Haem
Haem, or heme, is an iron-containing prosthetic group found in a wide range of proteins. It consists of a porphyrin ring, specifically protoporphyrin IX, with a single central iron atom. The iron can undergo redox changes, enabling roles in oxygen binding, electron transfer, and catalysis across different biological contexts.
In most haem-containing proteins, the iron is coordinated within the plane of the porphyrin and linked to
Biosynthesis of haem proceeds via the porphyrin pathway, beginning with glycine and succinyl-CoA to form δ-aminolevulinic
Haem is a prosthetic group in hemoglobin and myoglobin for oxygen transport and storage, in cytochromes of
Haem is degraded by haem oxygenase to biliverdin, iron, and carbon monoxide. Biliverdin is reduced to bilirubin
Clinically, disorders of haem synthesis include porphyrias, characterized by the accumulation of porphyrin intermediates. Dietary sources