Kinetics and Redox-Sensitive Oligomerisation Reveal Negative Subunit Cooperativity in Tryparedoxin Peroxidase of Trypanosoma brucei brucei
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H. Budde
Abstract
Tryparedoxin peroxidases (TXNPx) are peroxiredoxintype enzymes that detoxify hydroperoxides in trypanosomatids. Reduction equivalents are provided by trypanothione [T(SH)2] via tryparedoxin (TXN). The T(SH)2-dependent peroxidase system was reconstituted from TXNPx and TXN of T. brucei brucei (TbTXNPx and TbTXN). TbTXNPx efficiently reduces organic hydroperoxides and is specifically reduced by TbTXN, less efficiently by thioredoxin, but not by glutathione (GSH) or T(SH)2. The kinetic pattern does not comply with a simple rate equation but suggests negative cooperativity of reaction centers. Gel permeation of oxidized TbTXNPx yields peaks corresponding to a decamer and higher aggregates. Electron microscopy shows regular ring structures in the decamer peak. Upon reduction, the rings tend to depolymerise forming openchain oligomers. Co-oxidation of TbTXNPx with TbTXNC43S yields a dead-end intermediate mimicking the catalytic intermediate. Its size complies with a stoichiometry of one TXN per subunit of TXNPx. Electron microscopy of the intermediate displays pentangular structures that are compatible with a model of a decameric TbTXNPx ring with ten bound TbTXN molecules. The redox-dependent changes in shape and aggregation state, the kinetic pattern and molecular models support the view that, upon oxidation of a reaction center, other subunits adopt a conformation that has lower reactivity with the hydroperoxide.
Copyright © 2003 by Walter de Gruyter GmbH & Co. KG
Articles in the same Issue
- Glutathione, Related Enzymology, and Leopold Flohé
- 'Lest I Forget Thee, Glutathione...'
- Glutathione Pathways in the Brain
- The Role of Glutathione Peroxidases in Trypanosomatids
- Cytoprotection against Oxidative Stress and the Regulation of Glutathione Synthesis
- The Parasite-Specific Trypanothione Metabolism of Trypanosoma and Leishmania
- Glutathione – Functions and Metabolism in the Malarial Parasite Plasmodium falciparum
- Oxidative Stress Caused by Inactivation of Glutathione Peroxidase and Adaptive Responses
- Versatility of Selenium Catalysis in PHGPx Unraveled by LC/ESI-MS/MS
- Modulation of the Chymotrypsin-Like Activity of the 20S Proteasome by Intracellular Redox Status: Effects of Glutathione Peroxidase-1 Overexpression and Antioxidant Drugs
- Microflora Trigger Colitis in Mice Deficient in Selenium-Dependent Glutathione Peroxidase and Induce Gpx2 Gene Expression
- Recruitment of the Interleukin-1 Receptor (IL-1RI)-Associated Kinase IRAK to the IL-1RI Is Redox Regulated
- Kinetics and Redox-Sensitive Oligomerisation Reveal Negative Subunit Cooperativity in Tryparedoxin Peroxidase of Trypanosoma brucei brucei
- Testis-Specific Expression of the Nuclear Form of Phospholipid Hydroperoxide Glutathione Peroxidase (PHGPx)
- Selective Recognition of Peptide Sequences by Glutathione Transferases: A Possible Mechanism for Modulation of Cellular Stress-Induced Signaling Pathways
- Biosynthesis of Trypanothione in Trypanosoma brucei brucei
- Transcriptional Regulation of Cytosol and Membrane Alanyl-Aminopeptidase in Human T Cell Subsets
- Regulation of Gene Transcription by a Constitutively Active Mutant of Activating Transcription Factor 2 (ATF2)
- Solvent Isotope Effect on the Reaction Catalysed by the Pyruvate Dehydrogenase Complex from Escherichia coli
- Selective Induction of Liver Parenchymal Cell Heme Oxygenase-1 in Selenium-Deficient Rats
Articles in the same Issue
- Glutathione, Related Enzymology, and Leopold Flohé
- 'Lest I Forget Thee, Glutathione...'
- Glutathione Pathways in the Brain
- The Role of Glutathione Peroxidases in Trypanosomatids
- Cytoprotection against Oxidative Stress and the Regulation of Glutathione Synthesis
- The Parasite-Specific Trypanothione Metabolism of Trypanosoma and Leishmania
- Glutathione – Functions and Metabolism in the Malarial Parasite Plasmodium falciparum
- Oxidative Stress Caused by Inactivation of Glutathione Peroxidase and Adaptive Responses
- Versatility of Selenium Catalysis in PHGPx Unraveled by LC/ESI-MS/MS
- Modulation of the Chymotrypsin-Like Activity of the 20S Proteasome by Intracellular Redox Status: Effects of Glutathione Peroxidase-1 Overexpression and Antioxidant Drugs
- Microflora Trigger Colitis in Mice Deficient in Selenium-Dependent Glutathione Peroxidase and Induce Gpx2 Gene Expression
- Recruitment of the Interleukin-1 Receptor (IL-1RI)-Associated Kinase IRAK to the IL-1RI Is Redox Regulated
- Kinetics and Redox-Sensitive Oligomerisation Reveal Negative Subunit Cooperativity in Tryparedoxin Peroxidase of Trypanosoma brucei brucei
- Testis-Specific Expression of the Nuclear Form of Phospholipid Hydroperoxide Glutathione Peroxidase (PHGPx)
- Selective Recognition of Peptide Sequences by Glutathione Transferases: A Possible Mechanism for Modulation of Cellular Stress-Induced Signaling Pathways
- Biosynthesis of Trypanothione in Trypanosoma brucei brucei
- Transcriptional Regulation of Cytosol and Membrane Alanyl-Aminopeptidase in Human T Cell Subsets
- Regulation of Gene Transcription by a Constitutively Active Mutant of Activating Transcription Factor 2 (ATF2)
- Solvent Isotope Effect on the Reaction Catalysed by the Pyruvate Dehydrogenase Complex from Escherichia coli
- Selective Induction of Liver Parenchymal Cell Heme Oxygenase-1 in Selenium-Deficient Rats
