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A TEXTBOOK OF PHYSIOLOGY 



The normal activator of the gastric zymogens pepsinogen and 

 prorennin is the hydrochloric acid (HC1) of the gastric juice. It 

 has been found, however, that these two zymogens may become 

 converted into the active enzymes in conditions where little or no HC1 

 is being secreted. In &uch canes, the exact activator is not known; 

 it is quite probable that bacteria play a part. Similarly, the normal 

 activator of the trypsinogen of the pancreatic juice is a substance 

 known as " enterokina^e," which is secreted in the succus entericus. 

 But it is protable that an enzyme " deutera&e " and calcium 

 salts also possess the power of converting this zymogen. The 

 other enzymes found in pancreatic juice are possibly secreted as 

 zymogens, but the exact nature of their activating agent is not known. 

 The same must be said in regard to the enzymes of the succus entericus. 

 The steapsin of the pancreas requires the presence of bile salts to act 

 as- co-enzyme. The enzyme loses its digestive power if these be 

 dialyzed away. It is quite possible that in some conditions of digestive 

 disturbance there is an inadequate liberation of the enzymes from the 

 zymogens,, in others en inadequate secretion of the zymogens. At 

 present, our knowledge on these points is fragmentary. 



Juice, 

 Saliva 

 Gastric 



Pancreati : 



Proenzymc. 

 Ptyalin 



Pepsinogen 

 Prorennin 



Trypsinogen 



Activator, 

 Bacteria. 

 Hydrochloric acid. 



Enterokinase. 

 Calcium salts. 

 Deuterase. 

 Bacteria (?). 



In regard to other enzymes, the present state of knowledge is in- 

 sufficient for them to be tabulated. 



