Interaction with substrate sensitises caspase-3 to inactivation by hydrogen peroxide

Mark B. Hampton, Ivan Stamenkovic, Christine C. Winterbourn

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Caspases have an active site cysteine whose oxidation blocks catalytic activity. Caspase activity, measured in lysates of apoptotic cells, was inhibited by H2O2 with an IC50 of 7 μM. Recombinant caspase-3 was directly inhibited by H2O2, with an estimated second-order rate constant of 750 M-1 s-1. These values were determined when H2O2 was added while the caspases were cleaving a peptide substrate. There was a 40-fold decrease in sensitivity to inactivation if the substrate was absent at the time of H2O2 addition. These results rationalise conflicting reports of the sensitivity of caspase-3 to H2O2, and identify a novel mechanism for sensitising a thiol enzyme to oxidative inactivation.

Original languageEnglish
Pages (from-to)229-232
Number of pages4
JournalFEBS Letters
Issue number1-3
StatePublished - 24 Apr 2002
Externally publishedYes


  • Apoptosis
  • Caspase
  • Cysteine
  • Hydrogen peroxide
  • Oxidation
  • Thiol


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