Proton-coupled transporter that transports a wide spectrum of oxo derivatives of heterocyclic nitrogen compounds, including allantoin, uric acid and xanthine, but not adenine (PubMed:11971139, PubMed:15308648). Mediates high affinity transport of uracil and 5-fluorouracil (a toxic uracil analog) (PubMed:15308648, PubMed:16897711). Mediates transport of free pyrimidines and may function during early seedling development in salvage pathways, by the utilization of pyrimidines from seed storage tissue (PubMed:15308648). Optimum pH is 4.75. Expressed in leaves, flowers, roots and stems. During seedling development, expression is high at 1 day after imbibition and then declines continuously to reach steady levels after 5 days. By nitrogen deficiency. Belongs to the plant ureide permease (TC 2.A.7.19) family.