STUDIES ON WHEAT PLANTS USING CARBON-14 COMPOUNDS: XIX. OBSERVATIONS ON THE METABOLISM OF LYSINE-C14

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Abstract
When generally labelled lysine-C14 or α-aminoadipic acid-6-C14 was administered to wheat seedlings 48% and 57%, respectively, of the carbon-14 was recovered in water-soluble materials. An additional 39% of the lysine carbon-14 was found in the insoluble residue whereas with α-aminoadipic acid-6-C14 only 11% of the carbon-14 was in the residue. When lysine-C14 was administered, lysine, pipecolic acid, and α-aminoadipic acid had high specific activities while glutamic acid and some related substances contained significant amounts of carbon-14. By contrast, when α-aminoadipic acid-6-C14 was used as tracer the lysine and pipecolic acid isolated were weakly labelled, although α-aminoadipic acid of very high specific activity was recovered from the tissues. Appreciable carbon-14 was also found in the glutamic acid, 63% of this being in position-5.The data are taken as evidence that α-aminoadipic acid and pipecolic acid are on the pathway of lysine metabolism, with acetate being a product of further degradation. The results provide no evidence that α-aminoadipic acid can serve as a precursor to lysine.