L-アスコルビン酸の分解に関する研究 : (XIX)細菌によるL-アスコルビン酸の分解機構 (8)L-アスコルビ酸代謝の全径路

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In this paper, two different pathways of L-ascorbic acid metabolism were established as shown in Fig.6. One of them was carried through dehydroascorbic acid and corresponding diketo acid. It was first decarboxylated to L-xylosone to be converted to D-arabinosone by epimerization of C_4-OH group and then reduced to D-ribose prior to phosphorylating process. On the other pathway, L-ascorbic acid was first converted to D-araboascorbic acid by inversion of C_5-OH group, which was presumed to form equilibrium with 3-keto-D-gluconic acid. The latter was phosphorylated and was introduced into Warburg-Dicken's pathway. D-Ribose-5-phosphate, which occurred as common intermediate in two different pathways of L-ascorbic acid metabolism, was cleaved to yield active glycolaldehyde and 3-phosphoglyceraldehyde, as shown already by many reports. The former was oxidized to acetic acid, and the latter was metabolized through several steps to pyruvic acid. Pyruvic acid was, as reported in the previous paper, further metabolized to CO_2 and H_2O through TCA cycle, remaining a small quantity of acetic acid, D-lactic acid and formic acid.
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