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Oxidative resistance of Na/K-ATPase
E G Kurella1, O V Tyulina, A A Boldyrev
1Laboratory of Clinical Neurochemistry, Institute of Neurology, Russian Academy of Medical Sciences, Moscow, Russia.
Cellular and Molecular Neurobiology
|March 18, 1999
Summary
Brain Na/K-ATPase is more susceptible to oxidative damage than kidney enzyme, with SH groups crucial for activity. Antioxidants protect the enzyme by neutralizing harmful radicals.
Area of Science:
- Biochemistry
- Neuroscience
- Physiology
Background:
- Na/K-ATPase (sodium-potassium adenosine triphosphatase) is a vital membrane protein responsible for maintaining electrochemical gradients.
- Oxidative stress can impair enzyme function, impacting cellular homeostasis.
- Isozymes of Na/K-ATPase may exhibit differential susceptibility to oxidative modification.
Purpose of the Study:
- To investigate the differential sensitivity of brain and kidney Na/K-ATPase to oxidative modification.
- To elucidate the role of sulfhydryl (SH) groups in Na/K-ATPase activity and oxidative stability.
- To evaluate the protective effects of various antioxidants against Na/K-ATPase oxidation.
Main Methods:
- Enzymatic assays to measure Na/K-ATPase activity.
- Exposure of enzyme preparations to oxidants like hydrogen peroxide (H2O2) and sodium hypochlorite (NaOCl).
- Quantification of sulfhydryl (SH) group content.
- Assessment of antioxidant protection using carnosine, alpha-tocopherol, ionol, and deferoxamine.
Main Results:
- Brain Na/K-ATPase demonstrated greater sensitivity to H2O2 and NaOCl inhibition compared to kidney Na/K-ATPase.
- Enzyme inhibition correlated with a reduction in SH groups, indicating their essential role in maintaining ATPase activity.
- Carnosine, alpha-tocopherol, ionol, and deferoxamine conferred protection to Na/K-ATPase against H2O2-induced oxidation.
- Antioxidant efficacy is attributed to their ability to scavenge or prevent the formation of hydroxyl radicals.
Conclusions:
- Isoform-specific differences in SH group number, location, or accessibility likely dictate the oxidative stability of Na/K-ATPase.
- Sulfhydryl groups are critical for the catalytic activity of Na/K-ATPase.
- Natural and synthetic antioxidants can protect Na/K-ATPase from oxidative damage, suggesting a therapeutic potential in conditions involving oxidative stress.