Selenocysteine

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selenocysteine

(Science: amino acid) An unusual amino acid of proteins, the selenium analogue of cysteine, in which a selenium atom replaces sulphur. Involved in the catalytic mechanism of seleno enzymes such as formate dehydrogenase of e. Coli and mammalian glutathione peroxidase. May be co translationally coded by a special opal suppressor tRNAase that recognises certain UGA nonsense codons.