Click here to close
Hello! We notice that you are using Internet Explorer, which is not supported by Xenbase and may cause the site to display incorrectly.
We suggest using a current version of Chrome,
FireFox, or Safari.
???displayArticle.abstract???
Plasmodium falciparum is a purine auxotroph. The transport of purine nucleosides and nucleobases from the host erythrocyte to the parasite cytoplasm is essential to support parasite growth. P. falciparum equilibrative nucleoside transporter 1 (PfENT1) is a major route for purine transport across the parasite plasma membrane. Malarial parasites are sensitive to inhibitors of purine salvage pathway enzymes. The immucillin class of purine nucleoside phosphorylase inhibitors and the adenosine analog, tubercidin, block growth of P. falciparum under in vitro culture conditions. We sought to determine whether these inhibitors utilize PfENT1 to gain access to the parasite cytosol. There is considerable controversy in the literature regarding the K(m) and/or K(i) for purine transport by PfENT1 in the Xenopus oocyte expression system. We show that oocytes metabolize adenosine but not hypoxanthine. For adenosine, metabolism is the rate limiting step in oocyte uptake assays, making hypoxanthine the preferred substrate for PfENT1 transport studies in oocytes. We demonstrate that the K(i) for PfENT1 transport of hypoxanthine and adenosine is in the 300-700microM range. Effects of substrate metabolism on uptake studies may explain conflicting results in the literature regarding the PfENT1 adenosine transport K(m). PfENT1 transports the tubercidin class of compounds. None of the immucillin compounds tested inhibited PfENT1 transport of [(3)H]hypoxanthine or [(3)H]adenosine. Although nucleobases are transported, modifications of the ribose ring in corresponding nucleoside analogs affect substrate recognition by PfENT1. These results provide new insights into PfENT1 and the mechanism by which purine salvage pathway inhibitors are transported into the parasite cytoplasm.
Carter,
Nucleoside transporters of parasitic protozoa.
2001, Pubmed
Carter,
Nucleoside transporters of parasitic protozoa.
2001,
Pubmed Carter,
Isolation and functional characterization of the PfNT1 nucleoside transporter gene from Plasmodium falciparum.
2000,
Pubmed
,
Xenbase Cassera,
Erythrocytic adenosine monophosphate as an alternative purine source in Plasmodium falciparum.
2008,
Pubmed
,
Xenbase Cheng,
Relationship between the inhibition constant (K1) and the concentration of inhibitor which causes 50 per cent inhibition (I50) of an enzymatic reaction.
1973,
Pubmed Clinch,
Third-generation immucillins: syntheses and bioactivities of acyclic immucillin inhibitors of human purine nucleoside phosphorylase.
2009,
Pubmed Coomber,
Adenosine analogues as antimetabolites against Plasmodium falciparum malaria.
1994,
Pubmed de Koning,
Purine and pyrimidine transport in pathogenic protozoa: from biology to therapy.
2005,
Pubmed Desai,
A voltage-dependent channel involved in nutrient uptake by red blood cells infected with the malaria parasite.
2000,
Pubmed Divo,
Nutritional requirements of Plasmodium falciparum in culture. I. Exogenously supplied dialyzable components necessary for continuous growth.
1985,
Pubmed Downie,
Purine nucleobase transport in the intraerythrocytic malaria parasite.
2008,
Pubmed
,
Xenbase Downie,
Purine salvage pathways in the intraerythrocytic malaria parasite Plasmodium falciparum.
2008,
Pubmed Downie,
Transport of nucleosides across the Plasmodium falciparum parasite plasma membrane has characteristics of PfENT1.
2006,
Pubmed
,
Xenbase Dumont,
Oogenesis in Xenopus laevis (Daudin). I. Stages of oocyte development in laboratory maintained animals.
1972,
Pubmed
,
Xenbase El Bissati,
The plasma membrane permease PfNT1 is essential for purine salvage in the human malaria parasite Plasmodium falciparum.
2006,
Pubmed El Bissati,
Genetic evidence for the essential role of PfNT1 in the transport and utilization of xanthine, guanine, guanosine and adenine by Plasmodium falciparum.
2008,
Pubmed Furneaux,
Improved Syntheses of 3H,5H-Pyrrolo[3,2-d]pyrimidines.
1999,
Pubmed Gardner,
Genome sequence of the human malaria parasite Plasmodium falciparum.
2002,
Pubmed Huber,
Patch-clamp analysis of the "new permeability pathways" in malaria-infected erythrocytes.
2005,
Pubmed Jansen,
State-dependent cross-linking of the M2 and M3 segments: functional basis for the alignment of GABAA and acetylcholine receptor M3 segments.
2006,
Pubmed
,
Xenbase Jespersen,
Dual-function vector for protein expression in both mammalian cells and Xenopus laevis oocytes.
2002,
Pubmed
,
Xenbase Kelly,
Control of cell volume in oocytes and eggs from Xenopus laevis.
1995,
Pubmed
,
Xenbase Kicska,
Purine-less death in Plasmodium falciparum induced by immucillin-H, a transition state analogue of purine nucleoside phosphorylase.
2002,
Pubmed Kicska,
Transition state analogue inhibitors of purine nucleoside phosphorylase from Plasmodium falciparum.
2002,
Pubmed Kirk,
Purine uptake in Plasmodium: transport versus metabolism.
2009,
Pubmed
,
Xenbase Lewandowicz,
Energetic mapping of transition state analogue interactions with human and Plasmodium falciparum purine nucleoside phosphorylases.
2005,
Pubmed Martin,
The 'permeome' of the malaria parasite: an overview of the membrane transport proteins of Plasmodium falciparum.
2005,
Pubmed Murkin,
Transition-state interactions revealed in purine nucleoside phosphorylase by binding isotope effects.
2008,
Pubmed Parker,
Identification of a nucleoside/nucleobase transporter from Plasmodium falciparum, a novel target for anti-malarial chemotherapy.
2000,
Pubmed
,
Xenbase Petrescu,
Phosphorylation and hydrolysis of 7-deazaadenine nucleotides by rat liver and beef heart mitochondria.
1982,
Pubmed Quashie,
A comprehensive model of purine uptake by the malaria parasite Plasmodium falciparum: identification of four purine transport activities in intraerythrocytic parasites.
2008,
Pubmed Queen,
Properties and substrate specificity of a purine phosphoribosyltransferase from the human malaria parasite, Plasmodium falciparum.
1988,
Pubmed Rager,
Localization of the Plasmodium falciparum PfNT1 nucleoside transporter to the parasite plasma membrane.
2001,
Pubmed Reyes,
Enzymes of purine and pyrimidine metabolism from the human malaria parasite, Plasmodium falciparum.
1982,
Pubmed Sauve,
Ionic states of substrates and transition state analogues at the catalytic sites of N-ribosyltransferases.
2003,
Pubmed Scott,
Synergistic antimalarial activity of dapsone/dihydrofolate reductase inhibitors and the interaction of antifol, antipyrimidine and antipurine combinations against Plasmodium falciparum in vitro.
1987,
Pubmed Shi,
Plasmodium falciparum purine nucleoside phosphorylase: crystal structures, immucillin inhibitors, and dual catalytic function.
2004,
Pubmed Ting,
Targeting a novel Plasmodium falciparum purine recycling pathway with specific immucillins.
2005,
Pubmed Traut,
Physiological concentrations of purines and pyrimidines.
1994,
Pubmed Ugarkar,
Adenosine kinase inhibitors. 1. Synthesis, enzyme inhibition, and antiseizure activity of 5-iodotubercidin analogues.
2000,
Pubmed Werner,
Determination of nucleotides, nucleosides and nucleobases in cells of different complexity by reversed-phase and ion-pair high-performance liquid chromatography.
1987,
Pubmed
