Leishmania infantum: provision of reducing equivalents to the mitochondrial tryparedoxin/tryparedoxin peroxidase system |
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Authors: | Castro Helena Romao Susana Gadelha Fernanda R Tomás Ana M |
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Institution: | aIBMC—Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua do Campo Alegre 823, 4150-180 Porto, Portugal;bDepartamento de Bioquímica, Universidade Estadual de Campinas, 13083-970 SP, Brazil;cICBAS—Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Largo Prof. Abel Salazar 2, 4099-003 Porto, Portugal |
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Abstract: | Within the mitochondrion of Leishmania infantum, hydroperoxide metabolism relies on the activity of tryparedoxin-dependent peroxidases (TXNPxs). Tryparedoxins (TXNs) are thioredoxin-related oxidoreductases, which in vitro are reduced by the trypanothione reductase/trypanothione TR/T(SH)2] redox couple. Still, there is no evidence that this actually occurs in the mitochondrion. This communication addresses the question of how the mitochondrial TXN/TXNPx system is reduced. First, using a digitonin fractionation assay, we show that TR activity is absent from the L. infantum mitochondrion. The possibility that this organelle possesses alternative electron sources for TXN/TXNPx is then investigated. Biochemical assays performed with purified recombinant enzymes, revealed that TR and T(SH)2 can be replaced, albeit less efficiently, by the dihydrolipoamide dehydrogenase/lipoamide redox system as TXN/TXNPx electron donor. This result challenges the classical view that T(SH)2 is the only reductant for TXNs and add new prospects regarding the involvement of 2-oxo acid dehydrogenase complexes in L. infantum mitochondrial hydroperoxide metabolism. |
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Keywords: | Leishmania Tryparedoxin Trypanothione reductase Dihydrolipoamide dehydrogenase Mitochondrion Trypanosoma brucei Trypanosoma cruzi Leishmania spp trypanosomatids TXN tryparedoxin TXNPx tryparedoxin peroxidase TR EC 1 8 1 12 trypanothione reductase T(SH)2 trypanothione TS2 trypanothione disulfide DLDH EC 1 8 1 4 dihydrolipoamide dehydrogenase |
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