Phosphate Turnover and Pasteur Effect 267 



energy production switched from respiration to fermentation 

 and vice versa. If it is true that inorganic phosphate governs 

 metaboUsm, this should be evident from the time sequence of 

 events. The respiration of a vigorously aerated suspension of 

 yeast cells in sugar solution is poisoned by 0-001 m cyanide; 



— 7'-P 



Fig. 8. Changes in inorganic and organic phosphates of baker's yeast, 



following the transition from repiration to fermentation. 

 Yeast, 10 per cent; glucose, 2 per cent; in 0-02 m citrate buffer, pH 5-4; 

 temp. 15°; oxygenated; 0-001 m-KCN added at arrow. Po = orthophos- 

 phate; 7'-P = labile phosphate, split by 7 minutes' hydrolysis in n-HCI at 

 100° ; G-6-P = glucose-6-phosphate ; FDP = fructose diphosphate ; TP = 

 triose phosphate. 



fermentation starts immediately, and under our experimental 

 conditions reaches its steady state within 2 minutes (Fig. 7). 

 The most striking event following the inhibition of respiration 

 is a rapid increase in the inorganic phosphate of the cell, 

 derived from the "labile phosphate" fraction (Fig. 8). At 

 the same time ATP decreases and ADP increases correspond- 

 ingly. All these changes are easily understood as the result of 



