154 



CONTROL MECHANISMS IN CELLULAR PROCESSES 



Such a mechanism of control would once more manifest itself as 

 inhibition at the triose phosphate dehydrogenase level, with a con- 

 sequent fluctuation of fructose diphosphate. It fails to explain the 

 lowering of glucose uptake seen in aerobic glycolysis. The effect of 

 subtle changes in DPNH removal may be enhanced by varying 

 phosphate concentrations and ADP concentrations, thus supplving 



6.0 n 



5.0- 



LACTATE 



yU-M PHOSPHATE ADDED 



Fig. 5-2. The effect of increasing phosphate concentrations on aerobic 

 glycolysis and respiration. All flasks contained hexokinase and 30 /xmole 

 2-deoxyglucose. The remainder of the additions were as described previously 

 (van Eys and Warnock, 1959). The values are corrected for changes in the 

 absence of fructose diphosphate. 



an interplay of many factors at the sensitive site. It must be noted 

 here, however, that under conditions of low pyruvate it is respira- 

 tion and not glycolysis which is sensitive to low phosphate concen- 

 trations (van Eys and Warnock, 1959). See Fig. 5-2. 



It is clear that no explanation of the Pasteur effect is completely 

 satisfying at the present time. No choice will be made, nor will any 

 new theories be advanced at this time. 



