Glutathione reductase Wikipedia Glutathione redox cycle. Glutathione (GSH) is synthesized from the Download Scientific Diagram TJ. Glutathione peroxidase is an important enzyme in cellular antioxidant defense systems, detoxifying peroxides and hydroperoxides. As a component of the glutathione cycle, it protects the liver from reactive oxygen metabolites. Selenocysteine Full article: Mimetics of the Selenoenzyme Glutathione Peroxidase: Novel Structures and Unusual Catalytic Mechanisms