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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 ...
Class III consists of the secretory plant peroxidases, which have multiple tissue-specific functions: e.g., removal of hydrogen peroxide from chloroplasts and cytosol; oxidation of toxic compounds; biosynthesis of the cell wall; defence responses towards wounding; indole-3-acetic acid (IAA) catabolism; ethylene biosynthesis; and so on. [7]
Heme oxygenase 1 (HMOX1, commonly HO-1) is a member of the heat shock protein (HSP) family identified as HSP32.HO-1 is a 32kDa enzyme which contains 288 amino acid residues encoded by the HMOX1 gene.
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 the first step of heme catabolism, it cleaves heme to form biliverdin. The HMOX gene is located on the long (q) arm of chromosome 22 at position 12.3, from base pair 34,101,636 to base pair ...
Molecular oxygen binds to the resulting ferrous heme center at the distal axial coordination position, initially giving a dioxygen adduct similar to oxy-myoglobin. A second electron is transferred, from either cytochrome P450 reductase , ferredoxins , or cytochrome b 5 , reducing the Fe-O 2 adduct to give a short-lived peroxo state.
Catabolism breaks down large molecules (such as polysaccharides, lipids, nucleic acids, and proteins) into smaller units (such as monosaccharides, fatty acids, nucleotides, and amino acids, respectively). Catabolism is the breaking-down aspect of metabolism, whereas anabolism is the building-up aspect.
The free heme can then accelerate tissue damage by promoting peroxidative reactions and activation of inflammatory cascades. Hemopexin (Hx) is another plasma glycoprotein that is able to bind heme with high affinity. It sequesters heme in an inert non-toxic form and transports it to the liver for catabolism and excretion. [7]
Biliverdin results from the breakdown of the heme moiety of hemoglobin in erythrocytes. Macrophages break down senescent erythrocytes and break the heme down into biliverdin along with hemosiderin, in which biliverdin normally rapidly reduces to free bilirubin. [1] [3] Biliverdin is seen briefly in some bruises as a green color.