Tryparedoxin peroxidases from Trypanosoma cruzi: High efficiency in the catalytic elimination of hydrogen peroxide and peroxynitrite

• Published in: Archives of biochemistry and biophysics 2011-03, Vol.507 (2), p.287-295
• Main Authors: Piñeyro, María Dolores, Arcari, Talia, Robello, Carlos, Radi, Rafael, Trujillo, Madia
• Format: Article
• Language: English
• Subjects: antioxidants; Biocatalysis; catalytic activity; Cellular Biology; cysteine; Cytosol; Cytosol - enzymology; Hydrogen Peroxide; Hydrogen Peroxide - isolation & purification; Hydrogen Peroxide - metabolism; Kinetics; Life Sciences; Microbiology and Parasitology; Mitochondria; Mitochondria - enzymology; nitrogen; Oxidation-Reduction; oxygen; parasites; Peroxidase; Peroxidases; Peroxidases - genetics; Peroxidases - isolation & purification; Peroxidases - metabolism; Peroxiredoxin; Peroxynitrite; Peroxynitrous Acid; Peroxynitrous Acid - isolation & purification; Peroxynitrous Acid - metabolism; Protozoan Proteins; Protozoan Proteins - genetics; Protozoan Proteins - isolation & purification; Protozoan Proteins - metabolism; Trypanosoma brucei brucei; Trypanosoma brucei brucei - enzymology; Trypanosoma cruzi; Trypanosoma cruzi - cytology; Trypanosoma cruzi - enzymology; Tryparedoxin peroxidase; virulence
• ISSN: 0003-9861; 1096-0384
• DOI: 10.1016/j.abb.2010.12.014

► Trypanosomacruzi TXNPxs reacted very efficiently with hydrogen peroxide and peroxynitrite. ► Rate constants of H2O2 and peroxynitrite reduction by TcTXNPxs were in the 106–107M−1s−1 range. ► mTcTXNPx reacted faster than cTcTXNPx with peroxynitrite. ► Rate constants for the reduction of c-TcTXNPx by TbTXNI was 1.3×106M−1s−1. ► TcTXNPxs peroxidatic and resolving cysteines identities were confirmed. During host cell infection, Trypanosoma cruzi parasites are exposed to reactive oxygen and nitrogen species. As part of their antioxidant defense systems, they express two tryparedoxin peroxidases (TXNPx), thiol-dependent peroxidases members of the peroxiredoxin family. In this work, we report a kinetic characterization of cytosolic (c-TXNPx) and mitochondrial (m-TXNPx) tryparedoxin peroxidases from T. cruzi. Both c-TXNPx and m-TXNPx rapidly reduced hydrogen peroxide (k=3.0×107 and 6×106M−1s−1 at pH 7.4 and 25°C, respectively) and peroxynitrite (k=1.0×106 and k=1.8×107M−1s−1 at pH 7.4 and 25°C, respectively). The reductive part of the catalytic cycle was also studied, and the rate constant for the reduction of c-TXNPx by tryparedoxin I was 1.3×106M−1s−1. The catalytic role of two conserved cysteine residues in both TXNPxs was confirmed with the identification of Cys52 and Cys173 (in c-TXNPX) and Cys81 and Cys204 (in m-TXNPx) as the peroxidatic and resolving cysteines, respectively. Our results indicate that mitochondrial and cytosolic TXNPxs from T. cruzi are highly efficient peroxidases that reduce hydrogen peroxide and peroxynitrite, and contribute to the understanding of their role as virulence factors reported in vivo.