Initiation of the extrinsic pathway of blood coagulation: evidence for the tissue factor dependent autoactivation of human coagulation factor VII

Biochemistry ◽  
1991 ◽  
Vol 30 (45) ◽  
pp. 10819-10824 ◽  
Author(s):  
Tomohiro Nakagaki ◽  
Donald C. Foster ◽  
Kathleen L. Berkner ◽  
Walter Kisiel
2007 ◽  
Vol 92 (11) ◽  
pp. 4352-4358 ◽  
Author(s):  
Guenther Boden ◽  
Vijender R. Vaidyula ◽  
Carol Homko ◽  
Peter Cheung ◽  
A. Koneti Rao

Abstract Context: Type 2 diabetes mellitus (T2DM) is a hypercoagulable state. Tissue factor (TF) is the principal initiator of blood coagulation. Objective: Our objective was to examine the effects of hyperglycemia and hyperinsulinemia on the TF pathway of blood coagulation in T2DM. Design: Three study protocols were used: 1) acute correction of hyperglycemia (with iv insulin) followed by 24 h of euglycemia, 2) 24 h of selective hyperinsulinemia, and 3) 24 h of combined hyperinsulinemia and hyperglycemia. Setting: The study took place at a clinical research center. Study Participants: Participants included 18 T2DM patients and 22 nondiabetic controls. Results: Basal TF-procoagulant activity (TF-PCA), monocyte TF mRNA, plasma coagulation factor VII (FVIIc), and thrombin-anti-thrombin complexes were higher in T2DM than in nondiabetic controls, indicating a chronic procoagulant state. Acutely normalizing hyperglycemia over 2–4 h resulted in a small (∼7%) but significant decline in TF-PCA with no further decline over 24 h. Raising insulin levels alone raised TF-PCA by 30%, whereas raising insulin and glucose levels together increased TF-PCA (by 80%), thrombin-anti-thrombin complexes, and prothrombin fragment 1.2. Plasma FVIIa and FVIIc declined with increases in TF-PCA. Conclusion: We conclude that the combination of hyperglycemia and hyperinsulinemia, common in poorly controlled patients with T2DM, contributes to a procoagulant state that may predispose these patients to acute cardiovascular events.


2002 ◽  
Vol 363 (2) ◽  
pp. 411 ◽  
Author(s):  
Raffaella TOSO ◽  
Mirko PINOTTI ◽  
Katherine A. HIGH ◽  
Eleanor S. POLLAK ◽  
Francesco BERNARDI

1990 ◽  
Vol 265 (2) ◽  
pp. 327-336 ◽  
Author(s):  
V J J Bom ◽  
R M Bertina

In the extrinsic pathway of blood coagulation, Factor X is activated by a complex of tissue factor, factor VII(a) and Ca2+ ions. Using purified human coagulation factors and a sensitive spectrophotometric assay for Factor Xa, we could demonstrate activation of Factor X by Factor VIIa in the absence of tissue-factor apoprotein, phospholipids and Ca2+. This finding allowed a kinetic analysis of the contribution of each of the cofactors. Ca2+ stimulated the reaction rate 10-fold at an optimum of 6 mM (Vmax. of 1.1 x 10(-3) min-1) mainly by decreasing the Km of Factor X (to 11.4 microM). In the presence of Ca2+, 25 microM-phospholipid caused a 150-fold decrease of the apparent Km and a 2-fold increase of the apparent Vmax. of the reaction; however, both kinetic parameters increased with increasing phospholipid concentration. Tissue-factor apoprotein contributed to the reaction rate mainly by an increase of the Vmax., in both the presence (40,500-fold) and absence (4900-fold) of phospholipid. The formation of a ternary complex of Factor VIIa with tissue-factor apoprotein and phospholipid was responsible for a 15 million-fold increase in the catalytic efficiency of Factor X activation. The presence of Ca2+ was absolutely required for the stimulatory effects of phospholipid and apoprotein. The data fit a general model in which the Ca2(+)-dependent conformation allows Factor VIIa to bind tissue-factor apoprotein and/or a negatively charged phospholipid surface resulting into a decreased intrinsic Km and an increased Vmax. for the activation of fluid-phase Factor X.


2019 ◽  
Vol 476 (19) ◽  
pp. 2909-2926
Author(s):  
Tina M. Misenheimer ◽  
Kraig T. Kumfer ◽  
Barbara E. Bates ◽  
Emily R. Nettesheim ◽  
Bradford S. Schwartz

Abstract The mechanism of generation of factor VIIa, considered the initiating protease in the tissue factor-initiated extrinsic limb of blood coagulation, is obscure. Decreased levels of plasma VIIa in individuals with congenital factor IX deficiency suggest that generation of VIIa is dependent on an activation product of factor IX. Factor VIIa activates IX to IXa by a two-step removal of the activation peptide with cleavages occurring after R191 and R226. Factor IXaα, however, is IX cleaved only after R226, and not after R191. We tested the hypothesis that IXaα activates VII with mutant IX that could be cleaved only at R226 and thus generate only IXaα upon activation. Factor IXaα demonstrated 1.6% the coagulant activity of IXa in a contact activation-based assay of the intrinsic activation limb and was less efficient than IXa at activating factor X in the presence of factor VIIIa. However, IXaα and IXa had indistinguishable amidolytic activity, and, strikingly, both catalyzed the cleavage required to convert VII to VIIa with indistinguishable kinetic parameters that were augmented by phospholipids, but not by factor VIIIa or tissue factor. We propose that IXa and IXaα participate in a pathway of reciprocal activation of VII and IX that does not require a protein cofactor. Since both VIIa and activated IX are equally plausible as the initiating protease for the extrinsic limb of blood coagulation, it might be appropriate to illustrate this key step of hemostasis as currently being unknown.


FEBS Letters ◽  
1992 ◽  
Vol 298 (2-3) ◽  
pp. 206-210 ◽  
Author(s):  
Bryan J. Clarke ◽  
Frederick A. Ofosu ◽  
Sampath Sridhara ◽  
Robert D. Bona ◽  
Frederick R. Rickles ◽  
...  

1974 ◽  
Vol 32 (01) ◽  
pp. 057-064 ◽  
Author(s):  
Y Nemerson ◽  
S.A Silverberg ◽  
J Jesty

SummaryTwo reactions of the extrinsic pathway of coagulation, the activations of Factor X and prothrombin, have been studied in purified systems and shown to be self-damping. Factor X was activated by the tissue factor - Factor VII complex, and prothrombin by two systems: the coagulant protein of Taipan venom, and the physiological complex of activated Factor X, Factor V, lipid, and calcium ions. In each case the yield of enzyme, activated Factor X or thrombin, is a function of the concentration of activator. These and other observations are considered as a basis for a control mechanism in coagulation.


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