Interaction with substrate sensitises caspase-3 to inactivation by hydrogen peroxide
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Updated: Sep 1, 2026

Caspase-3 Activity in the Rat Amygdala Measured by Spectrofluorometry After Myocardial Infarction
Published on: January 12, 2016
Mark B Hampton1, Ivan Stamenkovic, Christine C Winterbourn
1Free Radical Research Group, Christchurch School of Medicine and Health Sciences, Christchurch, New Zealand. mark.hampton@chmeds.ac.nz
Abstract:
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 microM. 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.
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