218 ZYMO-EXCITATORS OR KINASES 



activity in a given amount of trypsinogen. They hence regard 

 the enterokinase as a co-ferment, which serves to link together the 

 attacked protein and the trypsinogen, and so invokes the protein 

 cleavage. A further support for this view was the supposed 

 observation that enterokinase 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 degree 

 on extraction of the mucous membrane with boiling saline, and 

 Biery and Henri state that they have heated enterokinase for 

 twenty minutes to 120 C. without entirely destroying its action. 



Bayliss and Starling, however, have brought forward strong 

 evidence in favour of enterokinase being a ferment. Thus, they 

 have shown that there is no stoichiometric relationship between 

 the amount of trypsinogen and the amount of enterokinase neces- 

 sary to activate it, as little as 0-0001 c.c. of an active enterokinase 

 being capable of activating 5 c.c. of pancreatic juice provided 

 it was allowed two or three days to act. The rate of activation 

 was also found to be proportioned to the amount of enterokinase 

 added. Bayliss and Starling accordingly consider that the obser- 

 vation of Delezenne, that a definite amount of enterokinase is 

 required to produce full activation, was due to a sufficient atten- 

 tion not having been given to the time relationships of the 

 reaction, so that the full effects of the smaller quantities of added 

 enterokinase were not allowed to develop, and secondly to slow 

 auto-destruction of the trypsin first formed in the longer period 

 necessary to effect the conversion with the smaller quantities of 

 enterokinase. 



It is an observation dating back to Kiihne's earlier experiments 

 that in preparing active extracts of pancreas, the trypsinogen 

 of the fresh gland cells can be activated by extraction with very 

 dilute acids, such as acetic acid, and that such treatment always 

 yields more powerful extracts. 



Since the discovery of enterokinase, Vernon has also shown 

 that an inactive pancreatic extract can be rendered active by 

 addition of an active preparation, or of an active commercial 

 trypsin preparation. This was attributed by Vernon to the 

 presence of an enterokinase different in some of its reactions, 



