THE FUNCTIONAL LINK OF SUCCINIC DEHYDROGENASE 1 97 



they had been depleted of high energy phosphate by the arsenate-di- 

 coumarol pretreatment, no stimulation of the oxidation rate was observed, 

 and added ATP was required in order to restore the succinoxidase activity. 



Fig. 5. Stimulation of succinate oxidation by inorganic phosphate and ATP 

 in pretreated rat liver mitochondria [6]. Experimental conditions as in Fig. i. The 

 mitochondria used in this experiment were pretreated for 5 min. at 30" with 

 ooooi M DNP plus 0001 M AMP, and then washed with 025 M sucrose. 



As shown in Fig. 3, the time of preincubation with arsenate necessary 

 for inhibiting succinate oxidation corresponded approximatelv to the time 

 required for depleting the mitochondria of high energy phosphate. 



Additional support for the above conclusion was obtained with the use 

 of amytal. As reported elsewhere, the depleting etfect of arsenate on the 



