FIGURE 1.

The porphyrin biosynthesis pathway in the normal cell. In normal cells, endogenous 5‐aminolevulinic acid (5‐ALA) is generated from glycine and succinyl CoA in the mitochondria. It is converted into several precursors in the cytoplasm, and protoporphyrin IX (PpIX) is synthesized in the mitochondria. Subsequently, ferrochelatase catalyzes the insertion of ferrous iron into PpIX to form heme and bilirubin. Heme is an important protein that is incorporated into the electron transport chain, which regulates the production of adenosine triphosphate (ATP) in aerobic metabolism