Tartaric biosynthesis

Side-chain oxidized derivatives of ascorbic acid are also implicated in the catabolism of ascorbic acid in plants. Loewus et al. (62) have established the intermediacy of ascorbic acid in the biosynthesis of tartaric acid in the grape. Labeling studies have established a metabolic pathway that must involve C5 and C6 oxidation of ascorbic acid. 

An important discovery in 1969 (1) linked the catabolism of L-ascor-bic acid to tartaric acid biosynthesis. When immature grape berries were fed L-[l- C]ascorbic acid over a 24-h period, 72% of the acid extractable... 

Our results have led us to suggest a role for L-ascorbic acid in phloem transport (9) in which ascorbic acid is translocated from its biosynthetic site in the leaf to a catabolic site in the fruit cluster where C4-C5 cleavage of the carbon chain produces tartaric acid and a putative C2 precursor of carbohydrate biosynthesis. The sugar/organic acid balance that influences grape quality in winemaking may well be determined by the role of ascorbic acid as the precursor of tartaric acid. 

Since both (R,R)- and (5,5)-tartaric acid esters are readily available in optically pure form, this method allows the synthesis of both enantiomers of cyclopropanes from a,j8-unsaturated aldehydes in a predictable manner. The method has been successfully applied (see Table 1, entry 6) to the enantioselective synthesis of 5,6-methanoleukotriene A, a stable and selective inhibitor of leukotriene biosynthesis." ... 

Ascorbic acid (vitamin C) is utilized as a cofactor to stabilize the chloroplast stroma, in quenching free radicals and reacting with hydroxy radicals and in the biosynthesis of tartaric acid and oxalic acid (6), important organic acids in grapes, and many vegetables. The effect of CA on ascorbic acid content differs with commodity,... 

The utility of this methodology is illustrated by the stereoselective synthesis of ( + )-cer-ulenin (759), an antifungal antibiotic first isolated from the culture filtrate of Cephalosporium caerulens. Its ability to inhibit lipid biosynthesis in Escherichia coli by irreversibly binding P-keto-acyl-carrier protein synthetase, the enzyme responsible for the chain lengthening reaction in fatty acid synthesis, has attracted interest in its mechanism of action. D-Tartaric acid... 

Williams M, Loewus F A 1978 Biosynthesis of (+)-tartaric acid from L-[4- C]ascorbic acid in grape and Geranium. Plant Physiol 61 672-674... 

Important phenolic acids, dealt with in Sec- Tartaric acid biosynthesis in Vitis spp. starts tion 18.1.2.5.1, are quinic, caffeic, chlorogenic from glucose or fructose and probably proceeds... 

L-Tartaric acid biosynthesis starts from L-ascorbic acid or from D-gluconic acid (Figure 8.40). In grapes and other plants of the Vitaceae family, tartaric acid arises from the ascorbic acid intermediate D-xyto-5-hexulosonic acid via the cleavage between carbons C-4 and C-5. The second option, which is apparently used by most plants (the reaction is catalysed by ascorbate 2,3-dioxygenase), is the ascorbic acid cleavage between carbons C-2 and C-3, which simultaneously yields oxalic acid. The third possibility for the biosynthesis of L-tartaric acid from D-gluconic acid is used mainly by plants of the Fabaceae family. 

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