This family consists of several eukaryotic pyrimidine 5'-nucleotidase proteins. P5'N-1, also known as uridine monophosphate hydrolase-1 (UMPH-1), is a member of a large functional group of enzymes, characterised by the ability to dephosphorylate nucleic acids. P5'N-1 catalyses the dephosphorylation of pyrimidine nucleoside monophosphates to the corresponding nucleosides. Deficiencies in this proteins function can lead to several different disorders in humans [1].

1: Pyrimidine 5' nucleotidase deficiency. Rees DC, Duley JA, Marinaki AM; Br J Haematol 2003;120:375-383. PMID:12580951