This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Proteins and Amino Acids, Subject name: Biochemistry
Key enzyme in urea synthesis is: 
Select and explain. 
A. Urease, B. Carbamoyl Synthetase, C. Arginase, D. Ornithine
B: Carbamoyl Synthetase
Answer: B: Carbamoyl Synthetase 
Explanation: Ans. B. Carbamoyl SynthetaseCarbamoyl synthetase catalyses the first step in urea cycle or Krebs Henseleit cycle and it is a rate limiting step in urea synthesis.