Mechanism of Action and Some Properties of a Tissue Activator of Plasminogen

Summary

1. Improvements in preparations of tissue activator and plasminogen and termination of activation by epsilon aminocaproic acid have permitted the use of a quantitative caseinolytic assay for the measurement of the plasmin formed. The following data indicate that the activation of plasminogen by tissue activator is catalytic :

a) Biphasic curve obtained when velocity was plotted against plasminogen concentration.

b) First order kinetics.

c) Dependence of the turnover number on tissue activator concentration.

2. The temperature and pH stability of tissue activator were similar to those reported for urokinase. Since both of these enzymes have now been shown to activate plasminogen by a catalytic mechanism, these data support the suggestion that urokinase may be an excretory form of tissue activator which has been released into the circulation.

• References

• 1 Astrup T, Permin P. M. Fibrinolysis in the animal organism. Nature 159: 681 1947;
• 2 Tagnon H. J, Petermann M. J. Activation of proplasmin by a tissue fraction. Proc. Soc. exp. Biol. 70: 359 1949;
• 3 Lewis J. H, Ferguson J. H. Fibrinolysokinase activators for profibrinolysin. J. clin. Invest. 29: 1059 1950;
• 4 Astrup T, Stage A. Isolation of a soluble fibrinolytic activator from animal tissue. Nature 190: 929 1952;
• 5 Alkjaersig N, Fletcher A. P, Sherry S. II. A Kinetic study of activation with trypsin, urokinase and streptokinase. J. biol. Chem. 233: 86 1958;
• 6 Kjeldgaard N. O, Ploug J. Urokinase, an activator of plasminogen from human urine. II.Mechanism of plasminogen activation. Biochim. biophys. Acta. (Amst.) 24: 289 1957;
• 7 Mullertz S. Formation and properties of the activator of plasminogen and of human and bovine plasmin. Biochem. J. 61: 424 1955;
• 8 Kline D. L, Fishman J. B. Proactivator function of human plasmin as shown by lysine esterase activity. J. biol. Chem. 236: 2807 1961;
• 9 Astrup T. Activation of proteolytic enzyme in blood by animal tissue. Biochem. J. 50: 5 1951;
• 10 Abe T, Astrup T. Activation of bovine plasminogen by the plasminogen activator in animal tissue. Thrombos. Diathes. haemorrh. (Stuttg.) 04: 201 1960;
• 11 Bachmann F. W, Fletcher A. P, Sherry S. Partial purification of plasminogen activator from pig heart. Fed. Proc. 22: 562 1962;
• 12 Astrup T, Mullertz S. The fibrin plate method for estimating fibrinolytic activity. Arch. Biochem. 40: 346 1952;
• 13 Kline D. L, Fishman J. B. Improved procedure for the isolation of plasminogen. J. biol. Chem. 236: 3232 1961;
• 14 Remmert L. F, Cohen P. Partial purification and properties of a proteolytic enzyme of human serum. J. biol. Chem. 181: 431 1949;
• 15 Sgouris J. T, Storey R. W, McCall K. B, Anderson H. D. The purification, assay, sterilization and removal of pyrogenicity of human urokinase. Vox Sang. 07: 739 1962;
• 16 Fruton J, Simmonds S. General Biochemistry. 244-283 John Wiley & Son; New York: 1958
• 17 Smyrniotis F. E, Fletcher A. P, Alkjaersig N, Sherry S. Urokinase excretion in health and its alterations in certain disease states. Thrombos. Diathes. haemorrh. (Stuttg.) 03: 257 1959;
• 18 von Kaulla K. N, Riggenbach N. Urokinase excretion in man: A method of determination and consideration of its significance. Thrombos. Diathes. haemorrh. (Stuttg.) 05: 162 1960;
• 19 Celander D. R, Guest M. M. The biochemistry and physiology of urokinase. Amer. J. Cardiol. 00: 409 1960;
• 20 Ploug J, Kjeldgaard N. O. Urokinase, an activator of plasminogen from human urine. I. Isolation and properties. Biochim. biophys. Acta. (Amst.) 24: 282 1957;