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Catalytic Site Atlas

CSA LITERATURE entry for 1eso

E.C. namesuperoxide dismutase
SpeciesEscherichia coli (Bacteria)
E.C. Number (IntEnz)
CSA Homologues of 1esoThere are 128 Homologs
CSA Entries With UniProtID P0AGD1
CSA Entries With EC Number
PDBe Entry 1eso
PDBSum Entry 1eso
MACiE Entry 1eso

Literature Report

IntroductionCopper-zinc superoxide dimutase (CuZnSOD) catalyses the disproportionation of superoxide into dioxygen and hydrogen peroxide.
In higher organisms, superoxide anions are produced as an occasional byproduct during the one-electron reduction of dioxygen in respiration and photosynthesis. Superoxides are also produced by macrophages as a part of the immune response. Excess amounts of superoxides can inactivate enzymes with iron-sulphur clusters and can lead to the formation of highly oxidizing species that can damage cellular constituents. Therefore, organisms must have ways to regulate the concentration of superoxide concentrations. Many Gram-negative bacterial pathogens also possess CuZnSOD to counteract the phagocyte superoxide burst from their hosts.
MechansimBased on crystal structures, a mechanism is proposed. Guided by the electrostatic channel, superoxide enters the active site, displaces a water molecule, forms a hydrogen bond with Arg141 and binds to the copper(II) ion. Bound superoxide reduces Cu(II) to Cu(I) with simultaneous breaking of the bond between His61 and the Cu(I) ion. Dioxygen is released and His61 is protonated by the solvent. Another superoxide enters the active site. Electron is transferred from Cu(I) to the superoxide and at the same time, 2 protons are transferred to the superoxides from protonated His61 and a water molecule, forming hydrogen peroxide. Cu(II) then moves to reform the histidine bridge.
Zn(II) bound to His61 ND1 raises the pKa of NE2 to ~13, so that unliganded NE2 will always be protonated at physiological pH.

Catalytic Sites for 1eso

Annotated By Reference To The Literature - Site 2 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
HisA6192macie:sideChainIt acts as an acid to donate a proton to superoxide in the second part of the reaction cycle to form hydrogen peroxide.

Literature References

Tainer JA
Structure and mechanism of copper, zinc superoxide dismutase.
Nature 1983 306 284-287
PubMed: 6316150
Hart PJ
A structure-based mechanism for copper-zinc superoxide dismutase.
Biochemistry 1999 38 2167-2178
PubMed: 10026301