Oxidation of active center cysteine of bovine 1-Cys peroxiredoxin to the cysteine sulfenic acid form by peroxide and peroxynitrite

Peroxiredoxins are antioxidant enzymes whose peroxidase activity depends on a redox-sensitive cysteine residue at the active center. In this study we investigated properties of the active center cysteine, of bovine 1-Cys pero xiredoxin using a recombinant protein (BRPrx). The only cysteine residue of the BRPrx molecule was oxidized rapidly by an equimolar peroxide or peroxy nitrite to the cysteine sulfenic acid. Approximate rates of oxidation of BR Prx by different peroxides were estimated using selenium glutathione peroxi dase as a competitor. Oxidation of the active center cysteine of BRPrx by H 2O2 proceeded only several times slowly than that of the selenocysteine, of glutathione peroxidase. The rate of oxidation varied depending on peroxide s tested, with H2O2 being about 7 and 80 times faster than tert-butyl hydro peroxide and cumene hydroperoxide, respectively. Peroxynitrite oxidized BRP rx slower than H2O2 but faster than tert-butyl hydroperoxide. Further oxida tion of the cysteine sulfenic acid of BRPrx to higher oxidation states proc eeded slowly. Oxidized BRPrx was reduced by dithiothreitol, dihydrolipoic a cid, and hydrogen sulfide, and demonstrated peroxidase, activity (about 30 nmol/mg/min) with these reductants as electron donors. beta -Mercaptoethano l formed a mixed disulfide, and did not support peroxidase activity. Oxidiz ed BRPrx did not react with glutathione, cysteine, homocysteine, N-acetyl-c ysteine, and mercaptosuccinic acid. (C) 2001 Elsevier Science Inc.