Aminotransfer from Alanine and Glutamate to Glycine and Serine during Photorespiration in Oat Leaves

(15)N-Labeled glutamate and alanine were used to examine the photorespiratory nitrogen metabolism in oat (Avena sativa L.) leaf slices. Glutamate and alanine supply amino groups for glycine formation during photorespiration. The nitrogen flux from alanine to glycine was estimated to be 3 times higher than that from glutamate. It is concluded from these results that alanine is a direct and important amino donor for photorespiratory glycine formation in oat leaves. The (15)N labeling of serine was almost as high as that of glycine during the initial period of the labeling experiments. Thereafter, the ratio of (15)N label in serine to (15)N label in glycine declined substantially.