Sel include but not limited to glutathione peroxidases (GPx1-GPx6), thioredoxin reductases (TrxR1-TrxR3), iodothyronine deiodinases (ID1-ID3), selenophosphate synthetase 2 (SPS2), 15-kDa Sel (Sel15), SelH, SelI, SelK, SelM, SelN, SelO, SelP, SelR, SelS, SelT, SelV, SelW, as well as the 15-kDa Sel (Fep15), SelJ and SelU found in fish. 