NUCLEOTIDES AND MITOCHONDRIAL FUNCTION 



237 



by a slow reduction ; whereas the ATP-induced reduction of DPN or 

 flavoprotein is comparatively slow. Also the respiration is inhibited 

 immediately after the addition of ATP. Thus the rapid inhibition of the 

 overall electron transport by ATP appears to be reflected in the cyto- 

 chromes. This was to be expected since cytochromes c and a are thought 

 to be in the direct electron transport of succinate or glycerolphosphate 

 oxidation. On the other hand, the assumed reversal of electron transport 



400 



//-atom O 



liter 



300 



200- 



605- 

 630 m/x 



/1E = 

 00025 



Cyt a 

 reduction 



Fig. 9. The effect of albumin on respiration and on the redox state of cyto- 

 chrome a in the presence of glycerol- 1 -phosphate. 



can account for the lower velocity of the ATP-induced reduction of DPN 

 and of flavoprotein. These components receive reducing equivalents in a 

 reverse reaction from succinate of glycerolphosphate at a speed which may 

 depend on the velocity of the energy supply. The parallel behaviour 

 between cytochrome oxidation and the inhibition of respiration extends 

 also to the effect of albumin (Fig. 9). Both the inhibition of respiration and 

 initiation of cytochrome oxidation increase slowly after the addition of 

 albumin. This kinetic behaviour is understandable on the grounds of the 

 proposed mechanism of albumin action. 



