<prompt> Selenium is present in which enzyme -Glutathione reductaseGlutathione peroxidaseGlutathione deiodinaseThioredoxine peroxidase  <response>: Ans. is b i.e., Glutathione peroxidase Selenium is a trace element that acts as a cofactor for the following enzymes1. Glutathione peroxidase Glutathione is an antioxidant which is effective in detoxifying hydrogen peroxideH2O2 2GSH - GS - SG 2H2O The hydrogen atoms from GSH get added to hydrogen peroxidase to form water. To start with, the source of two hydrogen atoms is selenol side chain of glutathione peroxidase2. Thioredoxinereductase It generates reduced thioredoxin, a dithiol that serves as an electron source for peroxidases and also the important reducing enzyme ribonucleotidereductase that makes DNA precursors from RNA precursors3. Deiodinase All three deiodinases Dl, D2, D3 need selenium as a cofactor. These deiodinases help in the conversion ofT4 to T3 or rT3. 