Plasma proteins, xiii

Cohn, E.J. et al. (1947) Preparation and properties of serum and plasma proteins. XIII. Crystallization of serum albumins from ethanol-water mixtures./. Am. Chem. Soc. 69, 1753-1761. 

Injury to the endothelium and exposure of tissue factor on the subendothelial layer to plasma proteins also activate the blood coagulation cascade, which ultimately activates thrombin and Factor XIII Factor XIII cross-links strands of polymerized fibrin monomers to form a stable clot (the secondary hemostatic plug). The blood coagulation cascade consists of a series of enzymes (such as Factor X), which are inactive until proteolytically cleaved by the preceding enzyme in the cascade. Other proteins (Factor V and Factor VIII) serve as binding proteins, which assemble factor complexes at the site of injury. Ca and y-carboxyglutamate residues in the proteins (formed by a vitamin K-dependent process in the liver) attach the factor complexes to phosphoUpids exposed on platelet membranes. Consequently, thrombus formation is rapidly accelerated and localized to the site of injury. 

Figure 5.3. Intrinsic and extrinsic blood clotting cascades. Factor I, fibrinogen Factor II, prothrombin (vitamin K-dependent) Factor III, thromboplastin Factor V, proac-celerin Factor VII, proconvertin (vitamin K-dependent) Factor VIII, antihemophilic factor Factor IX, Christmas factor (vitamin K-dependent) Factor X, Stnart factor (vitamin K-dependent) Factor XI, plasma thromboplastin Factor XII, Hageman factor Factor XIII, fibrin-stabilizing factor and Factor XIV, protein C (vitamin K-dependent). What was at one time called Factor IV is calcinm no factor has been assigned nnmber VI.

Coagulation factors I, II, V, VII, IX-XIII are synthesized in hepato-cytes. To a minor extent, factor I is also synthesized in the intrahepatic RES, while factor Vlll is formed exclusively in the RES. Formation of factors II, VII, IX and X as well as of the two inhibitor proteins C and S depends on vitamin K, the absence of which will cause the synthesis to decline. Factors 1, V, XI, XII and Xni are formed without the mediation of vitamin K. Proteolytic enzymes convert coagulation factors into active factors in the plasma, (s. tab. 5.12)... 

Proteins that do not fit into the previous functional categories are fibrinogen, factor XIII (the plasma protransglutaminase), and von Willebrand factor. 

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