The activation of fatty acid oxidation by kidney and liver mitochondria.

Lehninger (1945) has shown that the initiation of fatty acid oxidation in cell-free preparations of animal tissues must be accompanied by oxidative phosphorylation. Grafflin & Green (1949) considered that the co-oxidation of a citric-acid cycle intermediate is also necessary to provide oxaloacetic acid to condense with the two-carbon fragments formed in the breakdown of fatty acids. The condensation thus permits the complete oxidation of the fatty acid via the citric acid cycle. Kennedy & Lehninger (1951), however, have demonstrated that the oxidation of reduced diphosphopyridine nucleotide will prime the oxidation of octanoate and palnitate by rat-liver mitochondria. This oxidation gives rise to phosphorylationgeneratingadenosinetriphosphate, but no citric-acid cycle intermediate is involved. The present paper considers these apparently conflicting views of fatty acid oxidation in mitochondrial systems. During these investigations 2:4-dinitrophenol (DNP) and fluoroacetic acid have proved useful reagents for the analysis of the fatty acid oxidase system.