Factors V and VIII

Hereditary deficiency of Factor V is a rare autosomal recessive disorder. Combined deficiencies of Factors V and VIII have been identified in several families. 

Combined deficiency of factors V and VIII, 227300 ERGIC-53, a mannosebinding lectin... 

Fig. 7. Our current understanding of the protein C pathway. V, and VIII, represent inactivated factors V and VIII, respectively. For an explanation of other abbreviations see text.

Thrombomodulin is a protein on the endothelium that (1) binds with thrombin, reducing its availability for the clotting process and (2) activates protein C, which acts as an anticoagulant by inactivating factors V and VIII. 

It has also been proposed that because of sequence and possible structural homology with the blood clotting factors V and VIII [6] that ceruloplasmin may also participate in blood clotting and its regulation [5]. 

Partially responsible for inhibition of the extrinsic pathway. Inactivates factors V and VIII and promotes fibrinolysis. Activity declines following warfarin administration. cofactor to accelerate the anticoagulant activity of protein C. Decreased levels occur following warfarin administration. ... 

In addition to its previously mentioned role in copper transport, ceruloplasmin is an amine oxidase, a superoxide dismutase, and a ferrooxidase able to catalyze the oxidation of Fe2+ to Fe3+. Ceruloplasmin contains three consecutive homologous 350-residue sequences which may have originated from an ancestral copper oxidase gene. Like ascorbate oxidase, this blue protein contains copper of the three different types. Blood clotting factors V and VIII (Fig. 12-17), and the iron uptake protein Fet3 (Section A,l) are also closely related. 

Protein C functions as an anticoagulant by proteolytically inactivating two protein cofactors of blood coagulation, factors V and VIII.402 It too circulates in a zymogen form and is activated by limited proteolysis. Protein C appears to contain about 16 sites for Ca2+, all of equal affinity, while activated protein C binds about nine Ca2+. Conformational rearrangement during activation results in loss of binding sites. 

Thrombin activates platelets, converts fibrinogen to fibrin, activates factor XIII, which stabilizes fibrin, and activates factors V and VIII, which accelerate the generation of prothrombinase. Therefore, the inhibition of thrombin is essential in preventing and treating thromboembolic disorders. 

I 14 Kane WH, Davie EW. Blood coagulation factors V and VIII structural and functional similarities and their relationship to hemorrhagic and thrombotic disorders. Blood 1988 71 539-555. 

Hie serine protease thrombin takes a central position in the clotting system. It splits off fibrinopeptides A and B from the amino terminal ends of the a- and -chains of fibrinogen. The resulting fibrin monomer then undergoes polymerization to forma fibrin dot. Via activation of the clotting factors V and VIII, further thrombin is Generated from wothramhin. and via activation of blood dale lets and... 

Fig. 7. Schematic representation of the domain organizadon, as well as ligand-, receptor-, and co-receptor-binding preferences of the semaphorins and their neuronal receptors. The individual domains are labeled. PSI, Plexin/Semaphorin//ntegrin domain IPX, /mmunoglobulin-like domain found in Plexins (and Met) and in some Transcription factors CUB, domain homologous to complement-binding factors Clr and Cls FV/VIII, domain homologous to coagulation factor V and VIII (also known as F5/8 type C or discoidin domain) MAM, Meprin/A5/fi domain SP, Sex-Plexin domain. Semaphorins, plexins and scatter-factor receptors (MET) share a common semaphorin domain (black heptagon).

Pereira, L.M.M.B., Langley, P.G., HayRar, K.M., Tredger, J.M., Williams, R. Coagulation factor V and VIII/V ratio as predictors of outcome in paracetamol induced fulminant hepatic failure relation to other prognostic indicators. Gut 1992 33 98-102... 

Experimental study of the rise in factor VIII concentrations, now known to occur in so many situations, has been almost entirely confined for practical reasons to a study of the effects of exercise or adrenaline administration. These situations, it will be recalled, are those in which an isolated rise in factor VIII can be observed, unaccompanied by changes in fibrinogen or factor V. It is thus uncertain to what extent the results may be applied to the more protracted, combined increase in fibrinogen and factors V and VIII. 

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