274 IMMUNO-CATALYSIS 



dilute acetic acid, to the splitting of the inhibitor-enzyme complex, the 

 inhibitor being adsorbable, acid soluble, and dialyzable. Despite the 

 similarity between the above cited activations and that by streptococcal 

 factor, Christensen and MacLeod are of the belief that streptococcal 

 factor functions in a manner comparable to the action of enterokinase 

 (Kunitz, 1938) on trypsinogen. They reported that, in the absence 

 of large amounts of serum inhibitor, the activation of the serum lytic 

 factor by streptococcal factor approaches that of a first order reaction, 

 suggesting to them a catalytic type of activation. The activated serum 

 protease is inhibited by serum inhibitor or crystalline trypsin inhibitor 

 (from pancreas). However, serum protease required very much more 

 trypsin inhibitor than required by trypsin. Unlike that of equimolar 

 trypsin-inhibitor complex several molecules of inhibitor were required 

 by serum protease before inhibition was complete. This inhibition, how- 

 ever, was not influenced by streptococcal factor, which was interpreted 

 to indicate that serum protease is not identical with pancreatic trypsin. 

 Since an excess amount of streptococcal factor did not increase the 

 activity of the serum protease which was partially inhibited by crys- 

 talline trypsin inhibitor, and since the streptococcal factor is capable 

 of converting the inactive serum lytic factor into a proteolytic enzyme, 

 it was concluded that the inactive state of serum protease is not due 

 to a combination of the protease with serum inhibitor but to some other 

 mechanism. 



In a later study, Christensen (1946) compared the activation of 

 serum lytic factor with chloroform and streptococcal factor. In this 

 study, he introduced the term plasminogen for the inactive state of 

 serum lytic factor and flasmin for the active state. Reaffirming his 

 claim, he stated that the activation of plasminogen by streptococcal 

 factor is a catalytic, and that by chloroform is a non-catalytic 

 process. 



The above claims that streptococcal factor functions as kinase is con- 

 tradicted by the finding that the active proteinase can be liberated by 

 drying the whole plasma. Shinowara (1947) reported that dried whole 

 plasma (and its fractions prepared by low-temperature-ethanol proce- 

 dure) contained a high degree of proteolytic activity. The dried plasma 

 and its fractions were not subjected to previous treatment with kinase 

 or chloroform or any other agents. This observation would indicate that 

 the union between the inhibitor substance and the proteinase is dis- 



