Macrophages process the two major portions through separate routes. Globin chains are dismantled into amino acids, which can be recovered as usable cellular building blocks. Heme undergoes enzymatic conversion by heme oxygenase, producing biliverdin, carbon monoxide, and iron. This division allows the body to recover both protein components and the metal required for future hemoglobin production.
Heme oxygenase initiates the processing of heme after hemoglobin has been taken apart inside macrophages. Its activity converts heme into biliverdin, carbon monoxide, and recyclable iron. This step is important because it separates a waste-processing route for the pigment portion from iron recovery, linking hemoglobin breakdown with the maintenance of iron availability.
Biliverdin reductase acts after heme oxygenase has converted heme into biliverdin. The reductase changes biliverdin into bilirubin, creating the pigment that must then be handled by the liver. The sequence matters because bilirubin production depends on this ordered enzymatic pathway, connecting cellular heme processing with hepatic excretion through bile.
Iron released during heme processing is not simply discarded. The body recovers it for use in new hemoglobin synthesis, supporting the replacement of hemoglobin lost as red blood cells age or become damaged. This recycling helps connect red blood cell turnover with iron balance and reduces the loss of a component needed for oxygen-carrying molecules.
Aged or damaged red blood cells are processed by macrophages, where globin breakdown and heme conversion occur. The resulting biliverdin is converted to bilirubin, which is then handled by the liver. Hepatic conjugation prepares bilirubin for excretion in bile, so the pathway spans cellular processing in macrophages and waste handling by the liver.
Disruption at different points can interfere with pigment disposal, iron recovery, or the balance of red blood cell turnover. The pathway is therefore relevant to jaundice, anemia, and disorders of bilirubin metabolism. These outcomes reflect failures in processing hemoglobin components or handling their products rather than a single uniform defect.