高等植物亚硝酸还原酶的纯化、性质及其对铁氧还蛋白的依赖性。

NADPH-dependent nitrite reductase from the leaves of higher plants was purified at least 70-fold and separated into two enzyme fractions. The first enzyme, a diaphorase with ferredoxin-NADP-reductase activity, is required only to transfer electrons from NADPH to a suitable electron acceptor, which then donates electrons to nitrite reductase proper. 2. Purified nitrite reductase accepted electrons from ferredoxin (the natural donor) or from reduced dyes. Ferredoxin was reduced by illuminated chloroplasts or dithionite, or by NADPH when diaphorase was present. The purified enzyme did not accept electrons directly from NADPH. 3. Ferredoxins purified from maize, spinach or Clostridium were interchangeable in the nitrite-reductase system. 4. Nitrite reductase had K(m) 0.15mm for nitrite. The pH optimum varied with plant and method of assay. The preparation had low sulphite-reductase activity. Ammonia was the product of nitrite reduction. 5. For some plants, the assay of crude preparations with NADPH was limited by diaphorase and the addition of diaphorase gave a better estimate of nitrite-reductase activity. A simple method of assay is described that uses dithionite with benzyl viologen as electron donor.

从高等植物叶片中提取的依赖于NADPH的亚硝酸还原酶被纯化了至少70倍，并被分离成两个酶组分。第一种酶是一种具有铁氧化还原蛋白-NADP还原酶活性的递氢体，仅用于将电子从NADPH转移到合适的电子受体，然后该受体将电子提供给亚硝酸还原酶本身。2. 纯化后的亚硝酸还原酶可从铁氧化还原蛋白（天然供体）或还原染料中接受电子。铁氧化还原蛋白可被光照的叶绿体或连二亚硫酸盐还原，或者当存在递氢体时被NADPH还原。纯化后的酶不能直接从NADPH接受电子。3. 从玉米、菠菜或梭状芽孢杆菌中纯化的铁氧化还原蛋白在亚硝酸还原酶系统中是可互换的。4. 亚硝酸还原酶对亚硝酸盐的K(m)为0.15mm。最适pH值随植物和测定方法而变化。该制剂的亚硫酸盐还原酶活性较低。氨是亚硝酸盐还原的产物。5. 对于某些植物，用NADPH对粗制剂进行测定受递氢体的限制，添加递氢体可更好地估计亚硝酸还原酶的活性。描述了一种简单的测定方法，该方法使用连二亚硫酸盐与苄基紫精作为电子供体。

The purification and properties of nitrite reductase from higher plants, and its dependence on ferredoxin.