page_title: Heme
hierarchical_section_title: Heme
context_page_description: Heme or haem is a coordination complex "consisting of an iron ion coordinated to a porphyrin acting as a tetradentate ligand, and to one or two axial ligands." The definition is loose, and many depictions omit the axial ligands. Among the metalloporphyrins deployed by metalloproteins as prosthetic groups, heme is one of the most widely used and defines a family of proteins known as hemoproteins. Hemes are most commonly recognized as components of hemoglobin, the red pigment in blood, but are also found in a number of other biologically important hemoproteins such as myoglobin, cytochromes, catalases, heme peroxidase, and endothelial nitric oxide synthase.
  The word haem is derived from Greek αἷμα haima meaning "blood".
context_section_description: Heme (American English) or haem (British English) is a coordination complex "consisting of an iron ion coordinated to a porphyrin acting as a tetradentate ligand, and to one or two axial ligands."  The definition is loose, and many depictions omit the axial ligands.  Among the metalloporphyrins deployed by metalloproteins as prosthetic groups, heme is one of the most widely used and defines a family of proteins known as hemoproteins. Hemes are most commonly recognized as components of hemoglobin, the red pigment in blood, but are also found in a number of other biologically important hemoproteins such as myoglobin, cytochromes, catalases, heme peroxidase, and endothelial nitric oxide synthase.
  The word haem is derived from Greek αἷμα haima meaning "blood".
caption: Space-filling model of the Fe-protoporphyrin IX subunit of heme B.  Axial ligands omitted.  Color scheme: grey=iron, blue=nitrogen, black=carbon, white=hydrogen, red=oxygen
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