*4.2.1 Glutathione*

*Antioxidants*

*4.1.3 Glutathione perioxidases (GPx)*

membranes and oxidized lipoproteins [30].

such as glutathione, vitamin C and E, Se, and GPx [3].

**4.2 Nonenzymatic antioxidants**

selenium independent [34].

*4.1.3.1 Application*

CAT enzyme is used in the textile industry for H2O2 removal from fabrics, to make sure the material is peroxide free. Recently, esthetics industries have begun to use CAT enzyme in facial masks, as the combination of CAT enzyme with H2O2 on the face can be used to increase cellular oxygenation in the upper layers of the epidermis [3].

Glutathione peroxidase (EC 1.11.1.9) contains a single selenocysteine residue in each of the four identical subunits, which is important for enzyme activity. GPx (80 kDa) is an imperative intracellular enzyme that catalyzes H2O2 to water and lipid peroxides to their corresponding alcohols mainly in the mitochondria and sometimes in the cytosol. In mammals, there are five GPx isoenzymes. Though their expression is ubiquitous, the level of each isoform differs depending on their tissue type. Mitochondrial and cytosolic glutathione peroxidase (GPx1 or cGPx) reduces

GPx1 is the main ubiquitous selenoperoxidase present in most cells; found in the cytosolic, mitochondrial, and peroxisomal compartments. It is an important antioxidant enzyme required in the detoxification of H2O2 and lipid hydroperoxides and preventing DNA, protein and lipids damage by harmful accumulation of intracellular H2O2 [33]. GPx1 uses GHS as an obligate co-substrate in the reduction of H2O2 to water [32]. Phospholipid hydroperoxidase glutathione (PHGPX) is found in most tissues and can directly reduce the phospholipid hydroperoxides, fatty acid hydroperoxides, and cholesterol hydroperoxides that are produced in peroxidized

GPx4 is found in both the cytosol and the membrane fraction, and is highly expressed in renal epithelial cells and tests. Cytosolic GPx2 or extracellular GPx3 is inadequately found in nearly all tissues except for the gastrointestinal tract and kidney. In recent, GPx5, a new kind, expressed particularly in mouse epididymis, is

Several studies underlined the clinical importance of GPx. In addition, GPx, especially GPx1, have been implicated in the progression and prevention of many frequent and complex diseases, including cancer and cardiovascular disease [34, 35].

GPx is an important antioxidant enzyme in the body. Glutathione (GHS), the master antioxidant, is important for GPx levels due to the closely linked relationship; GHS is a tripeptide that protects the cells against the negative effects of pollution and functions as the body's immune system booster. GHS plays an essential role in red blood cells to remain intact and protects white blood cells, which are responsible for the immune system. An antioxidant's role is specifically essential for the brain because it is sensitive to the presence of free radicals. To increase the body's protection from free radicals, it is imperative to combine certain antioxidants

In previous decades, there has been increasing evidence that large amounts of antioxidants present in our diet contribute to the antioxidant defense system by preventing oxidative stress and specific human diseases. Phytochemicals, the plant-derived compounds, are one of the classes of the dietary factors, which play an essential role in functions of the body. Food materials contain a number of natural compounds reported to have antioxidant characteristics due to the presence

fatty acid hydroperoxides and H2O2 at the expense of glutathione [32].

**10**

Glutathione (γ-glutamyl-cysteinyl-glycine; GSH) is a tripeptide and is the most abundant intracellular antioxidant protecting normal cells from oxidative injury due to its role as a substrate of ROS scavenging enzymes. Glutathione is primarily present in its reduced form (GSH) in normal conditions, with only a small amount being found in the fully oxidized state (GSSG) [41]. Glutathione functions as a nonenzymatic antioxidant through free radical scavenging in cells and serves as a cofactor for several enzymes, include GPx, glutathione reductase (GR), and glutathione transferase (GST) [42, 43].

### *4.2.1.1 Application*

Recently, there is a new era of therapeutic applications of glutathione through the association of decreased GSH levels with the common features of aging and a wide range of pathological conditions, including neurodegenerative disorders. Remarkably, depletion and alterations of GSH in its metabolism appear to be crucial in the onset of Parkinson's disease [44].
