**6. Conclusions**

*M. tuberculosis* is an extremely successful pathogen, despite of being exposed to cytotoxic peroxides formed inside the phagosome of activated macrophages, its primary host cells. The bacterium expresses a heme-dependent peroxidase, KatG, and various thioldependent peroxidases of the Prx type. From the data reviewed herein, it becomes clear that Prxs from *M. tuberculosis* differ in cellular location, and have diverse oxidizing and reducing substrate specificities, that may explain in part the presence of different subfamilies of Prxs in the bacterium. Available data indicate that at least two of them (*Mt*AhpC and *Mt*TPx) play a role in pathogenesis. The third one, *Mt*AhpE, has an outstanding reactivity with fatty-acid derived hydroperoxides, but since natural reducing substrate(s) has not been identified so far, its peroxidase catalytic activity *in vivo* remains to be confirmed. Similarly, further investigation is required to characterize the two putative Bcp proteins from *M. tuberculosis.*
