110 ZYMO-EXCITATORS OR KINASES 



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 stochiometric relationship between 

 the amount of trypsinogen and the amount of enterokinase neces- 

 sary to activate it, as little as O'OOOl 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 entero- 

 kinase 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, 

 such as greater sensitiveness to alkalies, from intestinal entero- 

 kinase. 



Bayliss and Starling found, however, that this did not apply 

 to pancreatic juice, which they found remained inactive not only 

 when treated with active glycerine pancreatic extract supplied 

 by Vernon, but also when acidified with weak or strong acid 

 and then neutralised or made alkaline after varying periods, or 

 when left in contact with fibrin, yeast, taka-diastase, platinum 

 black, gastric juice in aci4 or alkaline media, saliva, hydrogen 



