Definition: Porphyrins with four methyl, two vinyl, and two propionic acid side chains attached to the pyrrole rings. Protoporphyrin IX occurs in hemoglobin, myoglobin, and most of the cytochromes.
Arch Biochem Biophys 1979;197(2):396; Biochem Biophys Res Comm 78(1):429;1977; N Engl J Med 1980;302(14):765; Protein Nucleic Acid Enzyme (Tokyo) 20(12):1079;1975