214 E. Racker and R. Wu 



We come to conclusion four: the Pasteur effect in ascites 

 cells can be released to a considerable extent by high extra- 

 cellular phosphate. The Pasteur effect may be visualized to be 

 due to the low availability of intracellular Pi under aerobic 

 conditions which limits glycolytic synthesis of ATP and 

 therefore limits efficient glucose uptake. 



The total intracellular concentration of Pi represents a 

 balance of the processes which esterify Pi, on the one hand, 

 and release it from phosphate esters or transport Pi from the 

 outside, on the other hand. However, it has become apparent 

 from our studies that the total Pi, as well as the ATP concen- 

 tration, does not seem fully available for glycolysis, thus 

 indicating a compartmentation of the cell. We shall come 

 back to this point shortly. Here, mention should be made of 

 the work of other investigators who have carried out similar 

 work with yeast or tumour cells and who have come to similar 

 conclusions. First of all, we should give credit to the brilliant 

 vision of Johnson (1941) and Lynen (1941) who first proposed 

 that Pi is a key compound in the Pasteur effect. Lynen and 

 Koenigsberger (1951) have pursued this problem very actively 

 and have postulated aerobic inavailabihty of ATP for hexo- 

 kinase. Reference should also be made to the recent work of 

 Kvamme (1958) since his studies have in some respects 

 paralleled ours. 



Having dealt with some specific questions which were 

 susceptible to experimental approach, we would like to turn 

 now to some features of cellular metabolism which are more 

 difficult to investigate. Ascites cells, in common with other 

 cells, can glycolyse and respire in a phosphate-free medium. 

 The equations for these metabolic processes are unbalanced 

 unless we include the breakdown of ATP to ADP and Pi. 

 Moreover, in order to maintain a steady state this process of 

 ATP breakdown must proceed at a rate equal to its synthesis. 

 All enzyme systems which catalyse the breakdown of ATP to 

 ADP and Pi can be referred to as ATPase in its broadest 

 sense. This includes the biosynthesis of proteins, carbo- 

 hydrates, etc., transport mechanisms and any other work 



