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

FEBS Letters

Winterbourn, Christine C²  Hampton, Mark B²  Stamenkovic, Ivan¹ 

[1] Molecular Pathology Unit, Massachusetts General Hospital and Department of Pathology, Harvard Medical School, Cambridge, MA, USA;Free Radical Research Group, Christchurch School of Medicine and Health Sciences, P.O. Box 4345, Christchurch, New Zealand

关键词: Thiol;    Cysteine;    Hydrogen peroxide;    Oxidation;    Caspase;    Apoptosis;    AMC;    7-amino-4-methylcoumarin;    DTT;    dithiothreitol;   

DOI  :  10.1016/S0014-5793(02)02629-7

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

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.

【 授权许可】

Unknown