TARTARIC ACID SYNTHESIS FROM L-ASCORBIC ACID-1-14C IN GRAPE BERRIES

Young grape berries were exposed to 14CO2 for 10 min under light and dark conditions, and changes of 14C-assimilation products was surveyed during a short period. In the light, radioactivity was found in tartaric acid immediately after 14CO2-fixation, while in the dark, radioactivity was not detected in tartaric acid until 480 min after 14CO2-fixation. d-Glucurono-γ-lactone-6-14C, l-ascorbate-1-14C, d-glucuronate-6-14C and sucrose-U-14C were fed to young grape berries, and the incorporation into tartaric acid was investigated. A considerable amount of radioactivity was incorporated into tartaric acid from d-glucurono-γ-lactone-6-14C and l-ascorbic acid-1-14C, and, in the case of l-ascorbic acid-1-14C, 72 per cent of the total radioactivity was found in tartaric acid. The tartaric acid synthesized was partly degraded; when sucrose-U-14C was fed, uniformly labeled tartaric acid was obtained, but when d-glucurono-γ-lactone-6-14C or l-ascorbic acid-1-14C was used, most of radioactivity was localized in the carboxyl groups. © 1969.