Sources of reducing power for nitrate reduction in spinach leaves
A F Mann1, D P Hucklesby, E J Hewitt
1Long Ashton Research Station, Long Ashton, BS18 9AF, Bristol, UK.
Planta
|January 14, 2014
Summary
Spinach leaves generate NADH, the energy source for nitrate reductase, through glycolysis and the pentose phosphate pathway. Malate and isocitrate also contribute to NADH production in this in vivo study.
Area of Science:
- Plant Physiology
- Biochemistry
- Enzyme Activity
Background:
- Nitrate reductase is a key enzyme in plant nitrogen metabolism.
- Understanding the source of its energy donor, NADH, is crucial for plant physiology.
- Previous studies have not fully elucidated the in vivo pathways supplying NADH to nitrate reductase in spinach.
Purpose of the Study:
- To investigate the in vivo sources of NADH for nitrate reductase in Spinach (Spinacea oleracea L.).
- To identify specific metabolic pathways and organic acids that contribute to NADH generation for this enzyme.
Main Methods:
- Utilized an in vivo assay with frozen spinach leaves to increase tissue permeability to substrates.
- Assessed NADH generation from various metabolic pathways, including glycolysis and the pentose phosphate pathway.
- Tested the effect of different organic acids (malate, isocitrate, glycolate) on NADH production.
Main Results:
- Glycolysis and the pentose phosphate pathway were confirmed as significant sources of NADH via glyceraldehyde-3-phosphate dehydrogenase.
- Malate and isocitrate were identified as effective organic acid substrates for NADH generation.
- Glycolate proved ineffective in generating NADH, even under anaerobic conditions.
Conclusions:
- The study identifies key metabolic routes supplying NADH for nitrate reductase in spinach.
- Confirms the role of glycolysis, pentose phosphate pathway, malate, and isocitrate in NADH production.
- Highlights the importance of specific substrates for enzyme function in plant metabolism.
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