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)

The plasma of individuals, hetero- or homozygous for alpha1-antitrypsin deficiency, contains greatly decreased amounts of antithrombin activity as assayed against factor Xa. However, heparin stimulation of the residual antithrombin activity is observed, which is comparable to that of normal plasma. Antithrombins isolated from both normal and alpha1-antitrypsin deficient plasma by a simplified procedure are indistinguishable in both properties and yields. The microheterogeneity observed on isoelectric focusing of both preparations can be eliminated by treatment with neuraminidase. Neither purified human antithrombin nor alpha1-antitrypsin, when assayed against bovine trypsin, is stimulated by heparin. These results clearly establish the unique natures of antithrombin and alpha1-antitrypsin and show that about 75% of the antithrombin activity measured in normal plasma is due to alpha1-antitrypsin. Estimates of antithrombin III activity in normal plasma by assays dependent on enzymatic activity can probably be obtained only in the presence of heparin.
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PMID:Isolation of antithrombin III from normal and alpha1-antitrypsin-deficient human plasma. 30 58

Platelet aggregating activity of the NCG human neuroblastoma cell line was compared with that of the HL-60 human promyelocytic leukemia cell line. NCG, in intact cell suspensions and ultracentrifuged pellets, induced platelet aggregation most significantly in heparinized platelet rich plasma (PRP) containing 2.5 units/ml of heparin, but not in the presence of higher concentrations of heparin or 5 mM ethylenediamine-tetraacetate or in citrated PRP. NCG induced platelet aggregation was also inhibited by hirudin or (2R,4R)-4-methyl-1-[N2-(3-methyl-1,2,3,4-tetrahydro-8-quinolinesulfon yl)-L- arginyl]-2-piperidinecarboxylic acid (MD 805) in the same manner as that of tissue thromboplastin induced platelet aggregation. HL-60 cells did not induce platelet aggregation in our heparinized PRP assay systems; however, after treatment with neuraminidase HL-60 cells became active in aggregating platelets in either heparinized or citrated PRP. NCG demonstrated high procoagulant activity by either intact cell suspensions or ultracentrifuged pellets. The procoagulant activity of NCG was reduced in Factor VII deficient human plasma as it was in the results obtained by tissue thromboplastin. These results suggest that NCG induces platelet aggregation via thrombin generated through procoagulant activity which is shed in association with microvesicles demonstrated in the ultracentrifuged pellets. This type of platelet aggregating activity found in NCG is significantly different from that of HL-60.
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PMID:Platelet aggregating activity mediated by thrombin generation in the NCG human neuroblastoma cell line. 382 2

Sequential digestion of human thrombin and antithrombin with neuraminidase, beta-galactosidase, beta-N-acetylglucosaminidase, and endo-beta-N-acetylglucosaminidase D resulted in the successive removal of sialic acid, galactose, N-acetylglucosamine, and mannose and more N-acetylglucosamine residues. The products obtained after each stage of deglycosylation had electrophoretic mobilities that were consistent with the calculated change in mass expected from the cleavage of the sugar moieties. The modified thrombins did not lose fibrinogen-clotting activity, amidolytic activity, nor the ability to form complexes with antithrombin. In addition, asialothrombin and asialoagalactothrombin caused the same extent of platelet release as did control thrombin. The products obtained after removal of sugars from antithrombin retained thrombin-neutralizing activity. In the presence of heparin the inhibition of thrombin as well as factor Xa was enhanced. Thus, the sugar residues of thrombin and antithrombin are not required for the formation of enzyme-inhibitor complexes or for the other activities that were measured.
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PMID:Effects of enzymatic deglycosylation on the biological activities of human thrombin and antithrombin. 642 51

Factor X is a plasma protein involved in both the intrinsic and extrinsic pathways of blood coagulation. Post-translational modifications of the protein involve gamma-carboxylation of specific glutamic acid residues, beta-hydroxylation of one aspartic acid residue, and N- and O-linked glycosylation. Even though it is known that gamma-carboxylation is instrumental in regulating biological activity, the role of glycosylation in the function and properties of factor X has not been previously investigated. We utilized lectin binding and glycosidase treatment to investigate the functional role of carbohydrates on the activation peptide of factor X. Sambucus nigra agglutinin, a lectin that binds to sialic acid terminally linked alpha(2-6) to galactose or N-acetyl-galactosamine inhibits activation of human factor X in a dose-dependent manner. Inhibition of activation was observed for both intrinsic (factor IXa/VIIIa) and extrinsic (factor VIIa/tissue factor) pathway complexes. In accordance with this, selective removal of sialic acid residues on the activation peptide of factor X by neuraminidase also results in a drastic reduction of activation of the zymogen by these complexes. Corresponding reduction of activity in classical clotting assays (activated partial thromboplastin time and prothrombin time) also agrees with this observation. These results suggest a possible role of N-linked carbohydrates in the activation of factor X.
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PMID:Carbohydrate residues modulate the activation of coagulation factor X. 842 82

An important risk factor for thrombosis is the polymorphism R506Q in factor V that causes resistance of factor Va to proteolytic inactivation by activated protein C (APC). To study the potential influence of the carbohydrate moieties of factor Va on its inactivation by APC, factor V was subjected to mild deglycosylation (neuraminidase plus N-glycanase) under nondenaturing conditions. The APC resistance ratio values (ratio of activated partial thromboplastin time [APTT] clotting times with and without APC) of the treated factor V were increased (2.4 to 3.4) as measured in APTT assays. O-glycanase treatment of factor V did not change the APC resistance ratio. The procoagulant activity of factor V as well as its activation by thrombin was not affected by mild deglycosylation. Treatment of factor V with neuraminidase and N-glycanase mainly altered the electrophoretic mobility of the factor Va heavy chain, whereas treatment with O-glycanase changed the mobility of the connecting region. This suggests that the removal of the N-linked carbohydrates from the heavy chain of factor Va, which is the substrate for APC, is responsible for the increase in susceptibility to inactivation by APC. Thus, variability in carbohydrate could account for some of the known variability in APC resistance ratios, including the presence of borderline or low APC resistance ratios among patients who lack the R506Q mutation.
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PMID:The carbohydrate moiety of factor V modulates inactivation by activated protein C. 919 57

Factor V (FV) is a single-chain plasma protein containing 13-25% carbohydrate by mass. Studies were done to determine if these carbohydrate moieties altered the activated protein C (APC)-catalyzed cleavage and inactivation of both FV and the cofactor which results from its activation by alpha-thrombin, factor Va(IIa) (FVa(IIa)). Treatment of purified FV with N-glycanase and neuraminidase under nonprotein-denaturing conditions removed approximately 20-30% of the carbohydrate from the heavy chain region of the molecule. When glycosidase-treated FV was analyzed in an aPTT (activated partial thromboplastin time)-based APC sensitivity assay, the APC sensitivity ratio (APC-SR) increased from 2.34 to 3.33. In contrast, when glycosidase-treated FV was activated with alpha-thrombin, the addition of the resulting FVa(IIa) to the plasma-based APC sensitivity assay produced no substantial increase in the APC-SR. Additional functional analyses of the APC-catalyzed inactivation of FVa(IIa) in an assay consisting of purified components indicated that both glycosidase-treated and untreated FVa(IIa) expressed identical cofactor activities and were inactivated at identical rates. Analyses of the APC-catalyzed cleavage of glycosidase-treated FV at Arg(306), the initial cleavage site, revealed a 10-fold rate increase when compared to untreated FV. In contrast, and consistent with functional assays, similar analyses of FVa(IIa), derived from those FV species, revealed near-identical rates of APC-catalyzed cleavage at both the Arg(506) and Arg(306)sites. These combined results indicate that N-linked carbohydrate moieties play a substantial role in the APC-catalyzed cleavage and inactivation of FV but not FVa(IIa) at position Arg(306) and that the Arg(306) cleavage sites of FV and FVa(IIa) are distinct substrates for APC.
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PMID:Carbohydrate moieties on the procofactor factor V, but not the derived cofactor factor Va, regulate its inactivation by activated protein C. 1181 62

A novel software (VSDMIP) for the virtual screening (VS) of chemical libraries integrated within a MySQL relational database is presented. Two main features make VSDMIP clearly distinguishable from other existing computational tools: (i) its database, which stores not only ligand information but also the results from every step in the VS process, and (ii) its modular and pluggable architecture, which allows customization of the VS stages (such as the programs used for conformer generation or docking), through the definition of a detailed workflow employing user-configurable XML files. VSDMIP, therefore, facilitates the storage and retrieval of VS results, easily adapts to the specific requirements of each method and tool used in the experiments, and allows the comparison of different VS methodologies. To validate the usefulness of VSDMIP as an automated tool for carrying out VS several experiments were run on six protein targets (acetylcholinesterase, cyclin-dependent kinase 2, coagulation factor Xa, estrogen receptor alpha, p38 MAP kinase, and neuraminidase) using nine binary (actives/inactive) test sets. The performance of several VS configurations was evaluated by means of enrichment factors and receiver operating characteristic plots.
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PMID:VSDMIP: virtual screening data management on an integrated platform. 1894 2