ChEBI: 4-aminofolic acid is a dicarboxylic acid. It has a role as a mutagen and an EC 1.5.1.3 (dihydrofolate reductase) inhibitor. It derives from a folic acid.NCI Thesaurus (NCIt): Aminopterin is a synthetic derivative of pterins with antineoplastic and immunosuppressive properties. As a folate analogue, aminopterin competes for the folate binding site of the enzyme dihydrofolate reductase, thereby blocking tetrahydrofolate synthesis, and resulting in depletion of nucleotide precursors and inhibition of DNA, RNA and protein synthesis. (NCI04)