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Superoxide and peroxynitrite inactivate aconitases, but nitric oxide does not
1Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710.
The Journal of Biological Chemistry
|November 25, 1994
Summary
Superoxide inactivates aconitase enzymes, while nitric oxide does not directly. Peroxynitrite, formed from superoxide and nitric oxide, rapidly inactivates aconitase, suggesting it mediates NO effects in vivo.
Area of Science:
- Biochemistry
- Enzymology
- Oxidative Stress
Background:
- Aconitase is a key enzyme in the citric acid cycle.
- Aconitase is sensitive to oxidative damage.
- Nitric oxide (NO) has been implicated in aconitase inactivation in vivo.
Purpose of the Study:
- To investigate the direct inactivation of aconitase by superoxide (O2-.) and nitric oxide (NO).
- To determine the role of peroxynitrite in aconitase inactivation.
Main Methods:
- Enzyme kinetics assays were used to measure the inactivation rates of Escherichia coli, human cytosolic, and porcine mitochondrial aconitases.
- Enzymes were incubated with superoxide, nitric oxide, and peroxynitrite under controlled conditions.
Main Results:
- Superoxide rapidly inactivated both cytosolic and mitochondrial aconitases.
- Nitric oxide did not significantly inactivate aconitase at perceptible rates.
- Peroxynitrite caused rapid loss of aconitase activity.
Conclusions:
- Superoxide is a direct inactivator of aconitase.
- The reported in vivo inactivation of aconitase by nitric oxide is likely mediated by peroxynitrite, a reaction product of superoxide and NO.