protoporphyrin(redirected from protoporphyrin III)
Also found in: Dictionary.
protoporphyrin/pro·to·por·phy·rin/ (-por´fĭ-rin) any of several porphyrin isomers, one of which is an intermediate in heme biosynthesis; it is accumulated and excreted excessively in feces in erythropoietic protoporphyria and variegate porphyria.
A metal-free porphyrin, C34H34N4O4, that combines with ferrous iron to form the heme group in hemoglobin and myoglobin, and with ferric iron to form the hemin group in catalase and some cytochromes.
Etymology: Gk, protos + porphyros
a kind of porphyrin that combines with iron and protein to form various important organic molecules, including catalase, hemoglobin, and myoglobin. See also heme.
protoporphyrinA porphyrin occurring in the course of the synthesis of HAEMOGLOBIN. Excess of this porphyrin, protoporphyria, causes intense itching, swelling and redness of the skin on exposure to sunlight and leads to a strikingly weatherbeaten appearance.
A precursor molecule to the porphyrin molecule.
Mentioned in: Porphyrias
a porphyrin whose iron complex united with protein occurs in hemoglobin, myoglobin and certain respiratory pigments.
combines with 4 moles of iron to form the heme moiety of hemoglobin.