Preparation of bovine milk xanthine oxidase as a dehydrogenase form.
Preparation of bovine milk xanthine oxidase as a dehydrogenase form.
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脱氢酶形式的牛乳黄嘌呤氧化酶的制备。
DOI：
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发表时间：
1982
期刊：
影响因子：
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通讯作者：
I. Yamazaki
中科院分区：
文献类型：
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作者：
M. Nakamura;I. Yamazaki
以新鲜生牛奶为原料，在二硫赤藓糖醇的存在下制备黄嘌呤氧化酶，其黄嘌呤氧化活性的94%为脱氢酶型。当二硫代赤藓糖醇被去除时，酶可逆地转化为氧化酶类型。这种转化是由于酶的巯基被氧氧化。两种形式的酶具有相同的可见光谱，但在添加NAD+后，脱氢酶单独具有特征差异光谱。NADH是脱氢酶形式的良好电子供体，而不是氧化酶形式的。当黄嘌呤作为电子供体时，氧化酶和脱氢酶形式的对苯醌还原的总速率相同，但脱氢酶形式反应中酶对对苯醌的单电子通量比例明显大于氧化酶形式反应。
When xanthine oxidase was prepared from fresh raw cow's milk in the presence of dithioerythritol, 94% of its xanthine-oxidizing activity was found as a dehydrogenase type. The enzyme was reversibly converted to an oxidase type when dithioerythritol was removed. The conversion was ascribable to the oxidation of sulfhydryl groups of the enzyme by oxygen. The two forms of the enzyme gave the same visible spectrum, but the dehydrogenase form alone gave a characteristic difference spectrum upon addition of NAD+. NADH served as a good electron donor for the dehydrogenase form of the enzyme but not for the oxidase form. When xanthine was used as an electron donor, the overall rate of p-benzoquinone reduction was the same for the oxidase and dehydrogenase forms, but the proportion of one-electron flux from the enzyme to p-benzoquinone was considerably greater in the reaction of the dehydrogenase form than in that of the oxidase form.