Enzymes and Fermentation in Yeast Cells 281 



Lynen, 1956). From this the assumption was obvious that a 

 lack of acetaldehyde prevents a reoxidation of the DPNH 

 formed by triose phosphate dehydrogenation, thus leading to 

 the observed accumulation of fructose diphosphate. Fig. 3 

 shows that, in fact, this explanation is the right one. If 

 glucose is added together with acetaldehyde to yeast cells 



alcohol 



Fig. 3. Concentrations of fructose diphosphate (FDP) after 

 the addition of glucose to starved yeast cells with and without 

 alcohol and acetaldehyde (From Holzer and Freytag-Hilf, 

 1959 : Reproduced by permission of the Editors, Biochem. Z.). 



kept under anaerobic conditions, the characteristic accumula- 

 tion of fructose diphosphate fails to occur. In other words, by 

 the addition of an acceptor for the hydrogen of the reduced 

 DPN the accumulation of fructose diphosphate can be pre- 

 vented. If glucose is added together with alcohol, the reverse 

 effect is found: the DPNH formed during triose phosphate 

 dehydrogenation cannot transfer any hydrogen to acetalde- 

 hyde, because a strong " hydrogenating pressure" is exerted 

 upon DPN due to alcohol dehydrogenase which is present 



