STUDIES ON WHEAT PLANTS USING C14 COMPOUNDS: III. THE UTILIZATION OF ACETATE FOR AMINO ACID BIOSYNTHESIS

Abstract

Sixteen amino acids were isolated from the gluten of wheat plants, the stems of which had been injected with acetate-1-C14 or -2-C14. With both tracers the C14 labelled amino acids varied markedly from each other in specific activity. Glutamic acid, proline, and arginine were most active, followed by the four-carbon amino acids aspartic acid and threonine, while the short-chain amino acids glycine, alanine, serine, and methionine possessed medium activity. Branched-chain and aromatic amino acids, and the two basic amino acids lysine and histidine were weakly labelled, but showed marked differences from each other not only in specific activity but in the relative amounts of carboxyl and methyl groups of acetate incorporated. Acetate-2-C14 generally gave amino acids of highest activity, but acetate-1-C14 was most effective for labelling glycine, histidine, and serine. Partial degradation by ninhydrin decarboxylation clearly showed that the carboxyl group of acetate tended, in general, to appear to a greater extent in the carboxyl group of amino acids than did the methyl group. Direct incorporation of the carboxyl carbon of acetate in C1 of leucine was observed.