In enzymology, a phosphoribosylformylglycinamidine synthase (EC 6.3.5.3) is an enzyme that catalyzes the chemical reaction The 4 substrates of this enzyme are ATP, N2-formyl-N1-(5-phospho-D-ribosyl)glycinamide, L-glutamine, and H2O, whereas its 4 products are ADP, phosphate, 2-(formamido)-N1-(5-phospho-D-ribosyl)acetamidine, and L-glutamate.

The systematic name of this enzyme class is N2-formyl-N1-(5-phospho-D-ribosyl)glycinamide:L-glutamine amido-ligase (ADP-forming).

[3] As of late 2007, 8 structures have been solved for this class of enzymes, with PDB accession codes 1T3T, 1VK3, 1VQ3, 2HRU, 2HRY, 2HS0, 2HS3, and 2HS4.

Oncogenic and physiological signals lead to the ERK-dependent PFAS phosphorylation at the T619 site, stimulating de novo purine synthesis flux.

In addition, ERK-mediated PFAS phosphorylation is required for cell and tumor growth.