Phosphoribosyl-N-formylglycineamide

Phosphoribosyl-N-formylglycineamide is a biochemical intermediate in the formation of purine nucleotides via inosine-5-monophosphate, and hence is a building block for DNA and RNA. The vitamins thiamine and cobalamin also contain fragments derived from FGAR.
FGAR is formed when the enzyme phosphoribosylglycinamide formyltransferase adds a formyl group from 10-formyltetrahydrofolate to glycineamide ribonucleotide in reaction :
The biosynthesis pathway next converts FGAR to an amidine by the action of phosphoribosylformylglycinamidine synthase, transferring an amino group from glutamine and giving 5'-phosphoribosylformylglycinamidine in a reaction that also requires ATP: