Metabolic incorporation of l-[14C]valine into protein and bound non-protein forms in Italian ryegrass

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Abstract
Uniformly labelled L-[C14] valine of high specific activity was administered to severed shoots of Italian ryegrass in the transpiration stream and extensive incorporation of labelled valine residues into protein resulted. The distribution of labelled protein in the plant was observed by radio-autography. The specific activities acquired under these conditions by valine residues in bound non-protein form suggest that most of such compounds are not directly concerned in the biosynthesis or the catabolism of protein. Extraction with ether-water resulted in some catabolism of protein to peptides not present when the tissue was extracted by boiling water. A non-volatile radioactive impurity, presumably a product of radiochemical decomposition, was present in the [C14] valine as purchased. Evidence was obtained for the occurrence of a metastable tautomeric form of N-24-dinitrophenyl-L-valine exhibiting mutarotation in acetic acid.