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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.
In organic chemistry, a moiety (/ ˈ m ɔɪ ə t i / MOY-ə-tee) is a part of a molecule [1] [2] that is given a name because it is identified as a part of other molecules as well.
The name hemoglobin (or haemoglobin) is derived from the words heme (or haem) and globin, reflecting the fact that each subunit of hemoglobin is a globular protein with an embedded heme group. Each heme group contains one iron atom, that can bind one oxygen molecule through ion-induced dipole forces.
(b) structure of the heme molecular component of hemoglobin. Normal human hemoglobins are tetrameric proteins composed of two pairs of globin chains, each of which contains one α (alpha) chain and one β (beta) chain. Each globin chain is associated with an iron-containing heme moiety. Throughout life, the synthesis of the α and the β chains ...
During this process, the parasite releases the toxic and soluble molecule heme. The heme moiety consists of a porphyrin ring called Fe(II)-protoporphyrin IX (FP). To avoid destruction by this molecule, the parasite biocrystallizes heme to form hemozoin, a nontoxic molecule. Hemozoin collects in the digestive vacuole as insoluble crystals.
The mammalian enzyme contains one heme per dimer, with a proximal histidine ligand located in the HNOX domain of the beta 1 subunit. In its Fe(II) form, this heme moiety is the target of nitric oxide, which is synthesized by endothelial cells following appropriate stimulation. Binding of nitric oxide to the heme results in activation of the C ...
The globins are a superfamily of heme-containing globular proteins, involved in binding and/or transporting oxygen. These proteins all incorporate the globin fold, a series of eight alpha helical segments. Two prominent members include myoglobin and hemoglobin. Both of these proteins reversibly bind oxygen via a heme prosthetic group.
Stercobilin is a tetrapyrrolic bile pigment and is one end-product of heme catabolism. [1] [2] It is the chemical responsible for the brown color of human feces and was originally isolated from feces in 1932. Stercobilin (and related urobilin) can be used as a marker for biochemical identification of fecal pollution levels in rivers. [3]