REGULATORY MECHANISMS IN ENERGY METABOLISM 161 



acid, which iii]iil)its hictic deln ch^ogeiiase only in the direction of 

 pyruvate reduction (No\oa et ai, 1959), show that it completely in- 

 hibits the glycolysis of ascites cells (Papaconstantinou and Colowick, 

 1957, 1960a) and the growth of HeLa cells (Papaconstantinou and 

 Colowick, 1959, 1960b) and of Tetrahijmena (Warnock and yan Eys, 

 unpublished). If the action of oxamic acid is really as limited as it 

 appears, then lactic acid formation ma\' be a required function of 

 the cell. \\' hether this is because the lactic acid formation is an in- 

 dication of a need for glycolysis at a rate in excess oyer pyruvate 

 respu-ation, or whether TPNH reoxidation in excess oyer biosyn- 

 thetic processes is required, remains to be seen. 



Furthermore, if methylglyoxal is a possible intermediate, aerobic 

 lactic acid formation may not reflect pyruvate reduction solely. We 

 must be cautious, therefore, not to limit our view of glycolysis as a 

 single metabolic process, and keep an open mind on its possible 

 physiological role. Control of glycol\'sis is therefore possibly of even 

 greater significance than a single adaptation to energy requirements. 



Conclusions 



It is impossible to remain completely divorced from hypotheses. 

 Yet it is the strong feeling that no hypothesis explains the Pasteur 

 effect theory completely satisfactorily at present. The view taken is 

 that there is one Pasteur effect, which is fundamental but unex- 

 plained. The position taken on the Crabtree effect is that it is an 

 expression of the properties of certain cells and constitutes no funda- 

 mental regulatory process but rather a biological artifact. Even 

 these limited conclusions are open to criticism. 



References 



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 Eine Erklarung des Fehlens des Pasteur-Effektes bei den Ehrlich'sen Aszites- 

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AiSENBERG, A. C., and V. R. Potter. 1957. Studies on the Pasteur effect. II. Spe- 

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AiSENBERG, A. C., B. Reinfarje, and V. R. Potter. 1957. Studies on the Pasteur 

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Balasz, R. 1959. The point of the aerobic inhibition of glycolytic acti\itv asso- 

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