This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: miscellaneous, Subject name: Biochemistry
Azaserine inhibits? 
Select and explain. 
A. Glycinamide ribonucleotide synthetase, B. Glycinamide ribonucleotide transformylase, C. Formyl glycinamide ribonucleotide amidotransferase, D. Inosine monophosphate synthase
C: Formyl glycinamide ribonucleotide amidotransferase
Answer: C: Formyl glycinamide ribonucleotide amidotransferase 
Explanation: In de novo synthesis of purine nucleotides, there are 10 steps. The 4th step (addition of N3) is catalysed by the enzyme Formyl glycinamide ribonucleotide amidotransferase. This enzyme is inhibited by azaserine, an anticancer drug. Reference: Harpers illustrated biochemistry 30th edition