Oxidative Phosphorylation by Sweet Potato Mitochondria and Its Inhibition by Polyphenols.

Abstract

A mitochondrial system from sweet potatoes prepared in EDTA-su-crose carried out oxidative phosphorylation at very good rates during oxidation of [alpha]-ketoglutarate. Oxidation and phosphorylation proceed at constant rates for at least 1 hour. In this time approximately 60 micro-atoms of phosphorus were taken up and a P/O ratio of approximately 2 was obtained. In the presence of malonate the P/O ratios approached 3DNP uncoupled oxidation from phosphorylation at concentrations of 1 x 10-4 [image], 3 x 10-4 [image], and 5 x 10-4 [image]. The polyphenols, catechol and chlorogenic acid, in concentrations of 3 x 10-4 [image] almost completely inhibited phosphorylation and oxidation during the dissimilation of a-keto-glutarate by the mitochondrial system. This inhibition was prevented by ascorbic acid or diethyldithiocarbamate, suggesting that the quinone form is the inhibitor. A scheme which attributes senescence in plant cells to interaction of the polyphenol-ascorbic acid systems was proposed.