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)

The association between plasma coagulant activity and the presence of diabetic nephropathy was investigated in 31 patients with Type 1 diabetes, 12 with and 19 without nephropathy, and in 11 healthy subjects. Thrombin generation was assessed by computer assisted chromogenic method and expressed as time (in seconds) to 50% maximal thrombin activity (T50). Factor VIII:C levels related to thrombin activity, glycaemic control, and renal function. Median (IQ) FVIII:C concentration was increased in patients with nephropathy (1590 (1130-1900) IU l-1) compared to those without renal disease and with controls (960 (750-1090); 1020 (810-1100) IU l-1, p < 0.01, respectively). There were no significant differences in T50 values between the groups. FVIII:C correlated with age in all subjects and in the diabetic group (r = 0.33, p = 0.036; r = 0.39, p = 0.031) and inversely with T50 in all subjects and in controls (r = -0.35, p = 0.02; r = -0.62, p = 0.04). In all subjects and in patients, FVIII:C was related to urinary albumin excretion and creatinine clearance. FVIII:C and T50 were not related to HbA1c. The results show that FVIII:C levels are increased in Type 1 diabetes complicated by nephropathy and are related to degree of renal impairment but not levels of glycaemia. No associated enhancement of plasma procoagulant activity was detected.
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PMID:Thrombin generation and factor VIII:C levels in patients with type 1 diabetes complicated by nephropathy. 850 16

Functions and structure of FVIII which is a cofactor in the internal way of blood coagulation are described as well as the known activation and inactivation mechanisms of FVIII following from its domain structure. The effect exerted by the Willibrandt factor (Wf), thrombin, factor X alpha(FX), activated protein C(APC) on the FVIII functions and interrelation between internal and external ways of blood coagulation in FVIII activation are discussed. The homologous structure of factors V and VIII which is a result of their cofactor action is described.
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PMID:[Structural-functional features of factor VIII (FVIII) and its role in the cascade system of blood coagulation]. 855 66

Recombinant two-chain factor VIII, from which the B domain had been deleted, was expressed in Chinese hamster ovary cells. In addition to the major product, three minor factor VIII forms were isolated. The A2 domains generated by thrombin cleavage showed different electrophoretic mobilities. Peptide mapping of the A2 domains showed that two of the factor VIII forms had the expected C-terminus of the heavy chain at Arg740 [FVIII-(1-740)] and that the other factor VIII forms had C-termini at Tyr729 [FVIII-(1-729)] or Glu720 [FVIII-(1-720)]. The major FVIII-(1-740) form, FVIII-(1-729), and FVIII-(1-720) contained sulfated tyrosine residues at Tyr718, Tyr719 and Tyr723. The minor FVIII-(1-740) form was shown to lack sulfation at these positions. The specific clotting activity was approximately 1 x 10(4) U/mg for FVIII-(1-740) (both forms) and FVIII-(1-729), but twofold lower for FVIII-(1-720). A time study of thrombin activation showed that FVIII-(1-720) was activated slower than FVIII-(1-740), FVIII-(1-729) and plasma-derived factor VIII. Partially sulfated FVIII-(1-740) was activated at the same rate as the fully sulfated FVIII-(1-740). The equilibrium dissociation constant for binding of factor VIII to inactivated immobilized thrombin was the same for all factor VIII forms, showing that the slower activation of FVIII-(1-720) was not due to a lower affinity for the anion-binding exosite in thrombin.
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PMID:Amino acid residues 721-729 are required for full factor VIII activity. 857 34

Factor VIII-delta II is a genetically engineered deletion variant of factor VIII, expressed by recombinant Chinese hamster ovary cells. This 1436-residues-long protein has a molecular mass, calculated from its sequence, of 164,954 Da and exhibits seven potential glycosylation sites. The glycoprotein, secreted as a single polypeptide chain, can be cleaved after Arg740 to generate a heavy-light chain complex of 90-80 kDa as revealed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis. Due to its high mass range and excellent sensitivity, matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) has been chosen to play a key role in the precise determination of the molecular masses of recombinant factor VIII and the localization of the post-translational modifications within the protein. Native factor VIII-delta II displays a molecular mass of 178 kDa. The masses measured by MALDI for the heavy and light chains are respectively 89,900 Da and 87,100 Da. These mass values, found reproducible from batch to batch, are used to characterize factor VIII-delta II during the course of preclinical studies. The difference from the theoretical molecular molecular masses and the observation of broad molecular peaks suggest that recombinant FVIII-delta II has been effectively glycosylated by the host cell on both heavy and light chains. Similarly to plasma-derived factor VIII, the recombinant protein is proteolyzed by thrombin to generate the A1/A2/A3-C1-C2 trimer that is the active form of factor VIII in the coagulation pathway. MALDI-MS analysis of activated factor VIII-delta II suggested the presence of N-linked oligosaccharides in the proteolyzed light chain (A3-C1-C2 of 77,750 Da) and in the A1 domain (46,400 Da) of the heavy chain. By contrast, the similarity between the experimental and theoretical masses of the A2 domain indicated that its single potential glycosylation site has not been utilized.
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PMID:Characterization of a recombinant antihaemophilia-A factor (factor VIII-delta II) by matrix-assisted laser desorption/ionization mass spectrometry. 865 81

We studied exercise-induced changes in coagulation and fibrinolytic factors and activation products in different age categories. Thirty-eight sedentary males, divided in three age categories (cats I-III; 20-30, 35-45 and 50-60 y) were subjected to a standardized exercise test. Pre-exercise levels (cats I-III resp) of FVII:c (105 +/- 5, 121 +/- 6 and 123 +/- 7% NP), fibrinogen (2.35 +/- 0.12, 2.55 +/- 0.10 and 2.66 +/- 0.09 mg/ml), prothrombin activation fragment F1 + 2 (0.80 +/- 0.10, 0.80 +/- 0.11 and 1.22 +/- 0.16 nM), t-PA (5.2 +/- 0.6, 9.2 +/- 1.0, 8.6 +/- 1.2 ng/ml) and PAI-I (42.8 +/- 7.5, 67.6 +/- 7.6, 62.2 +/- 10.9 ng/ml) showed differences that seemed related to age. Regression analysis revealed associations with anthropometry (FVII:c, fibrinogen, F1+2, t-PA, PAI-1) rather than with age. Exercise-induced changes in coagulation (increase in von Willebrand factor and FVIII:c and a shortening of APTT) and fibrinolytic potential (increase in t-PA and u-PA) were of comparable magnitude for the three age categories. Hardly any change in F1 + 2 (6%) was observed, while thrombin-antithrombin complexes (93%), plasmin-antiplasmin complexes (79%) and D-dimer (77%) almost doubled during maximal exercise. We conclude that anthropometric differences play a more significant role than age on constitutive levels of haemostatic factors in participants up to 60 years of age. The magnitude of exercise-induced changes is comparable in the age categories under study, and simply super-imposed on constitutive (pre-exercise) levels. Clear evidence for prothrombin activation is lacking, but plasmin formation is enhanced during exercise.
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PMID:Changes in haemostatic factors and activation products after exercise in healthy subjects with different ages. 877 20

Twenty-five young subjects were divided into experimental (n = 13) and control (n = 12) groups in order to examine the acute and chronic effects of exercise on blood coagulation and fibrinolysis. Blood coagulation and fibrinolysis variables were ascertained in both groups before and after a physical conditioning programme both at rest and following maximal exercise. The experimental group exercised for 12 weeks [30 min, 3 x week at 70% (6 weeks) and 80% (6 weeks) of maximum heart rate]. The control group maintained normal activity patterns. Significant activation (P < 0.05) of blood coagulation was observed in response to maximal exercise before and after the conditioning programme in both groups in activated partial thromboplastin time (APTT), thrombin clotting time (TCT), factor VIII procoagulant activity (FVIII PA) and factor VIII antigen (FVIII A). Likewise, blood plasminogen activator showed a significant increase (P < 0.05) in response to maximal exercise before and after conditioning in both groups. Although VO2 max following the conditioning programme was significantly increased in the exercise group versus control, no significant changes (P > 0.05) were observed in either group in blood coagulation and fibrinolysis parameters at rest or in response to maximal exercise. It is concluded that maximal exercise transiently accelerates blood coagulation and activates blood fibrinolytic activity, however physical conditioning appears not to influence the haemostatic and fibrinolytic systems at rest or in response to maximal exercise.
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PMID:Blood coagulation and fibrinolysis at rest and in response to maximal exercise before and after a physical conditioning programme. 882 26

The haemostatic effectiveness of activated FVIII was compared to that of non-activated FVIII in a cross-over study in a canine model of haemophilia. Activation of FVIII in porcine concentrate was achieved by the addition of 3 x 10(-5) IU thrombin per ml of concentrate, which gave consistent increases in 1-stage FVIII activity of 13- to 14-fold and slow decay. The haemostatic effect was monitored by measurements of the cuticle bleeding time 10 and 45 min after infusion and there were no consistent differences between the activated and non-activated concentrates. One-stage factor VIII assays on plasmas 5 min after infusion showed identical mean values for activated and non-activated concentrates, indicating that most of the higher activity observed in vitro had disappeared rapidly from the circulation. These results suggest that controlled activation of FVIII by thrombin, which increases its activity in 1-stage assays, is unlikely to be of therapeutic benefit. For therapeutic concentrates which may contain small amounts of activated FVIII, the 1-stage assay may be an unreliable guide to their therapeutic effect.
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PMID:In vivo studies of activated porcine factor VIII. 895 Jul 84

Activated Protein C (APC) resistance, one of the most common genetic risk factors for venous thrombosis, is caused by a single base mutation (G1691-->A) in the factor V (FV) gene resulting in the replacement of Arg506 by Gln at a predominant cleavage site for APC. Great progress in understanding the mechanism of downregulation of FVa activity via the protein C pathway has been achieved by studying APC-mediated inactivation of FVa purified from homozygous APC-resistant individuals. This review briefly summarizes the role of FVa in prothrombin activation and the structure-function relationship of FV and FVa. Subsequently, APC-dependent inactivation of FVa and FVa Leiden and its modulation by protein S and factor Xa in model systems containing purified proteins is discussed. FV also has a function in increasing the inactivation of FVIII/VIIIa by APC. This cofactor activity appears diminished in FV Leiden. Thus, an intricate mechanism of regulation of thrombin formation via the protein C pathway is starting to emerge. Extensive studies in plasma milieu will be needed to gain more insight into the relation between the presence of FV Leiden and impaired downregulation of thrombin formation in APC-resistant individuals.
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PMID:Regulation of thrombin formation by activated protein C: effect of the factor V Leiden mutation. 924 9

We studied the effects of porcine factor VIII (P-FVIII; Hyate:C) and other coagulation products employed in the management of patients with hemophilia A, on platelet activation in vitro. Exposure of normal resting platelets to P-FVIII resulted in platelet activation, as manifested by increased expression of the platelet surface activation markers CD62, CD63, and activated-GPIIbIIIa, and by activation-induced modulation of expression of normal platelet membrane glycoproteins CD41, CD42, and CD36. In contrast, platelet activation was not observed after exposure of the platelets to human FVIII, FEIBA, recombinant FVIIa, or cryosupernatant plasma. As with thrombin, exposure of platelets to P-FVIII resulted in the generation of platelet microparticles, an effect not seen not with the other products. In contrast to the characteristic reduction in expression in the number of CD42 molecules detected on thrombin-activated platelets, P-FVIII-stimulated platelets showed a small increase in CD42 expression. In contrast to thrombin, P-FVIII did not cause platelet dense granule release. The results indicate that therapeutic P-FVIII activates platelets, likely in ways that are different from the platelet activation seen with thrombin. The observed platelet activation and microparticle generation may provide a "hypercoagulable" mechanism for hemostasis with P-FVIII therapy separate from, and additional to, that due to increased circulating FVIII levels.
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PMID:Platelet activation induced by porcine factor VIII (Hyate:C). 949 69

The prothrombinase complex (factor [F]Xa, FVa, calcium ions, and lipid membrane) converts prothrombin to thrombin (FIIa). To determine whether plasma lipoproteins could provide a physiologically relevant surface, we determined the rates of FIIa production by using purified human coagulation factors, and isolated fasting plasma lipoproteins from healthy donors. In the presence of 5 nmol/L FVa, 5 nmol/L FXa, and 1.4 micromol/L prothrombin, physiological levels of very low density lipoprotein (VLDL) (0.45 to 0.9 mmol/L triglyceride, or 100 to 200 micromol/L phospholipid) yielded rates of 2 to 8 nmol Flla x L(-1) x s(-1) in a donor-dependent manner. Low density lipoprotein (LDL) and high density lipoprotein (HDL) also supported prothrombinase but at much lower rates (< or =1.0 nmol FIIa x L(-1) x s[-1]). For comparison, VLDL at 2 mmol/L triglyceride yielded approximately 50% the activity of 2X10(8) thrombin-activated platelets per milliliter. Although the FIIa production rate was slower on VLDL than on synthetic phosphatidylcholine/phosphatidylsenne vesicles (approximately 50 nmol FIIa x L(-1) x s[-1]), the prothrombin Km values were similar, 0.8 and 0.5 micromol/L, respectively. Extracted VLDL lipids supported rates approaching those of phosphatidylcholine/phosphatidylserine vesicles, indicating the importance of the intact VLDL conformation. However, the presence of VLDL-associated, factor-specific inhibitors was ruled out by titration experiments, suggesting a key role for lipid organization. VLDL also supported FIIa generation in an assay system comprising 0.1 nmol/L FVIIa; 0.55 nmol/L tissue factor; physiological levels of FV, FVIII, FIX, and FX; and prothrombin (3 nmol/L FIIa x L(-1) x s[-1]). These results indicate that isolated human VLDL can support all the components of the extrinsic coagulation pathway, yielding physiologically relevant rates of thrombin generation in a donor-dependent manner. This support is dependent on the intact lipoprotein structure and does not appear to be regulated by specific VLDL-associated inhibitors. Further studies are needed to determine the extent of this activity in vivo.
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PMID:Plasma lipoproteins support prothrombinase and other procoagulant enzymatic complexes. 951 15


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