<prompt> Which of the following aminoacids is a component of Thioredoxin reductase?SelenocysteineCysteineMethionineHomocysteine  <response>: Ans. is a i.e., Selenocysteine Selenocysteine is present at the active site of some enzymes that catalyze redox reactions, e.g. thioredoxin reductase, glutathione peroxidase, and the deiodinase conves thyroxin to triiothyronine. 