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

Treatment of patients with interferon or inducers of interferon results in an enhanced level of a protein kinase activity found in platelets (1,3). The kinase activity is responsible for the phosphorylation of a 70-72,000 molecular weight protein (72K protein) found in blood plasma. By the means of a technique based on the precipitation of this protein kinase system (the protein kinase and its substrate), we show here that the 72K protein is the alpha-chain of fibrinogen. During the coagulation process induced by thrombin, the 32P-labelled 72K protein is recovered in the clot. After incubation in the presence of thrombin, the 72K protein looses a small polypeptide of 2-3000 in molecular weight resulting a shift in its isoelectric point (pI) from 6.8-7.0 to 7.5. At the end of the coagulation process, the 32P-labelled 72K protein becomes undetectable since it gives rise to a covalently linked alpha-polymer of a high molecular weight. In accord with these results, the 72K protein could be precipitated by antibodies against human fibrinogen.
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PMID:Phosphorylation of the alpha-chain of fibrinogen by a platelet kinase activity enhanced by interferon. 619 71

Experimental conditions required for the expression of maximum C5 activation upon limited trypsin hydrolysis were determined to be 0.008 mol of trypsin/mol C5 in a reaction mixture containing 1 mg C5/ml veronal-buffered saline incubated at 37 degrees C for 30 min. Employing these optimal incubation conditions, the primary or preferred site of trypsin hydrolysis of the C5 alpha-chain resulted in the production of C5 alpha 1 (molecular weight, 90,000) and C5 alpha 5 (molecular weight, 25,000) fragments that remained disulfide bonded to the modified C5 molecule (C5'try). Detailed structural-functional analyses clearly indicated the trypsin-mediated conversion of the C5 alpha-chain to C5 alpha 1 and C5 alpha 5 was responsible for the acquisition of neutrophil lysosomal enzyme-releasing and chemotactic activities. Gel filtration column chromatography under physiological ionic strength, pH 7.4, or in the presence of 0.2% SDS further demonstrated that at least 90% of the total recoverable C5a-like biological activity was mediated by the 210,000 molecular weight forms of trypsin-modified C5. Other physiologically relevant, noncomplement protease enzymes (alpha-thrombin, plasmin, and elastase) also activated C5 to express C5a-like reactivities. Analysis of alpha-thrombin-induced, C5 alpha-chain cleavage events by SDS-polyacrylamide slab gel electrophoresis indicated that the mechanism of alpha-thrombin-activation of C5 is similar to that described for trypsin. Reconciliation of this novel mechanism of C5 activation by trypsin with previously published results, and a discussion of the biological significance of noncomplement enzyme-mediated activation of C5 as it might relate to inflammatory processes in vivo, was presented.
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PMID:Expression of C5a-like biological activities by the fifth component of human complement (C5) upon limited digestion with noncomplement enzymes without release of polypeptide fragments. 622 37

Platelet glycoprotein (GP) Ib from 131 healthy Japanese was analyzed using SDS-polyacrylamide gel electrophoresis and specific staining with peroxidase-coupled wheat germ agglutinin after it was transferred to nitrocellulose membranes. Four slightly different species of GPIb were observed and designated as A, B, C, and D for glycoproteins with molecular weights of 168,000, 162,000, 159,000, and 153,000 daltons, respectively. The respective gene frequencies were calculated to be .073, .011, .561, and .355 for A-, B-, C-, D-type GPIb. Portions from each type of GPIb molecule (alpha-chain and glycocalicin) showed heterogeneity with the same molecular weight difference, indicating that the variance would be derived from the polypeptide portion that is exposed to the outer medium. The different types of GPIb were the same with respect to their accessibility to lactoperoxidase, reactivity to lectins, and affinity to TLCK-thrombin. Although Bolin et al reported patients with a bleeding tendency whose platelets have double GPIb bands, here we found that platelets with different GPIb phenotypes showed no significant differences in aggregating activity and platelet retention. Analysis of GPIb phenotype should be important for structural and physiologic studies on GPIb and glycocalicin.
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PMID:Genetic polymorphism of platelet glycoprotein Ib. 623 67

The anticoagulant properties of fibrinogen digestion products change with stage of digestion. On digestion with leukocyte elastase, in the presence of calcium ions, the anticoagulant potency of fibrinogen digests first increases, then decreases sharply, and in late stages increases again. This is different from plasmin digestion where only an increase in anticoagulant activity is seen followed by a slow decrease. From SDS-gel electrophoresis it appears that both the early rise and the decrease in anticoagulant activity are associated with the stage of elastase-produced X-like fragments. This is confirmed with pure fragments: X-like fragments (purified from elastase digests of fibrinogen of different stages by ammonium sulphate precipitation and ion-exchange chromatography) give an increase and decrease in anticlotting activity which correlates very well with that of the potency of the digest from which they are purified. As expected, and in contrast with (late) plasmic X-fragments, late elastase X-like fragments have a low anticoagulant potency. The molecular basis for the gain and loss in anticoagulant activity going from early to late X-like fragments is obscure. Immunological tests, calcium-binding experiments and affinity chromatography on immobilized thrombin-activated NDSK suggest that the changes in anticoagulant activity are not due to a proteolytic change in the carboxyl-terminal part of the gamma-chain in the D moiety of the molecule. Our data suggest a correlation with the stage of digestion of the A alpha-chain in the X-like fragments.
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PMID:Anticoagulant properties of purified X-like fragments of human fibrinogen produced by degradation with leukocyte elastase. 623 43

The incorporation of gentamycin, neomycin and Polymyxin E into fibrin seal results in prolonged clotting time after mixture with 4 NIH-units of thrombin per ml in vitro. The aminoglycoside antibiotics gentamycin and neomycin also diminished fibrin-alpha-chain crosslinkage and, as a consequence, clot rigidity, as demonstrated with clots containing gentamycin. Clotting time and the rate of alpha-chain crosslinking can be adjusted to normal values by the use of higher thrombin concentrations and incorporation of additional factor XIII into the sealing system. Drug release from the clots was similar for all three antibiotics tested and mainly dependent on the concentration gradient between the clot and its environment. Under the conditions of the present study, about 85% of the antibiotic content of fibrin seal clots were released within 72 h.
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PMID:In vitro properties of mixtures of fibrin seal and antibiotics. 660 97

A fibrinogenolytic enzyme was isolated from the venom of Western Diamondback rattlesnake (Crotalus atrox) by a three-step procedure involving gel filtration and anion-exchange chromatography. The molecular weight was estimated as 22 900 by SDS-polyacrylamide gel electrophoresis. The isoelectric point was found to be pH 4.65. The enzyme rapidly destroyed the ability of bovine fibrinogen to form a clot on incubation with thrombin. Incubation of fibrinogen with the fibrinogenolytic enzyme for 5 min resulted in the disappearance of the beta-chain of fibrinogen and the appearance of lower molecular weight fragments. Thus the enzyme can be classified as a beta-fibrinogenase. However, on prolonged incubation of the fibrinogen there was also a partial digestion of the alpha-chain. The fibrinogenase showed no activity towards fibrin or casein or arginine esters. The fibrinogenolytic activity was inhibited by phenylmethanesulphonyl fluoride (PMSF) but was unaffected by EDTA.
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PMID:Purification and characterization of a fibrinogenase from the venom of Western Diamondback rattlesnake (Crotalus atrox). 661 43

The number of described individuals with congenital dysfibrinogenemia continuously increases, but only a few fibrinogen variants have thus far been characterized with respect to their structural defect. Fibrinogen Bern II is a hereditary fibrinogen variant with impaired release of fibrinopeptide A (FPA) and a markedly prolonged coagulation time. It turned out that only half of the FPA was cleaved off at normal rate while the residual FPA was released much more slowly and incompletely, unless high thrombin concentrations were used. Amino acid analysis of normal and abnormal FPA revealed that the abnormal peptide, in contrast to the normal, contained histidine but hardly any arginine. It is therefore concluded that fibrinogen Bern II undergoes substitution of arginine in position 16 of the A alpha-chain by histidine. Thus, the structural alteration is identical with that of seven other recently described variants. The presence of 50% normal fibrinogen molecules provides the normal hemostasis in the heterozygous carriers of the Bern II-dysfibrinogenemia.
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PMID:[Fibrinogen Bern II: hereditary fibrinogen variant with amino acid substitution of arginine replaced by histidine in position 16 of the A alpha chain]. 664 27

One of the fractions obtained by the carboxymethylcellulose ion-exchange chromatography of northern copperhead (Agkistrodon contortrix mokasen) venom prevented the thrombin-induced clotting of fibrinogen by proteolytically degrading the fibrinogen. The active component has been further purified to apparent electrophoretic homogeneity by molecular sieve chromatography. Sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis indicated a molecular weight of 22 900 +/- 600 for the purified enzyme. In addition to its fibrinogenase activity, it catalyzed the hydrolysis of hide power azure and had an intraperitoneal LD50 value in mice of less than 5.1 microgram/g body weight. The enzyme rapidly destroyed fibrinogen's ability to form clots. Electrophoresis of fibrinogen which had been incubated only a few minutes with the fibrinogenase revealed the rapid disappearance of the alpha-chain and the appearance of lower molecular weight fragments. The neutral pH optimum and ethylenediamine-tetraacetic acid (EDTA) and dithiothreitol sensitivity indicated that this enzyme belonged to the class metalloproteinases. Atomic absorption studies have revealed one zinc atom per molecule of protein. The apoenzyme's activity was restored by incubation with ZnCl2.
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PMID:Characterization of a fibrinogenase from northern copperhead (Agkistrodon contortrix mokasen) venom. 678 89

Fibrinopeptides A and B were removed from purified human fibrinogen by bovine thrombin, whereas the snake venom protease batroxobin only split fibrinopeptide A from fibrinogen. Aggregation of the resulting desAB- and desA-fibrin monomers was evaluated by recording the turbidity of incubation mixtures. Fibrin assembly was strongly accelerated by increasing the calcium concentration from 10(-5) to 10(-3) M. Fragment D was obtained from fibrinogen by proteolytic degradation with plasmin in the presence of Ca2+. At a 4-fold molar concentration relative to fibrinogen, fragment D dramatically inhibited fibrin polymerization at up to 10(-4) M Ca2+. This anticlotting activity was, however, much less pronounced at 10(-3) M Ca2+. The thrombin clotting time, measured on human plasma, was prolonged by fragment D in a dose-dependent manner. In citrate-containing plasma, the fibrinogen clotting was significantly delayed by an equimolar concentration of fragment D. In barium sulfate-adsorbed oxalated plasma, containing 2.5 mM Ca2+, the same amount of fragment D hardly affected fibrin polymerization. We conclude that fragment D has no important anticlotting effect under physiological conditions. The synthetic peptide Gly-Pro-Arg, corresponding to the amino-terminal sequence of the fibrin alpha-chain, inhibited aggregation of both desA-fibrin and desAB-fibrin at 10(-3) M Ca2+. The inhibition of desAB-fibrin polymerization by Gly-Pro-Arg was abolished at 10(-5) M Ca2+. In addition, Gly-Pro-Arg depressed the anticlotting activity of fragment D at low calcium concentration. An analogue of the amino-terminus of fibrin beta-chain, Gly-His-Arg, strongly accelerated aggregation of desA-fibrin monomers, but only moderately enhanced polymerization of desAB-fibrin monomers at 10(-5) M Ca2+, both in the presence and in the absence of fragment D. This activating effect of Gly-His-Arg was abolished at 10(-3) M Ca2+. It is suggested that the binding of calcium, Gly-His-Arg, and possibly also Gly-Pro-Arg, induces a conformational change in fibrin monomers and thus accelerates the polymerization process.
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PMID:Inhibition of fibrin polymerization by fragment d is affected by calcium, Gly-Pro-Arg and Gly-His-Arg. 682 84

The role of fibrinogen as a cofactor in platelet aggregation is mediated by its binding to platelet receptors that are induced by stimuli such as ADP. In the present study, we demonstrate that the tetrapeptide glycyl-L-prolyl-L-arginyl-L-proline inhibits the interaction of fibrinogen with its platelet receptor. The primary effect of the peptide was on the extent rather than on the rate of fibrinogen binding. Significant inhibition occurred at a 1:1 molar ratio of peptide to fibrinogen and reached maximal levels at 100:1 ratio. The inhibition was dependent upon fibrinogen concentration and occurred in the presence of calcium or magnesium. The peptide inhibited the binding of fibrinogen to platelets with exposed receptors, suggesting that it interfered directly with the ligand-receptor interaction. Fibrinogen binding supported by epinephrine and thrombin as well as ADP was inhibited by the peptide. Fibrinogen-dependent aggregation of washed platelets by ADP was abolished by a 30-fold molar excess of the peptide. The tetrapeptide is an analog of the amino-terminal sequence of the alpha-chain of fibrin and has been shown to inhibit fibrin polymerization [Laudano, A. P. & Doolittle, R. F. (1978) Proc. Natl. Acad. Sci. USA 75, 3085-3089]. A peptide corresponding to the natural sequence, glycyl-L-prolyl-L-arginyl-L-valyl-L-valine, was also capable of inhibiting fibrinogen binding to the platelet. These results suggest that common structural features within fibrinogen may serve a dual function by permitting the molecule to participate in both platelet aggregation and fibrin formation.
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PMID:Inhibition of fibrinogen binding to human platelets by the tetrapeptide glycyl-L-prolyl-L-arginyl-L-proline. 695 14


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