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': 'Control of urea cycle involves the enzyme: \nSelect and explain. \nA. Carbamoyl phosphate synthetase, B. Ornithine transcarbamoylase, C. Argininosuccinase, D. Arginase', 'role': 'user'}, {'content': 'Answer: A \nExplanation: CPS-I reaction is the rate-limiting step in urea formation. It is irreversible and allosterically regulated.\nReference: Vasudevan 7th\xa0 ed, pg 203', 'role': 'assistant'}]