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Park Y.H.,Korea Greenhouse Crop Research Institute | Seo B.S.,Korea Greenhouse Crop Research Institute
Horticulture Environment and Biotechnology | Year: 2012

In this study, addition of ascorbic acid (AsA) to a reconstituted system composed of nitrite reductase (NiR) and ferredoxin (Fd) proteins could reduce nitrite at a rate nearly equal to that is obtainable with the NADPH-FNRFd-NiR system. The addition of spinach (Spinacia oleracea L. 'Birohurei') leaf extract (LES) enabled acceleration of nitrite reduction in the former system but not in the latter system. In the AsA-Fd-NiR-LES system, switching the incubation atmosphere from air to N2 gas also accelerated nitrite reduction. We added 15N-labeled nitrite to the system and examined the formation of ammonia by using a 15N-tracing technique. At pH 6.5, we observed quantitative recovery of 15N-labeled ammonia in reference with nitrite reduction, but ammonia loss was apparent in the assay at pH 7.5. © 2012 Korean Society for Horticultural Science. Source


Park Y.H.,Korea Greenhouse Crop Research Institute | Seo B.S.,Korea Greenhouse Crop Research Institute
Horticulture Environment and Biotechnology | Year: 2011

For verification that ascorbic acid can affect on the process of nitrite reduction, reduced form of ascorbic acid (AsA) dissolved in the pH 7.5 buffer solution was added and vacuum-infiltrated into spinach (Spinacia oleracea L.) leaf sections. The endogenous nitrite was reduced in accordance with AsA oxidation by the higher rate with addition of AsA than that without it. In addition, when 15N-labelled nitrite was added to the leaf sections together with AsA, higher 15N contents were found in ammonia and the reduced soluble form of N (ammonia and amino acids) within short periods in the leaf sections treated with AsA than without it. The crude enzymes in the leaf extract from spinach leaves could reduce nitrate to nitrite in the presence of AsA but the rate was less than that in the presence of NADH. Formation of nitric oxide from nitrite by nitrate reductase in leaf extract in the presence of AsA (at pH 7. 5) was estimated to be insignificant. Addition of AsA and (Fd) ferredoxin to the leaf extract could reduce nitrite at higher rate than that of NADPH(Nicotinamide Adenine Dinucleotide Phospate)-FNR(Ferredoxin NADP+ Reductase) -Fd system. These results suggest the possible electron donation from AsA to nitrite reduction via Fd in the dark. © 2011 Korean Society for Horticultural Science. Source

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