scholarly journals Plasmin‐mediated proteolysis of human factor IXa in the presence of calcium/phospholipid: Conversion of procoagulant factor IXa to a fibrinolytic enhancer

2020 ◽  
Vol 18 (5) ◽  
pp. 1171-1182
Author(s):  
Amy E. Schmidt ◽  
Kanagasabai Vadivel ◽  
Julian Whitelegge ◽  
Satya Paul Bajaj
Keyword(s):  
Human Factor ◽  
Factor Ixa

Activation of Human Coagulation Factor VIII by Activated Factor X, the Common Product of the Intrinsic and the Extrinsic Pathway of Blood Coagulation

1982 ◽  
Vol 47 (02) ◽  
pp. 096-100 ◽  
Author(s):  
K Mertens ◽  
R M Bertina
Keyword(s):  
Factor Viii ◽  
Human Factor ◽  
Intrinsic Factor ◽  
Factor Xa ◽  
Coagulation Factor ◽  
Factor X ◽  
Extrinsic Factor ◽  
Extrinsic Pathway ◽  
Factor Ixa ◽  
The Common

SummaryThe intrinsic activation of human factor X has been studied in a system consisting of purified factors and in plasma. In both these systems factor Xa stimulated the activation of factor X by factor IXa plus factor VIII This is due to the activation of factor VIII by factor Xa. When this factor Xa is formed via the extrinsic pathway, the extrinsic factor X activator functions as a stimulator of the intrinsic factor X activator.

scholarly journals Soluble Phosphatidylserine Binds to Two Sites on Human Factor IXa in a Ca2+ Dependent Fashion to Specifically Regulate Structure and Activity

PLoS ONE ◽  
2014 ◽  
Vol 9 (6) ◽  
pp. e100006 ◽  
Author(s):  
Rinku Majumder ◽  
Tilen Koklic ◽  
Tanusree Sengupta ◽  
Daud Cole ◽  
Rima Chattopadhyay ◽  
...  
Keyword(s):  
Human Factor ◽  
Factor Ixa ◽  
Structure And Activity

scholarly journals The role of the second growth-factor domain of human factor IXa in binding to platelets and in factor-X activation

1995 ◽  
Vol 310 (2) ◽  
pp. 427-431 ◽  
Author(s):  
S S Ahmad ◽  
R Rawala ◽  
W F Cheung ◽  
D W Stafford ◽  
P N Walsh
Keyword(s):  
Growth Factor ◽  
Human Factor ◽  
Factor Ix ◽  
Factor X ◽  
Binding Studies ◽  
Factor Ixa ◽  
Equilibrium Binding ◽  
Activated Platelets ◽  
Factor Viiia ◽  
Factor X Activation

To study the structural requirements for factor IXa binding to platelets, we have carried out equilibrium binding studies with human factor IXa after replacing the second epidermal growth factor (EGF) domain by the corresponding polypeptide region of factor X. The chimeric protein, factor IX(Xegf2), and the wild-type, factor IXwt, produced in embryonic kidney cells 293 were radiolabelled with 125I and activated with factor XIa. Direct binding studies with thrombin-activated platelets showed normal stoichiometry and affinity of binding of factor IXawt in the presence of factor VIIIa (2 units/ml) and factor X (1.5 microM). However, under similar experimental conditions, factor IXa(Xegf2) was bound to a smaller number of sites (396 sites/platelet) with decreased affinity, i.e. a dissociation constant (Kd) of 1.4 nM, compared with normal factor IXa, factor IXaN (558 sites/platelet; Kd 0.67 nM), or factor IXawt (590 sites/platelet; Kd 0.61 nM). The concentrations of factor IXaN and factor IXawt required for half-maximal rates of factor-X activation were 0.63 nM and 0.7 nM, indicating a close correspondence of the Kd, app. for binding of factor IXawt to the factor-X activating complex on activated platelets to the Kd obtained in equilibrium binding studies. In contrast, kinetic parameters for factor-X activation by factor IXa(Xegf2) showed a decreased affinity (Kd 1.5 nM), in agreement with results of binding studies. These studies with factor IX(Xegf2) suggest that the EGF-2 domain may be important for specific high-affinity factor IXa binding to platelets in the presence of factor VIIIa and factor X.

scholarly journals Activation of human factor VII by factors IXa and Xa on human bladder carcinoma cells

Blood ◽  
1989 ◽  
Vol 73 (7) ◽  
pp. 1888-1895
Author(s):  
P Wildgoose ◽  
W Kisiel
Keyword(s):  
Bladder Carcinoma ◽  
Human Factor ◽  
Factor Xa ◽  
Factor Vii ◽  
Activate Factor ◽  
Single Chain ◽  
Cell Surfaces ◽  
Human Bladder ◽  
Factor Ixa ◽  
Human Factor Viii

Single chain factor VII is converted by limited proteolysis to its activated form, factor VIIa, by a number of blood coagulation proteases including factor IXa and factor Xa. We have determined the relative rate of human factor VII activation by human factors IXa and Xa in two different systems: one containing Ca++ and human bladder carcinoma (J82) cells, and the other containing Ca++ and mixed brain phospholipids. The rate of factor VII activation was determined by a one stage coagulation assay, and proteolytic cleavage of factor VII was assessed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting techniques. On a molar basis, factor Xa was sixfold more efficient than factor IXa beta in activating factor VII when the activation reaction occurs on J82 cell surfaces. In contrast, when incubation takes place in a suspension of mixed phospholipids, factor Xa was 18-fold more efficient in activating factor VII than factor IXa beta. In addition, factor IXa alpha activated factor VII at a rate approximately one-half that observed using factor IXa beta. In the absence of cells or phospholipids, no activation of factor VII by either factors IXa or Xa was observed. The addition of stoichiometric amounts of either recombinant human factor VIII (des B-domain) or plasma-derived factor VIIIa failed to augment the rate of factor VII activation by either factors IXa alpha or IXa beta. Likewise, purified human factor Va failed to influence the rate of factor VII activation by factor Xa in either system. Collectively, our studies reveal that J82 cells possess procoagulant phospholipid capable of readily supporting the activation of factor VII by either factors IXa beta or Xa. Our data also demonstrate that the relative ability of factor IXa beta and Xa to activate factor VII is significantly different when these reactions occur on tumor cell surfaces as compared with suspensions of mixed phospholipids.

Purification and Properties of Human Factor IXa

1976 ◽  
Vol 35 (03) ◽  
pp. 576-585 ◽  
Author(s):  
Katalin Váradi ◽  
Susan Elödi
Keyword(s):  
Molecular Weight ◽  
Human Factor ◽  
Gel Filtration ◽  
Heat Stability ◽  
Ion Exchange Chromatography ◽  
Exchange Chromatography ◽  
Factor Ix ◽  
Clotting Factors ◽  
Factor Ixa ◽  
Purification And Properties

SummaryHuman factor IXa was purified 5,000-fold from serum by ion exchange chromatography. The preparation was free from other clotting factors. Both pH sensitivity and heat stability of purified factor IXa appeared to be different from those of factor IX in the plasma. The molecular weight of human factor IXa is 80,000 as estimated from gel-filtration experiments. Modification of seryl or histidyl side chains abolished the activity of factor IXa.

scholarly journals Effect of heparin on the inactivation rate of human factor XIa by antithrombin-III

Blood ◽  
1982 ◽  
Vol 60 (4) ◽  
pp. 940-947 ◽  
Author(s):  
CF Scott ◽  
M Schapira ◽  
RW Colman
Keyword(s):  
Clinical Practice ◽  
Human Factor ◽  
Antithrombin Iii ◽  
Fold Increase ◽  
Factor Ix ◽  
Inactivation Rate ◽  
Amidolytic Activity ◽  
Factor Ixa ◽  
Factor Xia ◽  
Plasma Heparin

Abstract Factor XIa catalyzes an important reaction in the early phase of blood coagulation by converting factor IX to an active enzyme (factor IXa). Although antithrombin-III, an inhibitor of factor XIa, normally accounts for only one-sixth of the plasma inhibitory activity against factor XIa, its effectiveness has been reported to be enhanced by heparin. We have reinvestigated the ability of heparin to potentiate factor XIa inhibition by both purified antithrombin-III and plasma using synthetic tripeptide amide substrates as well as a coagulant assay. No increase in the inactivation rate of factor XIa amidolytic activity by purified antithrombin-III was observed in the presence of therapeutic heparin concentrations (1 U/ml), although inhibition of the amidolytic activity of thrombin by purified antithrombin-III was enhanced at least 20-fold by the same concentration of heparin. Furthermore, despite the ability of heparin (1 U/ml) to increase the inactivation rate of thrombin by plasma, no acceleration of the rate of inhibition of factor XIa by plasma was observed. Similar results were found when the inhibition of factor XIa was monitored with a coagulant assay after first removing the heparin. Only at heparin concentrations of 5 and 10 U/ml, was a 2- and 4-fold increase in the inactivation rate of factor XIa by purified antithrombin III observed. Therefore, in both purified systems as well as plasma, heparin, at concentrations observed in clinical practice, does not accelerate the inactivation rate of human factor XIa by antithrombin-III.

scholarly journals Mapping of monoclonal antibodies to human factor IX

Blood ◽  
1989 ◽  
Vol 74 (3) ◽  
pp. 971-977 ◽  
Author(s):  
D Frazier ◽  
KJ Smith ◽  
WF Cheung ◽  
J Ware ◽  
SW Lin ◽  
...  
Keyword(s):  
Amino Acids ◽  
Monoclonal Antibodies ◽  
Heavy Chain ◽  
Human Factor ◽  
Recombinant Dna ◽  
Factor Ix ◽  
Amino Terminus ◽  
Factor Ixa ◽  
Human Factor Ix ◽  
Recombinant Dna Techniques

Abstract We used recombinant DNA techniques to map a panel of six monoclonal antibodies (MoAbs) to regions of the human factor IX molecule. A-2 maps to 17 amino acids at the amino terminus of the heavy chain of IXa; 2D5, an inhibitor of clotting, is defined to 36 amino acids of the first EGF- like domain of human factor IX. A-4, A-5, C10D, and FXC008 all map to a region of the heavy chain containing amino acids 180 through 310, suggesting an immunodominant site. FXC008 has been reported to interfere with binding of factor IXa to factor VIII:Ca.

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