Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P00750 (PLA)
 16,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Gastric juice from 15 normals, 20 patients with gastric ulcer and 14 patients with erosive haemorrhagic gastroduodenitis was investigated in respect of its activity on unheated and heated fibrin plates and its content of FDP and plasminogen or plasmin with immunochemical methods. Gastric juice from normals showed no activity on unheated and heated fibrin plates, and no FDP or plasminogen could be demonstrated. In the patients with gastric ulcer the gastric juice showed little or no fibrinolytic activity on fibrin plates except in 2, who had regurgitation of duodenal juice and neutral pH of the juice. These patients had equally high activity on heated as on unheated plates and no plasmin could be demonstrated. It was shown that this activity was not due to fibrinolysis, but to non-specific proteolytic activity (probably trypsin). The patients with erosive haemorrhage gastroduodenitis exhibited quite a different picture. The gastric juice from these patients showed extremely high activity on fibrin plates, the activity was higher on unheated than on heated plates. The activity was inhibited in vitro by addition of EACA and in vivo after administration of AMCA. The occurence of plasmic could be demonstrated directly immunologically in the gastric juice. By comparsion of plasmin and trypsin in various assays it could further be improved that the gastric juice in these cases contained plasminogen activator and plasmin. The patients with erosive haemorrhagic gastroduodenitis showed no increase in fibrinolysis in the blood, but low values for plasminogen and alpha2-M, and the serum contained FDP. These findings in the blood and gastric juice were interpreted as signs of local fibrinolysis in the stomach and duodenum. There is reason to assume that this gastric fibrinolysis contributes substantially to the bleeding tendency. The effect of administration of AMCA on fibrinolytic activity and the haemorrhage lends support to the assumption of such a mechanism.
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PMID:Gastric fibrinolysis. 0 Aug 7

It has previously been shown, that large differences exist between the effects of 6-aminohexanoic acid or alpha1-antitrypsin on fibrinolysis caused by a porcine tissue plasminogen activator or by human urokinase, while insignificant differences exist between the effects of a number of natural protease inhibitors on fibrinolysis caused by the two types of plasminogen activator. The present study shows that changes in substrate composition (pH, ionic strength fibrinogen concentration, plasminogen concentration) may influence to different degrees the fibrinolytic activities of human urokinase and the porcine tissue plasminogen activator. It is suggested, that this finding is partly related to marked differences in affinity for fibrin of the two activators.
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PMID:Differences in the reactivities of human urokinase and the porcine tissue plasminogen activator. 1 58

The major plasmin inhibitors namely alpha2-plasmin inhibitor and alpha2-macroglobulin were compared for their effects on lysis of fibrin clot. Plasmin fibrinolytic activity was immediately inhibited by alpha2-plasmin inhibitor, whereas alpha2-macroglobulin inhibited plasmin progressively. Urokinase(plasminogen activator)-induced clot lysis was inhibited efficiently by alpha2-plasmin inhibitor present in the clot. Inhibition of urokinase-induced clot lysis by alpha2-macroglobulin was weak and the molar concentration necessary for alpha2-macroglobulin to achieve the same degree of inhibition as that achieved with alpha2-plasmin inhibitor was about 10 times higher than that of alpha2-plasmin inhibitor. Binding of Lys-plasminogen to fibrin was inhibited by alpha2-plasmin inhibitor but not by alpha2-macroglobulin. Molar concentrations of alpha2-plasmin inhibitor which were effective in inhibiting the binding were 30 times less than that of 6-aminohexanoicacid. alpha2-Plasmin inhibitor was found to interact with Lys-plasminogen to form a weakly-bound complex which is dissociable in the presence of 6-aminohexanoic acid, suggesting that inhibition of binding of Lys-plasminogen to fibrin by alpha2-plasmin inhibitor may be due to interaction of alpha2-plasmin inhibitor with a specific site of the plasminogen molecule and that the site may be 6-aminohexanoic acid-binding site. It is suggested that alpha2-plasmin inhibitor is more reactive and efficient inhibitor of fibrinolysis than alpha 2-macroglobulin.
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PMID:Effects of alpha2-plasmin inhibitor on fibrin clot lysis. Its comparison with alpha2-macroglobulin. 7 50

Three types of plasminogen activator could be distinguished in extracts from human uterine tissue. The activators differed in thermostability or in mode of inhibition by EACA. All the extracts contained stable as well as labile activators. The saline extracts were uniformly inhibited by increasing concentrations of EACA. Extracts made with 2 M ammonium thiocyanate were either uniformly inhibited by EACA or showed deflections indicating contamination with an activator, which was inhibited in a biphasic manner. It was possible to distinguish between: (1) An activator, abundantly present in the tissue, which was uniformly inhibited and stable. (2) Another uniformly inhibited activator, which was labile. (3) An activator, inhibited in a biphasic manner, similar to urokinase, which was present in varying amounts in uteri with the endometrium in the proliferative phase. Gel filtration of the uterine extracts showed two major activity peaks corresponding to particle sizes of 60,000 dalton and about 10,000 dalton. Antiserum to purified plasminogen activator, prepared from porcine ovaries, inhibited the activity of the human uterine extracts, but not the activities of human urokinase or urine. Urokinase antiserum in a concentration completely inhibiting human urine or urokinase, inhibited only 10% or less of the activities of human uterine extracts.
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PMID:Separation of plasminogen activators from human uterine tissue and a comparison with activators from human urine and porcine tissue. 11 1

Fibrinogen was depleted in dogs injected with a single dose of bothropase even if pretreatment followed by a continuous infusion of antifibrinolytic drugs was performed during defibrination. The activation of the fibrinolytic system as a secondary effect of the defibrination syndrome induced by bothropase injection was blocked completely by aprotinin (Trasylol) but not by EACA. Plasmin activity in spite of the inhibition of plasminogen activator suggests that, either an excess of activator is released in circulation or a plasmin-antiplasmin complex is dissociated by the circulating fibrin, according to the hypothesis of Ambrus and Markus [1], and Back et al. [4] for the mechanism of fibrinolysis in vivo. An experimental model is suggested for the study of the fibrinolytic mechanism in vivo, by the association of defibrinating agents, antivenom and antifibrinolytic drugs.
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PMID:Experimental defibrination and bothropase: a study on the fibrinolytic mechanism in vivo. 14 12

Normal human plasma contains acid-stable as well as labile plasminogen activators. The activity of activators in plasma euglobulins was inhibited by EACA in an uniform pattern, similar to that obtained with the major activators in human uterine tissue or with the purified porcine tissue activator, but different from the patterns obtained with plasmin or with urokinase. Gel filtration at high ionic strength separated activators corresponding to particle sizes of 60,000 dalton and about 10,000 dalton, corresponding to two activators similarly obtained from human tissue. The 60,000 dalton activator was precipitated in the euglobulin fraction. Its concentration increased in plasma after exercise. The 10,000 dalton activator was found mainly in the supernatant. Gel filtration in 0.15 M solutions yielded activators in fractions of molecular sizes of 100-140,000 dalton and 200,000 dalton or larger. The activity of normal and exercise euglobulins was inhibited by antiserum to a plasminogen activator prepared from porcine tissue, but it was not inhibited by antiserum to urokinase. Plasminogen activators in human plasma euglobulins resembled immunochemically the activators in human uterine tissue.
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PMID:Separation of plasminogen activators from human plasma and a comparison with activators from human uterine tissue and urine. 48 46

The binding, internalization, and degradation of tissue-type plasminogen activator (t-PA) were studied in a rat hepatoma (Novikoff) cell line. Binding of t-PA to specific saturable high affinity binding sites (Kd = 12 nM, 54,000 sites/cell) was followed by internalization and degradation and did not require a functional active site. The catabolism of t-PA was not inhibited by an excess of urokinase-type plasminogen activator (u-PA), and t-PA bound to Novikoff membranes was not complexed to PAI-1, suggesting a mechanism independent of PAI-1. Additionally, a mannose receptor is not involved since t-PA binding was not influenced by an excess of mannose, galactose, ovalbumin, or EDTA. Furthermore, the degradation of t-PA was not influenced by 10 mM 6-aminohexanoic acid, a lysine analogue. The t-PA receptor binds to and can be eluted from wheat germ agglutinin-Sepharose. Cross-linking of t-PA with partially purified receptor and ligand blot analysis, suggest that t-PA binds to two proteins, a principal one of 55 kDa and a minor one of 43 kDa. Novikoff cells are able also to bind (Kd = 1.4 nM, 25,000 sites/cell) and degrade u-PA. The binding was inhibited by pro-u-PA and the amino-terminal fragment of u-PA, but not by an excess of t-PA. The u-PA receptor, but not the t-PA receptor, was removed by treatment with phosphatidylinositol-specific phospholipase C. Our results show that the clearance receptor for t-PA on Novikoff cells is different from the mannose receptor and the PAI-1-dependent receptor described in other cells. The rat hepatoma cells are thus a good model to study the PAI-1 independent hepatocyte-specific clearance of t-PA.
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PMID:Demonstration of a specific clearance receptor for tissue-type plasminogen activator on rat Novikoff hepatoma cells. 131 32

The specific binding sites for tissue-type plasminogen activator (t-PA) were investigated in human umbilical vein endothelial cells. After adding 125I-t-PA (M.W. 70 kDa) to endothelial cells in suspension culture, the ligand was recovered from the cell extract after disuccinimidyl suberate treatment as a high molecular complex with M.W. of 90 kDa on SDS-PAGE. The complex reacted to only anti-t-PA IgG but not to anti-PAI-1 IgG immunoblot analysis, indicating a t-PA specific binding protein. 125I-t-PA ligand blotting of the cell extract revealed that the binding protein had M.W. 20 kDa. The binding of 125I-t-PA to endothelial cells was reduced in the presence of an excess amount of t-PA, plasminogen and 6-aminohexanoic acid, indicating that the binding sites were also recognized by plasminogen, and that t-PA and plasminogen were bound via lysine binding sites in the molecule. These findings suggest that human endothelial cells have specific t-PA binding molecules which may be expressed on the cell surface as t-PA receptors.
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PMID:Analysis of binding protein for tissue-type plasminogen activator in human endothelial cells. 132 62

The properties of the cationic locus within the recombinant (r) kringle 2 domain (residues 180-261) of tissue-type plasminogen activator ([K2tPA]) that are responsible for stabilization of its interaction with the carboxylate moiety of omega-amino acid ligands have been assessed by determination of the binding constants of several such ligands to a variety of r-[K2tPA] mutants obtained by oligonucleotide-directed mutagenesis. We have generated, expressed in Escherichia coli, and purified alanyl mutants of individual histidyl,lysyl, and arginyl residues of r-[K2tPA] and determined the dissociation constants of several omega-amino acids, viz., 6-aminohexanoic acid (6-AHxA), 7-aminoheptanoic acid (7-AHpA), L-lysine (L-Lys), and trans-(aminomethyl)cyclohexane-1-carboxylic acid (AMCHA), to each of the r-[K2tPA] variants. We find that K33 plays the most significant role as a cationic partner of the complementary carboxylate group of these ligands. When K33 is altered to a variety of other amino acids, the K33R mutant best stabilizes binding of all of these ligands. However, the r-K33L and r-K33F variants selectively interact with 7-AHpA almost as strongly (ca. 2-fold reduction in binding strength) as wild-type r-[K2tPA]. Increased polarity (K33Q) or a negative charge (K33E) at this sequence position significantly destabilizes binding of omega-amino acids to the muteins. We also found that the r-K33E mutant and, to a lesser extent, the r-K33Q variant selectively interact with a new ligand, 1,6-diaminohexane. These observations show that the omega-amino acid binding site of wtr-[K2tPA] could be redesigned to provide a new binding specificity.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The cationic locus on the recombinant kringle 2 domain of tissue-type plasminogen activator that stabilizes its interaction with omega-amino acids. 133 68

Plasmin inhibition by alpha 2-antiplasmin (alpha 2AP) is regulated by the vascular components fibrin(ogen) fragments, plasminogen and lipoprotein (a). Kinetic analysis demonstrates that CNBr-derived fibrinogen fragments completely protect plasmin from alpha 2AP. Plasminogen and 6-aminohexanoic acid decrease the rate of inhibition by 5- and 10-fold respectively. These studies show that CNBr-derived fibrinogen fragments and 6-aminohexanoic acid bind plasmin kringle(s) with binding constants of 2 micrograms/ml and 120 microM respectively, and that plasminogen binds to alpha 2AP with an affinity of 0.5 nM. The unmodulated inhibition is not effected by the presence of lipoprotein (a), but in the presence of protective CNBr-derived fibrinogen fragments the rate of inhibition is increased by the presence of the lipoprotein. The kinetics demonstrate that lipoprotein (a) binds to CNBr-derived fibrinogen fragments with an affinity of 4 nM, displacing plasmin from the protective surface. In addition, tissue-type plasminogen activator and trypsin inhibition by alpha 2AP is not slowed by the presence of CNBr-derived fibrinogen fragments or plasminogen (Pg), respectively. These kinetics suggest that the initial reversible interaction between plasmin and alpha 2AP is mediated by binding of the inhibitor to the kringle 1 domain of plasmin, with a reversible inhibition constant (Ki) of 5.0 x 10(-10) M. Under conditions where this kringle-inhibitor interaction is blocked, the reversible inhibition still occurs between the plasmin and alpha 2AP, but the initial Ki is increased to 5.0 x 10(-9) M. These data suggest that, in the circulation, plasmin inhibition by alpha 2AP may be down-regulated by fibrin, fibrin(ogen) fragments and Pg, but up-regulated by lipoprotein (a) in the presence of fibrin or fibrin(ogen) fragments. The lipoprotein (a)-mediated promotion of plasmin inhibition may provide an additional mechanism by which the lipoprotein impairs fibrinolysis and promotes atherosclerosis.
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PMID:Lipoprotein (a) promotes plasmin inhibition by alpha 2-antiplasmin. 138 85


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