Glutathione peroxidase

protein
Name = glutathione peroxidase 1
caption =


width = 240 px
HGNCid = 4553
Symbol = GPX1
AltSymbols =
EntrezGene = 2876
OMIM = 138320
RefSeq = NM_000581
UniProt = P07203
PDB =
ECnumber = 1.11.1.9
Chromosome = 3
Arm = p
Band = 21.3
LocusSupplementaryData = protein
Name = glutathione peroxidase 3 (plasma)
caption =


width =
HGNCid = 4555
Symbol = GPX3
AltSymbols =
EntrezGene = 2878
OMIM = 138321
RefSeq = NM_002084
UniProt = P22352
PDB =
ECnumber = 1.11.1.9
Chromosome = 5
Arm = q
Band = 23
LocusSupplementaryData = protein
Name = glutathione peroxidase 5 (epididymal androgen-related protein)
caption =


width =
HGNCid = 4557
Symbol = GPX5
AltSymbols =
EntrezGene = 2880
OMIM = 603435
RefSeq = NM_001509
UniProt = O75715
PDB =
ECnumber = 1.11.1.9
Chromosome = 6
Arm = p
Band = 21.32
LocusSupplementaryData = protein
Name = glutathione peroxidase 6 (olfactory)
caption =


width =
HGNCid = 4558
Symbol = GPX6
AltSymbols =
EntrezGene = 257202
OMIM = 607913
RefSeq = NM_182701
UniProt = P59796
PDB =
ECnumber = 1.11.1.9
Chromosome = 6
Arm = p
Band = 21
LocusSupplementaryData =

Glutathione peroxidase (PDB|1GP1, EC number|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⁺.

tructure

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.cite journal |author=Ran Q, Liang H, Ikeno Y, "et al" |title=Reduction in glutathione peroxidase 4 increases life span through increased sensitivity to apoptosis |journal=J. Gerontol. A Biol. Sci. Med. Sci. |volume=62 |issue=9 |pages=932–42 |year=2007 |pmid=17895430 |doi=]

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

History

Glutathione peroxidase was discovered in 1957 by Gordon C. Mills. [Mills, G. Journal of Biological Chemistry 229:189-97.1957.]

References

ee also

* Glutathione reductase
* Selenium deficiency