Involved in heme degradation. Catalyzes the degradation of heme to biliverdin, with the release of iron. Forms biliverdin delta (70%) and beta (30%). 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 Mutants are unable to use heme as a source of iron. Belongs to the heme oxygenase family.