Bifunctional enzyme with both catalase and broad-spectrum peroxidase activity. Also displays NADH oxidase, isoniazid hydrazine lyase and isonicotinoyl-NAD synthase activities. AH2 + H2O2 = A + 2 H2O 2 H2O2 = 2 H2O + O2 Binds 1 heme b (iron(II)-protoporphyrin IX) group per dimer. Optimum pH is 4.25 for the peroxidase reaction and 6.5 for the catalase reaction. Homodimer. Formation of the three residue Trp-Tyr-Met cross-link is important for the catalase, but not the peroxidase activity of the enzyme. Reported mass includes mass of a C-terminal His6 tag, expressed in E.coli. In contrast to the M.tuberculosis enzyme, no Trp radical is formed on the proximal Trp residue (Trp-341). Belongs to the peroxidase family. Peroxidase/catalase subfamily.