Plasmin

Literature References: Mol wt about 90,000. Trypsin-like proteolytic enzyme which cleaves fibrin, fibrinogen, q.q.v., and other plasma proteins. Component of the mammalian fibrinolytic system specifically responsible for the dissolution of fibrin clots. Exists in plasma as an inactive precursor, plasminogen, q.v. Converted to the active enzyme at the clot site by tissue plasminogen activator, q.v. Also activated by streptokinase and urokinase, q.q.v. Rapidly inactivated in plasma by a2-antiplasmin, a glyceroprotein with high specific binding affinity for plasmin. Prepn: Christensen, MacLeod, J. Gen. Physiol. 28, 599 (1945); E. C. Loomis, US 2624691 (1953 to Parke, Davis); J. H. Hink, J. K. McDonald, US 3234106 (1966 to Cutter Labs); K. C. Robbins, L. Summaria, J. Biol. Chem. 238, 952 (1963). Converted from plasminogen by proteolysis of a single arg-val bond: K. C. Robbins et al., ibid. 242, 2333, 4279 (1967). Structure consists of two polypeptide chains connected by two disulfide bonds. The heavy (A) chain (MW ~65,000) originates from the amino-terminal portion of plasminogen and contains the binding sites. The light (B) chain (MW ~25,000) originates from the carboxy-terminus and contains the active site. Isolation and characterization of heavy and light chains: L. Summaria et al., J. Biol. Chem. 242, 5046 (1967); eidem, ibid. 246, 2143 (1971). Amino acid sequence studies: W. R. Groskopf et al., ibid. 244, 3590 (1969); Hartley, Philos. Trans. R. Soc. London Ser. B 257, 77 (1970); S. Nagasawa, T. Suzuki, Biochem. Biophys. Res. Commun. 41, 562 (1970). Amino acid sequence of active site: K. C. Robbins et al., J. Biol. Chem. 248, 1631 (1973). Review of structural studies: F. J. Castellino, Semin. Thromb. Hemostasis 10, 18-23 (1984). Enzyme specificity for lysine and arginine peptide bonds: W. Troll et al., J. Biol. Chem. 208, 85 (1954). Review of biochemistry: D. Ogston, J. Clin. Pathol. 33, Suppl. 14, 5-9 (1980). Reviews: D. Collen, Thromb. Haemostasis 43, 77-89 (1980); K. C. Robbins et al., Methods Enzymol. 80, 379-387 (1981); K. K. Kane, Ann. Clin. Lab. Sci. 14, 443-449 (1984).