Glycineamide ribonucleotide (or GAR) 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 GAR. GAR is the product of the enzyme [phosphoribosylamine—glycine ligase](https://bliptext.com/articles/[phosphoribosylamine](https://bliptext.com/articles/phosphoribosylamine)-[glycine](https://bliptext.com/articles/glycine)-ligase) acting on phosphoribosylamine (PRA) to combine it with glycine in a process driven by ATP. The reaction, forms an amide bond: The biosynthesis pathway next adds a formyl group from 10-formyltetrahydrofolate to GAR, catalysed by phosphoribosylglycinamide formyltransferase in reaction and producing formylglycinamide ribotide (FGAR):