Glutathione peroxidase (GPx) is a family of different enzymes with peroxidase activity and with the main functional mission of protecting the body from oxidative stress.
Glutathione peroxidase is one of the most important enzymes for removing peroxides from living cells. Glutathione peroxidase plays a very important role in protecting cells from damage caused by free oxygen species formed during the breakdown of peroxides. The lipid components of cells are particularly sensitive to reactions with active free radicals, which leads to lipid peroxidation. GPx reduces peroxides to alcohols thus preventing the formation of active free radicals, using glutathione as a reducing agent. There are many glutathione isoenzymes encoded by different genes that can be found in different cell compartments and use different compounds as substrates. So far, 8 different isoenzymes (GPx1-8) have been identified in humans.
Glutathione peroxidase catalyzes the reduction of hydrogen peroxide and many other organic peroxides to water and the corresponding stable alcohols using cellular glutathione as a reducing agent. Most cellular glutathione peroxidases are tetrameric enzymes consisting of four identical monomers with a molecular weight of 22 kDa, each containing selenocysteine at its active site. Selenocysteine is directly involved in the supply of electrons to the peroxide and is oxidized during the process. The enzyme then uses the reduced glutathione as a hydrogen donor to regenerate selenocysteine. Some of the GPx isoenzymes do not contain selenium at their active site.
Cellular glutathione peroxidase is found in all tissues. However, various diseases can affect its levels. Low levels of glutathione peroxidase, as measured in serum, have been shown to contribute to the appearance and progression of vitiligo. Lower levels of the enzyme were also observed in patients with type 2 diabetes with proteinuria. Glutathione peroxidase activity was found to be much lower in patients with recurrent multiple sclerosis. Glutathione peroxidase has also been shown to play a role in the development of celiac disease.
The measurement of glutathione peroxidase in the context of Oxidative Stress tests can help identify the underlying causes for many chronic diseases and clinical disorders, so as to design the appropriate individualized treatment interventions.