Erythroid heme biosynthesis and its disorders.

[erythropoietic protoporphyria]

Heme , which is composed of iron and the small organic molecule protoporphyrin , is an essential component of hemoglobin as well as a variety of physiologically important hemoproteins . During erythropoiesis , heme synthesis is induced before , and is essential for , globin synthesis . Although all cells possess the ability to synthesize heme , there are distinct differences between regulation of the pathway in developing erythroid cells and all other types of cells . Disorders that compromise the ability of the developing red cell to synthesize heme can have profound medical implications . The biosynthetic pathway for heme and key regulatory features are reviewed herein , along with specific human genetic disorders that arise from defective heme synthesis such as X-linked sideroblastic anemia and erythropoietic protoporphyria .