REGULATORY MECHANISMS IN ENERGY METABOLISM 149 



Furthermore, to impair l)oth glucose utilization and lactate formation 

 by the addition of mitochondria, the phosphate level in the recon- 

 structed system had to be very low indeed. 



Thus the experiments by Lynen and by Wu and Racker require 

 compartmentation of adeniile nucleotides as well (cf. Chance and 

 Hess, 1956; Racker, 1956). A more involved corollary exists: intra- 

 mitochondrial ATP must then be available for one process and not 

 for another. There is no doubt that ATP formed intramitochon- 

 drially can phosphorvlate glucose, even in vivo (Lynen et ah, 1959). 

 On the other hand, the behavior of phosphofructokinase as judged 

 by glucose-6-phosphate and fructose diphospliate levels appears to 

 indicate that it cannot utilize mitochondrial ATP. It is difficult to 

 accept this assumption. Every other process in the cell can utilize 

 ATP made intramitochondrially. Quastel and Bickis (1959) found 

 little difference between aerobic and anaerobic energy-requiring 

 processes. It is reasonable to postulate that intramitochondrial ATP, 

 in the first few minutes after a transition from the anaerobic to 

 aerobic state, may be formed at a rate faster than it can diffuse out 

 of the mitochondria. This will explain the rapid changes which 

 take place in the concentration of metabolites during such a transi- 

 tion. However, the final steady state which is still an inhibited 

 Pasteur state shows no difference in ATP or ADP levels, only a low- 

 ering of the concentration of fructose diphosphate and a raising of 

 the concentration of glucose-6-phosphate. The reversed experiment 

 shows the reverse to happen, raising of fructose diphosphate and 

 lowering of glucose-6-phosphate anaerobically ( Lvnen et ah, 1959 ) . 

 While the early transition stages shed light on the sequence of 

 events, the final anaerobic and aerobic steady states, reached in 2-10 

 minutes, are the important phenomena. 



Dinitrophenol is an uncoupler of oxidative phosphorylation and 

 releases the Pasteur inhibition in the presence of respiration. It does 

 not, however, inhibit the utilization of synthesized ATP for anabolic 

 reactions. This can be shown bv the experiment by Lynen ( Lynen 

 et ah, 1959) where glucose assimilation was unimpaired. Also valine 

 incorporation is nearly unimpaired by dinitrophenol (van Eys and 

 Neal, unpublished results) (Table 5-2). Therefore, dinitrophenol 

 seems to result in making glycolytic ATP in contrast to mitochon- 

 drial ATP. If this is the cause of an accelerated phosphofructokinase 

 reaction (Lynen et al., 1959), phosphofructokinase must occupy a 

 unique position in the cell. Furthermore, there is disagreement 



