水産動物のL-アスコルビン酸に関する生化学的研究-VIII : コイ肝膵臓のデヒドロ-L-アスコルビン酸還元酵素の精製および諸性質

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DAsA-reductase (EC 1.8.5.1) was purified from carp hepatopancreas by ammonium sulfate fractionation, Sephadex G-75 gel filtration and DEAE-Sephadex A-50 column chromatography, obtaining enzyme material enriched about 100-fold in specific activity with a 23% yield. Some properties of the purified enzyme were studied with the following results. Without bovine serum albumin, the enzyme was relatively unstable. Optimal pH and temperature for the enzyme reaction were near 6.7 and 30°C, respectively. Co2+, Zn2+, Hg+ and Fe3+ strongly inhibited the enzyme activity, while Cu2+, Mg2+ and Mn2+ had no effect. The enzyme activity was only slightly affected if at all by EDTA, o-phenanthrolic acid, sodium azide, sodium arsenate and nucleotides, but was inhibited by sodium cyanide and CO gas. The Km value was 5.7×10-4 for DAsA and 1.5×10-3 for GSH. The enzyme was specific for GSH as a hydrogen donor and less specific for DAsA as a hydrogen acceptor. Product inhibition was observed with excess GSSG but not with AsA.
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