CONICET | Buscador de Institutos y Recursos Humanos

10. Selenium in biological systems and health Maria S. Gimenez1, Liliana B. Oliveros1, Sandra E. Gomez-Mejiba2and Darío C. Ramirez2 1Departamento de Bioquímica y Ciencias Biológicas, Universidad Nacional de San Luis, IMIBIO-SLCONICET, San Luis, Argentina; 2Experimental Therapeutics Research Program, Oklahoma MedicalResearch Foundation, Oklahoma City, Oklahoma, USA Abstract. Selenium, an essential dietary trace mineral, is a critical component of numerous selenoproteins in humans. As a food component, selenium protects against a number of diseases, including atherosclerosis, coronary ischemic disease and cancer. Moderate selenium deficiency has been linked to many conditions, such as increased risk of infection, male infertility, decreased immune and thyroid function, and several neurologic conditions including Alzheimers and Parkinsons disease. In organisms, selenium occurs most frequently in amino acids where it replaces sulfur, such as selenocysteine (Sec) and selenomethionine, as well as in bonds with proteins. Many of the physiological roles of selenium are directly attributed to its presence within selenoproteins. Incorporation of Sec into selenoproteins employs a unique mechanism that involves decoding of the UGA codon. Selenoproteins are present in all lineages of life (i.e., bacteria, archaea, and eukarya). Between the domains, 30 selenoprotein families have been identified. The human selenoproteome consists of 17 selenoprotein families, some with multiple genes with similar functions. These include glutathione peroxidases (GPx) (five genes), thioredoxin reductases (TrxR) (three genes), iodothyronine deiodinases (DIO; three genes), and selenophosphate synthetases 2 (SPS2). Epidemiologic and animalstudies have provided evidence for a chemopreventive effect of selenium on colorectal cancer, which may be mediated by the antioxidative and anti-inflammatory properties of selenoenzymes.

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