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Effects of Electrophilic Modification on the Activity of Thioredoxin Peroxidase 1 from Saccharomyces cerevisiae

Organisms have evolved a variety of defense mechanisms to deal with adverse environmental challenges, including exposure to reactive oxidants and organic electrophiles. In Saccharomyces cerevisiae, one of the proteins involved in defense against oxidants is the peroxide‐detoxifying enzyme, thioredoxin peroxidase 1 (Tsa1p). Tsa1p possesses a highly reactive cysteine residue in its active site that reacts directly with peroxides, undergoing oxidation in the process. Here, we report that Tsa1p provides cellular protection against organic electrophiles as well as oxidants, as TSA1 deletion mutants have reduced survival when treated with toxic doses of the electrophilic thiol cross‐linker diethyl acetylenedicarboxylate (DAD). In addition, we have determined that Tsa1p is modified by DAD in vitro and in vivo, undergoing cross‐linking to itself and other proteins. Using a coupled peroxidase activity assay, we found that DAD inhibits the ability of recombinant Tsa1p to degrade hydrogen peroxide. Collectively, these results suggest that Tsa1p potentially functions in other capacities besides its peroxidase activity to mediate cellular protection against electrophiles