Involved in the recovery of exogenous heme iron. Extracts iron from heme while preserving the protoporphyrin ring intact. Also displays peroxidase activity on guaiacol in vitro. 2 H(+) + heme b = Fe(2+) + protoporphyrin IX Binds 1 heme b (iron(II)-protoporphyrin IX) group non-covalently per subunit. Homodimer. Part of a ferrous iron transporter composed of EfeU, EfeO and EfeB. However, this EfeUOB tripartite iron transporter is defective in E.coli strain K12 due to a frameshift mutation in EfeU. Repressed by Fur in the presence of iron. Repressed at high pH by the two-component regulatory system CpxA/CpxR. Exported by the Tat system. The position of the signal peptide cleavage has been experimentally proven. Can also be exported by the Sec system. Belongs to the DyP-type peroxidase family. EfeB subfamily.