Despite its very low level in humans, selenium plays an important and unique role among the (semi)metal trace essential elements because it is the only one for which incorporation into proteins is genetically encoded, as the constitutive part of the 21st amino acid, selenocysteine. Twenty-five selenoproteins have been identified so far in the human proteome. The biological functions of some of them are still unknown, whereas for others there is evidence for a role in antioxidant defence, redox state regulation and a wide variety of specific metabolic pathways. In relation to these functions, the selenoproteins emerged in recent years as possible biomarkers of several diseases such as diabetes and several forms of cancer. Comprehension of the selenium biochemical pathways under normal physiological conditions is therefore an important requisite to elucidate its preventing/therapeutic effect for human diseases. This review summarizes the most recent findings on the biochemistry of active selenium species in humans, and addresses the latest evidence on the link between selenium intake, selenoproteins functionality and beneficial health effects. Primary emphasis is given to the interpretation of biochemical mechanisms rather than epidemiological/observational data. In this context, the review includes the following sections: (1) brief introduction; (2) general nutritional aspects of selenium; (3) global view of selenium metabolic routes; (4) detailed characterization of all human selenoproteins; (5) detailed discussion of the relation between selenoproteins and a variety of human diseases.

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Selenium biochemistry and its role for human health

Mercury and selenium interaction: A review

Total mercury, methylmercury and selenium in mercury polluted areas in the province Guizhou, China

The interaction between mercury (Hg) and selenium (Se) is one of the best known examples of biological antagonism, yet the underlying mechanism remains unclear. This review focuses on the possible pathways leading to the Hg-Se antagonism, with an emphasis on the potential Hg-Se compounds that are responsible for the antagonism at the molecular level (i.e., bis[methylmercuric]selenide, methylmercury selenocysteinate, selenoprotein P-bound HgSe clusters, and the biominerals HgSexS1−x). The presence of these compounds in biological systems has been suggested by direct or indirect evidence, and their chemical properties support their potentially key roles in alleviating the toxicity of Hg and Se (at high Hg and Se exposures, respectively) and deficiency of Se (at low Se exposures). Direct analytical evidences are needed, however, to confirm their in vivo presence and metabolic pathways, as well as to identify the roles of other potential Hg-Se compounds. Further studies are also warranted for the determination of thermodynamic properties of these compounds under physiological conditions toward a better understanding of the Hg-Se antagonism in biota, particularly under real world exposure scenarios.

Mercury-selenium compounds and their toxicological significance: toward a molecular understanding of the mercury-selenium antagonism.

In July, 1988, more than 300 scientists from 29 different countries gathered at Tiibingen, W. Germany, in order to spend 4 days discussing their favourite trace element, selenium. This meeting continued the good tradition of three previous meetings held in Corvallis/Oregon, 1976, in Lubbock/Texas, 1980, and in Beijing/China, in 1984. Incidentally, the University of Tiibingen provided a unique historical background for a Symposium devoted to recent advances in biochemistry, pharmacology, human nutrition and human health; here, the first independent depart ment of Physiological Chemistry in Germany was founded in 1845. Pro fessor H9Ppe-Seyler elucidated here the hemin structure and his student Friedrich Miescher discovered the nucleic acids. This book contains one-half of the oral or poster presentations which were selected before the meeting was held on the basis of a one page abstract. It is the reader who will have to decide whether this time consuming policy of quality assessment was warranted or not."

Selenium in biology and medicine

THE ability of selenium compounds to modify profoundly the toxicity of both organic and inorganic mercury compounds has been demonstrated in experimental animals by Parizek and co-workers1,2. The analytical data of Ganther et al.3 on tuna and of Koeman et al.4 on marine mammals showed that natural levels of mercury and selenium are strongly correlated. Here we report an approximately molar ratio for these elements in certain human organs following exposure to high levels of inorganic mercury.

L. Kosta

Papers

Correlation between selenium and mercury in man following exposure to inorganic mercury