HYDROLYSIS. 119 



brought to an end, although their power to act would still be pres- 

 ent if these products were removed. In some instances the enzyme 

 is not the direct product of the cells, but the cells form what is 

 termed a zymogen, which is afterward converted into the enzyme. 

 Each zymogen is named from the enzyme which it produces : thus 

 the zymogen of trypsin is trypsinogen, that of pepsin is pepsinogen, 

 etc. It is an interesting and valuable fact that chloroform inhibits 

 the action of the organized ferments, but does not interfere with 

 that of the enzymes. 



As it is very important to have a clear idea of the meaning 

 of certain terms which occur repeatedly in the discussion of the en- 

 zymes and their action, these terms will here be defined, namely : 



Amylolytic Enzyme. The conversion of amyloses into 

 sugar is an amylolytic change, and an enzyme which has the 

 power of producing this change is an amylolytic enzyme ; such 

 are ptyalin of the saliva and amylopsin of the pancreatic juice. 



Diastatic or Diastasic Enzyme. There exists in barley 

 an enzyme, diastase, which has the power of changing starch into 

 sugar; the change itself, and also the enzyme, are spoken of as 

 diastatic or diastasic. It will be seen, therefore, that amylolytic, 

 diastatic, and diastasic are synonymous. 



Ptoteolytic Enzyme. The conversion of proteids into pro- 

 teoses and peptones is a proteolytic change, and an enzyme which 

 causes it is a proteolytic enzyme ; such are pepsin of the gastric 

 juice, and trypsin of the pancreatic juice. 



Steatolytic Enzyme. The splitting of fats into fatty acids 

 and glycerin is a steatolytic proces, and an enzyme which has this 

 power is a steatolytic enzyme ; such is steapsin or lipase of the pan- 

 creatic juice. These enzymes are also termed lipolytic and adipotytic. 



Sugar-splitting Enzymes. These enzymes split up sugar ; 

 thus, invertin or invertase splits cane-sugar into glucose and levu- 

 lose or fructose, this product being known as invert-sugar (p. 92) ; 

 lactase splits up lactose or milk-sugar into glucose and galactose ; 

 glucase hydrolyses maltose into glucose. 



Coagulating Enzymes. These enzymes change soluble 

 into insoluble proteids ; such are reunin, fibrin -ferment, and myo- 

 sin-ferment. 



Activating Enzymes. In the intestinal juice, produced by 

 the intestinal epithelium, there is an enzyme which " activates " 

 trypsinogen i. e., changes the trypsinogen into the active trypsin ; 

 this enzyme is called enterokinase. In general, enzymes which 

 have the power of activating zymogens are called kinases. 



Hydrolysis. It is now generally accepted that in many of 

 these various conversions the change consists in the assumption of 

 a molecule of water ; thus, 



(C 6 H 10 5 ) n + H 2 = C 6 H 12 6 



Starch. Water. Sugar. 



