THE NATURE OF ENZYMES AND THEIR ACTIONS 63 



their chemical characters, and consequently are obliged to 

 recognize them solely by their action. As far as we know, true 

 enzymes never occur except as the result of cell life they are 

 produced within the cell, and increased in amount by each new 

 cell that is formed, and, furthermore, they are present in every 

 living cell without exception. As the same facts are equally 

 true of the proteids, and apparently true of nothing else, it is 

 natural to associate the enzymes with proteids, and so explain 

 the importance of the proteids for cell life. 1 If enzymes are 

 obtained in any of the usual ways from animal cells or secre- 

 tions they are always found to give the reactions for proteids, 

 even if repurified many times. But it is well known that 

 whenever proteids are precipitated the other substances in the 

 solution tend to be dragged down by the colloids, and it is 

 possible that the enzymes are merely associated with the pro- 

 teids in this way. Furthermore, enzymes are known to become 

 so closely attached to stringy proteid 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 proteid reactions and contained 

 very little or no ash or carbohydrate ; but it has so far been 

 impossible to secure trypsin free from proteid, and diastase 

 seems to be certainly of proteid nature. Analyses of enzymes 

 purified as completely as possible do not have great worth, for 

 the " purified " enzymes are probably far from pure ; however, 

 it is of some importance that they vary greatly in the propor- 

 tions of carbon, hydrogen, and nitrogen which they contain, 

 indicating that possibly different enzymes may be of very 

 different nature. Active gum enzymes, with oxidizing proper- 

 ties, are said to have been prepared free from nitrogen. 2 Macal- 

 lum has shown microchemically 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-proteids. This is particularly true of the 

 oxidases, which seem also to contain iron and manganese. A 

 final point of importance in support of the proteid nature of 



translated by S. C. Prescott, New York, 1902. Keynolds Green, " Soluble 

 Ferments and Fermentation," 1901. In this chapter references will not 

 usually be cited unless they are from works published later than Oppenheimer's 

 book, in which all original work of importance can be found. 



1 Another important point is that the closest imitation of enzymes, Bredig's 

 " inorganic ferments, " seem to owe their action to their colloidal nature. 



2 A recent paper by Tschirsch and Stevens casts considerable doubt upon 

 this statement (Pharmac. Centrhalle., 1905 (56), 501.) 



