title: Glutathione peroxidases.
abstract: BACKGROUND
  With increasing evidence that hydroperoxides are not only toxic but rather exert essential physiological functions, also hydroperoxide removing enzymes have to be re-viewed. In mammals, the peroxidases inter alia comprise the 8 glutathione peroxidases (GPx1-GPx8) so far identified.
  
  
  OBJECTIVE
  Since GPxs have recently been reviewed under various aspects, we here focus on novel findings considering their diverse physiological roles exceeding an antioxidant activity.
  
  
  CONCLUSIONS
  GPxs are involved in balancing the H2O2 homeostasis in signalling cascades, e.g. in the insulin signalling pathway by GPx1; GPx2 plays a dual role in carcinogenesis depending on the mode of initiation and cancer stage; GPx3 is membrane associated possibly explaining a peroxidatic function despite low plasma concentrations of GSH; GPx4 has novel roles in the regulation of apoptosis and, together with GPx5, in male fertility. Functions of GPx6 are still unknown, and the proposed involvement of GPx7 and GPx8 in protein folding awaits elucidation.
  
  
  CONCLUSIONS
  Collectively, selenium-containing GPxs (GPx1-4 and 6) as well as their non-selenium congeners (GPx5, 7 and 8) became key players in important biological contexts far beyond the detoxification of hydroperoxides. This article is part of a Special Issue entitled Cellular functions of glutathione.
authors.affiliation: Department of Biochemistry of Micronutrients, German Institute of Human Nutrition, Nuthetal, Germany. flohe@dife.de
authors.forename: Regina
authors.initials: R
authors.lastname: Brigelius-Flohé
authors.forename: Matilde
authors.initials: M
authors.lastname: Maiorino
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism*; D005979:Glutathione Peroxidase / Q000378:metabolism*; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D010084:Oxidation-Reduction
chemical_list: D000975:Antioxidants; D006861:Hydrogen Peroxide; D005979:Glutathione Peroxidase; D005978:Glutathione