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

In order to approach an understanding of the mechanisms of fetal death in patients with antiphospholipid syndrome we investigated the association between protein C activity and anticardiolipin antibody. Protein C activity in vivo was decreased in some patients with recurrent fetal loss and a high ACA titer. This study suggests that anticardiolipin antibody in patients with recurrent fetal loss may inhibit activation of protein C by thrombomodulin.
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PMID:Effect of anticardiolipin antibody in patients with recurrent fetal loss on thrombomodulin-dependent protein C activation. 838 Nov 75

Two girls, 22 months and 12 years of age, presented with repeated cerebral infarctions in association with primary antiphospholipid syndrome. The younger patient also suffered from protein C deficiency, while the other one had protein S and complement C4 deficiencies. All other causes of cerebral infarction were excluded; however, vasculitis remains a possibility in one patient. Both girls developed spastic tetraparesis as a sequela of the previous infarctions. The two patients were treated with aspirin and prednisone, with remission of the infarctions during the next 8 months of observation. A primary deficiency of protein C or S is proposed which would produce cerebral thrombosis with exposure of phospholipids; this thrombosis then, like antigens, would generate antibodies acting on the thrombin-thrombomodulin complex, exacerbating the thrombotic process. The association of complement C4 deficiency is an additional risk factor.
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PMID:Childhood stroke associated with protein C or S deficiency and primary antiphospholipid syndrome. 845 4

We report 2 cases of portal vein thrombosis associated with a single point mutation in the factor V gene that replaces arginine in residue 506 with glutamine. This mutation induces abnormal resistance to anticoagulant activity of activated protein C and increases the risk of deep vein thrombosis. Both patients had a personal and familial history of deep vein thrombosis. Intraabdominal neoplasia or infection, myeloproliferative disorder, antiphospholipid syndrome, paroxysmal nocturnal hemoglobinuria and coagulation inhibitor deficiency (antithrombin, proteins C and S) were excluded by exhaustive investigation. However, an abnormal resistance to activated protein C was found, and DNA analysis showed the factor V Arg506 to Gln mutation in both cases. Anticoagulant treatment was begun. A study of family history made in one case, showed the same genetic disease in one of the relatives. Resistance to activated protein C with factor V gene mutation should be investigated in patients with portal vein thrombosis. A study of family history, and anticoagulant treatment are justified for symptomatic patients.
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PMID:[A new hereditary cause of portal vein thrombosis: the abnormal resistance to activated protein C by the Arg 506-->Gln mutation of the gene of factor V]. 852 25

Antiphospholipid syndrome is associated with venous, arterial, and placental thrombosis, possibly through autoantibody impairment of phospholipid-dependent protein C activation. Recently, a missense mutation in the factor V gene (1691 G-->A) has been identified that results in an abnormal factor V product (1). This mutation, known as the Leiden mutation, causes an amino acid substitution of glutamine for arginine at position 506 in the factor V molecule and renders the protein resistant to proteolytic inactivation by activated protein C and thus predisposes to thrombosis (2, 3). We hypothesized that some individuals with antiphospholipid syndrome may also carry the Leiden mutation, and thus have a "second hit" predisposition to thrombosis. To test this hypothesis, allele-specific hybridization and allele-specific restriction analysis were used to test for the Leiden mutation in thirty women with the antiphospholipid syndrome, 10 of whom had a history of thrombosis. None of the women were heterozygous or homozygous for the factor V mutation. We conclude that the presence of the factor V Leiden mutation is not a prerequisite for the thrombotic events in patients with antiphospholipid syndrome, due to the occurrence of thrombosis seen in patients lacking the factor V mutation.
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PMID:The factor V Leiden mutation which predisposes to thrombosis is not common in patients with antiphospholipid syndrome. 856 Apr 6

Activated protein C (APC) resistance is usually associated with a single DNA mutation predicting replacement of Arg506 by Gln in factor V (FV). Studies using synthetic peptides suggest that FV residues 493-506 provide factor Xa (FXa) and protein S binding sites. Biochemical studies were performed to test the hypothesis that the Arg506Gln FV mutation causes APC resistance and to define the nature of the resistance of Gln506-FVa to APC. Purified Gln506-FV conveyed APC resistance to FV-deficient plasma in APTT and FXa-1-stage assays. Purified Gln506-FVa, generated either by thrombin or by FXa, was resistant to APC. Nonetheless, Gln506-FVa was not completely resistant to APC since it was inactivated by APC approximately 10-fold slower than normal Arg506-FVa, probably due to cleavage at Arg306. This reduced but significant susceptibility of Gln506-FVa to APC inactivation may help explain why APC resistance, especially for heterozygotes, is a relatively moderate risk factor for venous thrombosis. Cardiolipin promotes APC anticoagulant activity better than FXa coagulant activity, and antibodies from some antiphospholipid antibody syndrome patients downregulate APC activity. Thus, acquired APC resistance may contribute to pathogenesis of thrombosis in the antiphospholipid antibody syndrome.
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PMID:Activated protein C resistance: molecular mechanisms. 857 3

The pathogenesis of the antiphospholipid syndrome remains uncertain. Antibodies that react with phospholipids may not be directly responsible for cellular injury, but may be part of the immune network through which autoantibodies with pathogenic potential are generated. The latter may recognize proteins such as beta 2-glycoprotein I that form complexes with phospholipids, proteins whose functions depend upon interaction with phospholipids such as protein C and its cofactors, altered lipoproteins such as oxidized low-density lipoproteins, or other molecules that share only antigenic similarity. Thus, a spectrum of autoantibodies that recognize different lipid-protein complexes may develop in these patients and contribute to the observed clinical heterogeneity of the syndrome. Current techniques do not permit identification of the subset of patients with antiphospholipid antibodies at risk for thrombosis or abortion and there are no prospective, controlled trials addressing the prophylaxis or treatment of affected individuals. Identification of the cellular targets of antibodies to lipid-protein moieties is needed to identify patients at risk for these complications and as a means to monitor therapy.
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PMID:The antiphospholipid-protein syndrome. 861 97

We studied both inherited and acquired activated protein C (APC) resistance in a group of 22 patients with primary antiphospholipid syndrome (APS). The APC resistance genotype was assessed using a PCR-based analysis for the factor V R506Q (Leiden) mutation. One patient with primary APS was found to be heterozygous for the factor V Leiden mutation. He and other family members were affected by severe thrombophilia and had a familial form of primary APS. The APC resistance phenotype was assessed by measuring the prolongation of the activated partial thromboplastin clotting time in response to APC. It was found in five out of six patients with APS, in one of them transiently. We have found that the APC resistance phenotype is more frequent than the genotype in primary APS. It would seem that patients with thrombophilia should be investigated for APC resistance even if found to have antiphospholipid antibodies and/or lupus anticoagulants.
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PMID:Activated protein C resistance phenotype and genotype in patients with primary antiphospholipid syndrome. 873 42

Cerebrovascular accidents are rare but well documented in patients with Crohn's disease. Up to 10% of hypercoagulable state manifestations reported in association with inflammatory bowel disease are ischemic strokes. However, no clear mediating factor has thus far been suggested. A 44-year-old woman with Crohn's disease for 25 years developed a left temporal stroke associated with anticardiolipin antibody and lupus anticoagulant suggesting antiphospholipid syndrome. A thorough evaluation did not reveal any other risk factor for ischemic stroke. No possible sources of emboli were found in the carotids and heart, and no deficiencies of protein C and activated protein C, protein S, and anti-thrombin III leading to hypercoagulable state were present. There may be a possible association between antiphospholipid syndrome and hypercoagulable state in Crohn's disease.
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PMID:Antiphospholipid syndrome manifested by ischemic stroke in a patient with Crohn's disease. 874 56

Although there are numerous risk factors for venous thromboembolic disease, the term 'thrombophilia' refers only to those familial or acquired disorders of the haemostatic system that result in an increased risk of thrombosis. The inherited thrombophilias include antithrombin III deficiency, resistance to activated protein C (factor V Leiden), protein C and protein S deficiencies as well as some rare forms of dysfibrinogenaemia. It is possible that other inherited conditions might also predispose to thrombosis. In contrast, when using the above definition, the antiphospholipid syndrome is the only genuine acquired thrombophilic state. Patients who have thromboembolic disease at a young age with no provoking event or who have a positive family history or whose thrombosis involves an unusual site should be investigated for thrombophilia. The management of a patient identified as having a laboratory abnormality associated with thrombophilia will depend on a variety of factors such as the patient's individual and family thrombotic history, the site of the thrombosis and the presence of other prothrombotic risk factors. The use of prophylactic anticoagulation during pregnancy and the puerperium requires particularly careful consideration in thrombophilic women. As more becomes known about the thrombophilias it will become possible to formulate more exact guidelines as to the management of these conditions.
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PMID:Guidelines for the management of thrombophilia. Department of Haematology, The Royal London Hospital, Whitechapel, London, UK. 887 58

The Antiphospholipid Syndrome is defined by the association between peculiar clinical manifestations, namely arterial and/or venous thrombosis, recurrent abortions and thrombocytopenia, and the antiphospholipid antibodies. These antibodies are directed to plasma proteins bound to anionic phospholipids or other anionic surfaces: so far, beta 2-glycoprotein I is the best known and characterized antiphospholipid 'cofactor' (this issue is specifically treated in other parts of this journal). In recent years, such a role has been reported also for prothrombin, activated Protein C, Protein S, Annexin V, Thrombomodulin, high- and low-molecular weight kininogens. Anti-prothrombin antibodies are detected in approximately 50% of the antiphospholipid-positive patients; conversely, limited data are available regarding the prevalence the other antibodies. 'Cofactors' are necessary for the expression of both the immunological and the functional properties of their respective antiphospholipid antibodies. In particular, the recognition of the calcium-mediated prothrombin/lipid complex by anti-prothrombin antibodies hampers prothrombin activation, thus causing the prolongation of the phospholipid-dependent coagulation reactions. The interaction between antiphospholipid antibodies and natural inhibitors of coagulation such as activated Protein C, its non-enzymatic accessory protein Protein S or Thrombomodulin might increase the risk to develop thromboembolic events. Similarly, the presence of antibodies to surface-bound Annexin V has been hypothesized to play a role in recurrent abortions and fetal deaths. However, to clearly establish whether and which antiphospholipid antibodies represent risk factors for the thromboembolic events of the antiphospholipid syndrome, further studies of their behaviour and properties as well as the identification and characterization of (possibly) other antibodies are required.
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PMID:Non beta 2-glycoprotein I cofactors for antiphospholipid antibodies. 890 67


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