260 F. Lynen, et al. 



Table I 



Orthophosphate and hexose phosphate content of baker's yeast, 

 respiring in glucose solution 



Glucose-l -phosphate Orthophosphate I 

 Orthophosphate Glucose-6-phosphate (calc.)* glucose-\-phosphate^ 



inorganic phosphate. Another explanation could be based on 

 the different orthophosphate levels in the cell compartments, 

 due to the unequal enzyme distribution. The latter idea is 

 supported by experiments where yeast cells were plasmolysed 

 by freezing in liquid air, the thawed material then separated 

 by immediate centrifugation into a "supernatant" containing 

 the elements of the cytoplasm, and a "residue" with the 

 structure -bound elements of the cell (Holzer and Lynen, 1950). 

 Actively respiring yeast cells had a considerably higher 

 percentage of their total inorganic phosphate in the "residue" 

 than had fermenting or " starved " cells. We may assume that 

 this unequal distribution is based on the accumulation of 

 inorganic phosphate in the particulate areas of the cell, e.g. 

 the mitochondria. 



From these experiments we may conclude that any inter- 

 pretation of phosphate determinations in terms of actual 

 phosphate concentration is only of limited value. However, 

 some information about the situation at the sites of active 

 metabolism may be obtained by kinetic measurements. They 

 can indicate in an indirect way what the turnover of inorganic 

 and organic phosphates inside the cell is like (Lynen and 

 Koenigsberger, 1951; Lynen et al., 1958). 



Before we go into the details of our findings, the principal 

 features of the Pasteur effect must be described further. As 



