ENERGY SUPPLY OF THE CELL 39 



yeast juice increases the rate of fermentation of a normal 

 yeast juice. Normal yeast juice can be separated by 

 ultrafiltration, or by dialysis, into two fractions neither 

 of which can cause the fermentation, while, combined, 

 they again have nearly their original fermenting capacity. 

 The nature of this co-enzyme has not been agreed upon. 

 Kluyver and Struyk (1927) believe that different 

 experimenters meant entirely different phenomena when 

 speaking of co-enzyme effects. These authors think it 

 to be a hydrogen acceptor which is necessary to start 

 the first production of acet aldehyde. After this has 

 been done, the fermentation can go on automatically 

 as will be shown on p. 49. Nilsson (1930) believes the 

 co-enzyme enters into various phases of the fermentation 

 process. Thus we have 4 factors connected in the 

 alcoholic fermentation. 



1. Alcoholase 



2. Phosphate-carbohydrate esters 



3. Co-enzyme 



4. Endotryptase 



The latter causes a deterioration of the alcoholase as well 

 as of the co-enzyme. Heat will destroy alcoholase and 

 endo-trj^tase, but not the co-enzyme. To complicate 

 matters still more, the endotryptase is inhibited to some 

 degree by the presence in the yeast juice of another 

 compound : 



5. Antiprotease 



and this compound No. 5 is destroyed by compound No. 6 



6. Lipase 



which also attacks the co-enzyme. 



The actual amount of alcohol and CO2 formed by the 

 enzjone is very small compared with that of the yeast 

 itself. Harden (1923 p. 30) estimates that the living 

 yeast produces about forty times as much alcohol as the 



