Glycineamide ribonucleotide

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.
 * Phosphoribosylamine.svg

GAR is the product of the enzyme phosphoribosylamine—glycine ligase acting on phosphoribosylamine (PRA) to combine it with glycine in a process driven by ATP. The reaction, forms an amide bond:
 * + + ATP →  + ADP + Pi

The biosynthesis pathway next adds a formyl group from 10-formyltetrahydrofolate to GAR, catalysed by phosphoribosylglycinamide formyltransferase in reaction and producing formylglycinamide ribotide (FGAR):
 * GAR + 10-formyltetrahydrofolate → FGAR + tetrahydrofolate