INTEGRATED OXIDATIONS IN ISOLATED MITOCHONDRIA 77 



DNP did not oxidize succinate at significant rates until ATP was added 

 (Fig. 7). I mM ATP, ADP or inosine triphosphate were all equally effective. 

 However, lower concentrations of ATP were less effective, unless oligomy- 

 cin (2 • 5 fig. /ml.) and amytal were added. Under these conditions 3 ni/xmoles 

 of ATP served to catalyze the oxidation of 2 ftmoles of succinate, and it is 

 apparent therefore that ATP is not required in stoicheiometric amounts. 

 Furthermore, since oligomycin inhibits the enzymes involved in oxidative 



Amytal 



12 3 4 

 Time (mm) 

 Fig. 7. Effect on succinate oxidation of preincubating liver mitochondria with 

 DNP and arsenate (cf. Azzone and Ernster, [12]). DXP, lo^^ m; amytal, i -8 mM ; 

 succinate, 10 mM; ATP, i mM. 



phosphorylation [10] it is unlikely that AIT acts by reversing this process 

 as suggested by Azzone and Ernster [12]. Indeed oligomycin accentuated 

 the effect of ATP, especially at low nucleotide concentrations, presumablv 

 because this antibiotic inhibits the mitochondrial DXP-stimulated ATPase 

 [10]. 



When I -8 niM amytal, as well as arsenate and DNP, was present during 

 the preincubation period, ATP was not required for succinate oxidation. 

 The amytal almost entirely abolished the endogenous respiration of the 

 liver mitochondria. With kidney mitochondria, which had an almost 



