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The role of atmospheric deposition in biogeochemical selenium cycling
Published in Gary Bañuelos, Zhi-Qing Lin, Dongli Liang, Xue-bin Yin, Selenium Research for Environment and Human Health: Perspectives, Technologies and Advancements, 2019
Selenium (Se) is an important micronutrient, and when it is present in selenocysteine, it is referred to as the 21st amino acid. Selenocysteine is incorporated in selenoproteins that serve a wide range of biological functions (Fairweather-Tait et al. 2011). However, Se only has a narrow range of safe dietary intake levels for humans; too low dietary intake can lead to deficiency and too high intake leads to toxicity. Generally, Se concentrations in the environment are low, and it has been estimated that up to 1 billion people around the globe have low dietary Se intakes. One of the reasons for low dietary Se levels are low content in food crops, which is due to low concentrations and bioavailability of Se in soils.
Clinical Effects of Pollution
Published in William J. Rea, Kalpana D. Patel, Reversibility of Chronic Disease and Hypersensitivity, Volume 5, 2017
William J. Rea, Kalpana D. Patel
Selenium is required for the biosynthesis of the “twenty-first amino acid,” selenocysteine. Twenty-five specific selenoproteins are derived from this amino acid. Selenium deficiency can lead to impairment in immune function and spermatogenesis in addition to thyroid function.1080 One very important selenoprotein is glutathione peroxidase, which protects cell membranes and cellular components against oxidative damage by both hydrogen peroxide and peroxynitrite (ONOO−).1081
Biosynthesis of selenium nanoparticles and their protective, antioxidative effects in streptozotocin induced diabetic rats
Published in Science and Technology of Advanced Materials, 2020
Dabei Fan, Li Li, Zhizhen Li, Ying Zhang, Xiaojun Ma, Lina Wu, Haohao Zhang, Feng Guo
Selenium (Se) is one among the trace elements necessary for humans. In human body, selenium is involved in various processes together with antioxidant defense and immune functions. However, the deficiency of selenium may cause osseous, cardiac, immune and muscular disturbances in the human body [1,2]. The existence of selenocysteine amino acid in the proteins is mainly responsible for biological functions of selenium. Earlier studies have reported that around 100 selenoproteins were found in mammals [2]. Among them, antioxidant enzymes such as thioredoxin reductase and glutathione peroxidase along with selenoprotein-P, are responsible for the transport and storage of Se [3–6]. In addition, it was already known that selenium supplements are protective against wide varieties of harmful factors involving physical factors, such as magnetic fields or heat stress and chemical factors, like drugs causing critical side effects, carcinogens, pesticides or mycotoxins and heavy metals. However, it is a complex issue to consider Se as a most effective supplement because of its narrow therapeutic index, applied form and its efficacy that depends on the method and dosage used in the treatment [5,7–10].
Understanding selenium metabolism in plants and its role as a beneficial element
Published in Critical Reviews in Environmental Science and Technology, 2019
Reshu Chauhan, Surabhi Awasthi, Sudhakar Srivastava, Sanjay Dwivedi, Elizabeth A. H. Pilon-Smits, Om P. Dhankher, Rudra D. Tripathi
In humans, dietary Se is converted to selenocysteine (SeCys), which is regarded as the 21st proteinogenic amino acid, an essential component of 25 different selenoproteins (Pappas, Zoidis, Surai, & Zervas, 2008). The translational incorporation of SeCys into proteins utilizes a specific t-RNA for SeCys that recognizes an opal UGA (stop) codon functioning as a SeCys codon in the presence of a SeCys insertion sequence in the adjacent mRNA (Lobanov, Hatfield, & Gladyshev, 2009). Selenocysteine functions in the catalytic center of several selenoproteins i.e. glutathione peroxidase, thioredoxin reductase, iodothyronine-deiodinases and selenophosphate synthetase. Apart from this specific SeCys insertion mechanism into selenoproteins, SeCys can also be inserted nonspecifically into other proteins, in place of cysteine. The incorporation of SeCys at the active site of enzymes (e.g. in case of methionine-R-sulfoxide reductase) in place of cysteine can alter their catalytic activity and electron donor specificity (Stadtman, 2005). This is thought to contribute to Se toxicity in humans.
Mechanistic studies on the reaction between glutathionylcobalamin and selenocysteine
Published in Journal of Coordination Chemistry, 2019
Ilia A. Dereven’kov, Sergei V. Makarov
Selenocysteine (Sec; Figure 1) is a proteinogenic amino acid found in the active site of several enzymes (e.g. glutathione peroxidase, thioredoxin reductase, methionine sulfoxide reductase, iodothyronine deiodinase) [22]. Its structure resembles cysteine, in which sulfur is replaced by selenium. Sec is highly reactive toward reactive oxygen and nitrogen species [23–25], as well as it can be bound by metal ions [26–29]. Sec is capable of reducing Cbls(III) (viz., H2OCbl and cysteinyl-Cbl) to Cbl(II) [30]. The reaction between H2OCbl and Sec proceeds via rate-determining complexation and further rapid decomposition of Sec-Cbl(III) complex to Cbl(II) and selanyl radical [30]. However, the mechanism of the reduction of thiolato-Cbls by Sec remains unclear. This work reports a kinetic and mechanistic study on the interaction between GSCbl and Sec.