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': 'All of the following regarding urea cycle is true, except: \nSelect and explain. \nA. On consumption\xa0 of high amount of proteins, excess urea is formed, B. Synthesis of argininosuccinate consumes energy, C. Rate limiting enzyme is ornithine transcarbamoylase, D. One nitrogen of urea comes from aspartate', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Carbamoyl phosphate synthase I, the rate-limiting enzyme of the urea cycle, is active only in the presence of N-acetylglutamate, an allosteric activator that enhances the affinity of the synthase for ATP.', 'role': 'assistant'}]