2.0 2012-07-30 14:55:13 -0600 2015-06-03 17:21:05 -0600 ECMDB21285 M2MDB001691 Superoxide anion The superoxide ion, also known by the obsolete name hyperoxide, is a compound that contains the superoxide anion with the chemical formula O2-. The systematic name of the anion is dioxide. The superoxide anion is particularly important as the product of the one-electron reduction of dioxygen O2, which occurs widely in nature. With one unpaired electron, the superoxide ion is a free radical, and, like dioxygen, it is paramagnetic.; Because superoxide is toxic, nearly all organisms living in the presence of oxygen contain isoforms of the superoxide scavenging enzyme, superoxide dismutase, or SOD. SOD is an extremely efficient enzyme; it catalyzes the neutralization of superoxide nearly as fast as the two can diffuse together spontaneously in solution. Other proteins, which can be both oxidized and reduced by superoxide, have weak SOD-like activity (e.g. hemoglobin). Genetic inactivation ('knockout') of SOD produces deleterious phenotypes in organisms ranging from bacteria to mice and have provided important clues as to the mechanisms of toxicity of superoxide in vivo.; Superoxide is the anionic form O2. It is important as the product of the one-electron reduction of dioxygen (oxygen gas), which occurs widely in nature. With one unpaired electron, the superoxide ion is a free radical. It is also paramagnetic. The biological toxicity of superoxide is due to its capacity to inactivate iron-sulfur cluster containing enzymes (which are critical in a wide variety of metabolic pathways), thereby liberating free iron in the cell, which can undergo fenton-chemistry and generate the highly reactive hydroxyl radical. In its HO2 form, superoxide can also initiate lipid peroxidation of polyunsaturated fatty acids. It also reacts with carbonyl compounds and halogenated carbons to create toxic peroxy radicals. As such, superoxide is a main cause of oxidative stress.; Highly reactive compounds produced when oxygen is reduced by a single electron. In biological systems, they may be generated during the normal catalytic function of a number of enzymes and during the oxidation of hemoglobin to Methemoglobin.; Because superoxide is toxic, nearly all organisms living in the presence of oxygen contain isoforms of the superoxide scavenging enzyme, superoxide dismutase, or SOD. SOD is an extremely efficient enzyme; it catalyzes the neutralization of superoxide nearly as fast as the two can diffuse together spontaneously in solution. With one unpaired electron, the superoxide ion is a free radical and therefore paramagnetic.; In living organisms, superoxide dismutase protects the cell from the deleterious effects of superoxides. (O2) Dioxidanidyl Dioxide(1) Dioxide(1-) Hyperoxid Hyperoxide O2 O2 free radical O2- O2.- O2- Peroxide radical Superoxide Superoxide anion Superoxide anion radical Superoxide radical Superoxide radical anion Superoxyde O2 31.9988 31.989829244 oxidanidyloxidanyl superoxide 11062-77-4 [O][O-] InChI=1S/HO2/c1-2/h1H/p-1 OUUQCZGPVNCOIJ-UHFFFAOYSA-M Solid Cytosol Extra-organism Periplasm logp -0.36 ChemAxon pka_strongest_acidic 5.8 ChemAxon pka_strongest_basic -6.8 ChemAxon iupac oxidanidyloxidanyl ChemAxon average_mass 31.9988 ChemAxon mono_mass 31.989829244 ChemAxon smiles [O][O-] ChemAxon formula O2 ChemAxon inchi InChI=1S/HO2/c1-2/h1H/p-1 ChemAxon inchikey OUUQCZGPVNCOIJ-UHFFFAOYSA-M ChemAxon polar_surface_area 23.06 ChemAxon refractivity 2.89 ChemAxon polarizability 1.67 ChemAxon rotatable_bond_count 0 ChemAxon acceptor_count 2 ChemAxon donor_count 0 ChemAxon physiological_charge -1 ChemAxon formal_charge -1 ChemAxon Superoxide Radicals Degradation Gram-negative bacteria commonly synthesize both cytoplasmic and periplasmic isozymes of SOD as their frontline defense against superoxide anion (O2-). E. coli contains two cytoplasmic SOD isozymes, one each of the manganese- and iron-cofactored types (MnSOD and FeSOD), and secretes a copper, zinc-cofactored enzyme (CuZnSOD) to the periplasm. Periplasmic superoxide may be generated by autooxidation of dihydromenaquinone in the cytoplasmic membrane. In E. coli, the MnSOD and FeSOD enzymes (encoded by sodA and sodB, respectively) are structurally and kinetically similar. Unlike MnSOD and FeSOD, CuZnSOD is monomeric. Regulation of the three enzymes is complex. Under anaerobic conditions, FeSOD is the only superoxide dismutase enzyme present in E. coli. MnSOD is induced by aerobic growth and a variety of environmental stress conditions. CuZnSOD constitutes only a small fraction of superoxide dismutase activity in the cell; its expression is induced in stationary phase. In E. coli, with rising H2O2 concentration, catalase is strongly induced and becomes the primary scavenging enzyme. E. coli expresses two catalases, known as HPI and HPII, that are encoded by katG and katE, respectively. While katG katE mutants could not degrade millimolar concentrations of H2O2, they were subsequently found to retain the ability to degrade H2O2 when it was present at low micromolar concentrations. This residual activity is due to an enzyme known as alkylhydroperoxide reductase (Ahp). This two-component enzyme had originally been identified as a scavenger of organic hydroperoxides. SOD mutants of E. coli are unable to perform normal sulfur metabolism. Both SOD and catalase/peroxidase mutants of E. coli are incapable of synthesizing aromatic products, including amino acids. SoxRS regulon is turned on by any condition that increases superoxide radical production in E. coli. One of its products is Mn-SOD. Another independent regulon turned on in response to H2O2 is referred to as the OxyR regulon. (EcoCyc) PW002053 Metabolic superoxide radicals degradation DETOX1-PWY Specdb::MsMs 28355 Specdb::MsMs 28356 Specdb::MsMs 28357 Specdb::MsMs 34913 Specdb::MsMs 34914 Specdb::MsMs 34915 Specdb::MsMs 2562840 Specdb::MsMs 2562841 Specdb::MsMs 2562842 HMDB02168 5359597 4514331 C00704 18421 SUPER-OXIDE Superoxide_anion Keseler, I. M., Collado-Vides, J., Santos-Zavaleta, A., Peralta-Gil, M., Gama-Castro, S., Muniz-Rascado, L., Bonavides-Martinez, C., Paley, S., Krummenacker, M., Altman, T., Kaipa, P., Spaulding, A., Pacheco, J., Latendresse, M., Fulcher, C., Sarker, M., Shearer, A. G., Mackie, A., Paulsen, I., Gunsalus, R. P., Karp, P. D. (2011). "EcoCyc: a comprehensive database of Escherichia coli biology." Nucleic Acids Res 39:D583-D590. 21097882 Superoxide dismutase [Mn] P00448 SODM_ECOLI sodA http://ecmdb.ca/proteins/P00448.xml Probable quinol monooxygenase ygiN P0ADU2 YGIN_ECOLI ygiN http://ecmdb.ca/proteins/P0ADU2.xml Superoxide dismutase [Cu-Zn] P0AGD1 SODC_ECOLI sodC http://ecmdb.ca/proteins/P0AGD1.xml Superoxide dismutase [Fe] P0AGD3 SODF_ECOLI sodB http://ecmdb.ca/proteins/P0AGD3.xml Catalase-peroxidase P13029 KATG_ECOLI katG http://ecmdb.ca/proteins/P13029.xml Catalase HPII P21179 CATE_ECOLI katE http://ecmdb.ca/proteins/P21179.xml Outer membrane protein N P77747 OMPN_ECOLI ompN http://ecmdb.ca/proteins/P77747.xml Outer membrane pore protein E P02932 PHOE_ECOLI phoE http://ecmdb.ca/proteins/P02932.xml Outer membrane protein F P02931 OMPF_ECOLI ompF http://ecmdb.ca/proteins/P02931.xml Outer membrane protein C P06996 OMPC_ECOLI ompC http://ecmdb.ca/proteins/P06996.xml 2 Hydrogen ion + 2 Superoxide anion > Hydrogen peroxide + Oxygen SUPEROX-DISMUT-RXN Menaquinol 8 + 2 Oxygen >2 Hydrogen ion + Menaquinone 8 +2 Superoxide anion 2 Oxygen + Ubiquinol-8 >2 Hydrogen ion +2 Superoxide anion + Ubiquinone-8 2 3-Hydroxyanthranilic acid + 4 Oxygen <> Cinnavalininate +2 Superoxide anion +2 Hydrogen peroxide +2 Hydrogen ion R02670 Oxygen + Iron > Superoxide anion + Fe3+ RXN-12541 menadiol + Oxygen > Hydrogen ion + menadione + Superoxide anion RXN0-3441 Hydrogen ion + Superoxide anion > Hydrogen peroxide + Oxygen SUPEROX-DISMUT-RXN