Effects of Storage and Aging on Properties of Phosphofructokinase From Jerusalem Artichoke Tubers

The dramatic and complex metabolic changes which occur as a result of aerating tuber or storage root slices in dilute salt solutions (aging) include a rise in respiratory rate. The increased respiratory increment is sensitive to inhibition by malonate while the basal respiration of freshly prepared slices is insensitive to this inhibitor (12). There is other evidence that the increased respiration of aged tissue is due to release of inhibition of tricarboxylic acid cycle activity (6). Both pentose phosphate and Embden-Meyerhof-Parnas glycolytic pathway activities increase in aged root and tuber tissues (12), and an increase in the amount of 6-phosphogluconate dehydrogenase from aged slices of red beet roots has been observed (11). After a lag period, auxinmediated water uptake is associated with the respiratory rise of aged tissue (1). Phosphofructokinase plays a key role in regulation of the glycolytic pathway in plants as well as other organisms (4). The enzyme from higher plants differs from that isolated from animals, yeast and E. coli in that inhibition by ATP 'is not released by AMP or ADP; indeed, these nucleotides are inhibitory to the plant enzyme. Inorganic phosphate is proposed as the positive effector for plant phosphofructokinase (3).