278 IMMUNO-CATALYSIS 



acting on plasma globulin preparations not treated with heat or chloro- 

 form is an hyberbolic function of the concentration of the streptococcal 

 factor. This is stated to be compatible with the law of mass action. 



b. A Suggestion as to the Possible Lipolytic Role of Streptococ- 

 cal Factor. It may be that the role of streptococcal factor in the libera- 

 tion of serum protease from its inactive complex truly involves an 

 enzyme action. Integrating the activating effect of organic solvents, sug- 

 gesting that a lipid-like inhibitor substance is thereby eliminated, and 

 the inhibition of the fibrinolytic activity of chloroform-activated serum 

 lytic enzyme by thromboplastin with the activating effect produced by 

 streptococcal factor on inactive serum lytic factor one may be per- 

 mitted to reason that the critical substance requiring elimination is a 

 lipid-like substance. This effect may suggest that the bacterial fibrino- 

 lytic factor is, perhaps, a lifolytic (lipase, lecithinase) enzyme. Such 

 an enzyme would be capable of digesting the lipoid component of 

 serum lytic factor, thus liberating the active enzyme, an effect which 

 would be comparable to the elimination of the same lipid-like com- 

 ponent by physical action of organic solvents, etc. Such a finding would 

 throw a new light on the subject and harmonize various observations. 



In connection with the possible lipase-like nature of streptococcal 

 factor it may be of interest to recall that both the streptococcal factor 

 and bacterial lecithinases are relatively thermostable (see Garner and 

 Tillett, 1934a; Dart, 1936; Reed, et al 1943; Christensen, 1945; Mac- 

 Farlane and Knight, 1941). The question of whether or not the com- 

 parable thermostability of the streptococcal factor and bacterial 

 lecithinases is suggestive of a similarity of activity may merit considera- 

 tion. 



G. MECHANISM OF FIBRIN AND MILK CLOT FORMATION 



1 . Enzymes Responsible for the Formation of Plasma Clot 



a. Comment on the Use of the Term Coagulation. The conversion 

 of plasma (or blood) or fibrinogen into a clot or fibrin has been called 

 coagulation, clotting or fihrin clot formation. One is struck by the wide 

 use of the term coagulation in this sense. The term coagulation as 

 defined stands for various chemically and physiologically non-related 

 processes, and for the formation of jelly-like soft masses or clots from 



