Heme B

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Heme B
Skeletal formula of heme B
Space-filling model of the heme B complex
Names
Other names
Iron protoporphyrin IX,
protoheme IX
Identifiers
  • 14875-96-8 checkY
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.114.904 Edit this at Wikidata
MeSH Heme+b
UNII
Properties
C34H32O4N4Fe
Molar mass 616.487
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Heme B or haem B (also known as protoheme IX) is the most abundant heme.[citation needed] Hemoglobin and myoglobin are examples of oxygen transport proteins that contain heme B. The peroxidase family of enzymes also contain heme B. The COX-1 and COX-2 enzymes (cyclooxygenase) of recent fame, also contain heme B at one of two active sites.

Generally, heme B is attached to the surrounding protein matrix (known as the apoprotein) through a single coordination bond between the heme iron and an amino-acid side-chain.

Both hemoglobin and myoglobin have a coordination bond to an evolutionarily-conserved histidine, while nitric oxide synthase and cytochrome P450 have a coordination bond to an evolutionarily-conserved cysteine bound to the iron center of heme B.

Since the iron in heme B containing proteins is bound to the four nitrogens of the porphyrin (forming a plane) and a single electron donating atom of the protein, the iron is often in a pentacoordinate state. When oxygen or the toxic carbon monoxide is bound the iron becomes hexacoordinated. The correct structures of heme B and heme S were first elucidated by German chemist Hans Fischer.[1]

References[]

  1. ^ Fischer, H.; Orth, H. (1934). . Liepzig: .
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