in the lysis profile of turbidity versus time. This is probably the result of plasminogen binding to fibrin and consequent restriction of the access of plasmin to its sites of cleavage in the fibrin. A simple model is proposed, and equations have been derived, for the kinetics of lysis which adequately describe the mechanism and which are confirmed by experimental data. This model results in estimates of the Km and kcat for the activation of plasminogen by t-PA during clot lysis of approximately 150 nM and 0.1 s-1, respectively, in excellent agreement with published values. The assay should therefore prove useful in quantitative evaluations of the molecular phenomena occurring during fibrinolysis. The more rapid activation of lys-plasminogen than glu-plasminogen by t-PA was confirmed. However, evidence was obtained that the lys-form binds more tightly to fibrin by the same factor. This observation suggested that the appropriate substrate in the kinetic model is fibrin-bound plasminogen.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:A precise and rapid microtitre plate clot lysis assay: methodology, kinetic modeling and measurement of catalytic constants for plasminogen activation during fibrinolysis. 212 76


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