Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.69 (APC)
 16,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Resistance to activated protein C (APC) is a risk factor for venous thromboembolism also in absence of the FV Leiden mutation. To evaluate the influence of genetic factors on APC resistance, we evaluated the heritability of the APC resistance phenotype in 1,519 sib-parent pairs randomly selected from the VITA Project. After adjustment for known influencing factors, a high heritability coefficient (0.58) was observed and parental response to APC was the single most important factor in predicting the corresponding phenotype in sibs. In 32 parent-sib pairs in which phenotypic resistance to APC unrelated to FV Leiden was present in both parents and sibs, no additional mutation on the 306-aminoacid residue of FV (FV Cambridge and FV Hong Kong) was found. In these 32 parent-sib pairs, FVIII:C and vWf:Ag levels were not significantly increased and there was no excess prevalence of the R2 allele of exon 13 of FV gene. This study suggests that the response to APC is significantly influenced by genetic factors also at a population level, but the responsible mechanisms are still undefined.
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PMID:The VITA Project: heritability of resistance to activated protein C. Vincenza Thrombophilia and Arteriosclerosis. 1112 61

The paper describes the production of a prothrombin complex concentrate (PCC) with high virus safety and a well-balanced content of vitamin K-dependent clotting factors and inhibitors. Solid-phase extraction is followed in a second step by optimized anion exchange chromatography using a radial column. A step for virus removal by nanofiltration is introduced in addition to the solvent/detergent step. By speeding up the chromatographic step, the period of time required for production is reduced considerably. The activities of the four vitamin K-dependent clotting factors II, VII, IX and X are in ratios of about 1:1:1:1. Protein C, Protein S, and Protein Z are also present in therapeutically effective concentrations. The product shows no thrombogenicity, in either in vivo nor in vitro models. Clinical investigations show that the PCC is a safe and efficient preparation for the substitutive treatment of FIX or FVII in patients suffering from the respective deficiencies. All bleeding episodes have been efficiently controlled with relatively low doses of the concentrate. The surgical procedures have been conducted without any problems in severely FIX and FVIII deficient patients.
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PMID:Manufacturing of a prothrombin complex concentrate aiming at low thrombogenicity. 1115 May 87

Factor XI (FXI) is the zymogen of a plasma serine protease (FXIa) that contributes to hemostasis by activating factor IX (FIX). This reaction appears to be important for sustaining thrombin production after initial fibrin formation, to consolidate and protect fibrin clots from degradation by fibrinolysis. Humans with congenital FXI deficiency have a variable propensity to bleed after trauma or surgery, but do not experience the "spontaneous" hemorrhage in joints and soft tissue characteristic of hemophilia (FVIII or FIX deficiency). Mice homozygous for a disruption of the FXI gene (FXI-/-) have prolonged activated partial thromboplastin times and no detectable plasma FXI activity. Like their human counterparts, FXI-/- animals are generally healthy, reproduce normally, and do not develop spontaneous hemorrhage. In tail bleeding time assays, FXI-/- animals may have slightly prolonged bleeding compared to FXI+/+ and FXI+/- animals, however, a consistent hemostatic deficit has not been identified. More impressive results are obtained when FXI-/- mice are crossed with protein C deficient mice. Severe FXI deficiency partially ameliorates the devastating hypercoagulable state associated with severe protein C deficiency, indicating that FXI plays a role in certain thrombotic conditions.
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PMID:Gene targeting in hemostasis. factor XI. 1117 49

Carriership of the factor V (FV) gene marked by the R2-haplotype, a series of linked polymorphisms encoding several amino acid changes in FV, is associated with mild resistance to activated protein C (APC) and with an increased risk of thrombosis. We compared the functional properties of normal FV(a) and R2-FV(a) in model systems and in plasma. FV and R2-FV were equally well activated by thrombin and expressed identical cofactor activities in prothrombin activation. Rate constants of APC-catalyzed inactivation of FVa and R2-FVa were similar both with and without protein S. However, significant differences were observed between haemostatic parameters determined in plasma from homozygous carriers of the R2-gene (n = 5) and age-matched non-carriers (n = 19). Plasma from R2-carriers contained significantly lower FV levels and the ratio of the two FV isoforms (FV1 and FV2) was shifted in favor of FV1. The FV2/FV1 ratio was 1.4 (95% CI = 1.3-1.5) in homozygous carriers of R2 and 2.8 (95% CI = 2.5-3.1) in controls (p < 0.00001). In an APC resistance test which quantifies the cofactor activity of FV in APC-catalyzed FVIII(a) inactivation, homozygous R2-carriers had significantly lower (p < 0.00001) APC sensitivity ratios (APCsr = 1.54, 95% CI = 1.48-1.60) than controls (APCsr = 2.17, 95% CI = 2.05-2.28). This indicates that R2-FV has reduced cofactor activity in APC-catalyzed FVIII(a) inactivation. The changes of the relative amounts of FV1 and FV2 in carriers of the R2-gene will result in increased thrombin formation in the presence of APC and may provide a mechanistic explanation for the increased thrombotic risk associated with the R2-haplotype.
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PMID:Functional properties of factor V and factor Va encoded by the R2-gene. 1120 92

Protein C (PC) is an important anticoagulant protein in blood and converted to its active form, activated protein C (APC), by thrombin bound with thrombomodulin. APC exhibits an anticoagulant effect by the inactivation of FV a and FVIII a. In addition, APC exerts a profibrinolytic effect by inactivation of PAI-1 and inhibition of TAFI activation. APC is strongly anti-thrombotic because of its anticoagulant and profibrinolytic effect. APC has gamma-carboxyglutamic acid residues that bind to acidic phospholipids expressed on activated platelet or injured endothelial cells. Thus APC works only at the site where clots are formed and has a weak effect in primary hemostasis; this means that the use of APC is expected not to have any hemorrhagic risk. In both DIC animal models and clinical studies, we confirmed safer amelioration by APC than heparin. Recently, a specific receptor for PC/APC was found on endothelial cell membrane and anti-inflammatory effects of APC were also reported. Thus APC is thought to play an important regulatory role in blood coagulation, fibrinolysis and inflammation, especially in thrombotic diseases.
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PMID:[Anti-thrombotic effect of activated protein C]. 1121 79

Plasma was subjected to methylene blue (MB) photochemical virus inactivation using the Maco Pharma Maco-Tronic system which allows three units to be illuminated together, thus reducing processing time. The plasma bag system used incorporates an integral membrane plasma filter and a dry MB pill which dissolves in the plasma to give a 1-microM concentration. There is computer-controlled processing and datalogging. In an assessment of 10 pools of Group A plasma, the losses of coagulation factors, following MB/light treatment, were 23% fibrinogen, 10% FV, 26% FVIII, 11% FIX and 13% FXI. Group O, Group B and Group AB plasmas were not tested. Von Willebrand factor (vWf) multimers showed no substantial change when treated with MB, and no losses were seen for antithrombin III (ATIII), protein C and vWf:Ag. Measurements of C3a, C5a, prothrombin fragment 1+2 and FXIIa indicated that there was no activation as a result of filtration.
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PMID:A potentially improved approach to methylene blue virus inactivation of plasma: the Maco Pharma Maco-Tronic system. 1132 69

We determined the numbers, cellular origin and thrombin-generating properties of microparticles in healthy individuals (n = 15). Microparticles, isolated from fresh blood samples and identified by flow cytometry, originated from platelets [237 x 10(6)/L (median; range 116-565)], erythrocytes (28 x 10(6)/L; 13-46), granulocytes (46 x 10(6)/L; 16-94) and endothelial cells (64 x 10(6)/L; 16-136). They bound annexin V, indicating surface exposure of phosphatidylserine, and supported coagulation in vitro. Interestingly, coagulation occurred via tissue factor (TF)-independent pathways, because antibodies against TF or factor (F)VII were ineffective. In contrast, in our in vitro experiments coagulation was partially inhibited by antibodies against FXII (12%, p = 0.006), FXI (36%, p <0.001), FIX (28%, p <0.001) or FVIII (32%, p <0.001). Both the number of annexin V-positive microparticles present in plasma and the thrombin-generating capacity inversely correlated to the plasma concentrations of thrombin-antithrombin complex (r = -0.49, p = 0.072 and r = -0.77, p = 0.001, respectively), but did not correlate to prothrombin fragment F1+2 (r = -0.002, p = 0.99). The inverse correlations between the number of microparticles and their thrombin-forming capacity and the levels of thrombin-antithrombin complex in plasma may indicate that microparticles present in the circulation of healthy individuals have an anticoagulant function by promoting the generation of low amounts of thrombin that activate protein C. We conclude that microparticles in blood from healthy individuals support thrombin generation via TF- and FVII-independent pathways, and which may have an anticoagulant function.
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PMID:Cell-derived microparticles circulate in healthy humans and support low grade thrombin generation. 1134 98

The duration of anticoagulant treatment after a first episode of venous thromboembolism primarily depends on the risk of recurrence. Variability of recurrence rates in factor (F) V Leiden carriers may be due to concomitant thrombophilic disorders. A retrospective study was performed in 329 FV Leiden carriers with a history of venous thromboembolism (262 probands, 67 relatives). The annual rate of first recurrence was estimated in relatives. The contribution of concomitant thrombophilic disorders to the recurrence rate was evaluated in probands and relatives by a nested case--control analysis in 105 matched pairs of carriers either with or without recurrence. The overall annual recurrence rate was 2.3 per 100 patient-years. The adjusted risk of recurrence for concomitant thrombophilic disorders was: 9.1 (1.3-62.8) for the FII mutation; 1.0 (0.2-4.9) for homozygosity for FV Leiden; 1.5 (0.2-9.5) for inherited deficiencies of protein C or S; 1.8 (0.7-4.9) for FVIII coagulant activity (FVIII:C) levels >122%; 5.4 (1.6-18.6) for fasting homocysteine levels >15.2 micromol/l; and 4.4 (1.0-18.7) for loading homocysteine levels >45.8 micromol/l. Of these disorders, only the FII mutation and hyperhomocysteinaemia significantly increased the risk of recurrence in FV Leiden carriers. The estimated recurrence rate ranged from 0.45 per 100 patient--years after a secondary first event in the absence of concomitant disorders to 4.8 per 100 patient-years when a spontaneous first event was combined with concomitant disorders. Our study provides supportive evidence that the incidence of recurrent venous thromboembolism in heterozygous FV Leiden carriers depends on the concomitance of other thrombophilic disorders, in addition to whether the first thrombotic event occurred spontaneously.
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PMID:The incidence of recurrent venous thromboembolism in carriers of factor V Leiden is related to concomitant thrombophilic disorders. 1184 22

Persons who have been in contact with Lonomia achelous or Lonomia obliqua caterpillars present external and internal bleeding and opening of recently healed wounds. Hematological tests show normal platelet count, prolonged prothrombin time, activated partial thromboplastin time and thrombin time, totally corrected by normal plasma. Decreased fibrinogen (Fg), factor (F) V, FXIII, plasminogen and alpha(2)-antiplasmin with increased FVIII: C, von Willebrand factor, Fg degradation products and D dimers. Tissue plasminogen activator, plasminogen activator inhibitor and protein C varied. In L. achelous biological fluids, compounds with anticoagulant or procoagulant properties have been identified. In L. obliqua bristle extracts, mainly procoagulant activities have been identified. Subcutaneous injections of L. achelous crude extracts and a semipurified fraction reduce Fg, plasminogen and FXIII in rabbits. Intravenous injections of a very purified fraction of L. achelous in rabbits produce lysis of preformed thrombi, a decrease of Fg, plasminogen, alpha(2)-antiplasmin, FXIII and inhibition of postthrombolytic thrombus growth. Subcutaneous injections of L. obliqua bristle extracts prolong prothrombin time and activated partial thromboplastin time and reduce FXIII. Intravenous injections of crude bristle extract and a purified fraction of L. obliqua induce disseminated intravascular coagulation.
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PMID:Lonomia genus caterpillar envenomation: clinical and biological aspects. 1191 Jan 97

The 558-565 loop region in the A2 subunit of factor (F) VIIIa forms a direct interface with FIXa. We have expressed and purified B-domainless FVIII (FVIII(WT)) and B-domainless FVIII containing the hemophilia A-associated mutations Ser558Phe, Val559Ala, Asp560Ala, Gln565Arg, and the activated protein C cleavage site mutant Arg562Ala. Titration of FVIIIa in FXa generation assays showed that the mutant and wild-type proteins had similar functional affinities for FIXa (dissociation constant [K(d)] values approximately 5 nM-20 nM and approximately 100 nM-250 nM in the presence and absence of phospholipid, respectively). The catalytic activities of the factor Xase complex composed of the hemophilia A-associated FVIII species were markedly reduced both in the presence and absence of phospholipid. FVIII(WT) and FVIII(Arg562Ala) showed catalytic rate constant (k(cat)) values of approximately 60 minute(-1) in the presence of phospholipid, whereas the hemophilia A-associated mutants showed k(cat) values ranging from 3.3 minute(-1) to 7.5 minute(-1). In the absence of phospholipid, all k(cat) values were reduced but FVIII(WT) and FVIII(Arg562Ala) retained higher activities as compared with the hemophilic mutant FVIII forms. Fluorescence anisotropy experiments using fluorescein-modified FIXa confirmed that all FVIII forms interacted with FIXa. However, the presence of factor X yielded minimal increases in anisotropy observed with the mutant factor VIII forms, consistent with their reduced activity. These results show that residues within the 558-565 loop are critical in modulating FIXa enzymatic activity but do not contribute significantly to the affinity of FVIIIa for FIXa.
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PMID:Mutations associated with hemophilia A in the 558-565 loop of the factor VIIIa A2 subunit alter the catalytic activity of the factor Xase complex. 1209 41


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