The Incorporation of C14-labelled Substrates into the Amino-acids of Groundnut Plants (Arachis hypogaea)

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Abstract
The amino-acid metabolism of groundnut plants has been studied with special reference to γ-methyleneglutamic acid (γ-MGA) and y-methyleneglutamine (γ-MG), constituents not found in the great majority of plant species. The sequence in which C14 from radioactive C14-carbon dioxide enters the amino-acids of leaves was determined. The pattern of labelling was very similar to that found for leaves of other species. The metabolic relationships existing between photosynthesis and amino-acid synthesis therefore do not seem to be affected by the large quantities of γ-MGA and γ-MG present in the leaves. γ-MGA and γ-MG only gained traces of radioactivity. Experiments designed to study the incorporation of C14 from uniformly labelled C14-alanine into the amino-acids of roots, immature leaves and cotyledons of seedlings and young plants indicated that the main site of synthesis of γ-MGA was the cotyledons. Various CI4-labelled substrates were fed to germinating seeds and, after a period of growth, the specific activities of the amino-acids of seedlings receiving different treatments were determined. Comparison of the specific activities enabled certain deductions to be made concerning the probable biosynthetic pathways leading to γ-MGA and γ-MG. The results were consistent with the intact incorporation of pyruvate molecules, or another related 3-carbon-atom containing compound, into γ-MGA.

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