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

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.