ENZYMES AND THEIR ACTION 3 



is not attended with very great difficulties. They are ordinarily classi- 

 fied according to the nature of the substrate 1 or according to the type 

 of reaction they bring about. Thus we have various classes of enzymes, 

 such as amylolytic,' 2 ' proteolytic, lipolytic, glycolytic, uricolytic, autolytic, 

 oxidizing, reducing, inverting, protein-coagulating, deamidizing, etc. In 

 every instance the class name indicates the individual type of enzy- 

 matic activity which the enzymes included in that class are capable of 

 accomplishing. For example, amylolytic enzymes facilitate the hydro- 

 lysis of starch (amylum) and related substances, lipolytic enzymes 

 facilitate the hydrolysis of fats (\ITTOS), whereas through the agency of 

 uricolytic 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 nomen- 

 clature, all starch-transforming enzymes, or so-called amylolytic en- 

 zymes, 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 amy- 

 lase (amylopsin) and vegetable amylases (diastase, etc.). According 

 to the same system, the fat-splitting enzyme of the gastric juice would 

 be termed gastric lipase to differentiate it fro~ii -Pancreatic lipase (steap- 

 sin), the fat-splitting enzyme of the pancreatic juice. 



Defensive (protective) enzymes are those believed to be manufac- 

 tured by certain cells (perhaps the leucocytes) and passed into the 

 circulating blood in order to digest any foreign material of endogenous 

 or exogenous origin that may have found its way into the circulation. 

 The most important defensive enzymes are proteolytic enzymes. 

 Abderhalden 3 claims that the parenteral introduction of any foreign 

 protein into the animal body will be followed by the appearance in the 

 blood of a defensive enzyme capable of digesting that protein. He also 

 claims that in pregnancy the passage into the blood of protein material 

 in the form of cells and fragrnents of chorionic villi will cause the 

 appearance in the blood of a defensive proteolytic enzyme capable of 

 digesting placenta protein. The Abderhalden reaction for pregnancy 

 is based upon this hypothesis. The reaction has been widely employed 

 and much has been said both for and against its accuracy. 4 Modifications 

 of the reaction have been employed as an aid in the diagnosis of various 

 disorders, e.g., cancer, tuberculosis, dementia praecox, etc. Taylor 5 



1 Substance acted upon. See Lippmann: Ber. d. Deutsch. Chem. Ges., 36, 331, 1903. 



2 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 suggests the use of amyloclastic, 

 proteoclastic, etc. 



3 Abwehrfermente des tierischen Organismus, 5th Ed., Berlin, 1915, Springer. 

 4 Bronfenbrenner: Jour. Am. Med. Assn., 65, 1268, 1915. Van Slyke: New York Med. 



Jour., 103, 219, 1916. 



5 Taylor: Jour. Biol. Chem., 22, 59, 1915. 



