Abstract Background: The intracellular concentration of heavy–metal cations, such as copper, nickel, and zinc is pivotal for the mycobacterial response to the hostile environment inside macrophages. To date, copper transport mediated by P–type ATPases across the mycobacterial plasma membrane has not been sufficiently explored. Results: In this work, the ATPase activity of the putative Mycobacterium tuberculosis P1B–type ATPase CtpB was associated with copper (I) transport from mycobacterial cells. Although CtpB heterologously expressed in M. smegmatis induced tolerance to toxic concentrations of Cu2+ and a metal preference for Cu+, the disruption of ctpB in M. tuberculosis cells did not promote impaired cell growth or heavy–metal accumulation in whole mutant cells in cultures under high doses of copper. In addition, the Cu+ ATPase activity of CtpB embedded in the plasma mem–brane showed features of high affinity/slow turnover ATPases, with enzymatic parameters KM 0.19 ±0.04 μM and Vmax 2.29 ±0.10 nmol/mg min. In contrast, the ctpB gene transcription was activated in cells under culture conditions that mimicked the hostile intraphagosomal environment, such as hypoxia, nitrosative and oxidative stress, but not under high doses of copper. Conclusions: The overall results suggest that M. tuberculosis CtpB is associated with Cu+ transport from mycobacterial cells possibly playing a role different from copper detoxification.

This paper compares the catalytic activities of some transition metal ions (Fe3+, Co2+, Cu2+, Ni2+, Zn2+) in the H2O2 decomposition in homogenous and heterogeneous processes, including solid mixed systems (Fe-Cu-Co/Al2O3, Fe-Cu/Al2O3, Fe-Co/Al2O3 and Co-Cu/Al2O3). The solids were characterised by X-ray diffraction to explore evolution of phases or possible changes. Different trends of the catalytic activity were observed: in homogeneous medium the most active species was Fe3+, whereas in heterogeneous one the higher activities were shown for Co/Al2O3 and Co-Cu/Al2O3. A strong cooperative effect for the Co-Cu/Al2O3 system was observed, which can be considered as a new catalyst of interest for this type of reactions.