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)

In this study, protein C (PC), protein S (PS), heparin cofactor II (HCFII), prothrombin fragment 1+2(PF1,2), thrombin-antithrombin III complex (TAT), von Willebrand factor (vWF) and thrombomodulin (TM) were investigated in 13 patients with beta thalassemia intermedia (TI) not requiring transfusion, six patients with sickle cell disease (SCD), and seven patients with HbS-beta thalassemia (S-BT) who were not in crisis. These hemostatic parameters were also studied in 12 healthy children assigned as a control group. Protein C and Protein S (PC-PS) were found to be decreased in TI patients and normal in S-BT patients. PC was decreased in SCD patients. In the patients with TI and SCD, the mean PF1,2 level was elevated, whereas the TAT level was not statistically different from that of the control group. These results suggested that in patients with hemoglobinopathies: a) decreased natural anticoagulants and b) enhanced procoagulant activation have been encountered. Other unexpected and interesting results of this study are the decreased vWF and elevated HCFII levels in all three patient groups.
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PMID:Changes of hemostatic factors in patients with hemoglobinopathies. 1077 92

Protein S functions as a cofactor with activated protein C in the down-regulation of the blood coagulation cascade. In vitro studies have historically produced conflicting data with regard to the extent of various protein S activity in clotting assays which typically involve adding CaCl(2) to initiate reactions. We report here that protein S reversibly self-associates in the absence of Ca(2+). Sedimentation experiments showed a transition in sedimentation velocity from 7.2 to 4.2 S with a transition midpoint (T(m)) of 0.42 mM Ca(2+) for intact protein S. Studies of thrombin cleaved (Arg(70)) protein S revealed similar results with a transition in sedimentation velocity from 7.9 to 4.4 S with a T(m) of 0.42 mM Ca(2+). This transition is reversible with the addition of 10 mM EDTA. Sedimentation equilibrium data suggest at a minimum, a monomer-dimer-trimer association. Sedimentation velocity experiments were also performed on mixtures of protein S and prothrombin which showed no heterodimer formation in either Ca(2+) or EDTA solutions. These data suggest that previous interpretations of protein S structure and function may have been confounded by the self-associative behavior of protein S in non-Ca(2+) solutions.
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PMID:Self-association of human protein S. 1082 19

Recently, basic and clinical advances have provided insights into the molecular events that link inflammation with blood coagulation and thrombosis. At least in cell culture, the inflammatory cytokines, especially tumour necrosis factor alpha (TNF) and interleukin 1-beta (IL-1), are major mediators that can elicit changes in cell phenotype. With respect to coagulation, one of the clot-promoting and one of the inhibitory pathways seem especially prone to modulation by these cytokines. Whenever Tissue Factor contacts the blood, coagulation is initiated rapidly. These cytokines can elicit Tissue Factor production on endothelium and monocytes. Thus, the cytokines elaborate Tissue Factor formation intravascularly. This contrasts with the normal situation in which Tissue Factor is located exclusively in the extravascular space, largely on fibroblasts, where it is expressed constitutively. Furthermore, cytokines, especially interleukin 6 (IL-6), can stimulate new platelet formation, and the new platelets responding to IL-6 have increased sensitivity to thrombin activation and increased procoagulant activity. Regulating the clotting process are a large number of anticoagulant and fibrinolytic mechanisms. The three major anticoagulant mechanisms appear to involve antithrombin-heparin, Tissue Factor pathway inhibitor (TFPI) and the Protein C pathway. Of these, the Protein C pathway appears to be the primary target for cytokine action. The Protein C pathway is initiated when thrombin binds to thrombomodulin (TM). TM is expressed constitutively on endothelium. In tissue culture, TNF, IL-1 or endotoxin lead to a slow loss of TM and endothelial cell Protein C receptor (EPCR) from the cell surface. In addition, Protein S levels decrease in patients with disseminated intravascular coagulation (DIC). Taken together, these results suggest that cytokines should elicit massive thrombotic responses when administered systemically. At near toxic levels, TNF fails to elicit an overt DIC or thrombotic response in patients, although sensitive markers of coagulation do detect changes in coagulation in response to TNF. In baboons, very high levels of TNF also fail to elicit fibrinogen or platelet consumption. However, if the Protein C pathway is blocked, these cytokines can elicit either DIC or deep-vein thrombosis, depending on the conditions. Thrombus formation is potently potentiated by impeding flow and/or by catheterization. DIC is facilitated by providing membrane surfaces, possibly mimicking complement mediated platelet activation/damage that occurs in shock. Thus, available evidence suggests important roles for inflammatory cytokines in DIC and thrombosis, but they seem insufficient by themselves to elicit overt thrombotic responses without secondary stimuli. Current data suggest that anti-inflammatory drugs are a viable candidate to blocking DIC or thrombosis without impairing the haemostatic balance.
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PMID:Possible involvement of cytokines in diffuse intravascular coagulation and thrombosis. 1085 74

Protein S functions as a cofactor to activated protein C (APC) in the degradation of FVa and FVIIIa. In protein S, the thrombin sensitive region (TSR) and the first EGF-like domain are important for expression of the APC cofactor activity. A naturally occurring Thr103Asn (T103N) mutation in the first EGF-like domain of protein S has been associated with functional (type II) protein S deficiency. To elucidate the functional consequences of the T103N mutation, recombinant protein S mutant was expressed in mammalian cells and functionally characterised. The expression level of protein S T103N from transiently transfected COS 1 cells was equal to that of wild type protein S. The mutant protein S and wild type protein S were also expressed in 293 cells after stable transfection, and the recombinant proteins purified. In APTT- and PT-based coagulation assays, the mutant protein demonstrated approximately 50% lower anticoagulant activity as compared to wild type protein S. The functional defect was further investigated in FVa- and FVIIIa-degradation assays. The functional defect of mutant protein S was attenuated at increasing concentrations of APC. The results demonstrate the region around residue 103 of protein S to be of functional importance, possibly through a direct interaction with APC.
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PMID:Protein S Thr103Asn mutation associated with type II deficiency reproduced in vitro and functionally characterised. 1101 64

Recombinant factor VIII SQ (r-VIII SQ), ReFacto, is a recombinant factor VIII product similar to the smallest active factor VIII protein found in plasma-derived factor VIII (p-VIII) concentrates. The protein comprises two polypeptide chains of 80 and 90 kDa and lacks the major part of the heavily glycosylated B-domain i.e. amino acids Gln744 to Ser1637. r-VIII SQ retains six potential glycosylation sites for N-linked oligosaccharides at asparagine residues 41, 239, 582, 1685, 1810 and 2118. We describe a thorough comparison of the characteristics of r-VIII SQ with those of p-VIII. The primary and secondary structures of r-VIII SQ were in good agreement with that of B-domain-deleted p-VIII (p-VIII-LMW) as shown by SDS-PAGE, Western blotting with antifactor VIII antibodies, tryptic mapping, amino acid sequence analysis and circular dichroism spectroscopy. A few divergences also existed. Thus r-VIII SQ was shown to contain a small amount of the single chain primary translation product of 170 kDa and also the product specific sequence of 14 amino acids, the SQ-link, in the C-terminal end of the 90 kDa chain. It was shown that r-VIII SQ had a high specific activity of about 14,000 IU VIII:C/mg as determined by use of a chromogenic substrate assay. The r-VIII SQ protein was comparable to p-VIII forms with a retained B-domain, in terms of potency measured by a chromogenic substrate or a two-stage clotting assay, in interactions with thrombin, and with activated protein C (APC) in combination with Protein S. The ability of r-VIII SQ to participate as a cofactor in factor Xa generation in a mixture of factors IXa and X, phospholipid and calcium was in conformity with that of p-VIII. Furthermore r-VIII SQ had a good binding capacity for phospholipid vesicles and von Willebrand factor (vWF) as shown in gel filtration studies. The same kinetics in binding to von Willebrand factor was found for r-VIII SQ and p-VIII as determined by real-time biospecific interaction analysis (BIA) with use of the BIAcore instrument. The apparent association rate constant was 4 x 10(6) M(-1)s(-1). Two dissociation rate constants were found, 1 X 10(-2)s(-1) and 4 x 10(-4)s(-1). The results extend the present knowledge that the factor VIII B-domain is dispensable for the factor VIII cofactor function in hemostasis.
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PMID:Structural and functional characteristics of the B-domain-deleted recombinant factor VIII protein, r-VIII SQ. 1120 95

This study aimed to identify specific haemostatic changes that might account for previous observations of higher venous thromboembolic risk among users of combined oral contraceptives (COCs) containing desogestrel (DSG) than levonorgestrel (LNG). Sixty-three current users of monophasic 30 microg oestrogen COCs containing either LNG or DSG omitted one pill-free interval (PFI), switching immediately either to the opposite formulation for one cycle or continuing with the same pill. Venesection followed the initial PFI after one cycle (21 tablets) and two cycles (42 tablets) of continuous pill taking, and after the following PFI. Protein S was lower in users of DSG than LNG formulations after the first PFI (mean +/- SD, 0.67 +/- 0.09 vs 0.76 +/- 0.10, P < 0.001) and after one cycle (0.61 +/- 0.09 vs 0.76 +/- 0.09, P < 0.0001). Protein S decreased when switching from LNG to DSG pills (0.77 +/- 0.07-0.65 +/- 0.06, P < 0.0001), mirrored by an increase at switching from DSG to LNG formulations (0.61 +/- 0.08-0.73 +/- 0.10, P < 0.005). Mean protein S levels remained within the normal range. Three different markers of thrombin generation remained unaltered. Potential explanations for COC-related thrombotic events are 'acquired resistance to activated protein C' or inhibition of fibrinolysis. A potential role has been described for protein S deficiency in both. A further triggering factor is a probable prerequisite for actual thrombosis, but pill-takers whose levels of protein S were in the lowest percentiles may be at greatest risk.
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PMID:Protein S levels are lower in women receiving desogestrel-containing combined oral contraceptives (COCs) than in women receiving levonorgestrel-containing COCs at steady state and on cross-over. 1144 81

Protein S (PS) is a vitamin K-dependent plasma protein and serves as a cofactor for the anticoagulant activities of activated protein C (APC). We investigated the effects of different PS concentrations on prothrombin activation and thrombin generation in cord and adult plasma containing APC and different amounts of alpha 2-macroglobulin (a2-M). Prothrombin activation was assessed by monitoring the time-course of prothrombin fragment 1+2 (F1+2) generation. Thrombin generation curves were determined by means of a subsampling technique using the chromogenic substrate S-2238. We demonstrate a dose-dependent inhibition of the anticoagulant action of PS by a2-M: suppression of F1+2 and thrombin generation due to addition of PS was stronger in plasma containing low amounts of a2-M than in plasma with elevated a2-M levels. Since no complex formation between a2-M and PS was observed by means of SDS-PAGE, we attribute decreased anticoagulant action of PS at high a2-M levels to enhanced complex formation between APC and a2-M. Thereby, APC is subtracted from its cofactor PS, resulting in suppressed formation of the anticoagulant APC/PS complex. Thus, our data suggest that a2-M, besides its well-known anticoagulant effects, also acts as a procoagulant by suppressing the formation of the anticoagulant APC/PS complex. Our findings have implications particularly on thrombin generation and inhibition in cord plasma, since a2-M levels in newborns are elevated over adult values and the antithrombotic APC/PS pathway is up-regulated at birth. Therefore, elevated levels of a2-M might restrict the up-regulation of the APC/PS pathway.
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PMID:Alpha 2-macroglobulin enhances prothrombin activation and thrombin potential by inhibiting the anticoagulant protein C/protein S system in cord and adult plasma. 1206 45

Brain injury is known to result in various degrees of disordered haemostasis. Moreover, the recently developed assays of molecular markers of haemostasis can give an accurate reflection of its activation in vivo. The aim of this study was to monitor the levels of prothrombin fraction 1 + 2 (F1 + 2), thrombin antithrombin complexes (TAT) and D-dimer on the admission of patients to the ICU and up to the fourth day postinjury. Seventeen patients with head injury (Glasgow Coma scale 12 or less) were studied at King Khalid University Hospital, Riyadh. Their ages ranged from 10 to 40 years (mean 26). Blood samples were collected from the internal jugular vein, peripheral vein and artery. The mean levels of TAT and F1 + 2 in the internal jugular vein was significantly higher than in both peripheral venous and arterial blood on admission and 24 h later. Thereafter, the levels in the three locations dropped significantly, but remained elevated above controls. D-dimer levels were very markedly elevated to a similar extent in the three locations throughout the study period. The prothrombin time was significantly prolonged in the three locations in the first two days. Plasma fibrinogen levels dropped very significantly in the jugular vein, and increased to above reference values later. Protein S and factor VII showed a significant drop in the first two days and increased to normal range thereafter. Outcome was evaluated using the Glasgow Outcome Scale at 6 months postinjury. Haemostatic measurements could not predict good outcome (12 patients) or bad outcome (four deaths). It was concluded that haemostatic activation is a transient, but common phenomenon after head injury and is more prominent in cerebrovascular than in peripheral blood. The number of patients studied is too small to allow reliable association to be drawn between haemostatic changes on admission and prediction of outcome.
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PMID:The coagulopathy in acute head injury: comparison of cerebral versus peripheral measurements of haemostatic activation markers. 1238 89

Therapeutic apheresis is a widely used treatment alternative for several diseases. In 29 patients with different diseases, we have monitored the PT, aPTT, thrombin time (TT), fibrinogen, D-dimer, factor VIII, IX, X, XI, XII, VWF, Protein C, S, Active Protein C Resistance (APCR) and Antithrombin-III during TPE. Patients were divided into four groups based on the replacement fluids used: 3% VARIHES or ISOHES + 4% albumin (1:1) (group 1), fresh frozen plasma (FFP) (group 2), 3% VARIHES or ISOHES (group 3) and 4% albumin (group 4). In our study, the fibrinogen level decreased to 83% of the base line level after the end of 48 h therapy. The APTT, PT, and TT increased during TPE. However no statistical difference was observed between the groups. We found a significant change in factor levels with time, only the difference in factors IX and XI between the groups was significant. In addition, factor levels measured at 48 h were close to the levels measured before aphereses. In our study, time the related change in AT-3 values was significant. Time-related changes of the Protein S and APCR were not statistical significant significant but on the other hand, we found a significant difference in AT-III and Protein C values between groups. The side effects of HES on coagulation factors and tests were comparable to those of other replacement fluids. Its low cost makes it favourable.
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PMID:Effects of replacement fluids on coagulation system used for therapeutic plasma exchange. 1262 Feb 62

Oral contraceptive (OC) use is associated with an increased risk of venous thromboembolism. Previous data reported higher thrombotic risk in women using third-generation combined OC than in those using second generation OC. The difference could be explained by differential effects of progestagens on plasma sensitivity to activated protein C (APC). The main purpose of this cross-sectional study was to assess the influence of a progestagen-only OC (chlormadinone acetate) as well as the effect of several combined OC with different progestagen components on APC resistance. The effect of APC on endogenous thrombin potential (ETP) was investigated in the plasma of healthy women using either combined OC (n=82) or progestagen-only OC (n=28), and in non-users (n=64). Carriers of factor V Leiden were excluded. Compared with non-users, there was no significant change in APC resistance in women using progestagen-only OC. Women who used combined OC were less sensitive to APC than non-users (P < 0.001) and the difference was significantly more pronounced in women using third-generation OC (n=41) than in those who used second-generation OC containing levonorgestrel (n=22) (P < 0.05). Compared with OC containing levonorgestrel, use of norethisterone-containing OC (n = 9) was associated with an increased resistance to APC (P < 0.05). Women who used cyproterone-containing OC (n = 10) were less sensitive to APC than those using third-generation OC (P < 0.05) or second-generation OC containing levonorgestrel (P < 0.05). Protein S, factor II and FVIII levels explained in part the OC-related changes in APC sensitivity variations. ETP-based APC resistance may contribute to explain why different brands of OC can be associated with different levels of thrombogenicity.
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PMID:Impact of progestagens on activated protein C (APC) resistance among users of oral contraceptives. 1533 36


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