Metabolism ofd-[1-14C]alanine fed to rice leaf blades

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Abstract
D-[1-14C]Alanine was fed to excised rice leaf blades and a pulse chase of the radioactivity in various compounds in the tissues was made. Most of the radioactivity was detected in compound(I) and d-alanylglycine on 1 hr of exposure following feeding of d-[1-14C]alanine. The radioactivity in compound(I) decreased rapidly thereafter, whereas the changes in radioactivity in d-alanylglycine were rather small throughout the feeding period. The radioactivity in neutral compounds increased rapidly with time, in contrast to the decrease in radioactivity in compound(I). Radioactivity was also detected in the conjugated d-alanine in the acid fraction but the radioactivity in this compound was small throughout the feeding period. On the other hand, the radioactivity in the ethanol insoluble materials increased gradually with time, in contrast to a decrease in radioactivity in the ethanol soluble fraction. A short-term d-alanine feeding experiment was next carried out, and the patterns of distribution of radioactivity between compound(I) and d-alanylglycine were compared. The radioactivity in compound(I) increased rapidly at the early feeding time and decreased smoothly thereafter, whereas that in d-alanylglycine increased gradually with time. Based on these results, the metabolic pathways of d-alanine fed to rice leaf blades are discussed.