Glutathione peroxidase

The enzyme glutathione peroxidase ( PDB 1GP1 (http://www.rcsb.org/pdb/cgi/explore.cgi?pid=60591045867525&pdbId=1GP1), EC 1.11.1.9) is found in the erythrocytes of mammals, and helps prevent peroxidation of cell membranes by consuming free peroxide in the cell. The summary reaction the enzyme catalyzes is:

2GSH + H₂O₂ → GSSG + 2H₂O

Where GSH represents reduced monomeric glutathione, and GSSG represents oxidized glutathione. Glutathione reductase[?] then reduces the oxidized glutathione to complete the cycle:

GSSG + NADPH + H⁺ → 2 GSH + NADP⁺

Glutathione peroxidase is a tetramer, and the bovine erythrocyte enzyme has a molecular weight of 84,000. It is a selenium containing enzyme with 4 selenocysteine amino acid residues that participate in the actual mechanism of this enzyme.