Heme metabolism
Heme is an iron-containing pigment mostly produced in the bone marrow and where it is incorporated into hemoglobin of RBCs and CYP450 enzymes of hepatocytes.
Heme synthesis requires 8 enzymes that produce and modify molecules known as porphyrins.
- The first enzyme is ALA synthase, the rate-limiting step; its deficiency leads to sideroblastic anemia (iron accumulation in mitochondria)
- Heme is a negative regulator of ALA synthase; a decrease in heme