Glutathione Peroxidase Assay

Glutathione peroxidase (GPx) is an antioxidant enzyme located in cytoplasma and mitochondria. It catalyzes the reduction of hydrogen peroxide (H2O2) and a variety of organic hydroperoxides (R-O-O-H) to water and the corresponding stable alcohols (R-OH) using glutathione as the reducing reagent, thus inhibiting the formation of free radicals and protecting the cells from oxidative damage. The ScienCell GPx Assay provides an indirect method to quantify the activity of total glutathione peroxidase. In this assay, oxidized glutathione, produced upon reduction of peroxide substrate by glutathione peroxidase, is then recycled back to glutathione using glutathione reductase and NADPH. The oxidation of NADPH to NADP+ is monitored by a decrease in the absorbance at 340 nm. Since all other reagents are provided in excess, the GPx activity is rate-limiting. The rate of decrease in A340nm is directly proportional to the GPx activity. In this assay, cumene hydroperoxide is used as the peroxide substrate, so the total GPx (selenium and non-selenium containing) activity in a variety of samples can be measured.