Activation of Nitrate Reductase by Extracts from Corn Scutella

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Abstract
NADH-nitrate reductase (NR) from the primary leaves and root tips of corn (Zea mays L.) seedlings (cv. W64A .times. W182E) were activated by extracts from corn scutella. The activator extracted in potassium phosphate buffer (pH 7.5) or 80% (vol/vol) ethanol and fractionated by Dowex 1 (acetate) and Dowex 50 (H+) resins was recovered in the cationic fraction. The activator was not detected in extracts from shoots, roots or endosperm of the seedlings. It activated the nitrate-induced cytochrome c reductase of NR complex but had slight inhibitory effects on the activities of FMNH2-NR and reduced methylviologen-NR. In addition, the activator inhibited the activities of purified NR-inactivating proteins from corn roots (var. Wf9 .times. 38-11) and rice cell cultures.