Heme is the "color-furnishing portion of hemoglobin. It is found free in tissues and as the prosthetic group in many hemeproteins."
Porphyrias are metabolic diseases in the heme biosynthetic pathway characterized by buildup of porphyrin precursors such as porphobilinogen (PBG).
- ↑ Anonymous (2015), Heme (English). Medical Subject Headings. U.S. National Library of Medicine.