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Effect of membrane environment on succinate dehydrogenase activity
The Journal of Biological Chemistry
|March 10, 1977
Summary
Succinate dehydrogenase activity is highest in intact mitochondria, decreasing when the enzyme is detached from the membrane. Reintegration with the membrane restores and enhances enzyme function, highlighting the membrane's crucial role.
Area of Science:
- Biochemistry
- Enzyme kinetics
- Mitochondrial respiration
Background:
- Succinate dehydrogenase (SDH) is a key enzyme in the mitochondrial electron transport chain.
- Its activity is influenced by its membrane-bound state and potential interactions with other components.
Purpose of the Study:
- To investigate the effect of membrane association on the catalytic activity and kinetic properties of mammalian heart succinate dehydrogenase.
- To determine the role of the membrane environment in modulating SDH function.
Main Methods:
- Spectrophotometric assays using phenazine methosulfate (PMS) and ferricyanide.
- Enzyme extraction and reconstitution experiments.
- Determination of turnover numbers and Michaelis constants (Km).
Main Results:
- Intact mitochondria and inner membrane preparations show a high turnover number (~21,000).
- Soluble, detached SDH exhibits reduced turnover numbers (11,500-14,500) and altered Km for PMS.
- Recombination with the membrane restores and increases total enzyme activity by over 60%.
Conclusions:
- The membrane environment positively modulates succinate dehydrogenase activity, even in its fully activated state.
- Loss of membrane association or components leads to decreased enzyme efficiency.
- SDH function is optimized within its native membrane context.