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Biopterin conversion to reduced folates by Leishmania donovani promastigotes
1Department of Biochemistry and Molecular Biology, Oregon Health Sciences University, Portland 97201-3098.
Abstract:
The ability of Leishmania donovani promastigotes to proliferate in folate-deficient medium supplemented with pterins suggests that pterins can serve as a source of folate in these parasites [16]. Using reversed-phase high-performance liquid chromatography, the ability of intact L. donovani to transform [3H]biopterin into tetrahydrofolates was demonstrated. Radioactivity was primarily associated with 5-methyltetrahydrofolate and 10-formyltetrahydrofolate. A mutant strain of L. donovani, MTXA5, that was genetically deficient in folate transport capacity and incapable of growing in pterin-supplemented folate-deficient growth medium, exhibited a greatly reduced capacity to metabolize [3H]biopterin to reduced folates. These data indicated that wild-type L. donovani promastigotes, unlike mammalian cells, were able to convert biopterin to tetrahydrofolates and supported the hypothesis that folate transport deficiency in mutant organisms is associated with an inability to transform pterins to reduced folates.
Insights
Leishmania donovani parasites can convert biopterin into essential folates, unlike human cells. This highlights a unique metabolic pathway crucial for parasite survival and potential drug targeting.
Area of Science:
- Parasitology
- Molecular Biology
- Biochemistry
Background:
- Leishmania donovani are protozoan parasites responsible for visceral leishmaniasis.
- Folates are essential for parasite growth and survival, and their metabolism is a target for antiparasitic drugs.
- Pterins, including biopterin, are structurally related to folates, but their role as folate precursors in Leishmania is not fully understood.
Purpose of the Study:
- To investigate the ability of Leishmania donovani promastigotes to utilize pterins as a source of folate.
- To determine if L. donovani can convert biopterin into biologically active tetrahydrofolates.
- To characterize the folate transport capacity of a mutant L. donovani strain (MTXA5) and its impact on pterin metabolism.
Main Methods:
- Cultivation of Leishmania donovani promastigotes in folate-deficient medium supplemented with pterins.
- Radiolabeling of biopterin ([3H]biopterin) and its administration to intact parasites.
- Analysis of radiolabeled metabolites using reversed-phase high-performance liquid chromatography (HPLC).
- Comparison of pterin metabolism in wild-type and a folate transport-deficient mutant (MTXA5) strain.
Main Results:
- Wild-type L. donovani promastigotes demonstrated the ability to proliferate in pterin-supplemented folate-deficient medium.
- Intact L. donovani transformed [3H]biopterin into tetrahydrofolates, primarily 5-methyltetrahydrofolate and 10-formyltetrahydrofolate.
- The folate transport-deficient mutant strain MTXA5 showed significantly reduced capacity to metabolize [3H]biopterin to reduced folates.
- These findings indicate that L. donovani, unlike mammalian cells, can convert biopterin to tetrahydrofolates.
Conclusions:
- Leishmania donovani possesses a unique metabolic capability to convert biopterin into essential tetrahydrofolates.
- This pterin-to-folate conversion pathway is dependent on functional folate transport mechanisms.
- The study supports the hypothesis that folate transport deficiency in mutant strains is linked to impaired pterin transformation, offering potential therapeutic targets.