COFACTORS OF EnZYMIC ADAPTATION 221 



(d) The results obtained in the presence of euflavine are very 

 similar to those obtained in the absenee of the dye. 



It is concluded that adenine and E favour the transmission 

 of the genetic material responsible for cytochrome oxidase 

 synthesis, while T acts in the opposite way. 



Cytochrome oxidase adaptation 



Cytochrome oxidase synthesis is the heterocatalytic func- 

 tion of the genetic material sensitive to euflavine. This 

 synthesis can be easily studied in yeast that has been first 

 grown anaerobically, then washed, suspended in glucose- 

 containing buffer and aerated. In the absence of molecular 

 oxygen there is no formation of respiratory enzymes but the 

 genetic material remains unchanged even after hundreds of 

 cellular generations. In such an anaerobically grown yeast, 

 oxygen induces the formation of the whole chain of haemo- 

 proteinic enzymes (including cytochrome oxidase) with conse- 

 quent re-establishment of respiration. The synthesis of these 

 enzymes takes place in the absence of an external nitrogen 

 source and in the absence of cellular multiplication. The 

 references concerning various aspects of this phenomenon can 

 be found in Ephrussi and Slonimski (1950), Slonimski (1953a 

 and b; 1956). 



When yeast is harvested during certain phases of anaerobic 

 growth and exposed to oxygen in glucose-containing buffer, its 

 cytochrome oxidase adaptation is very sluggish. Addition of 

 small amounts of E at the beginning of adaptation stimulates 

 considerably the rate of enzyme synthesis. Addition of T 

 produces the opposite effect, inhibiting adaptation (Fig. 3 and 

 Table IX). 



In such sluggishly adaptable cells the addition of a mixture 

 of all nucleic acid bases produces a certain stimulation of 

 adaptation. There are two important features of this pheno- 

 menon: firstly, that E acts synergistically with the nucleic 

 acid bases; secondly, only a complete mixture of bases is 

 stimulatory. Certain incomplete mixtures, on the contrary, 

 are inhibitory (Table VII). The synergistic action of E and 



