ATP protects against free radical induced inhibition of the cardiac Na+,K+-ATPase

Kai Y. Xu, Perianoan Kuppusamy, Jay L. Zweier, Lewis C.becker

Research output: Contribution to journalArticlepeer-review


It has been reported that highly reactive oxygen free radicals may play a crucial role in sarcolemmal injury following ischemia/reperfusion, and cause irreversible inhibition of Na+,K+-ATPase activity. To determine whether the ATP binding site of the cardiac Na+K+-ATPase is directly Involved in oxygen radical injury, purified rat cardiac Na+,K+-ATPase was exposed to the hydroxyl radical (OH) generated from 80 μM Fe3+-NTA and l mM H2O2 under various conditions. Exposure of Na+,K+-ATPase to OH for 20 min at 25 °C caused a 79% decrease in Na+,K+-ATPase activity. SDS-gel electrophoresis indicated that OH did not damage the primary structure of the enzyme. When Na+,K+-ATPase was premixed with 1 mM ATP before exposure to -OH, complete protection was observed: there was no loss of enzymatic activity. No inhibition was seen when purified Na+,K+-ATPase was exposed to 1 mM H2O2 or 80 μM Fe3+-NTA by themselves. EPR spectroscopy demonstrated that ATP did not scavenge OH. These results suggest that: 1} OH denatures the cardiac sarcolemmal Na+,K+-ATPase by directly attacking the ATP binding site; 2) occupation of the ATP binding site of the enzyme protects against -OH induced loss of enzymatic activity, and 3) the depletion of ATP that occurs during ischemia may enhance the toxic effect of OH formed at the time of reperfusion.

Original languageEnglish (US)
JournalFASEB Journal
Issue number3
StatePublished - 1996

ASJC Scopus subject areas

  • Agricultural and Biological Sciences (miscellaneous)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Biochemistry
  • Cell Biology


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