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4-hydroxynonenal inhibits Na(+)-K(+)-ATPase
W G Siems1, S J Hapner, F J van Kuijk
1Department of Chemistry and Biochemistry, Montana State University, Bozeman 59717, USA.
Free Radical Biology & Medicine
|January 1, 1996
Summary
4-Hydroxynonenal (HNE) irreversibly inhibits Na(+)-K(+)-ATPase by binding to sulfhydryl groups, leading to significant enzyme activity loss. Recovery is limited, suggesting HNE adducts form at inaccessible sites or with other amino acids.
Area of Science:
- Biochemistry
- Enzymology
- Cellular Biology
Background:
- Na(+)-K(+)-ATPase is a crucial ion pump involved in maintaining cellular homeostasis.
- Oxidative stress generates reactive aldehydes like 4-hydroxynonenal (HNE).
- HNE is known to modify proteins, potentially affecting enzyme function.
Purpose of the Study:
- To investigate the interaction between 4-hydroxynonenal (HNE) and Na(+)-K(+)-ATPase.
- To determine the impact of HNE binding on enzyme activity and structure.
- To explore the reversibility of HNE-induced inhibition.
Main Methods:
- Enzyme inhibition assays measuring Na(+)-K(+)-ATPase activity.
- Quantification of sulfhydryl groups.
- Treatment with reducing agents (beta-mercaptoethanol, hydroxylamine) to assess reversibility.
Main Results:
- 4-Hydroxynonenal (HNE) rapidly binds to Na(+)-K(+)-ATPase, decreasing sulfhydryl groups and enzyme activity (I50 = 120 microM).
- While beta-mercaptoethanol partially restored activity, a combination with hydroxylamine achieved 85% recovery, indicating significant irreversible inhibition.
- Evidence suggests HNE adducts form at beta-mercaptoethanol-inaccessible sites and with other amino acids like lysine.
Conclusions:
- 4-Hydroxynonenal binding causes irreversible inhibition of Na(+)-K(+)-ATPase.
- HNE modification of critical sulfhydryl groups and potentially lysine residues underlies the functional impairment.
- These findings highlight HNE as a potent inhibitor of Na(+)-K(+)-ATPase, with implications for cellular function during oxidative stress.