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Human Exposure to Metals Through Consumption of Marine Foods: A Case Study of Exceptionally High Intake Among Greenlanders
Published in Robert W. Furness, Philip S. Rainbow, Heavy Metals in the Marine Environment, 1990
Selenium is now recognized to be an essential nutrient. As part of the active groups in the enzyme glutathione peroxidase, it is, together with other antioxidants, such as vitamin E. part of the defence mechanism against cellular oxidative damage. Beside this function, it may play a protective role with regard to the toxic effects of heavy metals, mercury, cadmium, and probably also lead.
N-Acetylcysteine, Glutathione, and Glutathione Disulfide on NIH 3T3, VH10 and MCF-7 Cells Exposed to Ascorbate and Cu(II) Ions
Published in Satish A. Dake, Ravindra S. Shinde, Suresh C. Ameta, A. K. Haghi, Green Chemistry and Sustainable Technology, 2020
Katarína Valachová, Ivana Šušaníková, Dominika Topoľská, Eszter Bögi, Ladislav Šoltés
Glutathione (γ-l-glutamyl-l-cysteinylglycine) is a tripeptide that is synthesized in the cytosol from glutamic acid, cysteine, and glycine in two adenosine triphosphate-dependent steps. Intracellular levels of glutathione (0.5–10 mmol/l) are controlled by γ-glutamyltranspetidase. Glutathione is a continuous source of cysteine because cysteine can auto-oxidize to cystine and generate potentially unstable reactive oxygen species. Glutathione is present in many cellular compartments, including the endoplasmic reticulum, the nucleus, and mitochondria and is found at higher concentrations in the liver. Glutathione is also found in the extracellular space, such as in bile and plasma. The key function of glutathione is to reduce hydrogen peroxide and other organic peroxides with participation of glutathione peroxidase. Glutathione co-localized in the nucleus has a profound impact on cellular redox homeostasis and nuclear gene expression. Low levels of glutathione are correlated with many autoimmune diseases [41, 42]. Glutathione has an important role in maintaining intracellular redox homeostasis inevitable during hypoxia and production of reactive oxygen species and ·NO. Glutathione exists in cells in reduced (GSH) and oxidized (glutathione disulfide, GSSG) states. About 90% of total glutathione is present in a reduced form and less than 10% in disulfide form. The decreases in the GSH:GSSG ratios indicate the status classified as oxidative stress [5, 42–44]. Glutathione directly reacts with reactive oxygen and nitrogen species such as HO·, HOCl, RO·, RO ·2, 1O2 and ONOO−, whose reaction often might result in the formation of thiyl radicals (GS·) [45]. Glutathione is also involved in several metabolic processes, including the synthesis of proteins and DNA, signal transduction, enzyme activity, gene expression, metabolism, and the intensification of cytoplasmic and transmembrane transport. It is also used to moderate chronic obstructive pulmonary disease, prevent kidney damage, attenuate influenza, and treat pulmonary fibrosis [34, 46]. Another relevant function of glutathione is the detoxification of xenobiotics. Considering the complex physiological function of the glutathione system, its disequilibrium is involved in several pathological pathways and thus plays an important role in cancer and regulation of the progression through the cell cycle and cell survival, growth, and death. The levels of glutathione and enzymes that are related to biosynthesis of glutathione are high in cancer cells, thus leading cancer cells to become resistant to cell death through oxidative stress mechanisms [42, 47, 48].
The effects of imidacloprid on 8-hydroxy-2-deoxyguanosine (8-OHdG) and antioxidant parameters in gill and liver tissues of trout
Published in Chemistry and Ecology, 2022
Aebi (1984) method was used to determine the catalase activity [28]. It is based on the principles of the destruction of hydrogen peroxide (H2O2) radical by catalase enzyme. The enzymatic reaction can be determined by measuring at 240 nm in the spectrophotometer. Results were expressed as mmol/min/ mg of tissue. Glutathione (GSH) reduced by hydrogen peroxide is oxidised to oxidised glutathione (GSSG) via GPx, as in sequential reactions with free radicals. Afterward, NAPDH in the medium is used in the process of reducing GSSG back to GSH with the glutathione reductase enzyme in the reverse direction. Glutathione peroxidase enzyme activity is calculated by measuring the decrease in absorbance that occurs during the oxidation of NADPH to NADP+ in a spectrophotometer at 340 nm [29].
Antioxidant response mechanism of freshwater microalgae species to reactive oxygen species production: a mini review
Published in Chemistry and Ecology, 2020
Adamu Yunusa Ugya, Tijjani Sabiu Imam, Anfeng Li, Jincai Ma, Xiuyi Hua
Catalase and Peroxidase are tetrameric and heme-containing antioxidant enzymes produced by freshwater microalgae to reduce hydrogen peroxide and more active hydroperoxide such as lipid peroxide equation (5).The production site for catalase in freshwater microalgae is peroxisome although several studies including Mhamdi et al. [127] show that catalase can be produced in the chloroplast, cytosol, and mitochondria. The three known groups of catalases are two heme-containing catalases (monofunctional and bifunctional) and one non-heme containing catalases [128]. Both monofunctional and bifunctional heme-containing catalases are sensitive to cyanide although they are both different in sequences, structures and action mechanisms [129]. The two types of peroxidase are ascorbate peroxidase and glutathione peroxidase. Ascorbate peroxidase is regarded as a heme-containing peroxide that plays an important role in H2O2 conversion by freshwater microalgae. Although, scanty or no literature on isozyme of ascorbate peroxidase has been reported these enzymes used ascorbate as a specific electron donor [130]. Glutathione peroxidase plays a vital role in the reduction of H2O2 by oxidation of glutathione, the oxidised glutathione is then reduced by glutathione reductase as a result of electron derived from NADPH.
Predominant role of antioxidants in ameliorating the oxidative stress induced by pesticides
Published in Archives of Environmental & Occupational Health, 2021
Srujana Medithi, Padmaja R. Jonnalagadda, Babban Jee
Glutathione (GSH), an endogenous thiol tripeptide antioxidant is considered as the first line of defense mechanism against cell injuries which are oxidant-mediated. GSH can perform the function by undergoing oxidation to form GSSG, which is later reduced to GSH by the NADPH-dependent glutathione reductase enzyme. Additionally, glutathione peroxidase (a selenium-containing enzyme) catalyzes the GSH-dependent reduction of H2O2 and other peroxides. A study conducted in Methomyl pretreated rats supplemented with vitamins C, E and GSH (100 mg/kg body weight each) observed to have protected rat’s liver showing a significant decrease in the oxidative stress and improved antioxidant SOD levels.64