Pathways of Oxidation in Cell-Free Potato Fractions

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Abstract
An attempt was made to reconstruct the pathway of electron transfer from reduced diphosphopyridine nucleotide (and succinate) to oxygen in cell free fractions from potato tubers. Particles, assumed to be mitochondria, were isolated by differential centrifugation from a sucrose-phosphate homogenate. The following enzymes and enzyme systems were assayed spectrophotometrically and their inhibitor sensitivities studied: cytochrome oxidase, DPNH oxidase, diaphorase, DPNH-cytochrome c reductase, and succinic-cytochrome c reductase. All of these enzymes are present on the mitochondria, and it is suggested that the oxidation of DPNH involves a successive electron transfer to flavoprotein, an Antimycin-A-sensitive factor, the cytochrome system, and oxygen. The isolated particles can also by-pass the AA-sensitive factor when DPNH is oxidized in the presence of added cytochrome c. The 10,000 x g supernatant fraction can oxidize DPNH rapidly and possesses an active DPNH-cytochrome c reductase system.