Glycolysis and the Pasteur Effect 213 



functional availability for the hexokinase reaction. It is 

 possible that the impairment of glucose utilization is due to the 

 aerobic accumulation of an inhibitor which, however, is not 

 formed in the presence of DNP. Glucose-6-phosphate 

 actually exerts a pronounced product inhibition on hexokinase 

 obtained from ascites cells and, interestingly enough, the 

 intracellular concentration of this compound is greater 

 aerobically than anaerobically, in particular shortly after the 

 addition of glucose. However, at no time is the intracellular 

 concentration of glucose-6-phosphate sufficiently high to 

 account for the inhibition of glucose uptake. Moreover, 

 glucose-6-phosphate could not affect lactate production un- 

 less it inhibits, directly or indirectly, a step subsequent to 

 its formation. It is deemed more likely that the inhibition of 

 glucose uptake is due to a structural non-availability of ATP. 

 Whatever the detailed mechanism of this inhibition phenome- 

 non, we can come to our third conclusion: glycolytically pro- 

 duced ATP is more efficiently utilized for glucose phosphoryla- 

 tion than ATP produced during oxidative phosphorylation. 



In Table VI the effect of high Pi concentrations on the 

 Pasteur effect is shown. It can be seen that high concentra- 

 tions of extracellular Pi diminish the magnitude of the 

 Pasteur effect, both in respect to lactic acid production and 

 glucose uptake. 



Table VI 



The effects of high Pi concentrations on the Pasteur effect 



Incubation made at 30°C for 30 minutes. The results are expressed as 

 [xmoles/140 mg. protein/hour. 



