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Updated: Aug 8, 2026
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Simultaneous Measurement of Superoxide/Hydrogen Peroxide and NADH Production by Flavin-containing Mitochondrial Dehydrogenases
Published on: February 24, 2018
Characteristics of External NADH Oxidation by Beetroot Mitochondria
D A Day1, J R Rayner, J T Wiskich
1Department of Botany, University of Adelaide, Adelaide, S.A. 5001, Australia.
Plant Physiology
|July 1, 1976
Summary
Mitochondria from fresh red beetroot (Beta vulgaris L.) lack external NADH oxidation. This activity develops with tissue aging, suggesting a role for aged beetroot mitochondria in specific metabolic pathways.
Area of Science:
- Plant Physiology
- Mitochondrial Respiration
- Biochemistry
Background:
- Mitochondria are key organelles for cellular respiration.
- Plant mitochondria exhibit diverse respiratory pathways.
- Red beetroot (Beta vulgaris L.) mitochondria have unique characteristics.
Purpose of the Study:
- To investigate the NADH oxidation capabilities of red beetroot mitochondria.
- To identify the mechanisms of external NADH oxidation in plant mitochondria.
- To understand the changes in mitochondrial function during tissue aging.
Main Methods:
- Isolation of mitochondria from fresh and aged red beetroot tissue.
- Assays for NADH oxidation with different electron acceptors (O2, cytochrome c, potassium ferricyanide).
- Enzyme activity measurements and inhibitor sensitivity analysis (rotenone, antimycin).
- Investigation of internal and external NADH oxidation pathways.
- Analysis of malate-oxaloacetate shuttle system and oxaloacetate transport.
Main Results:
- Fresh red beetroot mitochondria do not oxidize external NADH with O2.
- A rotenone- and antimycin-insensitive NADH oxidation pathway exists on the outer membrane, reducing cytochrome c or potassium ferricyanide.
- Internal NADH oxidation occurs via the inner membrane electron transport chain with normal sensitivity.
- A malate-oxaloacetate shuttle system facilitates external NADH oxidation in fresh mitochondria.
- The capacity for external NADH oxidation develops during tissue aging.
Conclusions:
- Red beetroot mitochondria lack the typical outer surface NADH dehydrogenase found in other plant mitochondria.
- A functional malate-oxaloacetate shuttle system and rapid oxaloacetate transport are present in fresh beetroot mitochondria.
- Tissue aging induces changes in beetroot mitochondrial respiration, enabling external NADH oxidation.
- These findings highlight the plasticity of plant mitochondrial function in response to environmental cues.
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