MECHANISM OF METABOLISM 211 



called fermentation products; these may result from alcoholic, lactic, 

 butyric fermentations or some other. 



Emulsin is an enzyme which is able to hydrolyze glucosides. Gluco- 

 sides occurring in plants are complex bodies which contain a sugar- 

 radical. Emulsin splits glucosides liberating the sugar, usually dex- 

 trose. The typical example for emulsin action is the hydrolysis of 

 amygdalin to hydrocyanic acid, benzaldehyde and dextrose. 



C 20 H 27 OiiN + 2H 2 O = C 6 H 5 COH + 2C 6 H 12 O 6 + HCN. 



Amygdalin Benzaldehyde Dextrose Hydrocyanic acid 



Emulsin is found in many molds and bacteria, and recently has 

 been found in yeasts. Glucoside-splitting enzymes play an important 

 role in the fermentations of coffee-beans, cocoa, mustard and indigo. 

 In most of these fermentations, however, the emulsin is probably not 

 formed by microorganisms, but by the plant, from which the ferment- 

 ing material is derived. 



ENZYMES OF FATS. All the enzymes, acting on fat, decompose it 

 in the same manner; the fat molecule takes up three molecules of water, 

 breaking up into glycerin and three molecules of fatty acid, as indicated 

 on page 239. It is possible that there are several fat-splitting enzymes, 

 but the result of the cleavage process is always the same. The name 

 formerly assigned to enzymes of fat is steapsin, but this term is now 

 almost exclusively substituted by the more significant word lipase. 

 Occasionally they are called lipolytic enzymes which expression is 

 analogous to the proteolytic enzymes; in the same way, the term 

 amylolytic enzyme is used for diastase. 



ENZYMES OF PROTEINS. The enzymes composing protein bodies, 

 generally called proteolytic enzymes or proteases, have been known 

 for nearly a century. Though the difficulty of analyzing protein bodies 

 accurately prevents an absolute knowledge of proteolysis, much effort 

 has been made to become acquainted with the very important group 

 of enzymes which accomplish the digestion of protein food. Naturally 

 most experimenting has been conducted with pepsin and trypsin 

 of the animal body and accordingly these are better understood than 

 others; only little work has been done with microbial enzymes. There 

 is so far as can be determined little appreciable difference between 

 the proteolytic enzymes obtained from different organisms, whether 

 low or high in the plant or animal world, consequently many experi- 



