We report the characterization of a new Leishmania major gene, Imaj3'nt/nu, encoding a 382 amino acids protein, Lmaj3'NT/NU, that belongs to the 3'nucleotidase/nuclease family. Interestingly, sequence and phylogenetic analysis show that this Protein is Leishmania major specific and thus constitutes a new 3'nucleotidase/nuclease subgroup. Lmaj3'NT/NU displays nuclease enzymatic activity and Western blot analysis shows that it is exclusively expressed in promastigotes. Immunofluorescence microscopy using a specific anti-Lmaj3'NT/NU shows that the protein has a plasma membrane localization. Surprisingly, contrary to the previously described Leishmania mexicana 3'NT/NU, Imaj3'nt/nu is not up-regulated when parasites are cultured Under purine starvation conditions. Together, these findings suggest Lmaj3'NT/NU may constitute a new important compound of the L. major purine scavenging pathway and Could be involved in sandfly parasite survival and colonization. (C) 2008 Elsevier Inc. All rights reserved.