Definitions

Glutathione peroxidase

Glutathione peroxidase

Glutathione peroxidase 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.

Isozymes

There are several isozymes encoded by different genes, which vary in celullar location and substrate specificity. Glutathione peroxidase 1 is the most abundant version, found in the cytoplasm of nearly all mammalian tissues, whose preferred substrate is hydrogen peroxide.

Reaction

An example reaction that glutathione peroxidase catalyzes is:

2GSH + H2O2 → GS–SG + 2H2O,

where GSH represents reduced monomeric glutathione, and GS–SG represents glutathione disulfide.

Glutathione reductase then reduces the oxidized glutathione to complete the cycle:

GS–SG + NADPH + H+ → 2 GSH + NADP+.

Structure

Glutathione peroxidase is a selenium-containing tetrameric glycoprotein, that is, a molecule with four selenocysteine amino acid residues. 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.

GP reaction mechanism

The mechanism is at the Selenocystein site, which is in a Se(-) form as resting state. This is oxidized by the peroxide to SeOH which is then trapped by a GSH molecule to Se-SG and by another GSH molecule to Se(-) again, releasing a GS-SG by-product.

GP in other animals

Mice genetically engineered to lack glutathione peroxidase 1 (Gpx1 knockout mice) are phenotypically normal, indicating that this enzyme is not critical for life.

However, glutathione peroxidase 4 knockout (Gpx4 knockout) mice die during early embryonic development.

There is some evidence that reduced levels of glutathione peroxidase 4 can increase life expectancy in mice.

The bovine erythrocyte enzyme has a molecular weight of 84 kDa.

History

Glutathione peroxidase was discovered in 1957 by Gordon C. Mills.

References

See also

Search another word or see glutathione peroxidaseon Dictionary | Thesaurus |Spanish
Copyright © 2014 Dictionary.com, LLC. All rights reserved.
  • Please Login or Sign Up to use the Recent Searches feature
FAVORITES
RECENT

;