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': 'N acetylglutamate serve as allosteric actor of which of the following enzyme in the urea cycle? \nSelect and explain. \nA. Argininosuccinate lyase, B. Argininosuccinate synthase, C. Ornithine transcarbamoylase, D. Carbamoyl phosphate synthetase I', 'role': 'user'}, {'content': 'Answer: D \nExplanation: N acetylglutamate serve as allosteric actor of Carbamoyl phosphate synthetase I, by enhancing the affinity of the synthase for ATP. N acetyl glutamate is synthesized from acetyl CoA and glutamate in a reaction for which arginine is an activator. Some reactions of urea cycle occur in the mitochondria and some occur in the cytoplasm. Synthesis of 1 mol of urea requires 3 mol of ATP, 1 mol each of ammonium ion and of aspaate, and employs five enzymes. Carbamoyl phosphate synthetase I which catalyse the condensation of CO2, ammonia, and ATP to form carbamoyl phosphate is the rate limiting enzyme in urea synthesis. Ref: Biochemistry By Pamela C. Champe, page 253.', 'role': 'assistant'}]