CO2 impairs peroxynitrite-mediated inhibition of human caspase-3

Paolo Ascenzi, Maria Marino, Enea Menegatti

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Peroxynitrite (ONOO-) is a transient powerful oxidant produced in vivo as the reaction of nitrogen monoxide ({radical dot}NO) with superoxide (O2 {radical dot} -). The peroxynitrite reactivity is modulated by carbon dioxide (CO2) which enhances the peroxynitrite-mediated nitration of aromatics and partially impairs the oxidation of thiols. Here, the effect of CO2 on the peroxynitrite-mediated inhibition of human caspase-3, the execution enzyme of the apoptotic cascade, is reported. Peroxynitrite inhibits the catalytic activity of human caspase-3 by oxidizing the Sγ atom of the Cys catalytic residue. In the absence of CO2, 1.0 equivalent of peroxynitrite inactivates 1.0 equivalent of human caspase-3. In the presence of the physiological concentration of CO2 (=1.3 × 10-3 M), 1.0 equivalent of peroxynitrite inactivates only 0.38 equivalents of human caspase-3. Peroxynitrite affects the kcat value of the human caspase-3 catalyzed hydrolysis of N-acetyl-Asp-Glu-Val-Asp-7-amido-4-methylcoumarin, without altering Km. Both in the absence and presence of CO2, the reducing agent dithiothreitol does not prevent human caspase-3 inhibition by peroxynitrite and does not reverse the peroxynitrite-induced inactivation of human caspase-3. These results represent the first evidence for modulation of peroxynitrite-mediated inhibition of cysteine proteinase action by CO2, supporting the role of CO2 in fine tuning of cell processes (e.g., apoptosis).

Original languageEnglish
Pages (from-to)367-371
Number of pages5
JournalBiochemical and Biophysical Research Communications
Issue number1
Publication statusPublished - Oct 13 2006


  • Carbon dioxide
  • Cysteine proteinase
  • Enzyme inhibition
  • Human caspase-3
  • Peroxynitrite

ASJC Scopus subject areas

  • Biochemistry
  • Biophysics
  • Molecular Biology


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