Hydrogen peroxide generation inTrypanosoma cruzi

Boveris, Alberto; Stoppani, A. O. M.

doi:10.1007/bf01920148

Cited by 79 publications

(26 citation statements)

References 12 publications

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“…Peroxisomes have been shown to be a major source of reactive oxygen species (44,45), and most organisms have evolved a peroxisomal oxidative defense system that includes copper/zinc superoxide dismutase, glutathione peroxidase, and catalase (39, 46 -48). T. cruzi microsomal fractions have been demonstrated to generate reactive oxygen species (49), although the detoxification pathways employed have yet to be determined. Catalase has been reported to be absent from trypanosomatids (1,2,(15)(16)(17).…”

Section: Discussionmentioning

confidence: 99%

The Trypanosoma cruzi Enzyme TcGPXI Is a Glycosomal Peroxidase and Can Be Linked to Trypanothione Reduction by Glutathione or Tryparedoxin

Wilkinson

Meyer

Taylor

et al. 2002

Journal of Biological Chemistry

131

102

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Trypanosoma cruzi glutathione-dependent peroxidase I (TcGPXI) can reduce fatty acid, phospholipid, and short chain organic hydroperoxides utilizing a novel redox cycle in which enzyme activity is linked to the reduction of trypanothione, a parasite-specific thiol, by glutathione. Here we show that TcGPXI activity can also be linked to trypanothione reduction by an alternative pathway involving the thioredoxin-like protein tryparedoxin. The presence of this new pathway was first detected using dialyzed soluble fractions of parasite extract. Tryparedoxin was identified as the intermediate molecule following purification, sequence analysis, antibody studies, and reconstitution of the redox cycle in vitro. The system can be readily saturated by trypanothione, the rate-limiting step being the interaction of trypanothione with the tryparedoxin. Both tryparedoxin and TcGPXI operate by a ping-pong mechanism. Overexpression of TcGPXI in transfected parasites confers increased resistance to exogenous hydroperoxides. TcGPXI contains a carboxyl-terminal tripeptide (ARI) that could act as a targeting signal for the glycosome, a kinetoplastid-specific organelle. Using immunofluorescence, tagged fluorescent proteins, and biochemical fractionation, we have demonstrated that TcGPXI is localized to both the glycosome and the cytosol. The ability of TcGPXI to use alternative electron donors may reflect their availability at the corresponding subcellular sites.

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Section: Discussionmentioning

confidence: 99%

The Trypanosoma cruzi Enzyme TcGPXI Is a Glycosomal Peroxidase and Can Be Linked to Trypanothione Reduction by Glutathione or Tryparedoxin

Wilkinson

Meyer

Taylor

et al. 2002

Journal of Biological Chemistry

131

102

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“…Since the observation was made that the cytosolic and mitochondrial fractions of T. cruzi extracts can both generate significant levels of H 2 O 2 (40,41) it has been assumed that an effective peroxide metabolizing system would be present in both compartments. However the mechanisms of peroxide detoxification in T. cruzi have remained unresolved, and it has even been proposed that the process is not enzyme-mediated (9).…”

Section: Discussionmentioning

confidence: 99%

Distinct Mitochondrial and Cytosolic Enzymes Mediate Trypanothione-dependent Peroxide Metabolism in Trypanosoma cruzi

Wilkinson

Temperton²,

Mondragon

et al. 2000

Journal of Biological Chemistry

158

134

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The American trypanosome Trypanosoma cruzi is exposed to toxic oxygen metabolites that are generated by drug metabolism and immune responses in addition to those produced by endogenous processes. However, much remains to be resolved about the parasite oxidative defense system, including the mechanism(s) of peroxide reduction. Here we show that reduction of peroxides in T. cruzi is catalyzed by two distinct trypanothione-dependent enzymes. These were localized to the cytosol and mitochondrion. Both are members of the peroxiredoxin family of antioxidant proteins and are characterized by the presence of two conserved domains containing redox active cysteines. The role of these proteins in protecting T. cruzi from peroxide-mediated damage was demonstrated following overexpression of enzyme activity. The parasite-specific features of T. cruzi cytoplasmic peroxiredoxin and T. cruzi mitochondrial peroxiredoxin may be exploitable in terms of drug development.

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“…The first line of defence involves removal of the superoxide radical by superoxide dismutase. Superoxide dismutase has been purified from C. fusciculata [39] and detected in I: cruzi [40].…”

Section: Discussionmentioning

confidence: 99%

Phenotype of recombinant Leishmania donovani and Trypanosoma cruzi which over‐express trypanothione reductase

Kelly

Taylor

Smith

et al. 1993

European Journal of Biochemistry

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Trypanothione reductase is thought to be important in maintaining an intracellular reducing environment in trypanosomatids. To investigate the role of trypanothione reductase we transfected Leishmania donovani and Trypanosoma cruzi with an expression vector containing the L. donovani trypanothione reductase gene and achieved over-expression of enzyme activity (10-14-fold) in transformed cells. Following treatment of L. donovani cells with the thiol-oxidizing agent diamide, the ability to regenerate dihydrotrypanothione from trypanothione disulphide was considerably enhanced in cells which over-expressed trypanothione reductase. However, the growth of transformed and control cells was equally sensitive to inhibition by nifurtimox, nitrofurazone and gentian violet, drugs that are thought to act by inducing oxidative damage. Likewise, growth of transformed and control cells were equally susceptible to inhibition by hydrogen peroxide, and control and transformed L. donovani promastigotes metabolized hydrogen peroxide at comparable rates. Thus, these experiments suggest that the ability to regenerate dihydrotrypanothione from trypanothione disulphide is not a rate-limiting step in the metabolism of hydrogen peroxide.Trypanosomatids are flagellated parasitic protozoa which include the causative agents of Chagas' disease (Trypanosoma cruzi) and visceral and cutaneous leishmaniasis (Leishmania spp.). Chagas' disease affects up to 20 million people in Latin America [l] and world-wide there are estimated to be 400000 new cases of leishmaniasis/year [2]. There are no reliable vaccines against trypanosomatid infections and in many cases, particularly with Chagas' disease, treatment with drugs currently available is unsatisfactory due to toxicity or limited efficacy [3]. The development of more effective chemotherapy for these diseases is thus a major research priority. Approaches to drug design are now aimed at the identification of essential biochemical processes which are pathogen-specific as targets for chemotherapy. One unique feature of trypanosomatid metabolism which would appear to fulfil these criteria is the trypanothione system [4] and in particular the enzyme trypanothione reductase, an NADPHdependent FAD-containing oxidoreductase [4, 51. Indeed the trypanothione system has been implicated as a possible target for several drugs currently used in the treatment of trypanosomatid infections (reviewed in [61).Trypanothione is maintained in its reduced form [T(SH),] by trypanothione reductase. The trypanothione reductase gene has now been cloned from Trypanosoma congolense

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Hydrogen peroxide generation inTrypanosoma cruzi

Cited by 79 publications

References 12 publications

The Trypanosoma cruzi Enzyme TcGPXI Is a Glycosomal Peroxidase and Can Be Linked to Trypanothione Reduction by Glutathione or Tryparedoxin

The Trypanosoma cruzi Enzyme TcGPXI Is a Glycosomal Peroxidase and Can Be Linked to Trypanothione Reduction by Glutathione or Tryparedoxin

Distinct Mitochondrial and Cytosolic Enzymes Mediate Trypanothione-dependent Peroxide Metabolism in Trypanosoma cruzi

Phenotype of recombinant Leishmania donovani and Trypanosoma cruzi which over‐express trypanothione reductase

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