The Haptoglobin-CD163-Heme Oxygenase-1 Pathway for Hemoglobin Scavenging

Figure 2

The intracellular pathway for heme-degradation subsequent to CD163 and CD91 mediated endocytosis in macrophages. Free heme is degraded to biliverdin, CO, and ferrous iron by the endoplasmic reticulum enzyme HO-1 facing the cytosol. Electrons are delivered by NADPH p450 cytochrome reductase. Biliverdin is reduced to bilirubin by biliverdin reductase and transported to the liver bound to albumin.