278 



Helmut Holzer 



from a value greater than 1 to a value less than 1. With 

 reversed signs, the same is valid for the occurrence of a mini- 

 mum: compare for instance the ATP concentration in Fig. 2. 

 First, we have tried to find the causes for the occurrence of 

 a maximum of fructose diphosphate concentration under 

 anaerobic conditions. For this reason the determination of the 

 concentration changes of fructose diphosphate, dihydroxy- 

 acetone phosphate, pyruvate, orthophosphate, adenosine 



00 "/o 0-1 



°/o N, 



Fig. 1. Changes in fructose diphosphate after the addition of glucose to 

 starved yeast cells (From Holzer and Freytag-Hilf, 1959. Reproduced 

 by permission of the Editors, Biochem. Z.). 



diphosphate (ADP), and adenosine triphosphate (ATP), as 

 recorded in Fig. 2, has been carried out (Holzer and Freytag- 

 Hilf, 1959; Holzer 1959). Fig. 2 shows that the concentration 

 of dihydroxyacetone phosphate changes in perfect parallel 

 with the concentration of fructose diphosphate. This proves 

 that the enzyme aldolase occurs with surplus activity and does 

 not play any rate-limiting role in the fermentation process. 

 According to earlier observations, this is also true for the 

 enzyme isomerase (Holzer and Holzer, 1953) since in glucose- 

 metabolizing yeast cells the phosphoglyceraldehyde concentra- 

 tion, too, is always in equilibrium with the dihydroxyacetone 



