ENZYMES AND THEIR ACTION. 3 



num, 1 however, the decomposition is much accelerated and ceases 

 only when the destruction of the hydrogen peroxide is complete. 

 Without multiplying instances, suffice it to say that there is an 

 analogy between inorganic catalyzers and enzymes, the main point 

 of difference between the enzymes and most of the inorganic cataly- 

 zers being that the enzymes are colloids. 2 



Inasmuch as each of the enzymes has an action which is more 

 or less specific in character, and since it is a fairly simple matter, 

 ordinarily, to determine the character of that action, the classifi- 

 cation of the enzymes is not attended with very great difficulties. 

 They are ordinarily classified according to the nature of the sub- 

 strate 3 or according to the type of reaction they bring about. Thus 

 we have various classes of enzymes such as amylolytic * proteolytic, 

 lipolytic, glycolytic, uricolytic, autolytic, oxidizing, reducing, in- 

 verting, protein-coagulating, deamidizing, etc. In every instance 

 the class name indicates the individual type of enzymatic activity 

 which the enzymes included in that class are capable of accomplish- 

 ing. For example, amylolytic enzymes facilitate the hydrolysis of 

 starch (amylum) and related substances, lipolytic enzymes facilitate 

 the hydrolysis of fats (XJTTO?) whereas through the agency of uri- 

 colytic enzymes, uric acid is broken down. There is a tendency, at 

 the present time, to harmonize the nomenclature of the enzymes 

 by the use of the termination, -ase. According to this system of 

 nomenclature, all starch-transforming enzymes, or so-called amy- 

 lolytic enzymes, are called amylases, all fat-splitting enzymes are 

 called Upases, etc. Thus ptyalin the amylolytic enzyme of the 

 saliva, would be termed salivary amylase in order to distinguish it 

 from pancreatic amylase (amylopsin) and vegetable amylases (di- 

 astase, etc.). According to the same system, the fat-splitting 

 enzyme of the gastric juice would be termed gastric lipase to dif- 

 ferentiate it from pancreatic lipase (steapsin), the fat splitting 

 enzyme of the pancreatic juice. 



Our knowledge regarding the distribution of enzymes has been 

 wonderfully broadened in recent years. Up to within a few years, 



1 Produced by the passage of electric sparks between two platinum terminals 

 immersed in distilled water, thus liberating ultra-microscopic particles. 



2 Bredig has been able to obtain certain inorganic catalyzers in colloidal 

 solution. These he calls "inorganic enzymes." 



3 Substance acted upon. 



4 Armstrong suggests the use of the termination " clastic " instead of " lytic." 

 He calls attention to the fact that amylolytic, in analogy with electrolytic, means 

 " decomposition by means of starch " and is therefore a misnomer. He sug- 

 gests the use of amyloclastic, proteoclastic, etc. 



