Prothrombin

Literature References: Mol wt 69,000-74,000. Coagulation proenzyme present in highest concentration in blood. Prothrombin is one of the vitamin-K dependent blood coagulation factors. It is converted to thrombin by the action of factor Xa, factor V and phospholipid in the presence of Ca2+ ions. Accounts for < 0.2% of total plasma protein. Prepn of human and bovine prothrombin: Goldstein et al., J. Biol. Chem. 234, 2857 (1959); Lanchantin et al., ibid. 238, 238 (1963). Chemistry of activation: Magnussen, Biochem. J. 115, 2P (1969). Synthesized normally by liver parenchymal cells in a cyclic asynchronous manner. Dicoumarol derivatives halt the synthesis, while vitamin K1 stimulates synchronized activity of all the liver parenchymal cells: Barnhart, Anderson, Biochem. Pharmacol. 9, 23 (1962). The glycoprotein structure probably consists of a single polypeptide chain containing between 8 and 10% carbohydrate: Magnussen, Thromb. Diath. Haemorrh. suppl. 54, 31 (1973). Reviews: W. H. Seegers, Prothrombin (Harvard Univ. Press, 1962) 728 pp; Magnussen "Prothrombin and Thrombin," in The Enzymes Vol. III, P. D. Boyer, Ed. (Academic Press, New York, 3rd ed., 1971) pp 277-321; K. G. Mann, Methods Enzymol. 45B, 123-156 (1976). Review on prothrombin activation: several authors in Ann. N.Y. Acad. Sci. 370, 336-528 (1981).

Properties: Most stable within the range pH 4-9.5. Isoelec pt pH 4.2. Very sol in water but pptd at pH 4.2-4.5. Solns tend to activate spontaneously. There is little loss of activity when drying from the frozen state but the dry material alters in a few months. Drying with organic solvents destroys activity.