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J.Health Sci., 51(2), 107-114, 2005
-Review-
Metabolomics of Selenium: Se Metabolites Based on Speciation Studies
Kazuo T. Suzuki*
Department of Toxicology and Environmental Health, Graduate School of Pharmaceutical Sciences, Chiba University, 1-8-1 Inohana,
Chuo, Chiba 260-8675, Japan
Selenium is a trace element essential for the normal function of the body. This metalloid is quite unique in its
metabolism compared with typical essential metals such as copper and zinc. In the present communication, the
metabolism of selenium in the body was reviewed from the viewpoint of metabolomics based on speciation studies.
Both inorganic and organic forms of slenium can be the nutritional source, and they are transformed to the common
intermediate, selenide or its equivalent. Selenite and selenate are reduced simply to selenide for further utilization
and/or excretion. On the other hand, organic selenocysteine is directly lysed to selenide, while selenomethionine is
transformed to selenocysteine (trans-selenation pathway), similarly to the trans-sulfuration pathway for methionine
to cysteine, and then lysed to selenide. Selenide is known to be transformed to selenocysteine on tRNA, and the
selenocysteinyl residue is incorporated into selenoprotein sequences by the codon specific to selenocysteine, UGA.
Diverse selenium chemicals in foods seem to be recognized as selenium species and transformed to selenide, and
then utilized for the synthesis of selenoproteins. Surplus selenium is methylated stepwise to methylated selenium
metabolites from the common intermediate selenide. The major urinary metabolite is
1beta-methylseleno-N-acetyl-D-galactosamine (selenosugar). Trimethylselenonium has been recognized as the urinary metabolite excreted in
response to excessive doses and as a biological marker for excessive doses. However, recent results contradicted this.
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