234 A SYMPOSIUM ON RESPIRATORY ENZYMES 



yet the growth does not deplete the ATP to such an extent that 

 glucose cannot be phosphorylated and hence glycolyzed. In other 

 tissues glycolysis is slowed down either by a depletion of inorganic 

 phosphate, as in resting tissue, or by a depletion of ATP, as in dying 

 tissue. (Liver and kidney under anaerobic conditions deplete ATP 

 by tending to maintain function and are hence unable to phos- 

 phorylate glucose; therefore glycolysis stops and death occurs.) In 

 the tumor tissue the glycolytic rate is so rapid in relation to the 

 oxidative mechanisms that lactate accumulates. The oxygen uptake 

 is limited by the amount of the oxidative enzymes present, but 

 since there is an excess of substrates, the Q02 is higher than might 

 be expected on the basis of the Qoo of normal tissue, in which the 

 oxidative enzymes are present in excess and the Q02 is limited by 

 the amount of substrate furnished by glycolysis. In the tumor tissue 

 the growth process outpaces the synthesis of the oxidative enzymes, 

 and the latter become diluted as compared with their concentration 

 in other active tissues. From this it would follow that growth may 

 not require as high a level of oxidative enzymes as does function. 

 Our experimental results are being reported elsewhere. At this 

 point it may be said that one component of the oxidative mech- 

 anism, namely, cytochrome c, appears to have been established as 

 definitely lower in the various types of tumor tissue than in normal 

 tissues. Assays on the succinoxidase system are at present being 

 carried out. Preliminary experiments with rapidly growing hver 

 support the idea that growth outpaces the synthesis of the oxidative 

 enzymes temporarily in this tissue. 



