Heme is a complex of iron with protoporphyrin IX that is essential for the function of all
aerobic cells. Heme serves as the prosthetic group of numerous hemoproteins (eg,
hemoglobin, myoglobin, cytochromes, guanylate cyclase, and nitric oxide synthase) and
plays an important role in controlling protein synthesis and cell differentiation. Cellular heme
levels are tightly controlled; this is achieved by a fine balance between heme biosynthesis
and catabolism by the enzyme heme oxygenase. On a per-cell basis, the rate of heme …