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Figure 1 Schematic of Hemoxygenase-1–Catalyzed Biochemical Reactions

Hem released from red blood cells is enzymatically converted into carbon monoxide, bilirubin, and iron. The former is a vasodilator and promoter of angiogenesis. Bilirubin has potential antioxidant activity. Free ferrous iron has potential pro-oxidant activity, although this may be limited by its sequestration by ferritin.