Glutathione peroxidase
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Glutathione_peroxidase".

glutathione peroxidase 1
Identifiers
Symbol	GPX1
Entrez	2876
HUGO	4553
OMIM	138320
RefSeq	NM_000581
UniProt	P07203
Other data
EC number	1.11.1.9
Locus	Chr. 3 p21.3

Glutathione peroxidase (PDB 1GP1, EC 1.11.1.9) 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.^[1]

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

History

Glutathione peroxidase was discovered in 1957 by Gordon C. Mills. ^[2]

References

1. ^ Ran Q, Liang H, Ikeno Y, et al (2007). "Reduction in glutathione peroxidase 4 increases life span through increased sensitivity to apoptosis". J. Gerontol. A Biol. Sci. Med. Sci. 62 (9): 932–42. PMID 17895430. 
2. ^ Mills, G. Journal of Biological Chemistry 229:189-97.1957.

See also

• Glutathione reductase

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