<i>Trypanosoma brucei</i> pteridine reductase 1 is essential for survival <i>in vitro</i> and for virulence in mice

Sienkiewicz, Natasha; Ong, Han B.; Fairlamb, Alan H.

doi:10.1111/j.1365-2958.2010.07236.x

Cited by 53 publications

(71 citation statements)

References 78 publications

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“…• Extent of enzyme inhibition : Although the extent to which PTR1 has to be inhibited to cause growth effects is not known with certainty, gene knockout experiments indicate that halving enzyme activity has no effect on growth and RNAi depletion studies suggest >90 % knockdown of PTR1 protein is required to exert a trypanocidal effect 9. Therefore, it is possible that compounds have insufficient potency at the enzyme level to cause an effect at the cellular level.…”

Section: Discussionmentioning

confidence: 99%

Design, Synthesis and Biological Evaluation of Novel Inhibitors of Trypanosoma brucei Pteridine Reductase 1

et al. 2010

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Genetic studies indicate that the enzyme pteridine reductase 1 (PTR1) is essential for the survival of the protozoan parasite Trypanosoma brucei. Herein, we describe the development and optimisation of a novel series of PTR1 inhibitors, based on benzo[d]imidazol-2-amine derivatives. Data are reported on 33 compounds. This series was initially discovered by a virtual screening campaign (J. Med. Chem., 2009, 52, 4454). The inhibitors adopted an alternative binding mode to those of the natural ligands, biopterin and dihydrobiopterin, and classical inhibitors, such as methotrexate. Using both rational medicinal chemistry and structure-based approaches, we were able to derive compounds with potent activity against T. brucei PTR1 (=7 nm), which had high selectivity over both human and T. brucei dihydrofolate reductase. Unfortunately, these compounds displayed weak activity against the parasites. Kinetic studies and analysis indicate that the main reason for the lack of cell potency is due to the compounds having insufficient potency against the enzyme, which can be seen from the low Km to Ki ratio (Km=25 nm and Ki=2.3 nm, respectively).

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Section: Discussionmentioning

confidence: 99%

Design, Synthesis and Biological Evaluation of Novel Inhibitors of Trypanosoma brucei Pteridine Reductase 1

et al. 2010

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“…Pteridine reductase (PTR1) has emerged as a promising target for the development of novel therapeutics against the protozoan parasites Trypanosoma and Leishmania [1,9,10]. PTR1 is an essential broad spectrum enzyme responsible for pteridine salvage in these organisms.…”

Section: Introductionmentioning

confidence: 99%

3D-QSAR based pharmacophore modeling and virtual screening for identification of novel pteridine reductase inhibitors

et al. 2011

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Pteridine reductase is a promising target for development of novel therapeutic agents against Trypanosomatid parasites. A 3D-QSAR pharmacophore hypothesis has been generated for a series of L. major pteridine reductase inhibitors using Catalyst/HypoGen algorithm for identification of the chemical features that are responsible for the inhibitory activity. Four pharmacophore features, namely: two H-bond donors (D), one Hydrophobic aromatic (H) and one Ring aromatic (R) have been identified as key features involved in inhibitor-PTR1 interaction. These features are able to predict the activity of external test set of pteridine reductase inhibitors with a correlation coefficient (r) of 0.80. Based on the analysis of the best hypotheses, some potent Pteridine reductase inhibitors were screened out and predicted with anti-PTR1 activity. It turned out that the newly identified inhibitory molecules are at least 300 fold more potent than the current crop of existing inhibitors. Overall the current SAR study is an effort for elucidating quantitative structure-activity relationship for the PTR1 inhibitors. The results from the combined 3D-QSAR modeling and molecular docking approach have led to the prediction of new potent inhibitory scaffolds.

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“…Similarly, the PAH gene is absent in trypanosomes, which like Leishmania require H 4 B [50]. Future studies may consider other metabolic roles for PAH , perhaps in Phe anabolism, drug resistance or in other metabolic pathways such as thioether metabolism [45, 51].…”

Section: Discussionmentioning

confidence: 99%

Phenylalanine hydroxylase (PAH) from the lower eukaryote Leishmania major

Lye

Kang

Nosanchuk

et al. 2011

Molecular and Biochemical Parasitology

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Aromatic amino acid hydroxylases (AAAH) typically use tetrahydrobiopterin (H4B) as the cofactor. The protozoan parasite Leishmania major requires biopterin for growth and expresses strong salvage and regeneration systems to maintain H4B levels. Here we explored the consequences of genetic manipulation of the sole L. major phenylalanine hydroxylase (PAH) to explore whether it could account for the Leishmania H4B requirement. L. major PAH resembles AAAHs of other organisms, bearing eukaryotic-type domain organization, and conservation of key catalytic residues including those implicated in pteridine binding. A pah− null mutant and an episomal complemented overexpressing derivative (pah−/+PAH) were readily obtained, and metabolic labeling studies established that PAH was required to hydroxylate Phe to Tyr. Neither WT nor overexpressing lines were able to hydroxylate radiolabeled tyrosine or tryptophan, nor to synthesize catecholamines. WT but not pah− parasites showed reactivity with an antibody to melanin when grown with L-3,4-dihydroxyphenylalanine (L-DOPA), although the reactive product is unlikely to be melanin sensu strictu. WT was auxotrophic for Phe, Trp and Tyr, suggesting that PAH activity was insufficient to meet normal Tyr requirements. However, pah− showed an increased sensitivity to Tyr deprivation, while the pah−/+PAH overexpressor showed increased survival and could be adapted to grow well without added Tyr. pah− showed no alterations in H4B-dependent differentiation, as established by in vitro metacyclogenesis, or survival in mouse or macrophage infections. Thus Leishmania PAH may mitigate but not alleviate Tyr auxotrophy, but plays no essential role in the steps of the parasite infectious cycle. These findings suggest PAH is unlikely to explain the Leishmania requirement for biopterin.

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Trypanosoma brucei pteridine reductase 1 is essential for survival in vitro and for virulence in mice

Cited by 53 publications

References 78 publications

Design, Synthesis and Biological Evaluation of Novel Inhibitors of Trypanosoma brucei Pteridine Reductase 1

Design, Synthesis and Biological Evaluation of Novel Inhibitors of Trypanosoma brucei Pteridine Reductase 1

3D-QSAR based pharmacophore modeling and virtual screening for identification of novel pteridine reductase inhibitors

Phenylalanine hydroxylase (PAH) from the lower eukaryote Leishmania major

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