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26-493: GPX may refer to: Science and technology [ edit ] Glutathione peroxidase (GPx), an enzyme family GPS Exchange Format (GPX), for GPS data (released 2002) Kawasaki Ninja GPX-250R , a motorcycle model (released 1986) Other uses [ edit ] Gautampura Road railway station , Ujjain, Madhya Pradesh, India GP Strategies Corporation , an American consulting firm (NYSE ticker: GPX ) Topics referred to by

52-689: A molecular weight of 84 kDa . Glutathione peroxidase was discovered in 1957 by Gordon C. Mills. Activity of glutathione peroxidase is measured spectrophotometrically using several methods. A direct assay by linking the peroxidase reaction with glutathione reductase with measurement of the conversion of NADPH to NADP is widely used. The other approach is measuring residual GSH in the reaction with Ellman's reagent . Based on this, several procedures for measuring glutathione peroxidase activity were developed using various hydroperoxides as substrates for reduction, e.g. cumene hydroperoxide, tert-butyl hydroperoxide and hydrogen peroxide. The other methods include

78-577: A high preference for lipid hydroperoxides; it is expressed in nearly every mammalian cell, though at much lower levels. Glutathione peroxidase 2 is an intestinal and extracellular enzyme, while glutathione peroxidase 3 is extracellular, especially abundant in plasma. So far, eight different isoforms of glutathione peroxidase (GPx1-8) have been identified in humans. The main reaction that glutathione peroxidase catalyzes is: where GSH represents reduced monomeric glutathione , and GS–SG represents glutathione disulfide . The mechanism involves oxidation of

104-406: A potent reducing agent, donates electrons to disulfide bonds in the nanogels, initiating a thiol-disulfide exchange reaction. This reaction breaks the disulfide bonds, converting them into two thiol groups, and facilitates targeted drug release where it is needed most. This reaction is called a thiol-disulfide exchange reaction. where R and R' are parts of the micro-nanogel structure, and GSSG

130-482: A role in the development of celiac disease . The activity of this enzyme has been reported to be decreased in case of copper deficiency in the liver and plasma. Glutathione Glutathione ( GSH , / ˌ ɡ l uː t ə ˈ θ aɪ oʊ n / ) is an organic compound with the chemical formula HOCOCH(NH 2 )CH 2 CH 2 CONHCH(CH 2 SH)CONHCH 2 COOH . It is an antioxidant in plants , animals , fungi , and some bacteria and archaea . Glutathione

156-494: Is a measure of cellular oxidative stress where increased GSSG-to-GSH ratio is indicative of greater oxidative stress. In the reduced state, the thiol group of cysteinyl residue is a source of one reducing equivalent . Glutathione disulfide (GSSG) is thereby generated. The oxidized state is converted to the reduced state by NADPH . This conversion is catalyzed by glutathione reductase : GSH protects cells by neutralising (reducing) reactive oxygen species . This conversion

182-588: Is capable of preventing damage to important cellular components caused by sources such as reactive oxygen species , free radicals , peroxides , lipid peroxides , and heavy metals . It is a tripeptide with a gamma peptide linkage between the carboxyl group of the glutamate side chain and cysteine . The carboxyl group of the cysteine residue is attached by normal peptide linkage to glycine . Glutathione biosynthesis involves two adenosine triphosphate -dependent steps: While all animal cells are capable of synthesizing glutathione, glutathione synthesis in

208-450: Is different from Wikidata All article disambiguation pages All disambiguation pages Glutathione peroxidase Several isozymes are encoded by different genes , which vary in cellular location and substrate specificity. Glutathione peroxidase 1 (GPx1) is the most abundant version, found in the cytoplasm of nearly all mammalian tissues, whose preferred substrate is hydrogen peroxide. Glutathione peroxidase 4 (GPx4) has

234-434: Is illustrated by the metabolism of N -acetyl- p -benzoquinone imine (NAPQI). NAPQI is a reactive metabolite formed by the action of cytochrome P450 on paracetamol (acetaminophen). Glutathione conjugates to NAPQI, and the resulting ensemble is excreted. In plants, glutathione is involved in stress management. It is a component of the glutathione-ascorbate cycle , a system that reduces poisonous hydrogen peroxide . It

260-412: Is illustrated by the reduction of peroxides: and with free radicals: Aside from deactivating radicals and reactive oxidants, glutathione participates in thiol protection and redox regulation of cellular thiol proteins under oxidative stress by protein S -glutathionylation, a redox-regulated post-translational thiol modification. The general reaction involves formation of an unsymmetrical disulfide from

286-419: Is in the mitochondria . Human beings synthesize glutathione, but a few eukaryotes do not, including some members of Fabaceae , Entamoeba , and Giardia . The only known archaea that make glutathione are halobacteria . Some bacteria , such as " Cyanobacteria " and Pseudomonadota , can biosynthesize glutathione. Systemic availability of orally consumed glutathione has poor bioavailability because

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312-401: Is oxidized glutathione (glutathione disulfide). The breaking of disulfide bonds causes the nanogel to degrade into smaller fragments. This degradation process leads to the release of encapsulated drugs. The released drug molecules can then exert their therapeutic effects, such as inducing apoptosis in cancer cells. The content of glutathione in must , the first raw form of wine, determines

338-409: Is shown below: Glutathione reductase then reduces the oxidized glutathione to complete the cycle: Mammalian GPx1 , GPx2 , GPx3 , and GPx4 have been shown to be selenium -containing enzymes, whereas GPx6 is a selenoprotein in humans with cysteine-containing homologues in rodents . GPx1, GPx2, and GPx3 are homotetrameric proteins, whereas GPx4 has a monomeric structure. As the integrity of

364-865: Is the precursor of phytochelatins , glutathione oligomers that chelate heavy metals such as cadmium . Glutathione is required for efficient defence against plant pathogens such as Pseudomonas syringae and Phytophthora brassicae . Adenylyl-sulfate reductase , an enzyme of the sulfur assimilation pathway, uses glutathione as an electron donor. Other enzymes using glutathione as a substrate are glutaredoxins . These small oxidoreductases are involved in flower development, salicylic acid , and plant defence signalling. Among various types of cancer , lung cancer , larynx cancer , mouth cancer , and breast cancer exhibit higher concentrations (10-40 mM) of GSH compared to healthy cells. Thus, drug delivery systems containing disulfide bonds , typically cross-linked micro-nanogels, stand out for their ability to degrade in

390-413: The organelles . The concentration of glutathione in the cytoplasm is significantly higher (ranging from 0.5-10 mM) compared to extracellular fluids (2-20 μM), reaching levels up to 1000 times greater. In healthy cells and tissue, more than 90% of the total glutathione pool is in the reduced form (GSH), with the remainder in the disulfide form (GSSG). 80-85% of cellular GSH is in the cytosol and 10-15%

416-478: The selenol of a selenocysteine residue by hydrogen peroxide. This process gives the derivative with a selenenic acid (RSeOH) group. The selenenic acid is then converted back to the selenol by a two step process that begins with reaction with GSH to form the GS-SeR and water . A second GSH molecule reduces the GS-SeR intermediate back to the selenol, releasing GS-SG as the by-product. A simplified representation

442-1058: The cellular and subcellular membranes depends heavily on glutathione peroxidase, its antioxidative protective system itself depends heavily on the presence of selenium . Mice genetically engineered to lack glutathione peroxidase 1 (Gpx1 mice) are grossly phenotypically normal and have normal lifespans, indicating this enzyme is not critical for life. However, Gpx1 mice develop cataracts at an early age and exhibit defects in muscle satellite cell proliferation. Gpx1 mice showed up to 16 dB higher auditory brainstem response (ABR) thresholds than control mice. After 110 dB noise exposure for one hour, Gpx1 mice had up to 15 dB greater noise-induced hearing loss compared with control mice. " Mice with knockouts for GPX3 (GPX3 ) or GPX2 (GPX2 ) also develop normally However, glutathione peroxidase 4 knockout mice die during early embryonic development. Some evidence, though, indicates reduced levels of glutathione peroxidase 4 can increase life expectancy in mice. The bovine erythrocyte enzyme has

468-451: The function of citrulline as part of the nitric oxide cycle. It is a cofactor and acts on glutathione peroxidase . Glutathione is used to produce S-sulfanylglutathione, which is part of hydrogen sulfide metabolism. Glutathione facilitates metabolism of xenobiotics . Glutathione S -transferase enzymes catalyze its conjugation to lipophilic xenobiotics, facilitating their excretion or further metabolism. The conjugation process

494-403: The hydrolysis of S - D -lactoylglutathione to glutathione and D -lactic acid . It maintains exogenous antioxidants such as vitamins C and E in their reduced (active) states. Among the many metabolic processes in which it participates, glutathione is required for the biosynthesis of leukotrienes and prostaglandins . It plays a role in the storage of cysteine. Glutathione enhances

520-405: The liver has been shown to be essential. GCLC knockout mice die within a month of birth due to the absence of hepatic GSH synthesis. The unusual gamma amide linkage in glutathione protects it from hydrolysis by peptidases. Glutathione is the most abundant non-protein thiol ( R−SH -containing compound) in animal cells, ranging from 0.5 to 10 mmol/L. It is present in the cytosol and

546-417: The presence of high concentrations of glutathione (GSH). This degradation process releases the drug payload specifically into cancerous or tumorous tissue, leveraging the significant difference in redox potential between the oxidizing extracellular environment and the reducing intracellular cytosol. When internalized by endocytosis , nanogels encounter high concentrations of GSH inside the cancer cell. GSH,

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572-423: The protectable protein (RSH) and GSH: Glutathione is also employed for the detoxification of methylglyoxal and formaldehyde , toxic metabolites produced under oxidative stress. This detoxification reaction is carried out by the glyoxalase system . Glyoxalase I (EC 4.4.1.5) catalyzes the conversion of methylglyoxal and reduced glutathione to S - D -lactoylglutathione. Glyoxalase II (EC 3.1.2.6) catalyzes

598-403: The same term [REDACTED] This disambiguation page lists articles associated with the title GPX . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=GPX&oldid=1171391363 " Category : Disambiguation pages Hidden categories: Short description

624-454: The stage of diabetic nephropathy . In one study, the activity of glutathione peroxidase along with other antioxidant enzymes such as superoxide dismutase and catalase was not associated with coronary heart disease risk in women. Glutathione peroxidase activity was found to be much lower in patients with relapsing-remitting multiple sclerosis . One study has suggested that glutathione peroxidase and superoxide dismutase polymorphisms play

650-429: The tripeptide is the substrate of proteases (peptidases) of the alimentary canal , and due to the absence of a specific carrier of glutathione at the level of cell membrane. The administration of N-acetylcysteine (NAC), a cysteine prodrug, helps replenish intracellular GSH levels. Glutathione exists in reduced (GSH) and oxidized ( GSSG ) states. The ratio of reduced glutathione to oxidized glutathione within cells

676-412: The use of CUPRAC reagent with spectrophotometric detection of the reaction product or o -phtalaldehyde as a fluorescent reagent. It has been shown that low levels of glutathione peroxidase as measured in the serum may be a contributing factor to vitiligo . Lower plasma glutathione peroxide levels were also observed in patients with type 2 diabetes with macroalbuminuria and this was correlated to

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