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Superoxide dismutases: I. Occurrence in higher plants.
1Department of Horticulture, Michigan State University, East Lansing, Michigan 48824.
Plant Physiology
|February 1, 1977
Summary
Superoxide dismutase, an important antioxidant enzyme, was found in corn, oats, and peas. This study identified multiple forms of the enzyme and their distribution within plant tissues.
Area of Science:
- Plant biochemistry
- Enzymology
- Antioxidant defense mechanisms
Background:
- Superoxide dismutase (SOD) is a crucial antioxidant enzyme that catalyzes the dismutation of superoxide radicals into oxygen and hydrogen peroxide.
- Understanding SOD distribution and forms in different plant species is vital for comprehending oxidative stress responses.
Purpose of the Study:
- To quantify and characterize superoxide dismutase (SOD) content in shoots, roots, and seeds of corn, oats, and peas.
- To investigate the different molecular forms of SOD present in these plant species.
- To determine the cellular localization and potential metal cofactor of identified SOD forms.
Main Methods:
- A photochemical assay using methionine, riboflavin, and p-nitro blue tetrazolium was employed to measure SOD activity.
- Electrophoresis was used to separate and identify distinct SOD isoenzymes.
- Cyanide treatment was utilized to differentiate between potential cupro-zinc and manganese SOD forms.
- Cellular fractionation was performed to determine the localization of SOD in mitochondria and chloroplasts.
Main Results:
- Superoxide dismutase (SOD) activity was detected in shoots, roots, and seeds across all three species (corn, oats, peas).
- Shoots exhibited higher SOD content per dry weight compared to roots.
- Electrophoresis revealed 10 distinct SOD forms; corn had seven, oats had three, and peas possessed one corn-specific and two oat-specific forms.
- Nine SOD activities were sensitive to cyanide, suggesting a cupro-zinc nature, while one form was cyanide-resistant, indicative of a manganese enzyme.
- Some leaf SODs were localized in mitochondria or chloroplasts, and peroxidases could interfere with gel-based assays.
Conclusions:
- Superoxide dismutase (SOD) is ubiquitously present in vegetative and reproductive tissues of corn, oats, and peas.
- Significant variation exists in the number and types of SOD isoenzymes among these cereal and legume species.
- The presence of both cyanide-sensitive (cupro-zinc) and cyanide-resistant (manganese) SOD forms highlights diverse roles in antioxidant defense.
- Subcellular localization studies indicate specific compartmentalization of SOD activity within plant cells, particularly in organelles involved in energy metabolism and photosynthesis.