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Heme oxygenase or haem oxygenase HO is an enzyme that catalyzes the degradation of heme. This produces biliverdin , ferrous iron , and carbon monoxide. Indeed, monitored small doses of CO are being studied for therapeutic benefits.
HO-1 is a 32kDa enzyme contains amino acid residues. Though present throughout the body, HO has significant activity in the spleen in the degradation of hemoglobin during erythrocyte recycling 0. Heme oxygenase 1 HO-1 is a stress-induced isoform present throughout the body with highest concentrations in the spleen, liver, and kidneys.
A study has found levels of HO-1 in lung tissue were directly related to infection with Tuberculosis or infection-free areas, and knockout mice were found susceptible, showing the essential role of this enzyme. Heme oxygenase 2 HO-2 is a constitutive isoform that is expressed under homeostatic conditions in the testes, endothelial cells and the brain. A third heme oxygenase HO-3 is considered to be catalytically inactive and is thought to work in heme sensing or heme binding.
HO-3 is 33 kDa with greatest presence in the liver, prostate, and kidneys. Heme oxygenase is conserved across phylogenetic kingdoms.
Certain strains of Escherichia coli express the non-CO producing Chu W isoform, whilst HO-like enzymes in other microbes have been reported to produce formaldehyde. The human microbiome contributes to endogenous carbon monoxide production in humans. Heme oxygenase cleaves the heme ring at the alpha-methene bridge to form either biliverdin or, if the heme is still attached to a globin , verdoglobin.
Biliverdin is subsequently converted to bilirubin by biliverdin reductase. The reaction comprises three steps, which may be: . This reaction can occur in virtually every cell; the classic example is the formation of a contusion , which forms different chromogens as it gradually heals: red heme to green biliverdin to yellow bilirubin.
In terms of molecular mechanisms, the enzyme facilitates the intramolecular hydroxylation of one meso carbon centre in the heme. HO-1 is induced by countless molecules including heavy metals , statins , paclitaxel , rapamycin , probucol , nitric oxide , sildenafil , carbon monoxide , carbon monoxide-releasing molecules , and porphyrins. Phytochemical inducers of HO include: curcumin , resveratrol , piceatannol , caffeic acid phenethyl ester , dimethyl fumarate , fumaric acid esters , flavonoids , chalcones , ginkgo biloba , anthrocyanins , phlorotannins , carnosol , rosolic acid , and numerous other natural products.
Endogenous inducers include i lipids such as lipoxin and epoxyeicosatrienoic acid ; and ii peptides such as adrenomedullin and apolipoprotein ; and iii hemin. Heme oxygenase expression is induced by oxidative stress, and in animal models increasing this expression seems to be protective.
Carbon monoxide released from heme oxygenase reactions can influence vascular tone independently or influence the function of nitric oxide synthase. The first detection of CO in humans was in CO is formed at a rate of Among these, the microbial HO system within the digestive tract is believed to contribute to systemic CO-Hb concentrations. From Wikipedia, the free encyclopedia. Physiological Reviews. Characterization of the enzyme".
The Journal of Biological Chemistry. Nature Reviews. Drug Discovery. Current Pharmaceutical Design. In Wang R ed. Carbon Monoxide and Cardiovascular Functions 2nd ed. CRC Press. Proceedings of the Association of American Physicians.
Oxidative Medicine and Cellular Longevity. Redox Report. Eukaryotic Cell. Iron acquisition requires oxidative cleavage of the heme macrocycle". Microbiology and Immunology. Carbon Monoxide and Cardiovascular Functions. Oxidation of alpha-meso-phenylheme". The reference does not give the exact stoichiometry of each reaction. Journal of Inorganic Biochemistry. In Folkerts G, Garssen J eds.
Springer, Cham. Scandinavian Journal of Clinical and Laboratory Investigation. Acta Physiologica Scandinavica. Annual Review of Medicine. Physiology and medicine of hyperbaric oxygen therapy. Health Dis. Enzymes involved in the metabolism of heme and porphyrin. Heme oxygenase Biliverdin reductase.
Oxidoreductases : dioxygenases , including steroid hydroxylases EC 1. Phenylalanine hydroxylase Tyrosine hydroxylase Tryptophan hydroxylase. Dopamine beta-hydroxylase.
Tyrosinase Stearoyl-CoA desaturase Allosteric regulation Cooperativity Enzyme inhibitor Enzyme activator. EC number Enzyme superfamily Enzyme family List of enzymes. Biology portal. Categories : EC 1. Hidden categories: All articles with unsourced statements Articles with unsourced statements from September Namespaces Article Talk.
Heme oxygenase or haem oxygenase HO is an enzyme that catalyzes the degradation of heme. This produces biliverdin , ferrous iron , and carbon monoxide. Indeed, monitored small doses of CO are being studied for therapeutic benefits. HO-1 is a 32kDa enzyme contains amino acid residues. Though present throughout the body, HO has significant activity in the spleen in the degradation of hemoglobin during erythrocyte recycling 0.
Genetic analysis of heme oxygenase-1 (HO-1) in German Parkinson’s disease patients
Biochem Biophys Res Commun ; Characterization of two constitutive forms of rat liver microsomal heme oxygenase: only one molecular species of the enzyme is inducible. J Biol Chem ; Purification andcharacterization of the major constitutive form of testicular heme oxygenase: the noninducible isoform. Maines MD. Heme oxygenase: function, multiplicity, regulatory mechanisms, and clinical applications.
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