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A Rapid and Specific Microplate Assay for the Determination of Intra- and Extracellular Ascorbate in Cultured Cells
Published on: April 11, 2014
Effectiveness of ascorbate and ascorbate peroxidase in promoting nitrogen fixation in model systems
E J Ross1, S B Kramer, D A Dalton
1Biology Department, Reed College, Portland, OR 97202, USA.
Phytochemistry
|January 27, 2000
Summary
Ascorbate and ascorbate peroxidase significantly boost nitrogenase activity in legume root nodules. These antioxidants protect vital oxygen-binding proteins, enhancing nitrogen fixation for improved plant growth.
Area of Science:
- Biochemistry
- Plant Science
- Microbiology
Background:
- Ascorbate and ascorbate peroxidase are key antioxidants in legume root nodules.
- Leghemoglobin's high concentration in nodules makes it susceptible to autoxidation and reactive oxygen species (ROS) production.
- Maintaining a favorable environment for nitrogen fixation is crucial for legume health.
Purpose of the Study:
- To investigate the role of ascorbate and ascorbate peroxidase in supporting nitrogen (N2) fixation.
- To evaluate the impact of these antioxidants on oxygen-binding proteins and nitrogenase activity in model systems.
Main Methods:
- Used model systems with oxygen-binding proteins (myoglobin, leghemoglobin) and N2-fixing microorganisms (Azorhizobium, Bradyrhizobium japonicum bacteroids).
- Assessed the effects of adding ascorbate and ascorbate peroxidase on hemeprotein oxygenation and nitrogenase activity (acetylene reduction).
- Determined optimal concentrations for ascorbate and ascorbate peroxidase.
Main Results:
- Ascorbate alone enhanced hemeprotein oxygenation and nitrogenase activity.
- Combined ascorbate and ascorbate peroxidase increased nitrogenase activity up to 4.5-fold.
- Superoxide dismutase showed no benefit; catalase provided minimal benefit.
- Optimal concentrations were 2 mM ascorbate and 200 µg/ml ascorbate peroxidase.
Conclusions:
- Ascorbate and ascorbate peroxidase are beneficial for maintaining conditions favorable for N2 fixation in legume nodules.
- These antioxidants protect against oxidative damage, supporting nitrogenase function.
- The findings support the endogenous role of ascorbate and ascorbate peroxidase in nodule physiology.
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