Journal
ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS
Volume 507, Issue 2, Pages 287-295Publisher
ELSEVIER SCIENCE INC
DOI: 10.1016/j.abb.2010.12.014
Keywords
Trypanosoma cruzi; Tryparedoxin peroxidase; Peroxiredoxin; Peroxynitrite; Hydrogen peroxide; Peroxidase
Categories
Funding
- Howard Hughes Medical Institute
- Programa de Desarrollo Tecnologico [PDT 079]
- Ministerio de Educacion y Cultura
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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 x 10(7) and 6 x 10(6) M-1 s(-1) at pH 7.4 and 25 degrees C, respectively) and peroxynitrite (k = 1.0 x 10(6) and k = 1.8 x 10(7)M(-1) s(-1) at pH 7.4 and 25 degrees 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 x 10(6) M-1 s(-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. (C) 2010 Elsevier Inc. All rights reserved.
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