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 are Urea cycle enzymes except: 
Select and explain. 
A. Ornithine transcarbamylase, B. Carbamoyl-phosphate synthetase I, C. Argininosuccinase, D. Citrulline synthase
D: Citrulline synthase
Answer: D: Citrulline synthase 
Explanation: Answer: (D) Citrulline synthase [Ref Harper 30th/290-96, 29th/274-88; Lippincott