A unique surface membrane anchored purine-salvage enzyme is conserved among a group of primitive eukaryotic human pathogens

Previously, we isolated and characterized the gene encoding the 3'-Nucleoti dase/Nuclease (Ld3'NT/NU) from the human pathogen, Leishmania donovani. Thi s unique cell surface enzyme has been shown to be involved in the salvage o f host-derived purines, which are essential for the survival of this import ant protozoan parasite. In this report, we assessed whether the 3'-Nucleoti dase/Nuclease was conserved amongst other pathogenic Leishmania and related trypanosomatid parasites. Results of pulsed field gel electrophoresis and Southern blotting showed that a Ld3'NT/NU gene homolog was present in each of the visceral and cutaneous Leishmania species tested (i.e. isolates of L . donovani, L. infantum, L. tropica, L. major and L. mexicana, respectively ). Further, results of colorimetric assays using 3'-adenosine monophosphate as substrate demonstrated that each of these organisms also expressed sign ificant levels of 3'-nucleotidase enzyme activity. In addition, we showed t hat a Ld3'NT/NU gene homolog was expressed in each of these Leishmania spec ies as a > 40 kDa 3'-nucleotidase enzyme activity. A Ld3'NT/NU gene homolog was also identified in two Crithidia species (C. fasciculata and C. lucili ae) and Leptomonas seymouri but was only marginally detectable in Trypanoso ma brucei, Trypanosoma cruzi and Phytomonas serpens. Cumulatively, results of this study showed that an Ld3'NT/NU homolog was conserved amongst pathog enic Leishmania sp. which suggests that this enzyme must play an critical r ole in purine salvage for all members of this group of human pathogens.