Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.6 (thromboplastin)
 13,278 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Increased plasma sialidase activity was demonstrated in 25 patients with acute myocardial infarction. The mean plasma sialic acid level after incubation with substrate neuramin lactose was 0.060 +/- 0.003 (SEM) mumol/sample compared with 0.017 +/- 0.003 mumol/sample in 24 patients without infarction (p less than 0.001). The erythrocyte endothelial cell adhesion index was highest when both cell types were sialidase treated (0.35 vs control 0.00 [p less than 0.05]). When sialidase (50 U/ml) was added to whole blood in plastic tubes, the mean clotting time was 7.17 +/- 1.0 (SD) minutes (n = 8) compared with a mean control of 15.45 +/- 3.9 minutes (p less than 0.01). Sialidase had no effect on prothrombin or partial thromboplastin times. The above studies suggest that increased plasma sialidase activity in patients with acute myocardial infarction may be associated with clumps of desialylated erythrocytes that may alter flow in the microcirculation.
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PMID:Plasma sialidase activity in acute myocardial infarction. 360 73

Factor IX and factor X have sialic acid in O-linked and N-linked oligosaccharides on their activation peptides, and a terminal sialic acid is found on a recently described O-linked tetrasaccharide at Ser-61 in the light chain of human factor IXa. In studies presented here, the potential role of sialic acid residues in mediating activity of human coagulation factors IX and X was tested after enzymatic removal of sialic acid residues. In contrast to previous reports, treatment of factor IX or factor IXa with recombinant sialidase did not decrease the rate of factor IX activation or proteolytic properties of human factor IXa. The activation rates of factor IX and desialated factor IX were indistinguishable when treated with factor XIa, with factor VIIa/tissue factor complex, and with the factor X activating enzyme from Russell's viper venom. Desialated human factor IXa showed full activity in the non-activated partial thromboplastin time assay and retained full "tenase" activity in a coupled amidolytic assay. Similar experiments with human factor X showed no detectable loss of clotting activity in the prothrombin time assay after desialation. Additionally, desialated human factor X was cleaved by the factor X activating enzyme from Russell's viper venom and intrinsic tenase at the same rate as untreated factor X when analyzed by SDS-polyacrylamide gel electrophoresis. These studies have shown that factor IX and factor X clotting activity are not dependent on sialic acid content. Further studies are needed to determine whether desialated factor IX binds to endothelial cells, and whether factors IX and X are more rapidly cleared from circulation or have altered susceptibility to proteolysis after enzymatic removal of sialic acid.
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PMID:Enzymatic removal of sialic acid from human factor IX and factor X has no effect on their coagulant activity. 789 89

Conversion of factor X to factor Xa results in release of a heavily glycosylated activation peptide. Analysis of protease-digested glycopeptides derived from the activation peptides of bovine and human blood coagulation factor X allowed the identification of sites of the O-linked oligosaccharide chains in these peptides. Glycopeptides were prepared from the activation peptides by digestion with chymotrypsin or Staphylococcus aureus V8 protease. By combined analysis of amino acid sequence and sialic acid content, we found that bovine factor X had an O-linked oligosaccharide chain linked to Thr26, and human factor X had four carbohydrate-attachment sites, namely, O-glycosidic linkages to Thr17 and Thr29, respectively, and N-glycosidic linkages to Asn39 and Asn49, respectively, in their activation peptides. The O-linked carbohydrate-attachment sites were identified since the yields of phenylthiohydantoin derivatives of amino acids that corresponded to their residues were increased during amino acid sequencing after deglycosylation of the glycopeptides with sialidase and O-glycanase. The effect of deglycosylation of bovine factor X1 was investigated with factor-X-activating enzyme from Russell's viper venom or extrinsic Xase (factor VIIa/tissue factor/phospholipid) by examining the activation rates of derivatives of factor X prepared using O-glycanase, sialidase, and/or N-glycanase. The removal of O-linked carbohydrate resulted in a decrease in the rate of activation. It appears that carbohydrate residues in factor X play an important role in the activation of the zymogen.
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PMID:Identification of O-linked oligosaccharide chains in the activation peptides of blood coagulation factor X. The role of the carbohydrate moieties in the activation of factor X. 824 61