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Escherichia coli K-12 substr. MG1655 Pathway: superoxide radicals degradation
Inferred from experiment

Pathway diagram: superoxide radicals degradation

If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.

Locations of Mapped Genes:

Schematic showing all replicons, marked with selected genes

Genetic Regulation Schematic

Genetic regulation schematic for superoxide radicals degradation

Synonyms: removal of superoxide radicals

Superclasses: DetoxificationReactive Oxygen Species Degradation

General Background

All organisms living in an aerobic environment are exposed to reactive oxygen species (ROS) that are formed through metabolic processes and various environmental stresses such as drought, air pollutants, UV light and high light intensities, chilling temperatures and external chemicals [Van99, Alscher02]. For example, reactive oxygen species (ROS) are produced during the β-oxidation of fatty acids or as a result of photorespiration in photosynthetic organisms [Frugoli96]. ROS such as superoxide and hydroxyl radicals as well as hydrogen peroxide can cause significant damage to proteins, nucleic acids and cell organelles.

Most of the aerobic organisms have developed defense systems to face oxidative stress and to scavenge oxidative radicals in the form of enzymes that can detoxify ROS, such as superoxide dismutase (SOD) and catalase/hydroperoxidase (HP) [Beyer87]. SODs represent the first line of defense against ROS, converting superoxide radicals to hydrogen peroxide and water. SODs are differentiated with regard to their metal cofactor. There are iron-dependent, manganese-dependent and copper/zinc-dependent SODs, which differ not only in their metal cofactor, but also in their subcellular location. Catalase is second in the defense line against active oxygen, converting hydrogen peroxide into water and oxygen.

About This Pathway

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 [Korshunov06].

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 [Battistoni95, Battistoni96]. Regulation of the three enzymes is complex. Under anaerobic conditions, FeSOD is the only superoxide dismutase enzyme present in E. coli [Hassan77, Kargalioglu94]. 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 [Imlay96].

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 [Seaver01]. 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 [Jacobson89].

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 [Imlay08].

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 [Fridovich97].

Reviews: [Fridovich97, Imlay08]

Markus Krummenacker on Tue May 21, 1996:
kr96-5-21:I actually removed WATER again from the primaries for CATAL-RXN ,because it did look more confusing upon closer examination.
Markus Krummenacker on Tue May 21, 1996:
kr96-5-21:added OXYGEN-MOLECULE and WATER on the right side as primariesfor CATAL-RXN . Looks a bit better now.

Created 07-Dec-1994 by Riley M, Marine Biological Laboratory
Reviewed 30-Nov-2006 by Foerster H, TAIR
Revised 20-Feb-2009 by Caspi R, SRI International


Alscher02: Alscher RG, Erturk N, Heath LS (2002). "Role of superoxide dismutases (SODs) in controlling oxidative stress in plants." J Exp Bot 53(372);1331-41. PMID: 11997379

Battistoni95: Battistoni A, Rotilio G (1995). "Isolation of an active and heat-stable monomeric form of Cu,Zn superoxide dismutase from the periplasmic space of Escherichia coli." FEBS Lett 374(2);199-202. PMID: 7589534

Battistoni96: Battistoni A, Folcarelli S, Gabbianelli R, Capo C, Rotilio G (1996). "The Cu,Zn superoxide dismutase from Escherichia coli retains monomeric structure at high protein concentration. Evidence for altered subunit interaction in all the bacteriocupreins." Biochem J 320 ( Pt 3);713-6. PMID: 9003353

Beyer87: Beyer WF Jr, Fridovich I (1987). "Catalases-with and without heme." In MG Simic, KA Taylor, JF Ward, C Von Sonntag, eds, Oxygen Radicals in Biology and Medicine. Plenum, New York, 651-661.

Fridovich97: Fridovich I (1997). "Superoxide anion radical (O2-.), superoxide dismutases, and related matters." J Biol Chem 272(30);18515-7. PMID: 9228011

Frugoli96: Frugoli JA, Zhong HH, Nuccio ML, McCourt P, McPeek MA, Thomas TL, McClung CR (1996). "Catalase is encoded by a multigene family in Arabidopsis thaliana (L.) Heynh." Plant Physiol 112(1);327-36. PMID: 8819328

Hassan77: Hassan HM, Fridovich I (1977). "Enzymatic defenses against the toxicity of oxygen and of streptonigrin in Escherichia coli." J Bacteriol 129(3);1574-83. PMID: 321433

Imlay08: Imlay JA (2008). "Cellular defenses against superoxide and hydrogen peroxide." Annu Rev Biochem 77;755-76. PMID: 18173371

Imlay96: Imlay KR, Imlay JA (1996). "Cloning and analysis of sodC, encoding the copper-zinc superoxide dismutase of Escherichia coli." J Bacteriol 178(9);2564-71. PMID: 8626323

Jacobson89: Jacobson FS, Morgan RW, Christman MF, Ames BN (1989). "An alkyl hydroperoxide reductase from Salmonella typhimurium involved in the defense of DNA against oxidative damage. Purification and properties." J Biol Chem 264(3);1488-96. PMID: 2643600

Kargalioglu94: Kargalioglu Y, Imlay JA (1994). "Importance of anaerobic superoxide dismutase synthesis in facilitating outgrowth of Escherichia coli upon entry into an aerobic habitat." J Bacteriol 176(24);7653-8. PMID: 8002590

Korshunov06: Korshunov S, Imlay JA (2006). "Detection and quantification of superoxide formed within the periplasm of Escherichia coli." J Bacteriol 188(17);6326-34. PMID: 16923900

Seaver01: Seaver LC, Imlay JA (2001). "Alkyl hydroperoxide reductase is the primary scavenger of endogenous hydrogen peroxide in Escherichia coli." J Bacteriol 183(24);7173-81. PMID: 11717276

Van99: Van Breusegem F, Slooten L, Stassart J-M, Botterman J, Moens T, Van Montagu M, Inze D (1999). "Effects of overproduction of tobacco MnSOD in maize chloroplasts on foliar tolerance to cold and oxidative stress." Journal of Experimental Botany, 50(330), 71-78.

Other References Related to Enzymes, Genes, Subpathways, and Substrates of this Pathway

Abril90: Abril N, Pueyo C (1990). "Mutagenesis in Escherichia coli lacking catalase." Environ Mol Mutagen 15(4);184-9. PMID: 2192882

Ackerley06: Ackerley DF, Barak Y, Lynch SV, Curtin J, Matin A (2006). "Effect of chromate stress on Escherichia coli K-12." J Bacteriol 188(9);3371-81. PMID: 16621832

Aguirre12: Aguirre JD, Culotta VC (2012). "Battles with iron: manganese in oxidative stress protection." J Biol Chem 287(17);13541-8. PMID: 22247543

Argaman12: Argaman L, Elgrably-Weiss M, Hershko T, Vogel J, Altuvia S (2012). "RelA protein stimulates the activity of RyhB small RNA by acting on RNA-binding protein Hfq." Proc Natl Acad Sci U S A 109(12);4621-6. PMID: 22393021

Baker04: Baker RD, Cook CO, Goodwin DC (2004). "Properties of catalase-peroxidase lacking its C-terminal domain." Biochem Biophys Res Commun 320(3);833-9. PMID: 15240123

Baker06a: Baker RD, Cook CO, Goodwin DC (2006). "Catalase-peroxidase active site restructuring by a distant and "inactive" domain." Biochemistry 45(23);7113-21. PMID: 16752901

Battistoni98: Battistoni A, Donnarumma G, Greco R, Valenti P, Rotilio G (1998). "Overexpression of a hydrogen peroxide-resistant periplasmic Cu,Zn superoxide dismutase protects Escherichia coli from macrophage killing." Biochem Biophys Res Commun 243(3);804-7. PMID: 9501009

Beauchamp71: Beauchamp C, Fridovich I (1971). "Superoxide dismutase: improved assays and an assay applicable to acrylamide gels." Anal Biochem 44(1);276-87. PMID: 4943714

Beaumont93: Beaumont MD, Hassan HM (1993). "Characterization of regulatory mutations causing anaerobic derepression of the sodA gene in Escherichia coli K12: cooperation between cis- and trans-acting regulatory loci." J Gen Microbiol 139(11);2677-84. PMID: 8277251

Bebien02: Bebien M, Lagniel G, Garin J, Touati D, Vermeglio A, Labarre J (2002). "Involvement of superoxide dismutases in the response of Escherichia coli to selenium oxides." J Bacteriol 184(6);1556-64. PMID: 11872706

Belkin96: Belkin S, Smulski DR, Vollmer AC, Van Dyk TK, LaRossa RA (1996). "Oxidative stress detection with Escherichia coli harboring a katG'::lux fusion." Appl Environ Microbiol 62(7);2252-6. PMID: 8779563

Benov01: Benov L, Al-Ibraheem J (2001). "Glycerol metabolism in superoxide dismutase-deficient Escherichia coli." Free Radic Res 35(6);867-72. PMID: 11811537

Benov03: Benov L, Sequeira F (2003). "Escherichia coli deltafur mutant displays low HPII catalase activity in stationary phase." Redox Rep 8(6);379-83. PMID: 14980071

Benov94: Benov LT, Fridovich I (1994). "Escherichia coli expresses a copper- and zinc-containing superoxide dismutase." J Biol Chem 269(41);25310-4. PMID: 7929223

Benov95: Benov L, Chang LY, Day B, Fridovich I (1995). "Copper, zinc superoxide dismutase in Escherichia coli: periplasmic localization." Arch Biochem Biophys 319(2);508-11. PMID: 7786035

Benov95a: Benov L, Fridovich I (1995). "A superoxide dismutase mimic protects sodA sodB Escherichia coli against aerobic heating and stationary-phase death." Arch Biochem Biophys 322(1);291-4. PMID: 7574689

Benov95b: Benov L, Fridovich I (1995). "Superoxide dismutase protects against aerobic heat shock in Escherichia coli." J Bacteriol 177(11);3344-6. PMID: 7768839

Benov96: Benov LT, Beyer WF, Stevens RD, Fridovich I (1996). "Purification and characterization of the Cu,Zn SOD from Escherichia coli." Free Radic Biol Med 21(1);117-21. PMID: 8791100

Benov96a: Benov L, Fridovich I (1996). "Functional significance of the Cu,ZnSOD in Escherichia coli." Arch Biochem Biophys 327(2);249-53. PMID: 8619610

Benov97: Benov L, Sage H, Fridovich I (1997). "The copper- and zinc-containing superoxide dismutase from Escherichia coli: molecular weight and stability." Arch Biochem Biophys 340(2);305-10. PMID: 9143335

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Please cite the following article in publications resulting from the use of EcoCyc: Nucleic Acids Research 41:D605-12 2013
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