Figure 8. MtTPx catalytically detoxifies peroxynitrite formed from its radical precursors •NO and O2. Dihydrorhodamine (120 |M) oxidation to rhodamine by SIN-1-derived peroxynitrite in potassium phosphate buffer 100 mM pH 7.4 25 °C was followed spectroscopically at 500 nm. Since DHR oxidation by fluxes of peroxynitrite has a lag phase, protein additions and all DHR oxidation registers were done once that lag phase was completed, i.e. 15 minutes before beginning the incubation of DHR with SIN-1 (0.2 mM). A) Effect of increasing reduced M. tuberculosis thioredoxin peroxidase on peroxynitrite-dependent DHR oxidation. B) Effect of 1 |M reduced M. tuberculosis thioredoxin peroxidase (MtTPx), 4.6|M reduced M. tuberculosis thioredoxin C (MtTrx C) and 1 |M MtTPx plus 4.6|M MtTrx on peroxynitrite dependent DHR oxidation

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