FORMATION OF LABELED SUGARS FROML-TYROSINE-C14IN SOME HIGHER PLANTS

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Abstract
Radioactive sugars and organic acids, including glutamic and aspartic acids, were synthesized in leaf disks of live species of angiosperms from administered uniformly labeled L-tyrosine. The synthesis of sugars was appreciable in light; in the dark there was virtually no conversion to carbohydrate. In three different experiments, 28%, 36%, and 46% of the total activity of tyrosine-U-C14, administered to leaf disks of Pyrus communis, could be accounted for in identifiable aliphatic compounds. These results indicate that tyrosine is a glucogenic amino acid in higher plants and suggest also that three or more carbons of the tyrosine molecule are utilized. Ring cleavage is a possibility.