Involved in heme degradation (PubMed:15205415, PubMed:22627893, PubMed:28481076, PubMed:28607990). Catalyzes the degradation of heme to biliverdin, with the release of iron (PubMed:22627893, PubMed:28607990). Forms biliverdin beta and delta (PubMed:28607990). Binds heme with high efficiency (PubMed:15205415, PubMed:22627893). 3 AH2 + 2 H(+) + heme b + 3 O2 = 3 A + biliverdin beta + CO + Fe(2+) + 3 H2O 3 AH2 + 3 H(+) + heme b + 3 O2 = 3 A + biliverdin delta + CO + Fe(2+) + 3 H2O Activity is pH-dependent. A proximal hydrogen bond between Asp-132 and the heme axial ligant His-170 is essential for heme degradation activity (PubMed:28481076). Heme-degradation reaction is inhibited by iron chelators (PubMed:28352909). Homodimer (PubMed:22627893, PubMed:23013214). Interacts with HutX, leading to the transfer of the heme from HutX to apo-HutZ (PubMed:26807477). Negatively regulated by iron. Mutant is defective in heme utilization. Belongs to the heme oxygenase HugZ/HutZ family.