This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
[{'content': 'Which of the following aminoacids is a component of Thioredoxin reductase? \nSelect and explain. \nA. Selenocysteine, B. Cysteine, C. Methionine, D. Homocysteine', 'role': 'user'}, {'content': "Answer: A \nExplanation: 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).", 'role': 'assistant'}]