TRIGLYCERIDES AND FATTY ACIDS 103 



new iiltracentrifugal technic'*^ into cell nuclei, mitochondria, microsomes, 

 and soluble cytoplasm. In these tests, Kennedy and Lehninger^^^-^^^ 

 proved that the fatty acid oxidase system was localized in the mitochondrial 

 fraction ; the activity of the saline-washed preparations used earlier was at- 

 tributed to their content of agglutinated mitochondria. The activity of 

 mitochondria in fatty acid oxidation was confirmed by Schneider. ^^^ It is 

 now knoA\Ti that isolated mitochondria can catalyze all reactions of the 

 Krebs cycle, and also all necessary phosphorylations. Lehninger^ was mi- 

 able to dissociate oxidase activity from native mitochondrial structure. 



c'. The Requirement for a "Primer" or "Sparker." Even in the early 

 work of Munoz and Leloir^^ in 1943-1944, it was evident that some "prim- 

 ing" or "sparking" material was necessary to permit the oxidation to pro- 

 ceed. At first, Lehninger^"'^^* was of the opinion that it was necessary only 

 to generate ATP from adenylic acid by phosphorylations which were 

 coupled with the oxidations in the Krebs cycle. However, Lehninger^ 

 proved that a small quantity of "primer" was required in addition to ATP. 

 Cross et al^^^ suggested that the function of the "primer" is to cause oxida- 

 tive phosphorylation, since substances which bring about the reverse reac- 

 tion inhibit fatty acid oxidation. Kennedy and Lehninger^*^ later re- 

 ported that fatty acid oxidation in suspensions of rat liver mitochondria 

 could be activated not only by intermediates of the Krebs cycle but also by 

 the oxidation of relatively high concentrations of the reduced diphospho- 

 pyridme nucleotide (DPNH2), in which coupled oxidative phosphorj^lation 

 is kno^Mi to occur. The oxidation of fatty acids ceased when DPNH2 was 

 completely oxidized, but it could be prolonged if high concentrations of 

 adenine nucleotides were also present. WTien DPNH2 was used as the 

 priming agent, octanoate was quantitatively oxidized to two acetoacetate 

 molecules, while palmitate was converted to four acetoacetate molecules. 

 When succinate was employed as the activating agent, less acetoacetate 

 was formed, and part of it was completely oxidized via the Krebs cycle. 



In the more recent work of Judah and Rees,^^^ it was demonstrated that 

 variations occur in the activation agent in the case of liver mitochondria 



"^ G. H. Hogeboom, W. C. Schneider, and G. E. PaUade, /. Biol. Chem.y 172, 619-635 

 (1948). 



"« E. P. Kennedy and A. L. Lehninger, /. Biol. Chem., 172, 847-848 (1948). 



1" E. P. Kennedy and A. L. Lehninger, J. Biol. Chem., 179, 957-972 (1949). 



150 W. C. Schneider, J. Biol. Chem., 176, 259-266 (1948). 



'51 R. J. Cross, J. V. Taggart, G. A. Covo, and D. E. Green, /. Biol. Chem., 177, 655- 

 678 (1949). 



1" E. P. Kennedy and A. L. Lehninger, J. Biol. Chem., 190, 361-368 (1951). 



i*» J. D. Judah and K. R. Rees, Biochem. J., 55, 664-668 (1953). 



