Control of Rate of Intracellular Respiration 73 



synthesis of ATP in the respiratory chain. The residual 

 synthesis of HMP is due to the fact that the first step of the 

 a-ketoglutaric oxidase system is coupled with phosphorylation 

 in a reaction which is not sensitive to DNP. With increasing 

 concentrations of DNP, the rate of hydrogen transfer increases 



2x10-5 4x10-5 6x10-5 8x10-5 10-" 

 Concn. of 2 : 4-dinitrophenol (m) 



Fig. 4. Effect of increasing concentrations of DNP 

 on the rate of respiration of blowfly thoracic- 

 muscle sarcosomes, and on the accompanying 

 esterification of inorganic phosphate. AP = 

 esterified phosphate ((amoles), — AO = O2 uptake 

 (jjiatoms), — AaKg = aketoglutarate oxidized 

 ([xmoles). (From Slater and Lewis, 1954. Repro- 

 duced by permission of the Editors, Biochem. J.) 



and consequently the amount of phosphorylation associated 

 with the first step also increases, until eventually the increased 

 phosphorylation in this step mor« than compensates for the 

 complete inhibition of phosphorylation in the rest of the chain. 

 The net result is that DNP increases the rate of phosphoryla- 

 tion, although the efficiency of the conversion of oxidation 

 energy to the synthesis of ATP is of course decreased. 



This experiment illustrates the feasibility of Lardy's 



