GSH-Px

Related Reading

Introductions

Glutathione peroxidase (GSH-Px) is an important peroxidolytic enzyme widely present in the organism. the active center of GSH-Px is selenocysteine, and its activity level can reflect the selenium level of the organism. Selenium is a component of the GSH-Px enzyme system, which can catalyze the change of GSH to GSSG and reduce toxic peroxides to non-toxic hydroxyl compounds, thus protecting the structure and function of cell membranes from interference and damage by peroxides. the reduction of NADPH is linearly correlated with the activity of glutathione peroxidase. there are four main types of GSH-Px: cytosolic GSH-Px, plasma GSH-Px, plasma GSH-Px, plasma GSH-Px, and plasma GSH-Px. plasma GSH-Px, phospholipid hydroperoxide GSH-Px and gastrointestinal specific GSH-Px.

GSH-Px enzyme system

• Cytosolic GSH-Px

It is composed of four identical subunits of molecular weight 22 kDa in a tetramer, each containing one molecule of selenocysteine, and is widely present in various tissues in the body, with liver erythrocytes being the most abundant. Its physiological function is mainly to catalyze the participation of GSH in peroxidation reactions, scavenging peroxides and hydroxyl radicals generated during cellular respiratory metabolism, thus reducing the peroxidation of polyunsaturated fatty acids in cell membranes.

• Plasma GSH-Px

The composition is the same as cytosolic GSH-Px, which is mainly distributed in the plasma. Its function is not well understood, but it has been shown to be related to the scavenging of extracellular hydrogen peroxide and participation in GSH transport.

• Phospholipid hydrogen peroxide GSH-Px

is a monomer with a molecular weight of 20 kDa and contains 1 molecule of selenocysteine. Originally isolated from pig heart and liver, it is mainly found in testis, with a small distribution in other tissues. Its biological function is to inhibit membrane phospholipid peroxidation.

• Gastrointestinal specificity of GSH-Px

is a tetramer composed of four subunits with a molecular weight of 22 kDa, which is found only in the gastrointestinal tract of rodents, and its function is to protect animals from damage caused by ingested lipid peroxides.

Structure

Mammalian GPx1, GPx2, GPx3 and GPx4 have been shown to be selenium-containing enzymes, while GPx6 is a selenoprotein in humans and a cysteine-containing homolog in rodents. GPx1, GPx2 and GPx3 are homotetrameric proteins, while GPx4 has a monomeric structure. Since the integrity of cell and subcellular membranes depends heavily on glutathione peroxidase, their antioxidant protection system itself depends heavily on the presence of selenium.

Method for the determination of glutathione peroxidase activity

Glutathione peroxidase activity is measured spectrophotometrically using a variety of methods. A direct assay linking the peroxidase reaction with the measurement of the conversion of glutathione reductase to NADPH to NADP is widely used. Another method is the measurement of residual GSH in reactions with Ellman's reagent. On this basis, several procedures were developed to measure glutathione peroxidase activity using various hydroperoxides as reducing substrates, such as isopropylbenzene hydroperoxide, tert-butyl hydroperoxide [and hydrogen peroxide. Other methods include the use of CUPRAC reagents and spectrophotometric detection of reaction products or o-phthalaldehyde as a fluorescent reagent.

Clinical significance

1. One of the indicators of the body's ability to resist peroxidation.
2. Elevated: diabetes mellitus, sickle cell anemia, neonatal hemolysis, thalassemia.
3. Decreased: multiple sclerosis, cancer, coronary artery disease, chronic pancreatitis, burns, surgery.