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Heme (American English), or haem (Commonwealth English, both pronounced /hi:m/ HEEM), is a ring-shaped iron-containing molecular component of hemoglobin, which is necessary to bind oxygen in the bloodstream. It is composed of four pyrrole rings with 2 vinyl and 2 propionic acid side chains. [1] Heme is biosynthesized in both the bone marrow and ...
A heme transporter is a protein that delivers heme to the various parts of a biological cell that require it.. Heme is a major source of dietary iron in humans and other mammals, and its synthesis in the body is well understood, but heme pathways are not as well understood.
Heme is bound to the protein either covalently or noncovalently or both. [2] The heme consists of iron cation bound at the center of the conjugate base of the porphyrin, as well as other ligands attached to the "axial sites" of the iron. The porphyrin ring is a planar dianionic, tetradentate ligand.
Siroheme (or sirohaem) is a heme-like prosthetic group at the active sites of some enzymes to accomplish the six-electron reduction of sulfur and nitrogen. [1] It is a cofactor at the active site of sulfite reductase , which plays a major role in sulfur assimilation pathway, converting sulfite into sulfide , which can be incorporated into the ...
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Heme B is an essential cofactor in many proteins and enzymes. In particular, heme b plays a key role as the oxygen carrier in hemoglobin in red blood cells and myoglobin in muscle cells. Furthermore, heme B is found in cytochrome b , a key component in Q-cytochrome c oxidoreductase (complex III) in oxidative phosphorylation .
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 and is produced naturally by many organisms. Heme A, often appears a dichroic green/red when in solution, is a structural relative of heme B, a component of hemoglobin, the red pigment in blood.
In enzymology, a heme-transporting ATPase (EC 3.6.3.41) is an enzyme that catalyzes the chemical reaction ATP + H 2 O + hemein ⇌ {\displaystyle \rightleftharpoons } ADP + phosphate + hemeout The 3 substrates of this enzyme are ATP , H 2 O , and heme , whereas its 3 products are ADP , phosphate , and heme .