The Effect of Respiratory Inhibitors on NADH, Succinate and Malate Oxidation in Corn Mitochondria

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Abstract
Large amounts of alanine are produced in the first few seconds of photosynthesis in Portulaca oleracea L. The normal precursor-product relationship (phosphoglyceric acid → pyruvate → alanine) does not appear to operate in this species since labeling in pyruvate precedes that in phosphoglyceric acid. Pulse-chase experiments show that the alanine is rapidly metabolized. After a 6-second pulse of 14CO2, the percentage of 11C in alanine drops more than 30% in the first 10 seconds of a 12CO2 chase period. The percentage of 14C in the other early-labeled photosynthetic products, aspartate and malate, also decreases during the 12CO2 chase. The decrease of label in these compounds is concomitant with an increase in the labeling of sucrose and alanine, which in this case is formed via phosphoglyceric acid. Randomization of label within alanine increases gradually throughout the 2-minute chase.