ZYMO-EXCITATORS OR KINASES 109 



secretion or later, on coming in contact with certain substances 

 which have been termed zymo-excitators, or, in certain cases, 

 kinases. 



This action is possessed by all dilute acids, and it is probably 

 in this way that pepsinogen and prochymosin, the zymogens of 

 pepsin, and of rennin or chymosin, are activated in the stomach. 



In the case of the trypsinogen of the pancreatic juice it has 

 been shown by Pawlow and Chepowalnikoff that the activation 

 takes place by means of a substance secreted by the intestinal 

 mucosa. It was found that while the secretion from a pancreatic 

 fistula had scarcely any action upon proteid, the addition of a 

 small quantity of succus entericus caused it rapidly to become 

 very active. Such action took place only upon the trypsin and not 

 upon the other pro-ferments of the pancreatic juice, but an increase 

 in the activity of the lipo-clastic enzyme occurred on the addition 

 of bile. 



The substance which so behaved as a zymo-excitator or kinase 

 to trypsinogen was called enterokinase by Pawlow, and has since 

 been the subject of much investigation and discussion as to 

 whether it is itself a true ferment, a " ferment of ferment," as it 

 was styled by its discoverer, who regards it as a ferment on account 

 of the small quantity necessary to activate a much larger amount 

 of trypsinogen, and the fact that it is destroyed, although slowly, 

 at the usual temperature of destruction of enzymes (65 C.). 



Delezenne and Dastre and other French observers deny that 

 enterokinase is an enzyme, but consider that it forms a compound 

 with trypsinogen, which is the active proteoclastic ferment trypsin. 

 This view is based upon the observations that a definite amount 

 of enterokinase was required to develop the maximum amount 

 of activity in a given amount of trypsinogen. They hence regard 

 the enterokinase as an " amboceptor " in the language of Ehrlich, 

 which serves to link together the attacked proteid and the 

 trypsinogen, and so invokes the proteid cleavage. A further 

 support for this view was the supposed observation that entero- 

 kinase combines with fibrin and can be so removed from 

 solution. 



Other French observers have pointed out as evidence against 

 enterokinase being an enzyme, that it is much more slowly 

 destroyed by heat than are most other enzymes. Thus Largnier 

 des Barcels claims to have obtained activation although in lessened 



