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Effect of peroxynitrite on glutaredoxin
G Aykaç-Toker1, S Bulgurcuoğlu, N Koçak-Toker
1Department of Biochemistry, Istanbul Faculty of Medicine, Istanbul University, Turkey.
Human & Experimental Toxicology
|September 4, 2001
Summary
Peroxynitrite (ONOO-) inactivates glutaredoxin, an enzyme crucial for thiol homeostasis, in a non-reversible manner. However, overall dehydroascorbate reductase (DHAR) activity, including other enzymes, can be restored by dithiothreitol (DTT).
Area of Science:
- Biochemistry
- Enzymology
- Oxidative Stress
Background:
- Glutaredoxin maintains thiol homeostasis by reducing oxidized thiols.
- Glutaredoxin also possesses dehydroascorbate reductase (DHAR) activity.
- Peroxynitrite (ONOO-) is a reactive nitrogen species implicated in oxidative stress.
Purpose of the Study:
- To investigate the impact of peroxynitrite (ONOO-) on glutaredoxin's thioltransferase activity.
- To examine the effect of peroxynitrite (ONOO-) on the overall dehydroascorbate reductase (DHAR) activity in rat liver cytosol.
Main Methods:
- Incubation of rat liver cytosolic fractions with varying concentrations of peroxynitrite (0-250 microM).
- Assay of thioltransferase activity.
- Assay of dehydroascorbate reductase (DHAR) activity.
- Assessment of reversibility of inhibition using dithiothreitol (DTT).
Main Results:
- Peroxynitrite (ONOO-) significantly decreased glutaredoxin's thioltransferase activity in a dose-dependent manner.
- The inhibition of thioltransferase activity by peroxynitrite was irreversible by dithiothreitol (DTT).
- Overall cytosolic DHAR activity was inhibited by peroxynitrite, but this inhibition was largely reversible with dithiothreitol (DTT).
Conclusions:
- Peroxynitrite (ONOO-) causes irreversible inactivation of glutaredoxin's thioltransferase function.
- While glutaredoxin is irreversibly affected, the broader DHAR activity in the cytosol shows partial recovery, suggesting other DHAR enzymes are less sensitive or protected.
- These findings highlight the differential susceptibility of enzymes involved in redox homeostasis to reactive nitrogen species.