INCORPORATION OF O-18 INTO OXALIC, L-THREONIC AND L-TARTARIC ACIDS DURING CLEAVAGE OF L-ASCORBIC AND 5-KETO-D-GLUCONIC ACIDS IN PLANTS

摘要

L-[1,6-C-14]Ascorbic acid was administered to young leaves of Pelargonium. 5-Keto-D-[1-C-14]gluconic acid, a metabolic product of L-[1-C-14]ascorbic acid in grape, was supplied to young leaves of Pelargonium, parsley, bean and grape in the presence of O-18(2) or (H2O)-O-18. From the O-18 incorporated into oxalic and L-threonic acids, which were C2/C3 cleavage products of L-ascorbic acid, and into L-tartaric acid, which was a C4/C5 cleavage product of 5-keto-D-gluconic acid, the number of oxygen atoms incorporated into the respective organic acids was calculated. The data strongly suggest that a cleavage mechanism of C2/C3 of L-ascorbic acid involves both oxygenase and hydrolase reactions but that cleavage of C4/C5 of 5-keto-D-gluconic acid is due only to hydrolase.