1 66 LARS ERNSTER 



From these findings it is concluded that the reduction of acetoacetate by 

 succinate, catalyzed by tightly-coupled liver mitochondria, involves a reversal 

 of the DPN-flavin-linked oxidative phosphorylation ; that the energy 

 required for this process is equivalent to one high-energy bond per 

 molecule of acetoacetate reduced; that this energy can be supplied by one or 

 both of the two terminal respiratory chain phosphorylations without the 

 intermediary of extramitochondrial ATP; and that the succinate-linked 

 reduction of mitochondrial DPN does not involve the antimycin A- 

 sensitive site of the respiratory chain. 



3 . Liver mitochondria under anaerobic conditions catalyze an aminative 

 reduction of a-ketoglutarate to glutamate, coupled to the oxidation of 

 succinate to fumarate, which proceeds at the expense of high-energy 

 phosphate generated in the a-ketoglutarate-linked substrate-level phos- 

 phorylation. Some preliminary observations are presented which suggest 

 the existence of a complex pattern of compartmentation of mitochondrial 

 energy-transfer routes. 



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