Abbreviations: phosphoribosylamine (PRA), glycinamideribonucleotide (GAR), N-formylglycinamide ribonucleotide (FGAR), N-formylglycinamidine ribonucleotide (FGAMR), aminoimidazole ribonucleotide (AIR), carboxyaminoimidazole ribonucleotide (CAIR), N-succinocarboxamide-5-aminoimidazole ribonucleotide (SAICAR), 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR), 5-formamido-4-imidazolecarboxamide ribonucleotide (FAICAR), inosine-5-monophosphate (IMP), glutamine (Gln), glutamate (Glu), pyrophosphate (PPi), adenosine-5'-triphosphate (ATP), adenosine 5'-diphosphate (ADP), glycine (Gly), phosphate (Pi), N10-formyl tetrahydrofolate (N10-formyl THF), tetrahydrofolate (THF), hydrogen carbonic acid (HCO3-), aspartate (Asp). For enzyme abbreviations, see the second paragraph of the Introduction.