Phosphate Turnover and Pasteur Effect 



269 



account for the behaviour of fructose diphosphate (Fig. 10). 

 DNP which, contrary to the action of cyanide, induces 

 fermentation without inhibiting respiration, initiates the same 

 changes in inorganic phosphate and hexose phosphates. In this 

 experiment, too, glucose-6 -phosphate drops rapidly whereas 



Fig. 9. DPNH formation following the blocking of 



respiration by cyanide. The ordinate values refer to 



changes in concentration of compounds specified. 



fructose diphosphate is first maintained at a constant level 

 and then rises. 



These experiments suggest that oxidative phosphorylation 

 is not related to the rate of fructose diphosphate formation. 

 This would mean that mitochondrial ATP can phosphorylate 

 glucose by hexokinase, but has little or no action on the 

 further phosphorylation of hexose phosphate to form fructose 

 diphosphate. Probably the two enzymes are located at dif- 

 ferent sites in the cell. If it is true that phosphofructokinase 

 reacts only with cytoplasmic ATP, it is obvious that the 

 fructose diphosphate level will correspond somehow to the 



