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Inhibition of 2-oxoglutarate oxidation in plant mitochondria by pyruvate
Abstract:
Oxidation of 2-oxoglutarate (in the presence of malonate) by mitochondria isolated from turnip, pea leaf and cauliflower tissue was dramatically inhibited by micromolar concentrations of pyruvate. Pyruvate, however, had little or no effect on 2-OG oxidation when carried out in the absence of malonate. The inhibition was reversed by alpha-cyano-4-hydroxycinnamic acid, indicating pyruvate uptake into the matrix was required for the inhibitory effect. In contrast, pyruvate had no effect on 2-oxoglutarate oxidation by mitochondria isolated from rat heart. The possible significance of the effect in terms of the control of 2-oxoglutarate dehydrogenase activity during the operation of a malate/aspartate shuttle in plant mitochondria is discussed.
Insights
Pyruvate significantly inhibits 2-oxoglutarate oxidation in plant mitochondria, but not in rat heart mitochondria. This inhibition requires pyruvate uptake and suggests a role in regulating plant mitochondrial metabolism.
Area of Science:
- Biochemistry
- Plant Physiology
- Mitochondrial Respiration
Background:
- Mitochondria are crucial for cellular energy production.
- 2-oxoglutarate oxidation is a key step in the citric acid cycle.
- Regulation of mitochondrial enzymes is vital for metabolic control.
Purpose of the Study:
- To investigate the effect of pyruvate on 2-oxoglutarate oxidation in plant mitochondria.
- To compare the response of plant and animal mitochondria to pyruvate.
- To explore the regulatory role of pyruvate in plant mitochondrial function.
Main Methods:
- Isolation of mitochondria from turnip, pea leaf, and cauliflower.
- Measurement of 2-oxoglutarate oxidation in the presence and absence of malonate.
- Assessment of pyruvate's effect on oxidation rates.
- Use of alpha-cyano-4-hydroxycinnamic acid to investigate pyruvate transport.
Main Results:
- Micromolar pyruvate concentrations dramatically inhibited 2-oxoglutarate oxidation in plant mitochondria when malonate was present.
- Pyruvate had minimal effect on 2-oxoglutarate oxidation without malonate in plant mitochondria.
- The inhibitory effect of pyruvate in plant mitochondria was reversed by alpha-cyano-4-hydroxycinnamic acid, indicating matrix uptake.
- Pyruvate did not affect 2-oxoglutarate oxidation in rat heart mitochondria.
Conclusions:
- Pyruvate plays a regulatory role in 2-oxoglutarate dehydrogenase activity in plant mitochondria.
- Pyruvate uptake into the mitochondrial matrix is essential for this regulatory effect.
- The observed inhibition is specific to plant mitochondria and may be linked to the malate/aspartate shuttle operation.
- These findings highlight differences in mitochondrial metabolic regulation between plants and animals.