Phosphate Turnover and Pasteur Effect 259 



necessary to modify this hypothesis. As is well known today, 

 membranes divide the cell into numerous compartments with 

 different enzyme patterns. The transport of materials between 

 these various compartments is more or less limited. The 

 membranes separating cytoplasm from mitochondria are 

 apparently of particular importance for the Pasteur effect, as 

 shown below. The phenomenon of adsorption on certain cell 

 structures may also lead to an unequal distribution of material. 

 Finally, mention should be made of the many specific enzyme- 

 substrate and enzyme-coenzyme complexes. The situation is 

 such a complicated one that an exact analysis of this pattern 

 is not to be expected at present. 



That inorganic phosphate takes part in this uneven 

 mosaic-like distribution inside the cell is supported by data 

 obtained by Trevelyan, Mann and Harrison (1954). The fact 

 must be borne in mind that the metabolic degradation of 

 sugar in yeast, aerobically as well as anaerobically, is coupled 

 to the synthesis of glycogen-like polysaccharides. In fact, a 

 considerable part of the sugar metabolized is assimilated in 

 this process. The phosphorylase-catalysed glycogen synthesis 

 from glucose-1 -phosphate has been found to occur in yeast 

 extracts (Trevelyan, Mann and Harrison, 1954; Whelan, 

 1955). However, this process can proceed only if the ratio of 

 inorganic phosphate to glucose-1 -phosphate in the cell is 

 lower than the equilibrium constant of the phosphorylase 

 reaction. Otherwise, glycogen will be degraded by phosphory- 

 lation. When the ratio of inorganic phosphate to glucose- 

 1 -phosphate was determined in yeast cells assimilating sugar, 

 Trevelyan, Mann and Harrison (1954) surprisingly found a 

 value much higher than the equilibrium constant. Their 

 findings are confirmed by some data obtained by Netter and 

 Schuegraf (1958, unpubhshed) in our laboratory (Table I). 

 The discrepancy between experiment and theory can only be 

 eliminated by assuming an unequal distribution of these phos- 

 phates in the inner compartments of the cell. One possibility 

 would be that the volume available for the hexose phos- 

 phates would be substantially smaller than that available for 



