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Synthesis of l-(+)-Tartaric Acid from l-Ascorbic Acid via 5-Keto-d-Gluconic Acid in Grapes

1984; Oxford University Press; Volume: 76; Issue: 1 Linguagem: Inglês

10.1104/pp.76.1.170

1532-2548

Kazumi Saito, Zenzaburo Kasai,

Fermentation and Sensory Analysis

5-Keto-l-idionic acid ( identical with5-keto-d-gluconic acid, d-xylo-5-hexulosonic acid) was found as a metabolic product of l-ascorbic acid in slices of immature grapes, Vitis labrusca L. cv ;Delaware'. Specifically labeled compounds, recognized as metabolic products of l-ascorbic acid in grapes, were fed to young grape tissues to investigate the metabolic pathway from l-ascorbic acid to l-(+)-tartaric acid.Label from dehydro-l-[1-(14)C]ascorbic acid, 2-keto-l-[1-(14)C]idonic acid (l-xylo-2-hexulosonic acid), l-[1-(14)C]idonic acid, or 5-keto-l-[1-(14)C] idonic acid was incorporated into l-(+)-tartaric acid in high yields as it was in the l-[1-(14)C]ascorbic acid experiment. In a double label experiment involving a mixture of l-[1-(14)C]idonic acid and l-[2-(3)H]idonic acid, the (3)H/(14)C ratios of 5-keto-l-idonic acid and l-(+)-tartaric acid synthesized in young grape leaves were almost the same as the value of the l-idonic acid fed. Label from 5-keto-l-[6-(14)C]idonic acid was incorporated into sugars and insoluble residue in the same way as l-[6-(14)C]ascorbic acid was metabolized in grapes.These results provide strong evidence that in grapes l-(+)-tartaric acid is synthesized from the C(4) fragment that corresponds to the C1 to C4 group of the 5-keto-l-idonic acid derived from l-ascorbic acid via 2-keto-l-idonic acid and l-idonic acid.