Cargo of a type 1 encapsulin nanocompartment in situ; this cargo protects against oxidative stress at low pH. When expressed in the cytoplasm (absence of the encapsulin shell gene) it is almost as protective as the intact nanocompartment; its encapsulation has a modest yet significant effect on protection against oxidative stress at low pH (PubMed:34751132). A heme-dependent peroxidase, it probably does not have deferrochelatase activity. Converts guaiacol and H2O2 to tetraguaiacol, also acts on 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS). Retains peroxidase activity when encapsulated but has a reduced set of substrates; acts on ABTS but not guaiacol (PubMed:24855650, PubMed:34751132). 2 a phenolic donor + H2O2 = 2 a phenolic radical donor + 2 H2O Tetramer binds heme in a 1:1 ratio (PubMed:24855650). Addition of hemin to purified protein yields a tetrameric protein (Probable). Optimum pH is 4.0 or less. Homotetramer, presumably also in the encapsulin nanocompartment. Consistently identified in encapsulin nanocompartments isolated in situ (PubMed:34751132). Located inside the nanocompartment in E.coli (Probable). The C-terminus (residues 312-335) targets the protein to the encapsulin nanocompartment. No change in ability to grow on an exogenous siderophore (mycobactin), suggesting it does not have an iron-chelating function (PubMed:24855650). A double dyp-enc deletion mutant cannot produce encapsulin nanocompartments, cells are highly sensitive to H2O2 at pH 4.5 (mimics growth in the phagolysosome), mutants exhibit significant dysregulation of redox homeostasis, survive less well in C57BL/6 mouse-derived bone marrow cells and are more sensitive to pyrazinamide treatment in infected BALB/C mice (PubMed:34751132). Belongs to the DyP-type peroxidase family.