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Heme b

Heme b
CAS number 14875-96-8
PubChem 444098
MeSH Heme+b
Molecular formula C34H34O4N4Fe
Molar mass 616.487
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references

Heme B is the most abundant heme; both hemoglobin and myoglobin are examples of oxygen transport proteins that contain heme B and 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 evolutionary conserved histidine, while Nitric oxide synthase and Cytochrome P450 have a coordination bond to an evolutionary 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 bound with oxygen or the toxin carbon monoxide the iron is hexacoordinated.

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Heme_b". A list of authors is available in Wikipedia.
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