67 by: Maria Drozdz
Student – Maria Drozdz
Enzyme: Extracellular Superoxide Dismutase also known as : SOD3 and EcSOD,
EC: 1. 15. 1. 1
Extracellular superoxide dismutase contains 222 amino acids and 18 amino acids at the signal peptide. The enzyme can be found in the extracellular space and cell surfaces. The main responsibility of SOD3 is to convert superoxide radicals into hydrogen peroxide and molecular oxygen, to control oxidative stress. The active domain also referred to as the catalytic d main is found in residues 96 to 193 and has a beta-barrel structure. In the catalytic domain, zinc which is catalytically active, binds to amino acid residues 113, 121, and 124 all three of which are histidine. Zinc is also bound to the amino acid, aspartic acid located on residue 127. Copper in this region provides the enzyme with stability, it binds to four histidine amino acids found on residues 96, 98, 113, and 163. The superoxide radical gets guided to the sites of copper and zinc by an electrostatic loop, that is positively charged and created by lysine on amino acid 136 and arginine on amino acid 143. At the active site, the radical donates an electron to the metal cofactor creating a metal-peroxide complex. An additional superoxide radical allows for the hydrogen peroxide to be released and allows the metal cofactor involved to return to its original state. The second superoxide radical receives an electron and is released as molecular oxygen. Extracellular superoxide dismutase is an anti-inflammatory and plays a role in several different cardiovascular diseases. Other members of the superoxide dismutase group include SOD 1 found in the cytoplasm and mitochondrial matrix that also contains zinc and copper, along with SOD 2 found inside the mitochondria that has the metal cofactor of manganese.
References
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