Regulation of nitrate reductase in detached oat leaves by light and oxygen |
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Authors: | J D Kenis V S Trippi |
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Institution: | Lab. de Fisiología Vegetal, IMBIV. Facultad de C. E. F. y Naturales. Univ. Nacional de Córdoba, cc 395, 5000 Córdoba, Argentina. |
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Abstract: | Regulation of nitrate reductase (NR, EC 1.6.6.1) by oxygen concentration and light was studied in segments of oat ( Avena sativa L. cv. Suregrain) leaves, using the in vivo nitrate reductase assay. The activity of NR decreased after excision in either light or darkness; the addition of cycloheximide prevented this decrease. Treatments that increased tissue permeability (anoxia, Triton X-100) also increased NR activity. There was in general less NR activity in the light than in the dark and also less under aerobic (21–100% O2) than under anaerobic (0.3% O2) conditions. Treatments with antioxidants improved the activity in the light, but only at high O2 levels (21–100% O2). The results suggest that NR may be regulated by inhibitory proteins synthesized in either light or darkness, by permeability changes and by light-induced oxidations that occur when O2 is present. Oxygen may control the activity by stimulating the synthesis of inhibitory proteins in the light and in the dark and by promoting oxidation of SH-groups in the light. |
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Keywords: | Aerobic photooxidation Avena sativa inhibitory proteins permeability changes |
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