Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Chemical compound
Heme B or haem B (also known as protoheme IX) is the most abundant heme.[1] 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.[2]
HemeB or haem B (also known as protoheme IX) is the most abundant heme. Hemoglobin and myoglobin are examples of oxygen transport proteins that contain...
the heme group. There are several biologically important kinds of heme: The most common type is hemeB; other important types include heme A and heme C...
Heme A (or haem A) is a heme, a coordination complex consisting of a macrocyclic ligand called a porphyrin, chelating an iron atom. Heme A is a biomolecule...
the major B vitamins (2, 3, 5, 9, and 12) are shown as precursors for certain essential biochemical reactants (FAD, NAD+, coenzyme A, and hemeB respectively)...
Cytochromes are redox-active proteins containing a heme, with a central iron (Fe) atom at its core, as a cofactor. They are involved in the electron transport...
(about 20–25% of the total) as carbaminohemoglobin, in which CO2 binds to the heme protein. The molecule also carries the important regulatory molecule nitric...
helices maintain both hemeb groups, while only three provide the heme ligands thereby anchoring Fe-heme. The periplasmic hemeb group accepts electrons...
(haemin; ferric chloride heme) is an iron-containing porphyrin with chlorine that can be formed from a heme group, such as hemeB found in the hemoglobin...
now extended to many other heme C containing proteins. Heme C differs from hemeB in that the two vinyl side chains of hemeB are replaced by covalent,...
haemoprotein), or heme protein, is a protein that contains a heme prosthetic group. They are a very large class of metalloproteins. The heme group confers...
SDHC and SDHD remains unclear. Especially in case of hemeb insertion and even its function. Hemeb prosthetic group does not appear to be part of electron...
the eighth and terminal step in the biosynthesis of heme, converting protoporphyrin IX into hemeB. It catalyses the reaction: protoheme + 2 H+ = protoporphyrin...
Heme oxygenase, or haem oxygenase, (HMOX, commonly abbreviated as HO) is an enzyme that catalyzes the degradation of heme to produce biliverdin, ferrous...
containing iron groups. The cyanide component of Zyklon B can bind at one of these iron groups, heme a3, forming a more stabilized compound through metal-to-ligand...
bridges (=CH−). In vertebrates, an essential member of the porphyrin group is heme, which is a component of hemoproteins, whose functions include carrying oxygen...
mechanism results in a decrease in the amount of heme produced and a build-up of substances involved in making heme. Porphyrias may also be classified by whether...
PMID 27812577. Nam, Wonwoo (2007). "High-Valent Iron(IV)–Oxo Complexes of Heme and Non-Heme Ligands in Oxygenation Reactions" (PDF). Accounts of Chemical Research...
Cytochrome c peroxidase, or CCP, is a water-soluble heme-containing enzyme of the peroxidase family that takes reducing equivalents from cytochrome c and...
as part of different cofactors, such as iron–sulfur clusters (Fe-S) and heme groups, both of which are assembled in mitochondria. Human cells require...
released in the degradation (catabolism) of heme by the action of O2, NADPH and the enzyme heme oxygenase: Hemeb + 3 O 2 + 3 2 NADPH + 3 2 H + ⟶ biliverdin...
Heme O (or haem O) differs from the closely related heme A by having a methyl group at ring position 8 instead of the formyl group. The isoprenoid chain...
role in living organisms as a precursor to other critical compounds like heme (hemoglobin) and chlorophyll. It is a deeply colored solid that is not soluble...
HMOX1 (heme oxygenase 1 gene) is a human gene that encodes for the enzyme heme oxygenase 1 (EC 1.14.99.3). Heme oxygenase (abbreviated HMOX or HO) mediates...
heme. Pyrroles are components of more complex macrocycles, including the porphyrinogens and products derived therefrom, including porphyrins of heme,...
indoleamine 2,3-dioxygenase (IDO), which are heme dioxygenases that utilize iron coordinated by a hemeB prosthetic group. While these dioxygenases are...
such as heme protein or iron must be in its ferrous Fe2+ form. A ferric reductase enzyme on the enterocytes' brush border, duodenal cytochrome B (Dcytb)...
red-orange compound that occurs in the normal catabolic pathway that breaks down heme in vertebrates. This catabolism is a necessary process in the body's clearance...
to plastocyanin. The second electron is transferred to hemebL which then transfers it to hemebH which then transfers it to PQ. In the second reaction...
membrane-bound hemeprotein, but unlike cytochromes a and b, cytochrome D has a heme D instead of a heme A or hemeB group. Cytochrome d is part of the cytochrome...
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