What is Glutathione Peroxidase/Catalase?

Glutathione Peroxidase/Catalase (GPx) is the general name of an enzyme family with peroxidase activity whose main biological role is to protect the organism from oxidative damage. The biochemical function of glutathione peroxidase is to reduce lipid hydroperoxides to their corresponding alcohols and to reduce free hydrogen peroxide to water.
Structure
Mammalian GPx1, GPx2, GPx3, and GPx4 have been shown to be selenium-containing enzymes, whereas GPx6 is a selenoprotein in humans with cysteine-containing homologues in rodents. GPx1, GPx2, and GPx3 are homotetrameric proteins, whereas GPx4 has a monomeric structure. As the integrity of the cellular and subcellular membranes depends heavily on glutathione peroxidase, the antioxidative protective system of glutathione peroxidase itself depends heavily on the presence of selenium.
Reaction mechanism
The mechanism is at the selenocysteine site, which is in a Se(-) form as resting state. This is oxidized by the peroxide to SeOH, which then reacts with a GSH molecule to form GS-Se and water, and then by another GSH molecule to from Se(-) again, releasing GS-SG as the by-product.
Role in disease
Genetic polymorphisms in Glutathione Peroxidase enzymes and their altered expressions and activities are associated with oxidative DNA damage and, as a result, the individual’s risk of cancer susceptibility.
Catalase is a common enzyme found in nearly all living organisms exposed to oxygen. It catalyzes the decomposition of hydrogen peroxide to water and oxygen. It is a very important enzyme in reproductive reactions. Likewise, catalase has one of the highest turnover numbers of all enzymes; one catalase molecule can convert millions of molecules of hydrogen peroxide to water and oxygen each second.
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