NADH DEHYDROGENASE-ACTIVITY OF HIGHER-PLANT NITRATE REDUCTASE (NADH)

Squash nitrate reductase (NADH) was purified on blue-Sepharose and used to study the NADH dehydrogenase activity. In the presence of nitrate reductase. NADH will reduce: nitrate, ferricyanide, methylene blue, benzoquinone and menadione. Coenzyme Q10 and plastiquinone were not reduced. Reduction of nitrate and menadione were shown to require EDTA. Yeast glutathione reductase and lipoamide dehydrogenase differed in their ability to transfer electrons to menadione. The comparison of these three enzymes and other NAD(P)H dehydrogenases with respect to electron acceptor specificity and requirement for activators or protectors has led to the suggestion of two classes of NAD(P)H flavodehydrogenases: (1) soluble; (2) membrane bound or complexed. While glutathione reductase is a class 1 type, lipoamide dehydrogenase and nitrate reductase share the properties of class 2 types. © 1979.