FIGURE 2.
De novo purine nucleotide biosynthesis is a 10-step pathway in the cytoplasm that functions as a multienzyme complex referred to as a purinosome. Reactions 3 and 9 require 10-formyltetrahydrofolate as a cofactor. Enzyme abbreviations: AICAR Tfase, phosphoribosylaminoimidazole carboxamide formyltransferase; AIRS, aminoimidazole ribonucleotide synthetase; ASL, adenylosuccinate lyase; CAIRS, carboxyaminoimidazole ribonucleotide synthase; FGAMS, phosphoribosylformylglycinamidine synthase; GARS, glycinamide ribonucleotide synthetase; GAR Tfase, phosphoribosylglycinamide formyltransferase; HPRT, hypoxanthine phosphoribosyl transferase; IMPCH, IMP cyclohydrolase; PPAT, PRPP amidotransferase; SAICARS, succinylaminoimidazolecarboxamide ribonucleotide synthetase.