This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of protein and amino acid, Subject name: Biochemistry
[{'content': 'Which of the following is the rate-limiting enzyme in pyrimidine synthesis? \nSelect and explain. \nA. Aspoate transcarbamylase, B. Dihydro-orotase, C. Redvctase, D. UMP kinase', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Carbamoyl phosphate and aspaate combine to form carbamoyl aspaate is the rate-limiting step in pyrimidine synthesis. The enzyme is aspayl transcarbamoylase.', 'role': 'assistant'}]