FIG. 8. Purine biosynthetic pathway and sites of action of ad and gua genes (81, 120, 348, 393, 405a, 511, 525). PRPP, 5- phosphoribosyl pyrophosphate; PRA, 5-phosphoribosylamine-, GAR, 5'- phosphoribosyl-glycineamide; FGAR, 5'-phosphoribosyl-formylglycineamide; FGAM, 5'-phosphoribosyl-formylglycineamidine; AIR, 5'-phosphoribosyl-5-aminoimidazole; CAIR, 5'-phosphoribosyl-5- aminoimidazole-4-carboxylate; SAICAR, 5'-phosphoribosyl-5- aminoimidazole-4-N-succinocarboxamide; AICAR, 5'-phosphoribosyl-5- aminoimidazole-4-carboxamide; FAICAR. 5'-phosphoribosyl-5- formamidoimidazole-4-carboxamide.