抄録
Selenium is a naturally occurring trace element that belongs to the group 16 of the Periodic Table. The mineral is required as an essential micronutrient for mammals, birds, reptiles, amphibians, fishes, algae, and some microorganisms including archaea. Higher plants can accumulate selenium under the circumstances where selenium is abundant in soil, but their essentiality in plants is yet to be established. Inorganic forms of selenium take one of the four oxidation states including selenate SeO4 2-, selenite SeO3 2-, elemental selenium Se0 and divalent selenide Se2-. An activated form of divalent selenide, monoselenophosphate HSe-PO3H2 serves as a reactive substrate for the biogenesis of SeCys-tRNAUGA, which is cotranslationally inserted in the growing polypeptide chain at the in-frame UGA codon. This review summarizes present understanding regarding the reductive assimilation pathway of inorganic oxyanions of selenium, and introduces confronting two hypotheses on how the selenium could be specifically reduced and efficiently utilized for monoselenophosphate synthetase.
