STUDIES ON WHEAT PLANTS USING CARBON-14 COMPOUNDS: XII. UTILIZATION OF SERINE-C14WITH SPECIAL REFERENCE TO GLYCINE LABELLING

Abstract

Serine-C14(uniformly labelled) was injected into the top internode of wheat plant stems and the distribution of carbon-14 in the mature plants (harvested 24 days after injection) was studied. Fifty-six per cent of the carbon-14 injected was found in upper plant parts but only trace amounts occurred below the top internode. The kernels contained 48% of the tracer injected while only 4% remained in the stem. Gluten had the highest specific activity of any major kernel component, serine and glycine accounting for one third of the total carbon-14 of the protein. The high specific activity of serine in gluten indicates its direct incorporation into kernel proteins. The specific activity of the glycine was almost equal to that of serine. Since similar experiments with glycine-1-C14have yielded gluten with highly radioactive serine-1-C14, the ready interconvertibility of these two amino acids is demonstrated. The results indicate that interconversion takes place, at least in part, by the reversible condensation of "active" formate with carbon-2 of the glycine but that alternate pathways may also operate.