76 J. B. CHAPPELL 



pathway. The possibiHty must not be overlooked that glutamate dehydro- 

 genase serves a synthetic rather than a degradative function in hver mito- 

 chondria. 



The phosphate requirement for DPN-stimulated glutamate oxidation 

 [8, 9] and, when oligomycin [10] is present, the requirement for ADP [11] 

 are presumably reflections of the demands of the substrate level phos- 

 phorylation associated with a-ketoglutarate oxidation. These requirements 

 have also been observed when ferricyanide acted as terminal electron 

 acceptor. 



100 r 



90 



80 



S 70 



U 



-S 60 

 o 



I 50 



40 



30 

 20 



Lewisite 



12 3 4 5 



Time (min) 



Fig. 6. The effect of 2 :3-dimercaptopropanol (BAL) on the inhibition of 

 glutamate oxidation by ^-chlorovinylarsenious oxide. /3-chlorovinylarsenious oxide, 

 0"5 Mg-/4 rnl.; BAL, i ng./^. ml. 



Similarly, isocitrate oxidation showed the same requirement for 

 phosphate, and in the presence of oligomycin, for ADP, when respiration 

 was stimulated by DNP. In this case it is not the accumulation of a-keto- 

 glutarate, but the failure to produce sufiicient quantity of oxaloacetate, 

 required for the coupling process, which is responsible for the low rates 

 of oxygen consumption. The addition of malate, in catalytic quantities, 

 abolishes the requirement for phosphate and ADP, for isocitrate oxidation. 



Succinate oxidation 



In confirmation of the findings of Azzone and Ernster [12] liver mito- 

 chondria which had been pre-incubated with 2 mM arsenate and io~* m 



