Effect of Tissue Age on Hexose Metabolism. I. An Enzyme Study with Pea Root.

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Abstract
The purpose of this investigation was to determine whether the development age of the root of the pea plant had any effect of the enzyme concentration of fructose 1,6-diphosphate aldolase, 6-phosphogluconate dehydrogenase, fructose 1,6-diphosphatase and the enzymes catalyzing the anaerobic metabolism of ribose 5-phosphate. Extracts prepared from acetone powders of 7, 10, 13, 16, 20, 24, and 29 day-old roots and from seed which had been immersed overnight in water were assayed. In the extracts of the seed tissue aldolase activity was found to be approximately 2.5 times higher than that of 6-phosphogluconate dehydrogenase while the enzymes catalyzing ribose 5-phosphate disappearance were essentially absent. When the 1st root sample was taken on the 7th day, the activities of aldolase, 6-phosphogluconate, ribose 5-phosphate metabolism and fructose 1,6-diphosphatase had increased approximately by a factor of 5, 8, 50 and 8, respectively. In subsequent samples, both a decrease in aldolase activity and 6-phosphogluconate activity was found. However, the aldolase activity decreased significantly more, so that by the 20th day the dehydrogenase activity was approximately 50% higher. The ribose 5-phosphate metabolism rate remained about half that of the dehydrogenase. The phosphatase rate was the lowest of the systems investigated, being approximately one third that of the dehydrogenase. It is concluded that the concentration of enzymes of Embden-Meyerhof-Parnas glycolytic sequence and of the hexose monophosphate pathway may be an internal influence on determining the immediate fate of glucose 6-phosphate.
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