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:3.4.21.6 (thromboplastin)
13,278 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Blood clotting and fibrinolytic systems were studied in the plasma of a sei whale (Balaenoptera borealis). The sei whale belongs to the suborder baleen whales of the order Cetacea. Whale plasma had a greatly prolonged kaolin-activated partial thromboplastin time and was deficient in Hageman factor (factor XII), Fletcher factor (a plasma prekallikrein), and PTA (factor XI). All other clotting factor activities were present in amounts comparable to that of normal human plasma. Whale plasminogen was activated by human urokinase, but not by streptokinase. Whale plasma contained inhibitory activities against thrombin, activated Stuart factor, activated PTA, activated Fletcher factor, and plasmin.
...
PMID:Studies on the blood clotting and fibrinolytic system in the plasma from a sei (baleen) whale. 96 76

The amino-acid sequence of the heavy chain of bovine blood coagulation factor X1 (Stuart factor) isolated before and after activation has been determined. Sequence analysis was performed on fragments obtained by cleavage with cyanogen bromide and by tryptic digestion. Comparison of the complete sequence with those of other hepatic and pancreatic serine proteases demonstrates homology of the heavy chain of activated factor X1 (factor X1a) with the B chain of bovine thrombin as well as with bovine trypsin, chymotrypsins A and B, and porcine elastase. The activation peptide cleaved near the amino terminus by a protease from Russell's viper venom differs in both size and sequence from those of other serine proteases. With three exceptions, all of the residues which are important in the catalytic functions of trypsin and chymotrypsin occur in corresponding loci in the heavy chain of factor Xa. These finding suggest that the three-dimensional structure of the heavy chain is similar to that of the pancreatic serine proteases and that these enzymes have evolved from a common ancestral gene.
...
PMID:Bovine factor X1 (Stuart factor): amino-acid sequence of heavey chain. 105 93

Factor X, a vitamin K-dependent protein, is the plasma zymogen for the active serine protease factor Xa. Factor Xa is the proteolytic enzyme for prothrombinase, the multi-protein membrane complex that catalyses the cleavage of prothrombin to thrombin. A panel of 10 monoclonal antibodies (identified by their corresponding clone numbers: 1, 2, 3, 5, 7, 26, 27, 54, 73, and 79) to factor X were produced by immunizing mice with purified factor X. All of the antibodies bound both human factor X and factor Xa in a solid-phase ELISA and binding of the antibodies was not affected by removal of Ca2+ with EDTA. In immunoblot analysis, antibody alpha HFX-54 bound to the light chain and antibodies alpha HFX-1, -5, -7, and -26 bound to the heavy chain of reduced factor X. Antibodies alpha BFX-2b, alpha HFX-27, -54, and -73 prolonged both the factor X-dependent clotting time and activated partial thromboplastin time (APTT) of normal plasma while antibody alpha HFX-1 only prolonged the APTT. None of the antibodies significantly inhibited factor X activation by purified Russell's viper venom factor X activator. In prothrombin activation assays using purified factor Xa, factor Va, prothrombin, Ca2+ and phospholipid vesicles, seven of the antibodies (alpha HFX-1, -3, -26, -27, -54, -73 and alpha BFX2b) showed some inhibition of thrombin generation ranging from 18 to 60% of the control. The decrease in factor X plasma clotting activity was most likely due to inhibition of factor Xa activity in prothrombinase, although some antibody-dependent inhibition of factor X activation may contribute to the observed inhibition of plasma clotting. Prothrombinase activity on platelets was inhibited in an identical manner by the monoclonal antibodies. When prothrombin was activated in the absence of factor Va, only antibody alpha BFX-2b inhibited activation. Calcium-independent determinants on both the heavy chain (determinants 1 and 26) and light chain (determinant 54) of factor X may play a role in prothrombin activation by prothrombinase. Other epitopes (antibodies alpha HFX-3, -27, -73) appeared to be influenced by association of factor Xa with factor Va. Topographic regions on factor X important for factor X activation and factor Xa function may be identified by the use of these monoclonal antibodies.
...
PMID:Neutralization of factor X activity by factor X-specific monoclonal antibodies. 145 Mar 23

Prothrombinase assembly was studied on macroscopic planar bilayers consisting of 20% dioleoyl-phosphatidylserine (DOPS) and 80% dioleoyl-phosphatidylcholine (DOPC). The dissociation constant for the binding of factor Xa to the bilayer, measured by ellipsometry, was Kd = 47 +/- 8 nM (mean +/- S.D.) and this value was lowered to Kd = 2.2 +/- 0.3 pM by preadsorption of factor Va. This latter value was determined from direct measurement of steady-state thrombin production. A comparable value of Kd = 1.0 +/- 0.1 pM was found by repeating these experiments in suspensions of phospholipid vesicles, and it was verified that prothrombinase assembly was not influenced by the addition of prothrombin. Using a minute amount (0.094 fmol cm-2) of preadsorbed factor Va, it was found that the rate of prothrombinase assembly exceeds the rate of collisions between Xa molecules from the buffer and the sparse Va molecules on the bilayer. Apparently, factor Xa adsorbs first to the membrane and then associates rapidly with factor Va by lateral diffusion. The data indicate almost instantaneous equilibrium of this complex formation on the surface with a lower limit for the bimolecular rate constant of kon = 2.8 x 10(13) (mol/cm2)-1 s-1. In suspensions of small phospholipid vesicles, prothrombinase assembly is collisionally limited and the value of kon should be proportional to vesicle diameter. This was verified with a method for estimation of kon values from thrombin generation curves. Values of 0.36 x 10(9) and 1.6 x 10(9) M-1 s-1 were found for vesicles of 20-30- and 60-80-nm diameter, respectively.
...
PMID:Membrane-mediated assembly of the prothrombinase complex. 191 95

An inhibitor of procoagulant and fibrinolytic enzymes was derived from cabbage seeds by a procedure using acetone precipitation, ion-exchange chromatography, and gel filtration. The cabbage seed inhibitor was a 10-Kd monomeric protein with intrachain disulfide bonds. This preparation prevented clot formation in whole blood and blocked the ability of thrombin to induce clot formation in plasma and to induce platelet aggregation. A number of proteases were inhibited, as demonstrated by using purified enzymes in amidolytic assays. Tight-binding inhibition was observed for activated Stuart factor (factor Xa) and plasmin. Inhibition of thrombin and activated Hageman factor (factor XIIa) was observed with a molar excess of inhibitor. No inhibition was detected for activated plasma thromboplastin antecedent (factor XIa), plasma kallikrein, or C1 esterase. Reaction progress curves for trypsin indicated slow, tight-binding inhibition, with an apparent inhibition constant in the nanomolar range or less. The electrophoretic mobility of trypsin was altered by the inhibitor in nondenaturing polyacrylamide gel electrophoresis (PAGE) but not in sodium dodecyl sulfate (SDS)-PAGE, indicating noncovalent bonding. Only partial reversal of trypsin inhibition could be demonstrated by washing the inhibitor from enzyme immobilized on solid beads. A dot-blot technique with cabbage seed inhibitor was capable of detecting 10 ng nitrocellulose-bound trypsin. The dot-blot technique also appeared capable of detecting plasmin. These findings demonstrated the potential utility of this inhibitor as a probe for detection of tightly bound proteases. In summary, cabbage seed extracts contain an inhibitor with activity toward a broad range of proteases important to hemostasis. To our knowledge, this agent represents the first inhibitor isolated from a plant source that inhibits thrombin.
...
PMID:Cabbage seed protease inhibitor: a slow, tight-binding inhibitor of trypsin with activity toward thrombin, activated Stuart factor (factor Xa), activated Hageman factor (factor XIIa), and plasmin. 213

The effect of different heparins and a synthetic pentasaccharide on the inhibition of intrinsic prothrombinase and of its generation was studied by a new technique, using a defibrinated prothrombin poor human plasma, supplemented with phospholipids and calcium. Prothrombinase activity was evaluated on purified prothrombin with a chromogenic substrate. This technique is designed to bypass the interference of massive endogenous thrombin generation on the measurement of prothrombinase activity. We first validated the specificity of the technique by using specific Xa and IIa inhibitors. Then, the inhibition of prothrombinase generation and the inhibition of generated prothrombinase were both studied. The results showed that anti-Xa activity measured on exogenous bovine factor Xa added to plasma was not correlated with the inhibition of prothrombinase generation or prothrombinase activity. The concentrations required for unfractionated heparin (the 4th International Standard: 4th IS UH), 1st International Standard Low Molecular Weight Heparins (1st IS LMWH), enoxaparin, Fraxiparine, and pentasaccharide in order to inhibit preformed prothrombinase were significantly higher than those necessary to inhibit prothrombinase generation. These data suggest that anti-Xa activity of unfractionated heparin and its derivatives does not completely reflect the extent of the inhibition of intrinsic prothrombinase generation by UH, LMWH, and pentasaccharide. On the other hand, anti-IIa activity of heparins could be responsible for the inhibition of prothrombinase generation. The action of pentasaccharide devoid of anti-IIa activity on prothrombinase generation appears related to its indirect effect on the formation of initial thrombin traces. This new technique provides a tool to study the essential role played by thrombin during the early steps of coagulation.
...
PMID:The inhibition of intrinsic prothrombinase and its generation by heparin and four derivatives in prothrombin poor plasma. 216 62

The effect of pH and temperature on the apparent association equilibrium constant (Ka) for the binding of the bovine basic pancreatic trypsin inhibitor (BPTI, Kunitz inhibitor) to human and bovine factor Xa (Stuart-Prower factor; EC 3.4.21.6) has been investigated. Under all the experimental conditions, values of Ka for BPTI binding to human and bovine factor Xa are identical. On lowering the pH from 9.5 to 4.5, values of Ka (at 21.0 degrees C) for BPTI binding to human and bovine factor Xa decrease, thus reflecting the acidic pK shift of the His57 catalytic residue from 7.1, in the free enzyme, to 5.2, in the proteinase-inhibitor complex. At pH 8.0, values of the apparent thermodynamic parameters for BPTI binding to human and bovine factor Xa are: Ka = 2.1 x 10(5)M-1 (at 21.0 degrees C), delta G degree = -29.7 kJ/mol (at 21.0 degrees C), delta S degree = +161 entropy units (at 21.0 degrees C), and delta H degree = +17.6 kJ/mol (temperature-independent over the explored range, from 5.0 degrees C to 45.0 degrees C). Thermodynamics of BPTI binding to human and bovine factor Xa have been analysed in parallel with those of related serine (pro)enzyme/Kazal- and /Kunitz-type inhibitor systems. Considering the known molecular models, the observed binding behaviour of BPTI to human and bovine factor Xa was related to the inferred stereochemistry of the proteinase/inhibitor contact region.
...
PMID:Binding of the bovine basic pancreatic trypsin inhibitor (Kunitz inhibitor) to human and bovine factor Xa. A thermodynamic study. 219 85

Equilibrium binding studies of prothrombinase complex formation were undertaken using phospholipid vesicles composed of phosphatidylcholine and phosphatidylserine (PCPS), factor Va, and factor Xa modified with dansyl glutamylglycinylarginyl chloromethyl ketone (DEGR.Xa). The interaction between the Va.PCPS and DEGR.Xa.PCPS binary complexes was experimentally isolated using saturating concentrations of PCPS. Fluorescence titrations indicated that the membrane-bound proteins interact tightly (Kd approximately 10(-9) M) with a stoichiometry of 1 mol of Va bound/mol of DEGR.Xa at saturation. Complex formation was also investigated by kinetic studies of prothrombin activation using unmodified factor Xa. The kinetic studies yielded a Kd approximately 10(-9) M, which was independent of the concentration of prothrombin in the range of 0.5-5.0 microM. Fluorescence studies of complex assembly at limiting PCPS concentrations provided evidence for an altered DEGR.Xa-PCPS interaction when the enzyme was assembled into the complex. The data suggest that although both proteins are associated with PCPS when complexed with each other, the presence of factor Va on the membrane surface increases the affinity for the Xa-PCPS interaction by an estimated 100-fold. Prothrombinase complex assembly therefore proceeds independently of the availability of substrate and is stabilized by protein-protein and protein-phospholipid interactions. Linkage between the two protein-membrane combination events leads to the further stabilization of the complex on the vesicle surface.
...
PMID:Prothrombinase complex assembly. Contributions of protein-protein and protein-membrane interactions toward complex formation. 230 76

Studies of the clotting mechanisms in the plasma of a Burmese python (Python molurus bivittatus) confirm earlier information that both extrinsic and intrinsic pathways of thrombin formation participate in reptilian hemostasis. Plasma fibrinogen was present at a concentration comparable to that in human plasma. Other assays were hampered by the need to use nonreptilian reagents. The activated partial thromboplastin time was shorter than was that of human plasma, thus implying the presence of prothrombin in python plasma; however, this protein could be demonstrated only in trace amounts. Similarly, only small amounts of Hageman factor (factor XII) and antihemophilic factor (factor VIII) were detected, and none of plasma prekallikrein, high-molecular-weight kininogen, and Christmas factor (factor IX). The prothrombin time was slower than that of human plasma. Factor VII was not detected, but both proaccelerin (factor V) and Stuart factor (factor X) were present. Python plasma inhibited bovine thrombin and human plasmin, but it was deficient in fibrinolytic capacity.
...
PMID:Notes on clotting in a Burmese python (Python molurus bivittatus). 234 66

Prothrombinase activity was analysed in the plasma of a series of patients with lupus anticoagulants (LAC). In the presence of purified PS-PC (20-80%) vesicles the prothrombinase activity triggered by kaolin was retarded by 2-3 min with respect with normal plasma. The maximal values of prothrombinase activity increased by increasing the amount of phospholipid vesicles. However, in the plasma of the patients they were always lower than those of normal plasma at each phospholipid concentration. Platelet-dependent prothrombinase activity was subsequently investigated. Again, both a delay in appearance and reduced peak values of prothrombinase activity were observed in the plasma of the patients. This inhibition was partially overcome by the addition of an excess of purified phospholipids. Finally, the effect of LAC IgG on platelet rich plasma-dependent prothrombinase activity was investigated. The main effect observed was a delay of the peak time of prothrombinase activity, while the maximal peaks were affected only by one IgG preparation. We conclude that LAC antibodies can react with both purified negatively-charged phospholipids and platelet procoagulant phospholipids and inhibit prothrombinase activity in a similar way in both cases.
...
PMID:Inhibition of phospholipid and platelet-dependent prothrombinase activity in the plasma of patients with lupus anticoagulants. 250 34


1 2 3 4 5 6 7 Next >>

---