DHPS (Deoxyhypusine synthase) catalyzes the conversion of lysine to deoxyhypusine residue on the eukaryotic initiation factor 5A (eIF-5A) precursor using spermidine as the substrate. It belongs to the deoxyhypusine synthase family. It functions as a homodimer and is essential for de novo folate synthesis in prokaryotes, lower eukaryotes, and plants, but is absent in mammals, which obtain folate from the diet. This absence makes DHPS an important target for selective antimicrobial agents, including sulfonamide drugs such as sulfamethoxazole and dapsone. Mutations in DHPS are associated with sulfonamide resistance in pathogens such as Pneumocystis jirovecii and Plasmodium falciparum. This protein has 3 isoforms produced by alternative splicing.