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Effect of hydrogen peroxide on nitrate reductase activity in detached oat leaves in darkness
Author(s) -
Kenis J. D.,
Morlans J. D.,
Trippi V. S.
Publication year - 1989
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1989.tb05635.x
Subject(s) - avena , nitrate reductase , catalase , hydrogen peroxide , chemistry , in vivo , glutathione reductase , glutathione , peroxidase , antioxidant , biochemistry , cysteine , enzyme , enzyme assay , darkness , metabolism , reductase , glutathione peroxidase , botany , biology , microbiology and biotechnology
Nitrate reductase (NR, EC 1.6.6.1) is sensitive to O 2 concentration, and therefore it was of interest to study the action of H 2 O 2 , a normal substance in plant metabolism, on NR activity in segments of 7‐, 14‐ and 17‐day‐old leaves of oat ( Avena sativa L. ev. Suregrain). After 4 h of treatment in the dark, H 2 O 2 decreased NR activity as measured with the in vivo assay. The effect was stronger in 14‐ and 17‐ than in 7‐day‐old leaves. Vacuum infiltration of cysteine did not prevent this decrease. When NR was determined with the in vitro assay, H 2 O 2 did not seem to affect the activity after the 4 h treatment. but NR decreased when crude extracts prepared from untreated 14‐day‐old leaves were incubated directly with H 2 O 2 . This effect was prevented by addition of cysteine, ascorbate or reduced glutathione to the extracts. In order to study the possibility that low activity of the system for defense against oxidations could account for the age‐dependent response of NR to H 2 O 2 in the in vivo test, activities of catalase, ascorbate peroxidase and glutathione reductase were measured during leaf development and after a 4‐h treatment with H 2 O 2 in the dark. No clear correlation was found between the activities of those enzymes and changes in in vivo NR activity caused by H 2 O 2 . The results suggest that H 2 O 2 might affect NR both directly by oxidizing SH‐groups and indirectly by decreasing reductant availability as a result of NADH oxidation. The age‐dependent response of NR to H 2 O 2 treatment could also be explained in terms of decreased NADH availability in the tissues due to decreased NADH synthesis and/or increased degradation.