Modulation of lysozyme function and degradation after nitration with peroxynitrite

Tiana V. Curry-McCoy, Natalia A. Osna, Terrence M. Donohue

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


Background: Peroxynitrite (PN) is formed from superoxide and nitric oxide, both of which are increased during hepatic ethanol metabolism. Peroxynitrite forms adducts with proteins, causing structural and functional alterations. Here, we investigated PN-induced alterations in lysozyme structure and function, and whether they altered the protein's susceptibility to proteasome-catalyzed degradation. Methods: Hen egg lysozyme was nitrated using varying amounts of either PN or the PN donor, 3-morpholinosydnonimine (SIN-1). The activity, nitration status and the susceptibility of lysozyme to proteasome-catalyzed degradation were assessed. Results: Lysozyme nitration by PN or SIN-1 caused dose-dependent formation of 3-nitrotyrosine-lysozyme adducts, causing decreased catalytic activity, and enhanced susceptibility to degradation by the 20S proteasome. Kinetic analyses revealed an increased affinity by the 20S proteasome toward nitrated lysozyme compared with the native protein. Conclusion: Lysozyme nitration enhances the affinity of the modified enzyme for degradation by the proteasome, thereby increasing its susceptibility to proteolysis. General significance: Increased levels of peroxynitrite have been detected in tissues of ethanol-fed animals. The damaging effects from excessive peroxynitrite in the cell increase hepatotoxicity and cellular death by protein modification due to nitration. Cellular defenses against such changes include enhanced proteolysis by the proteasome in order to maintain protein quality control.

Original languageEnglish (US)
Pages (from-to)778-786
Number of pages9
JournalBiochimica et Biophysica Acta - General Subjects
Issue number8
StatePublished - Aug 2009
Externally publishedYes


  • 20S proteasome
  • Ethanol
  • Kinetics
  • Lysozyme
  • Oxidative stress
  • Peroxynitrite

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology


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