Glycolytic Control of Respiration during Aging of Carrot Root Tissue

Changes in respiration in aging carrot slices are correlated with a characteristic sequence of activation of the irreversible reactions of the glycolytic pathway. The induced "wound" respiration increases in two stages; these appear to correspond to a period of active synthesis, when ADP, produced in the cytoplasm from synthetic reactions, activates pyruvate kinase, and a period of readjustment when ATP, no longer reacting in synthetic reactions, activates phosphofructokinase. Although ATP is cited frequently as a negative effector of phosphofructokinase, unless the concentration of ATP at the site of phosphofructokinase is 50-fold higher than the concentration expressed per unit fresh weight of the tissue, it cannot act in this way in carrot slices. The activation of the oxidative pentose phosphate pathway observed by ap Rees and Beevers is restricted to the first stage of the induced respiration.