COFACTORS OF EnZYMIC ADAPTATION 225 



Maltozymase adaptation 



It is well known that glucose-grown yeast does not im- 

 mediately ferment certain disaccharides, e.g. maltose. It has 

 been shown by a number of workers (cf. Spiegelman, 1950; 

 Spiegelman and Halvorson, 1953), that fermentation can be 

 induced in the absence of a nitrogen source in cells suspended 

 in a buffer solution of the inducer. This phenomenon is 

 referred to as "maltozymase" adaptation. 



The nature of the enzymes, of the inducer and of the genetic 

 material involved in this system is very different from that of 

 the cytochrome oxidase system. 



The first questions to be asked are: 



(a) Do tetrose derivatives affect maltozymase formation? 



{b) If so, are they identical with cofactors involved in cyto- 

 chrome oxidase synthesis? 



(c) What is their relation in respect to inducer, energy and 

 building-block requirements and to maltozymase function? 



Our attempts were directed principally to providing ade- 

 quate answers to the first two questions, which are the basic 

 ones. Before presenting experimental evidence, it is however 

 necessary to consider a special feature of yeast growth that 

 may, at first, seem irrelevant. 



Maltozymase induction is carried out as follows. Yeast is 

 grown on glucose, harvested, washed, suspended in a buffer 

 solution of maltose and the rate of aerobic fermentation 

 measured. Now, growth of yeast on glucose is a biphasic 

 phenomenon. In the first phase glucose, even under maximum 

 aeration, is mostly fermented to ethanol (Swanson and Clifton, 

 1948 ; Lemoigne, Aubert and Millet, 1954). In the second 

 phase (and if oxygen is present) the accumulated alcohol is 

 oxidized. The inefficiency of respiration during the glucose 

 phase is the result of inhibition of synthesis of the cytochrome 

 system by aerobic fermentation brought about by high glucose 

 concentration (counter Pasteur-effect; Slonimski, 1956). A 

 detailed study of the growth cycle has shown profound modi- 

 fications not only in the enzymic constitution but also in the 



DRUG RES. — 8 



