152 LARS ERNSTER 



phosphate, provided that it caused no irreversible damage of their structural 

 integrity, led to a decrease of the succinoxidase activity. Furthermore, what 

 was only anticipated in 1955 (and even questioned later), namely, that 

 the observed inhibition was not due to an accumulation of oxaloacetate, 

 could now be ascertained by rigorous experimental means [7, 8]. 



(a) 



Jf=0020cm 



(b) 



Analytical 

 data © 



yumoles/g prot. 



DPNH 078 

 TPNH 3-60 



® (D © 



007 005 

 0-47 0-38 



015 

 083 



Fig. 8. Effect of ATP on succinate oxidation and pyridine nucleotide reduction 

 in rat liver mitochondria preincubated with arsenate and dicoumarol (from Azzone, 

 Ernster, and Klingenberg [34]). 



From work along these lines the concept was developed that in intact 

 liver mitochondria, the aerobic oxidation of succinate involves an activation 

 reaction by means of high-energy phosphate. Since this mechanism was 

 visualized as involving the formation of a high-energy intermediate in the 

 respiratory chain at the level where the electrons derived from succinate 

 enter the terminal respiratory chain, it seemed conceivable that this 

 intermediate might also be involved in the endergonic reduction of the 



