Complementary antioxidant defense by cytoplasmic and mitochondrial peroxiredoxins in Leishmania infantum

In Kinetoplastida 2-Cys peroxiredoxins are the ultimate members of unique enzymatic cascades for detoxification of peroxides, which are dependent on trypanothione, a small thiol specific to these organisms. Here we report on two distinct Leishmania infantum peroxiredoxins, LicTXNPx and LimTXNPx, that may be involved in such a pathway. LicTXNPx, found in the cytoplasm, is a typical 2-Cys peroxiredoxin encoded by LicTXNPx, a member of a multicopy gene family. LimTXNPx, encoded by a single copy gene, LimTXNPx, is confined to the mitochondrion and is unusual in possessing an Ile-Pro-Cys motif in the distal redox center, replacing the common peroxiredoxin Val-Cys-Pro sequence, apart from an N-terminal mitochondrial leader sequence. Based on sequence and subcellular localization, the peroxiredoxins of Kinetoplastida can be separated in two distinct subfamilies. As an approach to investigate the function of both peroxiredoxins in the cell, L. infantum promastigotes overexpressing LicTXNPx and LimTXNPx were assayed for their resistance to H2O2 and tert-butyl hydroperoxide. The results show evidence that both enzymes are active as peroxidases in vivo and that they have complementary roles in parasite protection against oxidative stress.