Oxidative Phosphorylation and Glycolate Oxidation by Particles from Spinach Leaves

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Abstract
The isolation from green spinach leaves of particles which carry out oxidative phosphorylation with high P/O ratios is described. Conditions are given for the oxidation of pyruvate, citrate, Ls-isocitrate, [alpha]-ketoglutarate, succinate, fumarate, L-malate, and reduced diphosphopyridine nucleotide. Some glycolate oxidizing activity of the leaf is associated also with this particulate system, but this reaction is not accompanied by significant synthesis of adenosine triphosphate. Studies with enzyme inhibitors indicate that O2 uptake is mediated by the cytochrome system when organic acids of the Krebs cycle are the substrates, and by a flavoprotein oxidase with glycolate. Certain inhibitory effects of glycolate and glyoxylate on the operation of the Krebs cycle have been described and their possible physiological importance considered.