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Interaction with substrate sensitises caspase‐3 to inactivation by hydrogen peroxide
Author(s) -
Hampton Mark B,
Stamenkovic Ivan,
Winterbourn Christine C
Publication year - 2002
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(02)02629-7
Subject(s) - hydrogen peroxide , cysteine , substrate (aquarium) , chemistry , caspase , recombinant dna , enzyme , peptide , apoptosis , thiol , caspase 3 , biochemistry , ic50 , biophysics , microbiology and biotechnology , in vitro , biology , programmed cell death , ecology , gene
Caspases have an active site cysteine whose oxidation blocks catalytic activity. Caspase activity, measured in lysates of apoptotic cells, was inhibited by H 2 O 2 with an IC 50 of 7 μM. Recombinant caspase‐3 was directly inhibited by H 2 O 2 , with an estimated second‐order rate constant of 750 M −1 s −1 . These values were determined when H 2 O 2 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 H 2 O 2 addition. These results rationalise conflicting reports of the sensitivity of caspase‐3 to H 2 O 2 , and identify a novel mechanism for sensitising a thiol enzyme to oxidative inactivation.