PROPERTIES OF EX/A.UES 55 



down by the colloids, and it is possible that the enzymes are merely 

 associated with the proteins in this way. Furthermore, enzymes are 

 known to become so closely attached to stringy protein masses, such as 

 fibrin and silk, that they cannot be removed by washing. Some have 

 claimed that they have secured active preparations of pepsin and 

 invertase that did not give protein reactions and contained very little 

 or no ash or carbohydrate ; but it has so far been impossible to secure 

 trypsin free from protein, and diastase seems to be certainly of 

 protein nature. Analyses of enzymes purified as completely as pos- 

 sible do not have great worth, for the ''purified" enzymes are prob- 

 ably far from pure; however, it is of some importance that they vary 

 greatly in the proportions of carbon, hydrogen, and nitrogen which 

 they contain, indicating that possibly different enzymes may be of 

 very different nature. The enzymes have been found to possess defi- 

 nite electrical charges, in neutral solutions trypsin is negative or 

 amphoteric, pepsin and invertase negative (INIichaelis).* jNIacallum 

 has shown microchemieally that phosphorus is closely associated with 

 the formation of zymogen granules in cells, which seem to be started 

 in the nucleus; and there are many other observations suggesting 

 that certain ferments are closely related to the nucleo-proteins. This 

 is particularly true of the oxidases, which seem also to contain iron 

 and manganese. A final point of importance in support of the pro- 

 tein nature of enzymes is that pepsin destroys tr\'psin and diastase, 

 while trypsin destroys pepsin. 



So uncertain, however, is our information concerning the chemical 

 nature of the enzymes, that it has become possible for an hypothesis to 

 be developed urging that enzymes are immaterial, that the actions 

 Ave consider as characterizing enzj^mes are the result of physical forces 

 which may reside in many substances, and perhaps even free from 

 visible matter, but the weight of evidence at present available is en- 

 lirel}' in favor of the view that enzjones are colloidal substances, al- 

 though perhaps of widely differing chemical nature. A valuable piece 

 of evidence of the material existence of enzymes is their specific na- 

 ture, lipase affecting only fats, and trypsin only proteins, indicating 

 chemical individuality. They are true secretions, formed A\ithin the 

 cell by recognizable steps; and, furthemiore, when injected into the 

 body of an animal, they give rise to the formation of specific innnune 

 bodies that antagonize their action. Emil Fischer's work with the 

 sugar-splitting enzymes, moreover, indicates that they owe their action 

 to their stereochemical configiiration. He prepared two .sets of sugar 

 derivatives which differed from each other solelj' in the arrangement 

 of their atoms in space (i. e., isomers) and found that one specific 

 enzyme w^ould split members of only one of the varieties, while nn- 

 other enzyme would act only on the variety with the opposite isomeric 

 form. These experiments make it very probable that there must be a 

 ^Biochem. Zeit., 1909 (16), 81 and 486; (17), 231. 



