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

---

Query: EC:3.4.21.5 (thrombin)
33,306 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Inhibition of blood coagulation by peptide aldehydes has been studied. Amino acid sequences were assembled from the P1-P2 portion of the cleavage sites(s) of clotting factors and residues selected experimentally. The thrombin-fibrinogen reaction could effectively be inhibited by D-Phe-Pro-Arg-H (GYKI-14,166) and Boc-D-Phe-Pro-Arg-H (GYKI-14,451). Plasmin digestion of fibrin could be retarded by Boc-Gln-Phe-Lys-H (GYKI-14,605) derived from a susceptible fragment, i.e. Asn-Phe-Lys decreases to Ser. However, such peptides could not retard the zymogen activations proceeding in Ca++ complexes (which seemed to be uneffected by heparin-antithrombin III, too). Inhibition of enzymes by peptide aldehydes showed marked substrate dependence.
...
PMID:Design and synthesis of peptide inhibitors of blood coagulations. 617 98

Factor VIII (FVIII) procoagulant activity is the function of a plasma glycoprotein that is missing or inactive in patients with classic hemophilia. Numerous studies have shown that trace thrombin causes rapid enhancement followed by gradual inactivation of FVIII procoagulant activity. Recent evidence suggests that thrombin activation of the FVIII/von Willebrand factor (vWF) protein is required for inactivation to occur. All of these studies have used the one-stage partial thromboplastin time to assay FVIII activity. Other investigators have used the two-stage assay of FVIII activity and have been unable to demonstrate thrombin-induced enhancement of FVIII activity, although inactivation has consistently occurred. We performed experiments designed to help resolve this disagreement, using the two-stage assay specifically modified to detect thrombin potentiation of FVIII activity. The length of the first-stage incubation time was found to be critical in demonstrating the initial effect of thrombin on FVIII activity. Taking advantage of this finding we were able to show a 4.1 +/- 0.5-fold enhancement of FVIII activity upon incubating purified FVIII/vWF with 0.04 NIH unit thrombin per ml. The apparent enhancement of FVIII activity declined with increasing thrombin concentration. Incubation with 0.08, 0.16, and 0.32 NIH unit thrombin per ml resulted in only 3.2 +/- 0.5, 2.6 +/- 0.5 and 1.5 +/- 0.3-fold enhancement, respectively, of FVIII activity. As with results from the one-stage assay, activation was followed by slow inactivation of FVIII/vWF. Using the two-stage assay we also showed 100% inactivation and 100% inhibition of FVIII activity by plasmin and human anti-FVIII IgG, respectively. Plasmin inactivation of FVIII activity showed a dose-response effect. Thrombin was unable to activate plasmin-degraded FVIII/vWF. Our results show that thrombin potentiation of FVIII activity is easily demonstrable in the two-stage assay. These findings support the contention that activation of FVIII activity by thrombin is prerequisite for inactivation and underscore the importance of thrombin activation of FVIII/vWF in the intrinsic clotting system.
...
PMID:Thrombin potentiation of factor VIII procoagulant activity: assessment by the two-stage assay. 621 66

A series of proteases of diverse substrate specificity were tested for their effect on respiratory syncytial virus-induced cytopathology. Three of the enzymes, thrombin, plasmin, and trypsin, were able to augment significantly the fusion of virus-infected A549 cells. On a concentration basis, thrombin was the most active promoter, followed by plasmin and then trypsin. Hirudin, a specific thrombin inhibitor, blocked the fusion-enhancing property of thrombin, yet had no influence on the basal rate of fusion in the absence of the enzyme. By contrast, the amidine-type inhibitors of trypsin-like proteases, bis(5-amidino-2-benzimidazolyl)-methane (BABIM), blocked not only the thrombin effect, but also the fusion in the thrombin-free controls. The suppressive activity of BABIM was observed at concentrations so low as to exclude any direct inhibitory effect on thrombin itself. These results make it seem very likely that thrombin advances cell fusion by activating a BABIM-sensitive protease. Plasmin and trypsin can be expected to act in a similar manner.
...
PMID:Enhancement of respiratory syncytial virus-induced cytopathology by trypsin, thrombin, and plasmin. 621 57

Fibrinolysin immobilized by a solid polysaccharide carrier capable of controllable biodegradation is shown to exert a local effective thrombolyzing action. Certain results of clinical studies of immobilized streptase (streptodecase) are presented. They show essential advantages of the new preparation over the known native enzymes. Experiments with animals show that the immobilized thrombin may be applied in therapeutic embolization for the hemorrhage cessation.
...
PMID:[Clinico-experimental study of the possibility of the use of immobilized enzymes for local thrombolysis and thromboformation]. 622 28

Interaction of human plasmin with a monolayer culture of mini-pig aortic endothelial cells was studied by using the 125I-labelled enzyme. The binding of plasmin was time- and concentration-dependent. Equilibrium between bound and free enzyme was obtained within 90s, and Scatchard analysis indicated a high- and a low-affinity population of binding sites of approx. 1.24 X 10(4) sites/cell having a Kd of 1.4 X 10(-9) M and 7.2 X 10(4) sites/cell with a Kd of 2 X 10(-8) M respectively. Plasmin, bound to cell, was spontaneously released within 2 min, suggesting a rapid equilibrium. Chemical modification of the enzyme with phenylmethanesulphonyl fluoride or pyridoxal 5'-phosphate revealed that neither the active centre nor the heparin-binding site of plasmin was involved in the interaction with the endothelial cell. In terms of endothelial-cell receptors, the binding sites of cells for plasmin and thrombin were different: the two enzymes did not compete with each other, and the pretreatment of cells with neuraminidase or chondroitin ABC lyase resulted in a 50% decrease of thrombin or plasmin binding respectively. Arachidonic acid incorporated into phospholipids of the cell was released by plasmin, but a change in the rate of prostacyclin formation was not measurable. The interaction of plasmin with endothelial cells seems to be specific in the fibrinolytic system, since plasminogen did not bind to these cells under similar conditions.
...
PMID:Interaction of plasmin with endothelial cells. 623 20

Treatment of platelets (10(9) cells/ml) with thrombin (1 U/ml) resulted in rapid disappearance of fibrinogen from the system as measured by the tanned red cell hemagglutination inhibition immunoassay (TRCHII). Plasmin digestion of individual pellet and supernatant fractions that had been previously separated from thrombin-treated platelet suspensions by centrifugation resulted in recovery of TRCHII-detectable material in platelet pellets. To elucidate the specific association of fibrin to platelet membranes, control and thrombin-treated platelets were homogenized by a modified glycerol-loading and nitrogen decompression technique. Ultracentrifugation of homogenates through 27% sucrose cushions yielded three subcellular fractions: supernatant, small membrane vesicles, and a particulate fraction for controls; and supernatant membrane vesicles, and aggregated membrane "ghosts" for thrombin preparations. Ultrastructurally identifiable fibrin was noted only in the thrombin fraction containing membrane ghosts. Fibrinogen recovered from 3 thrombin fractions was markedly decreased (3% of the control). Plasmin digestion produced 23% and 46-fold increase in TRCHII-detectable material from 3 subcellular fractions of control and thrombin preparations, respectively. More than 97% of TRCHII material recovered from thrombin preparations was in the fraction containing aggregated membrane fractions. Results suggest that platelet plasma membranes function as surfaces for fibrin deposition.
...
PMID:Localizaton of fibrin converted by thrombin from released platelet fibrinogen. 644 58

Interaction of urokinase (UK) activated plasmin with tranexamic acid and alpha 2 plasmin inhibitor (alpha 2PI) was studied by using a chromogenic substrate (S-2251) and immunoelectrophoresis. Plasma was activated by UK (P + U) in the presence of tranexamic acid (P + U + t) or in the presence of thrombin (P + U + thr) and thrombin plus tranexamic acid (P + U + thr + t). These mixtures were incubated for 10, 20, and 30 min at 37 degrees C, then an aliquot of each mixture was added to S-2251, and incubated for 3 or 10 min at 37 degrees C. Hydrolysis of S-2251 after 3 min incubation was significant in the presence of tranexamic acid or clot formation, thus the presence of tranexamic acid or clot formation enhancing the UK activation of plasminogen in both plasma and clot. Hydrolysis of S-2251 after 10 min incubation was higher in the presence of tranexamic acid than in its absence or clot formation without tranexamic acid. Tranexamic acid seems to be more effective in enhancement of activation of plasminogen by UK than clot formation. Plasmin formed by UK was coexistent with alpha 2PI in the plasma in contrast to a purified system in which alpha 2PI formed a complex with plasmin instantaneously. In an even purified system, clot formation and the presence of tranexamic acid protected plasmin from its inactivation by alpha 2PI to some extent.
...
PMID:Interaction of plasmin with tranexamic acid and alpha 2 plasmin inhibitor in the plasma and clot. 644 83

Purified human C9 was treated separately with three proteolytic enzymes: trypsin, plasmin, and alpha-thrombin, and the digestion products were analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Trypsin initially cleaved the Mr = 71,000 C9 to produce a Mr = 47,000 fragment plus numerous smaller fragments and prolonged digestion reduced the molecule to small polypeptides. Plasmin produced a Mr = 37,000 fragment which was stable to further digestion, plus fragments smaller than Mr = 10,000. Human alpha-thrombin cleaved C9 (7.8% carbohydrate) at a single internal site to produce a Mr = 37,000 fragment (11.3% carbohydrate) and a Mr = 34,000 fragment (3.9% carbohydrate). Statistical analysis of the amino acid compositions of the fragments and alkaline polyacrylamide gel electrophoresis showed that C9 is highly amphiphilic; the Mr = 34,000 fragment contains a majority of the acidic amino acids and migrates rapidly on alkaline gels; the Mr = 37,000 fragment is hydrophobic with a slow electrophoretic mobility. The two fragments remain noncovalently associated, but were separated by sodium dodecyl sulfate-hydroxylapatite chromatography. The NH2-terminal sequence analysis of native C9, of alpha-thrombin-cleaved C9, and for the isolated fragments showed that the acidic Mr = 34,000 fragment is the NH2-terminal C9a domain and the more hydrophobic Mr = 37,000 fragment is the carboxyl-terminal C9b domain. Hemolytic activity of C9 was unaffected by alpha-thrombin cleavage.
...
PMID:An amphiphilic structure of the ninth component of human complement. Evidence from analysis of fragments produced by alpha-thrombin. 646 Jul 61

Although plasmin can trigger strong platelet responses such as shape change and exocytosis of internal granules, limited platelet aggregation is induced by this proteinase, owing to its capacity to rapidly proteolyse secreted adhesive proteins. In this context, we have investigated the state of activation of the fibrinogen receptor, the integrin alpha IIb beta 3, on platelets exposed to plasmin. Following incubation with plasmin at 37 degrees C, washing, and resuspension, platelets exhibit a moderate, low-velocity aggregation when stirred in the presence of fibrinogen. Optimum aggregability is observed when platelets have been exposed to plasmin activity of approximately 0.5 CU/ml for 20 min, and aggregation is insensitive to the presence of antagonists such as prostaglandin (PG) E1 and apyrase. Plasmin-induced platelet aggregability is associated with the expression of active fibrinogen receptors on the cell surface, which, using a 125I-fibrinogen binding assay, can be quantified to approximately 2,300 molecules per platelet. Exposure of active alpha IIb beta 3 receptors appears to depend partially, but not totally on a metabolic activation and granule exocytosis at the time of incubation with plasmin. In contrast with alpha-thrombin, plasmin-induced activation of alpha IIb beta 3 is sustained and cannot be reversed by exposure of platelets to PGE1. Immunoblotting analysis of the receptor subunits shows no extensive proteolytic modification of alpha IIb beta 3 by plasmin, and only reveals a limited proteolysis of the aminoterminal domain of the alpha IIb subunit. In addition to their capacity to aggregate in the presence of fibrinogen alone, plasmin-treated platelets also show a potentiated aggregability in response to low doses of ADP.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Exposure of human platelets to plasmin results in the expression of irreversibly active fibrinogen receptors. 749 81

Binding of plasmin(ogen) to rat C6 glioma cells is saturable and kringle-domain dependent. This interaction was studied as a model of plasmin(ogen) receptor interactions in nucleated mammalian cells. Apparent 125I-plasmin dissociation from C6 cell binding sites was slow; however, the dissociation rate was increased when the solution contained diisopropyl phosphoryl-plasmin (0.3 microM), fibrinogen (0.16 or 0.8 mg/ml), 1.08 mM D-Val-L-Leu-L-Lys-p-nitroanilide-HCl (S-2251), or epsilon-amino-n-caproic acid (EACA, 5.0 mM). EACA promoted the most rapid dissociation of plasmin. C6 cell-associated plasmin and plasmin in solution demonstrated similar amidase activity. Only specifically bound plasmin (75% of total binding) was active against S-2251. Plasmin that was initially bound to C6 cells digested fibrinogen in a time- and plasmin concentration-dependent manner. alpha 2-Antiplasmin (alpha 2AP, 0.1 microM) completely inhibited fibrinogenolysis by plasmin that was initially C6- or human umbilical vein endothelial-cell associated. Since alpha 2AP reacts selectively with plasmin in solution (minimally with plasmin bound to cells), fibrinogen digestion by cell-associated plasmin probably occurred only after the plasmin dissociated into solution. Crosslinked fibrin clots were formed in uniform layers over C6 cells. If the cells were incubated with plasmin before addition of fibrinogen and thrombin, the clots were rapidly lysed. alpha 2AP incompletely inhibited fibrinolysis when added after fibrin polymerization (44% inhibition with 0.1 microM alpha 2AP). Fibrinolysis was completely inhibited when alpha 2AP was added before fibrin polymerization. These studies suggest that plasmin must first dissociate from cellular binding sites to mediate fibrinogenolysis or fibrinolysis.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Fibrinogenolytic and fibrinolytic activity of cell-associated plasmin. 767 97


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---