The ascorbateglutathione cycle coming of age Figure 1 from Depletion of Glutathione during Oxidative Stress and Efficacy of N Acetyl Cysteine: An Old Drug with New Approaches Semantic Scholar 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 science DrinkAid Ascorbate and Glutathione: The Heart of the Redox Hub1