82 PHYSIOLOGY OF ALIMENTATION. 



workers in this field. Persistence in the use of old methods 

 of naming even newly discovered enzymes, and the existence 

 of the same ferment under different names, are extremely 

 confusing. The best method of naming ferments to-day 

 is to add the ending ase to the root of the Latin or Greek name 

 of the substance upon which the ferment acts. Thus maltase 

 acts on maltose, sucrase on sucrose, tyrosinase on tyrosin, 

 amylase on starch, etc. Since the action of many, probably 

 all, ferments is reversible (as will be explained later), and as 

 in this way several names might be given to one and the 

 same ferment, it should be the rule to add the ending ase 

 to the root of the chemically more complex substance upon 

 which the ferment acts. The ferment which accelerates the 

 decomposition of sucrose into " invert-sugar" is therefore 

 better named sucrase than invertase, for sucrose is chem- 

 ically more complex than the dextrose or the laevulose which 

 constitute the invert-sugar. It is sometimes convenient to 

 add the ending ase to the Latin or Greek root of a word express- 

 ive of some striking characteristic of a group of ferments. 

 Under the oxidases, for instance, are classed a large number 

 of individual enzymes, all of which have the power of catalyz- 

 ing the oxidation of various chemical substances. But there 

 are many specific oxidases, and these are regrouped under 

 the general heading, according to the substance or sub- 

 stances with the oxidation of which they are particularly 

 concerned, as tyrosinase, laccase, olease, etc. 



Sometimes ferments having the same specific activity 

 show differences in their behavior toward altered external 

 conditions. For example, the lipase (steapsin) obtained 

 from the pancreas does not behave in exactly the same way 

 C toward changes in temperature and conceatration, toward 

 acids, alkalies, etc., as the lipase obtained fr.om certain vege- 

 table cells. This has aroused the suspicion that they may not 

 all be identical. For this reason ferments are often spoken 

 of in the plural, as Upases, meaning thereby fat-splitting 

 enzymes derived from any source. 



