動物組織におけるアスコルビン酸の生合成と生分解にかんする酵素学的研究 : (II)L-アスコルビン酸の生分解

概要

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Degradation of L-ascorbic acid proceeds from dehydroascorbic acid, which is in turn hydrolyzed irreversibly by liver supernatant fraction to form 2,3-diketo-L-gulonic acid. This heat labile degradative factor was purified about 10-fold. The preparation had no esterase activity, but the activity was accompanied by lactonase I activity, The low activity of this dehydroascorbic acid hydrolysing enzyme in primates is correlated with the slow rate of ascorbic acid metabolism in these species. 2,3-Diketo-L-gulonic acid is further degraded nonenzymatically under aerobic condition to L-threonic acid, oxalic acid and carbon dioxide. Enzymatically, however, this compound is decarboxylated by 2,3-diketoaldonic acid decarboxylase forming isomeric products, L-lyxonic acid and L-xylonic acid. This enzyme was purified about 50-fold from rat liver supernatant. The products were identified as a form of benzimidazole crystals. Further metabolism of these three L-aldonic acids produced from ascorbic acid was also examined. The significance of ascorbic acid degradation was discussed.
日本ビタミン学会の論文
1962-12-25