CATALYSIS AND THE ENZYMES 



substances in living protoplasm may be caused 

 by enzymes, but not directly by the living matter 

 itself. 



But it is true that in some cases substances 

 which are responsible for enzymatic actions cannot 

 be extracted from protoplasm. The expressed 

 sap proves ineffective and no means are known 

 for separating the hypothetical enzyme from the 

 protoplasm. In such cases it is, however, possible 

 to kill the protoplasm without destroying the 

 enzymes. Here, too, Buchner was the first to 

 show useful methods. He succeeded in killing 

 cells by means of acetone or ether without damag- 

 ing the enzyme. So killed yeast-cells were ob- 

 tained which possessed in a high degree the power 

 of acting on sugar. In the same way Buchner 

 prepared the bacteria of milk fermentation and 

 of acetic fermentation. The cell-bodies were com- 

 pletely dead, but nevertheless it was possible to 

 cause fermentations by specimens of these bacteria. 

 We may consider that such experiments fairly 

 prove the existence of specific enzymes which are 

 responsible for the fermentation effects by the 

 living cells. It is difficult to explain the reason 

 why the enzymes in these cases cannot be separated 

 from protoplasm. They may be entirely insoluble, 

 or may at least diffuse through membranes only 

 with difficulty, or adsorption effects may play a 

 part in such cases. 



Investigations of later years have shown dis- 



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