COFACTORS OF EnZYMIC ADAPTATION 227 



addition should have provoked an immediate fermentation. 

 As this is not the case, it seems most probable that it is in- 

 volved in the formation of maltozymase. Moreover, addition 

 oi E ov T is without effect on the fermentation of maltose by 

 fully adapted yeast. 



The addition of E is quite sufficient to transform non- 

 adaptable cells into normal ones, as judged by the rate and 

 extent of adaptation. Furthermore, E does not stimulate 

 adaptation of cells harvested during the glucose fermentation 

 growth phase. Therefore, it seems difficult to avoid the con- 

 clusion that the cells from the two phases of glucose growth 

 cycle differ by the presence or absence of cofactor E or some 

 substance derived metabolically from E. 



Cofactor T added to adaptable cells prevents maltozymase 

 formation. We are faced, therefore, with a situation com- 

 pletely parallel to the cytochrome oxidase one. However, 

 preliminary experiments indicate that erythrose derivatives 

 active in the cytochrome oxidase system are different from 

 those involved in maltozymase adaptation. 



A certain number of substances have been tested with 

 respect to their ability to replace cofactor E and found 

 ineffective. They are listed in Table X. To minimize variation 

 from one experiment to the other, a standard amount of co- 

 factor E contained in 100 \Lg. of a given impure preparation of 

 erythrose was run with every experiment and the results 

 recorded in relation to it. Perusal of Table X shows that : 



(a) E does not act as an energy source. A great number of 

 compounds listed are actually fermented or respired by yeast 

 while remaining ineffective. Furthermore, E is not fermented 

 or respired by yeast, although it is metabolized. 



(b) E does not act as a source of carbon units derived by means 

 of any known metabolic pathway. Representative members of 

 the glycolytic pathway, of the pentose oxidative cycle and of 

 the tricarboxylic cycle were found inactive. 



(c) It is possible that E or its natural homologue may be 

 synthesized by the cell from small carbon fragments like 



