This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Proteins and Amino Acids, Subject name: Biochemistry
[{'content': 'Amino acid responsible for Thioredoxin reductase activation: \nSelect and explain. \nA. Serine, B. Selenocysteine, C. Cysteine, D. Alanine', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. B. SelenocysteineSelenocysteine is seen in the active site of following Enzymes and ProteinsQThioredoxin reductaseGlutathione PeroxidaseIodothyronine DeiodinaseSelenoprotein P', 'role': 'assistant'}]