Reversible inactivation of maize leaf nitrate reductase |
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Authors: | Cristina Echevarría Sofía G Maur?no José M Maldonado |
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Institution: | 1. Departamento de Fisiología Vegetal, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain (C.E., S.G.M.);2. Departamento de Fisiología Vegetal, Facultad de Ciencias, Universidad de Córdoba, Córdoba, Spain (J.M.M.) |
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Abstract: | Preincubation of maize leaves crude extracts with NADH resulted in a progressive accumulation of nitrite which mimicked a rapid and lineal activation of nitrate reductase. Nevertheless, in partially purified preparations it was found that preincubation at pH 8.8 with NADH promoted a gradual inactivation of nitrate reductase. At pH 7.5, the enzyme was not inactivated by the presence of NADH alone, but, with the simultaneous presence of a low concentration of cyanide, a fast inactivation took place. The NADH-cyanide-inactivated nitrate reductase remained inactive after removing the excess of NADH and cyanide by filtration through Sephadex G-25. However, it could be readily reactivated by incubation with ferricyanide or by a short exposure to light in the presence of FAD. Prolonged irradiation caused a progressive inactivation of the photoreactivated enzyme. |
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Keywords: | Gramineae maize nitrate reductase activity redox regulation |
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