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
All of the following regarding urea cycle is true, except: 
Select and explain. 
A. On consumption  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
C: Rate limiting enzyme is ornithine transcarbamoylase
Answer: C: Rate limiting enzyme is ornithine transcarbamoylase 
Explanation: 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.