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': 'Aminoacids with its PKR valve within physiological range is: \nSelect and explain. \nA. Glycine, B. Histidine, C. Lysine, D. Arginine', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Histidine', 'role': 'assistant'}]