Folylpolyglutamate synthase (FPGS) (FPGS)

Folylpolyglutamate synthase (FPGS) is a critical enzyme in the folate metabolic pathway that catalyzes the ATP-dependent addition of glutamate residues to folates and antifolate drugs (UniProt: Q05932). This polyglutamylation process is essential for the intracellular retention of these compounds, as the addition of glutamate moieties increases their anionic charge and prevents them from exiting the cell via transporters like the reduced folate carrier (PubMed: 11560818). In oncology, FPGS is a key determinant of the efficacy of antifolate chemotherapeutics such as pralatrexate, methotrexate, and pemetrexed (PubChem: CID 155061). Pralatrexate was specifically engineered to be an exceptionally efficient substrate for FPGS, allowing for rapid conversion into polyglutamated forms that are sequestered within tumor cells (PubMed: 19773639). Once polyglutamated, pralatrexate exhibits a higher affinity for its primary target, dihydrofolate reductase (DHFR), leading to potent inhibition of DNA synthesis and induction of apoptosis (StatPearls: NBK548044). Resistance to antifolate therapy often arises from the downregulation or functional loss of FPGS, making it a significant focus for predicting treatment response and developing strategies to overcome resistance (PubMed: 12140166). Consequently, FPGS expression and activity levels are frequently evaluated as biomarkers in patients undergoing antifolate-based chemotherapy (PubMed: 22431115).

Other names

Folylpoly-gamma-glutamate synthetaseFolylpolyglutamate synthetaseFPGS

Pralatrexate acts as a high-affinity substrate for FPGS, which catalyzes the ATP-dependent addition of glutamate residues to the drug. This polyglutamylation process traps the drug intracellularly and significantly enhances its inhibitory activity against its primary target, dihydrofolate reductase (DHFR), thereby disrupting DNA synthesis and inducing apoptosis (PubMed: 19773639, PubChem: CID 155061).