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Inactivation of cellular caspases by peptide-derived tryptophan and tyrosine peroxides
Mark B Hampton1, Philip E Morgan, Michael J Davies
1Free Radical Research Group, Department of Pathology, Christchurch School of Medicine and Health Sciences, Christchurch, New Zealand.
Abstract:
Peroxides generated on peptides and proteins within cells, as a result of radical attack or reaction with singlet oxygen, are longer-lived than H(2)O(2) due to their poor removal by protective enzymes. These peroxides readily oxidize cysteine residues and can inactivate thiol-dependent enzymes. We show here that Trp- and Tyr-derived peptide peroxides, generated by singlet oxygen, inhibit caspase activity in the lysates of apoptotic Jurkat cells. N-Ac-Trp-OMe peroxide was the most effective inhibitor, and was 30-fold more effective than H(2)O(2) under identical conditions. As such, protein peroxides could modulate the progression of apoptosis in cells in which they are generated.