水産動物のL-アスコルビン酸に関する生化学的研究-IX : コイ肝膵臓におけるデヒドロアスコルバターゼの存在

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This study deals with the existence in fish tissues of dehydroascorbatase which catalyzes the delactonization of dehydro-L-ascorbic acid (DAsA) and is one of the key enzymes for the catabolism of L-ascorbic acid. The formation of 2, 3-diketo-L-gulonic acid from DAsA increased in the presence of crude extract of carp hepatopancreas as compared to nonenzymatic delactonization. The dependence of the initial reaction rate on enzyme concentration was established. Heating the enzyme for 5 min at 100°C resulted in the complete loss of its catalytic activity. These results indicate the presence of dehydroascorbatase in carp hepatopancreas. The enzyme activity was found only in the hepatopancreas of carp and exclusively in the soluble fraction, the activity of the carp enzyme being the same as in the rat and higher than in the guinea pig. This enzyme was not detected in any of the other fishes so far tested such as rainbow trout, yellow-tail, eel, mullet, red sea bream, “Ishidai” and “Shimaisaki”.
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