636 Discussion 



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DISCUSSION 



On ^Additional DPN'of Incubated Mitochondria 



Estabrook : Dickens has mentioned the recent studies of Purvis concerning the presence 

 of a DPN -^ I component in mitochondria detectable by differential chemical analysis. 

 Recently Purvis visited our laboratory and in collaboration with Ito and Chance we 

 were able to confirm the appearance of additional pyridine nucleotide in fractions of 

 rat liver mitochondria treated in phosphate buffer. This additional pyridine nucleotide 

 released on phosphate incubation is that material labelled DPN ~ I by Purvis. In 

 order to circumvent the complexity introduced by the high content of triphospho- 

 pyridine nucleotides in liver mitochondria we turned to guinea pig kidney mitochondria 

 where the content of TPN + TPNH represents only about 5 % of the total pyridine 

 nucleotides (Biicher and Klingenberg, Angew. Chem. 70, 552, 1958). With kidney 

 mitochondria, which show excellent control of respiration and phosphorylation 

 concomitant with respiration, the following type of results were obtained : the results 

 are expressed as /<moles/g of mitochondrial protein. 



(a) at time zero DPN = 1-6 

 DPNH = 1-3 



Total = 2-9 



