The Role of Factor IX in Tissue Thromboplastin Induced Coagulation

Besselaar, A.M.H.P. van den; Ram, I E; Alderkamp, G. H. J.; Bertina, Rogier M.

doi:10.1055/s-0038-1657215

Cited by 17 publications

(5 citation statements)

References 24 publications

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“…when limited amounts of fac tor Xa and factor IXa are formed), the relative contribution of the antihaemophilic factors to the overall factor Xa formation, might be relatively high especially under conditions of continuous flow (in vivo). However, if we study tissue factor-dependent coagulation in vitro in the test tube (closed system) it is conceivable that the first traces of factor Xa formed by the direct extrinsic activation of factor X, will be sufficient to form enough prothrombinase activity to induce clot formation; this might explain why the clotting time is virtually independent of the presence of factor IX (34).…”

Section: Discussionmentioning

confidence: 99%

Extrinsic Activation of Human Blood Coagulation Factors IX and X

Bom¹,

Reinalda-Poot²,

Cupers³

et al. 1990

Thromb Haemost

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SummaryWe studied activation of human coagulation factors IX and X by factor VIIa in the presence of calcium ions, phospholipid (phosphatidylserine/phosphatidylcholine, 50/50, mol/mol) and purified tissue factor apoprotein. Activation of factor IX and factor X was found to occur without a measurable lag-phase and hence initial rates of factor IXa and factor Xa formation could be determined. Like previously observed for the activation of factor X, the activation of factor IX was saturable with respect to factor VIIa, tissue factor apoprotein and phospholipid. The results suggested that in the presence of a Ca2+ ions the same ternary complex of factor VIIa-tissue factor apoprolein-phospholipid is responsible for the activation of factor IX and factor X. Roth the apparent Km of 22 nM-factor IX and the apparent Kcat of 28 min−1 were about 3-fold lower than the coiicsponding parameters of factor X activation by this complex. Hence, the catalytic efficiency (Kcat/Km) of factor IX and factor X activation was about equal. However, the two substrates inhibited the activation of each other by competition for the same catalytic sites. The apparent Kinh of factor IX for inhibition of extrinsic factor X activation is 30 nM. The apparent Kinh of factor X for inhibition of extrinsic factor IX activation is 116 nM. From these kinetic data it was calculated that at plasma concentration of factors IX and X, the rate of extrinsic factor IX activation would be half the rate of factor X activation. These relative rates of extrinsic factor IX and factor X activation in combination with previously reported kinetic data on the activation of factor X by factor IXa in the presence of factor VIIIa provide support for the concept that at low levels of tissue factor, factor IXa formation might play an important role in the extiinsic pathway of coagulation in vivo.

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Section: Discussionmentioning

confidence: 99%

Extrinsic Activation of Human Blood Coagulation Factors IX and X

Bom¹,

Reinalda-Poot²,

Cupers³

et al. 1990

Thromb Haemost

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“…The ability of normal, variant and modified FIX to bind to anti-FIX : Mg(II) antibodies, anti-FIX : Ca(II) antibodies or phospholipids was studied in a sandwich ELISA, using anti-FIX : Mg(II) antibodies, anti-FIX : Ca(II) antibodies or human brain phospholipids [27] respectively to coat microtitre plates. Bound FIX was detected with non-Ca(II)-dependent anti-(factor IX IgG)-HRP conjugate as described [24] and expressed as the A %&!…”

Section: Binding Of Fix To Anti-fix : Mg(ii) Antibodies Anti-fix : Cmentioning

confidence: 99%

Modification of the N-terminus of human factor IX by defective propeptide cleavage or acetylation results in a destabilized calcium-induced conformation: effects on phospholipid binding and activation by factor XIa

Wojcik¹,

Berg²,

Poort³

et al. 1997

Biochemical Journal

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The propeptide of human coagulation factor IX (FIX) directs the gamma-carboxylation of the first 12 glutamic acid residues of the mature protein into gamma-carboxyglutamic acid (Gla) residues. The propeptide is normally removed before secretion of FIX into the blood. However, mutation of Arg-4 in the propeptide abolishes propeptide cleavage and results in circulating profactor IX in the blood. We studied three such genetic variants, factor IX Boxtel (Arg-4-->Trp), factor IX Bendorf (Arg-4-->Leu) and factor IX Seattle C (Arg-4-->Gln). These variant profactor IX molecules bind normally to anti-FIX:Mg(II) antibodies, which indicates that the mutations do not seriously affect gamma-carboxylation. Metal ion titration of the binding of variant profactor IX to conformation-specific antibodies demonstrates that the calcium-induced conformation is destabilized in the variant molecules. Also the binding of FIX Boxtel to phospholipids and its activation by factor XIa requires a high (>5 mM) calcium concentration. The three-dimensional structure of the Gla domain of FIX in the presence of calcium indicates that the acylation of the amino-terminus, rather than the presence of the propeptide, was responsible for the destabilization of the calcium-induced conformation. In order to confirm this, the alpha-amino group of Tyr1 of FIX was acetylated. This chemically modified FIX showed a similar destabilization of the calcium-induced conformation to variant profactor IX. Our data imply that the amino-terminus of FIX plays an important role in stabilizing the calcium-induced conformation of the Gla domain of FIX. This conformation is important for the binding to phospholipids as well as for the activation by factor XIa. Our results indicate that mutations in FIX that interfere with propeptide cleavage affect the function of the protein mainly by destabilizing the calcium-induced conformation.

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“…The lipid extract was stored in chloroform at -20" C under nitrogen. Phospholipid content was determined by phosphate analysis after HCIO4 combustion (32) and contained (it mol %), sphingomyelin l3%; phosphatidylcholine '35%; phosphatidylethanolamide 40%; phosphatidylserine 8"/"; phosphatidylinositol 2% (33). Working solutions of phospholipid were prepared from the stock solution following the procedure described by Mertens et al (34).…”

Section: Proteinsmentioning

confidence: 99%

Activated Protein C Increases Fibrin Clot Lysis by Neutralization of Plasminogen Activator Inhibitor No Evidence for a Cofactor Role of Protein S

Fouw¹,

Jong²,

Haverkate³

et al. 1988

Thromb Haemost

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summaryThe effect of purified human activated protein G (APC) on fibrinolysis was studied using a clot iysis system consisting of purified glu-plasminogen, tissue-type plasminogen activator, plasminogen activator inhibitor (released from endothelial cells or blood platelets), fibrinogen, 125T-fibrinogen and thrombin. All proteins were of human origin.In this system APC could increase fibrinolysis in a dose dependent way, without affecting fibrin formation or fibrin crosslinking. However, this profibrinolytic effect of APC could only be observed when plasminogen activator inhibitor (PAI-l) was present. The effect of APC was completely quenched by pretreatment of APC with anti-protein C IgG or di-isopropylfluorophosphate. Addition of the cofactors of APC:protein S, Ca2+-ions and phospholipid-alone or in combination did not enhance the profibrinolytic effect of APC. These observations indicate that human APC can accelerate in vitro clot lysis by the inactivation of PAI-1 activity. However, the neutralization of PAI-1 by APC is independent of the presence or absence of protein S, phospholipid and Ca2+-ions.

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The Role of Factor IX in Tissue Thromboplastin Induced Coagulation

Cited by 17 publications

References 24 publications

Extrinsic Activation of Human Blood Coagulation Factors IX and X

Extrinsic Activation of Human Blood Coagulation Factors IX and X

Modification of the N-terminus of human factor IX by defective propeptide cleavage or acetylation results in a destabilized calcium-induced conformation: effects on phospholipid binding and activation by factor XIa

Activated Protein C Increases Fibrin Clot Lysis by Neutralization of Plasminogen Activator Inhibitor No Evidence for a Cofactor Role of Protein S

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