This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of protein and amino acid, Subject name: Biochemistry
Which of the following is the rate-limiting enzyme in pyrimidine synthesis? 
Select and explain. 
A. Aspoate transcarbamylase, B. Dihydro-orotase, C. Redvctase, D. UMP kinase
A: Aspoate transcarbamylase
Answer: A: Aspoate transcarbamylase 
Explanation: Carbamoyl phosphate and aspaate combine to form carbamoyl aspaate is the rate-limiting step in pyrimidine synthesis. The enzyme is aspayl transcarbamoylase.