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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Affiliation: | 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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