This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Urea cycle, Subject name: Biochemistry
Allosteric activator of NAG synthase is: 
Select and explain. 
A. Aspaate, B. Arginine, C. CPS-I, D. CPS-II
B: Arginine
Answer: B: Arginine 
Explanation: NAG is an allosteric activator of CPS-I (rate limiting enzyme) NAG is synthesized from N-acetyl glutamate synthase or NAG synthase, for which arginine is the activator.