Which Enzyme of the Inosinic Acid Biosynthesis Pathway Is the Major

Which enzyme of the inosinic acid biosynthesis pathway is the major control point for purine synthesis?

A) phosphoribosyl pyrophosphate amidotransferase
B) glycinamide ribonucleotide transformylase
C) formylglycinamidine ribonucleotide amidotransferase
D) 5-aminoimidazole ribonucleotide synthetase
E) 5-aminoimidazole ribonucleotide carboxylase