Antileishmanial natural products as potential inhibitors of the Leishmania pteridine reductase: insights from molecular docking and molecular dynamics simulations.

Although many natural product-derived compounds possess anti-leishmanial activities in vitro and in vivo, their molecular targets in the Leishmania parasite remain elusive. This is a major challenge in optimizing these compounds into leads. The Leishmania pteridine reductase (PTR1) is peculiar for folate and pterin metabolism and has been validated as a drug target. In this study, 17 compounds with anti-leishmanial activities were screened against Leishmania major PTR1 (LmPTR1) using molecular docking and molecular dynamics (MD) simulations. All ligands were bound in the active site pocket of LmPTR1 with binding affinities ranging from -11.2 to -5.2 kcal/mol. Agnuside, betulin, betulinic acid, gerberinol, ismailin, oleanolic acid, pristimerin, and ursolic acid demonstrated binding affinities similar to a known inhibitor, methyl 1-(4-{[2,4-diaminopteridin-6-yl) methyl] amino} benzoyl) piperidine-4-carboxylate (DVP). MD simulations revealed that betulin, betulinic acid, ismailin, oleanolic acid, pristimerin, and ursolic acid formed stable complexes with LmPTR1. The binding free energies of the complexes were very good (-87 to -148 kJ/mol), and much higher than the complex of the standard DVP inhibitor and LmPTR1 (-27 kJ/mol). Betulin, betulinic acid, ismailin, oleanolic acid, pristimerin, and ursolic acid likely exert their antileishmanial action by inhibiting PTR1 and could thus be used as a basis for the development of potential antileishmanial chemotherapeutic agents. Supplementary Information: The online version contains supplementary material available at 10.1007/s40203-024-00247-8.

Phytochemical investigation of Chrysanthellum americanum Vatke and its constituents- a targeted approach for the treatment of leishmaniasis.

The present study is focused on the isolation and identification of new therapeutic candidates from Chrysanthellum americanum Vatke., and their efficacy against pteridine reductase-1 (PTR1), a valid chemotherapeutic target in the Leishmania parasite. Henceforth, a new compound, chrysanamerine (1), along with 7 known compounds, polyacetylene 2, and flavonoids 3-8, were isolated from C. americanum. Their structures were determined by chemical and spectroscopic analyses and compared with the reported spectroscopic data. All compounds were evaluated for their anti-leishmanial activity against PTR1 via biochemical mechanism-based assay. The in vitro results showed five potential hits including a new compound, chrysanamerine (1), and four known compounds against the PTR1 enzyme. Among them, compound 1 showed a potent enzyme inhibition with an IC50 of 31.02 ± 2.36 µM, whereas a moderate inhibition was observed in cases of compounds 5 and 6 (IC50 = 59.86 ± 3.32, and 45.32 ± 3.5 µM, respectively). Whereas, compounds 3 and 8 showed mild inhibition (IC50 = 72.12 ± 1.12, and 97.18 ± 1.23 µM, respectively) against PTR1, compared with trimethoprim (positive control) (IC50 = 21.07 ± 1.6 µM). Moreover, the results were further validated via molecular docking and molecular dynamics (MD) simulations. Compound 1 showed a strong affinity to the binding site with a docking score of -11.83, along with the formation of a stable protein-ligand complex over the trajectory of 100 ns. Besides, compounds 1-8 were found to be non-cytotoxic on BJ (human fibroblast) cells.

Identification of Innovative Folate Inhibitors Leveraging the Amino Dihydrotriazine Motif from Cycloguanil for Their Potential as Anti-Trypanosoma brucei Agents.

Folate enzymes, namely, dihydrofolate reductase (DHFR) and pteridine reductase (PTR1) are acknowledged targets for the development of antiparasitic agents against Trypanosomiasis and Leishmaniasis. Based on the amino dihydrotriazine motif of the drug Cycloguanil (Cyc), a known inhibitor of both folate enzymes, we have identified two novel series of inhibitors, the 2-amino triazino benzimidazoles (1) and 2-guanidino benzimidazoles (2), as their open ring analogues. Enzymatic screening was carried out against PTR1, DHFR, and thymidylate synthase (TS). The crystal structures of TbDHFR and TbPTR1 in complex with selected compounds experienced in both cases a substrate-like binding mode and allowed the rationalization of the main chemical features supporting the inhibitor ability to target folate enzymes. Biological evaluation of both series was performed against T. brucei and L. infantum and the toxicity against THP-1 human macrophages. Notably, the 5,6-dimethyl-2-guanidinobenzimidazole 2g resulted to be the most potent (Ki = 9 nM) and highly selective TbDHFR inhibitor, 6000-fold over TbPTR1 and 394-fold over hDHFR. The 5,6-dimethyl tricyclic analogue 1g, despite showing a lower potency and selectivity profile than 2g, shared a comparable antiparasitic activity against T. brucei in the low micromolar domain. The dichloro-substituted 2-guanidino benzimidazoles 2c and 2d revealed their potent and broad-spectrum antitrypanosomatid activity affecting the growth of T. brucei and L. infantum parasites. Therefore, both chemotypes could represent promising templates that could be valorized for further drug development.

Computational investigation of turmeric phytochemicals targeting PTR1 enzyme of Leishmania species.

In this study, we used in silico techniques to identify available parasite treatments, representing a promising therapeutic avenue. Building upon our computational initiatives aimed at discovering natural inhibitors for various target enzymes from parasites causing neglected tropical diseases (NTDs), we present novel findings on three turmeric-derived phytochemicals as inhibitors of Leishmania pteridine reductase I (PTR1) through in silico methodologies. PTR1, a crucial enzyme in the unique folate metabolism of trypanosomatid parasites, holds established therapeutic significance. Employing MOE software, a molecular docking analysis assesses the efficacy of turmeric phytochemicals against Leishmania PTR1. Validation of the docking protocol is confirmed with an RMSD value of 2. Post-docking, compounds displaying notable interactions with critical residues and binding affinities ranging between -6 and -8 kcal/mol are selected for interaction pattern exploration. Testing twelve turmeric phytochemicals, including curcumin, zingiberene, curcumol, curcumenol, eugenol, bisdemethoxycurcumin, tetrahydrocurcumin, tryethylcurcumin, turmerones, turmerin, demethoxycurcumin, and turmeronols, revealed binding affinities ranging from -5.5 to -8 kcal/mol. Notably, curcumin, demethoxycurcumin, and bisdemethoxycurcumin exhibit binding affinities within -6.5 to -8 kcal/mol and establish substantial interactions with catalytic residues. These phytochemicals hold promise as lead structures for rational drug design targeting Leishmania spp. PTR in future applications. This work underscores the potential of these identified phytochemicals in the development of more effective inhibitors, demonstrating their relevance in addressing neglected tropical diseases caused by parasites.

Spiro-Acridine Compound as a Pteridine Reductase 1 Inhibitor: in silico Target Fishing and in†vitro Studies.

Among the many neglected tropical diseases, leishmaniasis ranks second in mortality rate and prevalence. In a previous study, acridine derivatives were synthesized and tested for their antileishmanial activity against L. chagasi. The most active compound identified in that study (1) showed a single digit IC50 value against the parasite (1.10 µg/mL), but its macromolecular target remained unknown. Aiming to overcome this limitation, this work exploited inverse virtual screening to identify compound 1's putative molecular mechanism of action. In vitro assays confirmed that compound 1 binds to Leishmania chagasi pteridine reductase 1 (LcPTR1), with moderate affinity (Kd=33,1 µM), according to differential scanning fluorimetry assay. Molecular dynamics simulations confirm the stability of LcPTR1-compound 1 complex, supporting a competitive mechanism of action. Therefore, the workflow presented in this work successfully identified PTR1 as a macromolecular target for compound 1, allowing the designing of novel potent antileishmanial compounds.

The discovery of aryl-2-nitroethyl triamino pyrimidines as anti-Trypanosoma brucei agents.

Pteridine reductase 1 (PTR1) is a catalytic protein belonging to the folate metabolic pathway in Trypanosmatidic parasites. PTR1 is a known target for the medicinal chemistry development of antiparasitic agents against Trypanosomiasis and Leishmaniasis. In previous studies, new nitro derivatives were elaborated as PTR1 inhibitors. The compounds showing a diamino-pyrimidine core structure were previously developed but they showed limited efficacy. Therefore, a new class of phenyl-, heteroaryl- and benzyloxy-nitro derivatives based on the 2-nitroethyl-2,4,6-triaminopyrimidine scaffold were designed and tested. The compounds were assayed for their ability to inhibit T. brucei and L. major PTR1 enzymes and for their antiparasitic activity towards T. brucei and L. infantum parasites. To understand the structure-activity relationships of the compounds against TbPTR1, the X-ray crystallographic structure of the 2,4,6-triaminopyrimidine (TAP) was obtained and molecular modelling studies were performed. As a next step, only the most effective compounds against T. brucei were then tested against the amastigote cellular stage of T. cruzi, searching for a broad-spectrum antiprotozoal agent. An early ADME-Tox profile evaluation was performed. The early toxicity profile of this class of compounds was investigated by measuring their inhibition of hERG and five cytochrome P450 isoforms (CYP1A2, CYP2C9, CYP2C19, CYP2D6 and CYP3A4), cytotoxicity towards A549 cells and mitochondrial toxicity. Pharmacokinetic studies (SNAP-PK) were performed on selected compounds using hydroxypropyl-ß-cyclodextrins (50 % w/v) to preliminarily study their plasma concentration when administered per os at a dose of 20 mg/kg. Compound 1p, showed the best pharmacodynamic and pharmacokinetic properties, can be considered a good candidate for further bioavailability and efficacy studies.

In Silico and In Vitro Search for Dual Inhibitors of the Trypanosoma brucei and Leishmania major Pteridine Reductase 1 and Dihydrofolate Reductase.

The parasites Trypanosoma brucei (Tb) and Leishmania major (Lm) cause the tropical diseases sleeping sickness, nagana, and cutaneous leishmaniasis. Every year, millions of humans, as well as animals, living in tropical to subtropical climates fall victim to these illnesses' health threats. The parasites' frequent drug resistance and widely spread natural reservoirs heavily impede disease prevention and treatment. Due to pteridine auxotrophy, trypanosomatid parasites have developed a peculiar enzyme system consisting of dihydrofolate reductase-thymidylate synthase (DHFR-TS) and pteridine reductase 1 (PTR1) to support cell survival. Extending our previous studies, we conducted a comparative study of the T. brucei (TbDHFR, TbPTR1) and L. major (LmDHFR, LmPTR1) enzymes to identify lead structures with a dual inhibitory effect. A pharmacophore-based in silico screening of three natural product databases (approximately 4880 compounds) was performed to preselect possible inhibitors. Building on the in silico results, the inhibitory potential of promising compounds was verified in vitro against the recombinant DHFR and PTR1 of both parasites using spectrophotometric enzyme assays. Twelve compounds were identified as dual inhibitors against the Tb enzymes (0.2 µM < IC50 < 85.1 µM) and ten against the respective Lm enzymes (0.6 µM < IC50 < 84.5 µM). These highly promising results may represent the starting point for the future development of new leads and drugs utilizing the trypanosomatid pteridine metabolism as a target.

Pteridine reductase (PTR1): initial structure-activity relationships studies of potential leishmanicidal arylindole derivatives compounds.

Leishmaniasis is a public health concern, especially in Brazil and India. The drugs available for therapy are old, cause toxicity and have reports of resistance. Therefore, this paper aimed to carry out initial structure-activity relationships (applying molecular docking and dynamic simulations) of arylindole scaffolds against the pteridine reductase (PTR1), which is essential target for the survival of the parasite. Thus, we used a series of 43 arylindole derivatives as a privileged skeleton, which have been evaluated previously for different biological actions. Compound 7 stood out among its analogues presenting the best results of average number of interactions with binding site (2.00) and catalytic triad (1.00). Additionally, the same compound presented the best binding free energy (-32.33 kcal/mol) in dynamic simulations. Furthermore, with computational studies, it was possible to comprehend and discuss the influences of the substituent sizes, positions of substitutions in the aromatic ring and electronic influences. Therefore, this study can be a starting point for the structural improvements needed to obtain a good leishmanicidal drug.

Structure and dynamics of pteridine reductase 1: the key phenomena relevant to enzyme function and drug design.

Pteridine reductase 1 (PTR1) is a folate and pterin pathway enzyme unique for pathogenic trypanosomatids. As a validated drug target, PTR1 has been the focus of recent research efforts aimed at finding more effective treatments against human parasitic diseases such as leishmaniasis or sleeping sickness. Previous PTR1-centered structural studies highlighted the enzyme characteristics, such as flexible regions around the active site, highly conserved structural waters, and species-specific differences in pocket properties and dynamics, which likely impacts the binding of natural substrates and inhibitors. Furthermore, several aspects of the PTR1 function, such as the substrate inhibition phenomenon and the level of ligand binding cooperativity in the enzyme homotetramer, likely related to the global enzyme dynamics, are poorly known at the molecular level. We postulate that future drug design efforts could greatly benefit from a better understanding of these phenomena through studying both the local and global PTR1 dynamics. This review highlights the key aspects of the PTR1 structure and dynamics relevant to structure-based drug design that could be effectively investigated by modeling approaches. Particular emphasis is given to the perspective of molecular dynamics, what has been accomplished in this area to date, and how modeling could impact the PTR1-targeted drug design in the future.

Binding profile of quinonoid-dihydrobiopterin to quinonoid-dihydropteridine reductase examined by in silico and in vitro analyses.

Quinonoid dihydropteridine reductase (QDPR) catalyses the reduction of quinonoid-form dihydrobiopterin (qBH2) to tetrahydrobiopterin (BH4). BH4 metabolism is a drug target for neglected tropical disorders because trypanosomatid protozoans, including Leishmania and Trypanosoma, require exogenous sources of biopterin for growth. Although QDPR is a key enzyme for maintaining intracellular BH4 levels, the precise catalytic properties and reaction mechanisms of QDPR are poorly understood due to the instability of quinonoid-form substrates. In this study, we analysed the binding profile of qBH2 to human QDPR in combination with in silico and in vitro methods. First, we performed docking simulation of qBH2 to QDPR to obtain possible binding modes of qBH2 at the active site of QDPR. Then, among them, we determined the most plausible binding mode using molecular dynamics simulations revealing its atomic-level interactions and confirmed it with the in vitro assay of mutant enzymes. Moreover, it was found that not only qBH2 but also quinonoid-form dihydrofolate (qDHF) could be potential physiological substrates for QDPR, suggesting that QDPR may be a bifunctional enzyme. These findings in this study provide important insights into biopterin and folate metabolism and would be useful for developing drugs for neglected tropical diseases.

Thiadiazine-thiones as inhibitors of leishmania pteridine reductase (PTR1) target: investigations and in silico approach.

Leishmaniasis is a widespread parasitic disease and is one of the major public health concerns in developing countries. Many drugs have been identified for leishmania as targets, but the potential toxicity and long-term treatment remain the most significant problems in terms of further development. The present study employed physicochemical investigations, structure-based virtual screening, ADMET analysis, molecular dynamics simulation, and MM-PBSA, to identify potential compounds for Leishmania. We evaluated 30,926 natural products from the NPASS database, and four potentials passed the pharmacokinetic ADMET studies and were verified using the molecular docking approach. Molecular docking results showed good binding interaction of the compounds with the active site of leishmania pteridine reductase enzyme PTR1, with compound TTC1 showing FRED and Autodock binding energies of -10.33 and -10.94, respectively, which were comparable with the antileishmania drugs of Allopurinol, Miltefosine and the original ligand, methotrexate. TTC1 compound was found to be favorable for hydrophobic interaction with PTR1. In addition, the physicochemical properties of the compounds were studied using the SwissADME web server. All compounds followed Lipinski's rule of five and can be considered as good oral candidates. The analysis of the 100 ns molecular dynamics simulation results based on the best-docked TTC1 with PTR1 receptor demonstrates stable interactions, and the complex undergoes low conformational fluctuations. The average of the calculated binding free energy of the TTC1-1e7w complex is (-68.67 kJ/mol), and the result demonstrated that the TTC1 promoted stability to the Leishmania-PTR1 complex. The potential compounds can be further explored for their antileishmanial activity.Communicated by Ramaswamy H. Sarma.

Design, Synthesis, and Anti-Proliferative Action of Purine/Pteridine-Based Derivatives as Dual Inhibitors of EGFR and BRAFV600E.

The investigation of novel EGFR and BRAFV600E dual inhibitors is intended to serve as targeted cancer treatment. Two sets of purine/pteridine-based derivatives were designed and synthesized as EGFR/BRAFV600E dual inhibitors. The majority of the compounds exhibited promising antiproliferative activity on the cancer cell lines tested. Compounds 5a, 5e, and 7e of purine-based and pteridine-based scaffolds were identified as the most potent hits in anti-proliferative screening, with GI50 values of 38 nM, 46 nM, and 44 nM, respectively. Compounds 5a, 5e, and 7e demonstrated promising EGFR inhibitory activity, with IC50 values of 87 nM, 98 nM, and 92 nM, respectively, when compared to erlotinib's IC50 value of 80 nM. According to the results of the BRAFV600E inhibitory assay, BRAFV600E may not be a viable target for this class of organic compounds. Finally, molecular docking studies were carried out at the EGFR and BRAFV600E active sites to suggest possible binding modes.

Design, synthesis, in vitro - In vivo biological evaluation of novel thiazolopyrimidine compounds as antileishmanial agent with PTR1 inhibition.

The leishmaniasis are a group of vector-borne diseases caused by a protozoan parasite from the genus Leishmania. In this study, a series of thiazolopyrimidine derivatives were designed and synthesized as novel antileishmanial agents with LmPTR1 inhibitory activity. The final compounds were evaluated for their in vitro antipromastigote activity, LmPTR1 and hDHFR enzyme inhibitory activities, and cytotoxicity on RAW264.7 and L929 cell lines. Based on the bioactivity results, three compounds, namely L24f, L24h and L25c, were selected for evaluation of their in vivo efficacy on CL and VL models in BALB/c mice. Among them, two promising compounds, L24h and L25c, showed in vitro antipromastigote activity against L. tropica with the IC50 values of 0.04 µg/ml and 6.68 µg/ml; against L. infantum with the IC50 values of 0.042 µg/ml and 6.77 µg/ml, respectively. Moreover, the title compounds were found to have low in vitro cytotoxicity on L929 and RAW264.7 cell lines with the IC50 14.08 µg/ml and 21.03 µg/ml, and IC50 15.02 µg/ml and 8.75 µg/ml, respectively. LmPTR1 enzyme inhibitory activity of these compounds was determined as 257.40 µg/ml and 59.12 µg/ml and their selectivity index (SI) over hDHFR was reported as 42.62 and 7.02, respectively. In vivo studies presented that L24h and L25c have a significant antileishmanial activity against footpad lesion development of CL and at weight measurement of VL group in comparison to the reference compound, Glucantime®. Also, docking studies were carried out with selected compounds and other potential Leishmania targets to detect the putative targets of the title compounds. Taken together, all these findings provide an important novel lead structure for the antileishmanial drug development.

Identification, characterization and differential expression analysis of a pteridine synthesis related gene, Ccptps, in koi carp (Cyprinus carpio L.).

6-pyruvoyl-tetrahydropterin synthase (PTPS) is the second key enzyme of the pteridine biosynthetic pathway and it plays vital roles in fish body color formation. In this study, Ccptps of koi carp (Cyprinus carpio L.) was cloned, identified and characterized. The full-length cDNA of Ccptps was 1140 bp and encodes for 139 amino acids. Multiple alignments revealed that the amino acids sequence of CcPTPS shared the highest identity to that of C. carpio, and Ccptps was clustered with cyprinid fishes in phylogenetic tree. Liver tissues of koi carp exhibited the highest expression of Ccptps, followed by muscle and skin tissues. During early developmental stages, the expression of Ccptps declined from 2 dph to 4 dph, and increased from 4 dph to 12 dph. The expressions of Ccptps in three color-related tissues (skin, scale and caudal fin) of whole red (WR) koi carp were significantly higher than that of whole while (WW) koi carp. Immunohistochemistry results of skin tissues showed that CcPTPS was mainly located in epidermis, stratum compactum of dermis and muscle layer, with the signal intensities in stratum compactum and muscle layer were stronger in WR koi carp compared to WW koi carp. Co-expressions of CcPTPS, CcSPR and CcXDH were detected in skin tissues of WW and WR koi carps, with CcPTPS exhibited stronger signal intensity compared to CcSPR and CcXDH. These findings imply that Ccptps is potentially involved in koi carp body color formation through the pteridine synthesis pathway.

Anti-trypanosomatid structure-based drug design - lessons learned from targeting the folate pathway.

INTRODUCTION: Trypanosomatidic parasitic infections in humans and animals caused by Trypanosoma brucei, Trypanosoma cruzi, and Leishmania species pose a significant health and economic burden in developing countries. There are few effective and accessible treatments for these diseases, and the existing therapies suffer from problems, such as parasite resistance and side effects. Structure-based drug design (SBDD) is one of the strategies that has been applied to discover new compounds targeting trypanosomatid-borne diseases. AREAS COVERED: We review the current literature (mostly over the last 5 years, searched in the PubMed database on 11 November 2021) on the application of structure-based drug design approaches to identify new anti-trypanosomatidic compounds that interfere with a validated target biochemical pathway, the trypanosomatid folate pathway. EXPERT OPINION: The application of structure-based drug design approaches to perturb the trypanosomatid folate pathway has successfully provided many new inhibitors with good selectivity profiles, most of which are natural products or their derivatives or have scaffolds of known drugs. However, the inhibitory effect against the target protein(s) often does not translate to anti-parasitic activity. Further progress is hampered by our incomplete understanding of parasite biology and biochemistry, which is necessary to complement SBDD in a multiparameter optimization approach to discovering selective anti-parasitic drugs.

Triphenyltin exposure induced abnormal morphological colouration in adult male guppies (Poecilia reticulata).

Fish morphological colouration is essential for their survival and reproduction success; however, it is vulnerable to environmental factors, such as pollutants. Triphenyltin (TPT) is widespread in aquatic ecosystems, and its impacts on fish have been problematic. Therefore, the purpose of this study was to investigate the effects of TPT at environment-related concentrations (0, 1, 10 and 100 ng Sn/L) on morphological colouration in male guppies (Poecilia reticulata). The results showed that TPT exposure affected both orange/red and dark morphological colouration in guppies. The faded orange/red colouration might be related to the decrease of coloured pteridine and Pts (6-Pyruvoyltetrahydropterin Synthase) expression. In addition, TPT exposure induced melanogenesis, however, much melanin was distributed diffusely in the skin and did not seem to form a spot pattern, giving the fish a dull appearance. According to the skin transcriptional profiles, the changes of dark morphological colouration might be related to the changes in genes related to the functions of melanosome components (Gpnmb, Slc45a2 and Tyr), construction (Ap3d1, Fig4, Hps3, Hps5, Lyst, Rabggta, Txndc5 and Vps33a), and transport (Rab27a). Additionally, genes related to the regulation of melanogenesis (Atrn and Pomc) and system effects (Atox1, Atp6ap2, Atp6v1f, Atp6v1h, Rpl24, Rps19 and Rps20) might also be involved in the molecular mechanisms of abnormal morphological colouration induced by TPT. The present study provides crucial data on the molecular basis of abnormal morphological colouration in fish exposed to TPT and underscores the importance of toxicological studies of the effects of pollutants in aquatic environments on fish morphological colouration.

Establishing pteridine metabolism in a progressive isogenic breast cancer cell model - part II.

INTRODUCTION: Determining the biological significance of pteridines in cancer development and progression remains an important step in understanding the altered levels of urinary pteridines seen in certain cancers. Our companion study revealed that several folate-derived pteridines and lumazines correlated with tumorigenicity in an isogenic, progressive breast cancer cell model, providing direct evidence for the tumorigenic origin of pteridines. OBJECTIVES: This study sought to elucidate the pteridine biosynthetic pathway in a progressive breast cancer model via direct pteridine dosing to determine how pteridine metabolism changes with tumorigenicity. METHODS: First, MCF10AT breast cancer cells were dosed individually with 15 pteridines to determine which pteridines were being metabolized and what metabolic products were being produced. Second, pteridines that were significantly metabolized were dosed individually across the progressive breast cancer cell model (MCF10A, MCF10AT, and MCF10ACA1a) to determine the relationship between each metabolic reaction and breast cancer tumorigenicity. RESULTS: Several pteridines were found to have altered metabolism in breast cancer cell lines, including pterin, isoxanthopterin, xanthopterin, sepiapterin, 6-biopterin, lumazine, and 7-hydroxylumazine (p < 0.05). In particular, isoxanthopterin and 6-biopterin concentrations were differentially expressed (p < 0.05) with respect to tumorigenicity following dosing with pterin and sepiapterin, respectively. Finally, the pteridine biosynthetic pathway in breast cancer cells was proposed based on these findings. CONCLUSIONS: This study, along with its companion study, demonstrates that pteridine metabolism becomes disrupted in breast cancer tumor cells. This work highlights several key metabolic reactions within the pteridine biosynthetic pathway that may be targeted for further investigation and clinical applications.

Crystal structure of the ternary complex of Leishmania major pteridine reductase 1 with the cofactor NADP+/NADPH and the substrate folic acid.

Pteridine reductase 1 (PTR1) is a key enzyme of the folate pathway in protozoan parasites of the genera Leishmania and Trypanosoma and is a valuable drug target for tropical diseases. This enzyme is able to catalyze the NADPH-dependent reduction of both conjugated (folate) and unconjugated (biopterin) pterins to their tetrahydro forms, starting from oxidized- or dihydro-state substrates. The currently available X-ray structures of Leishmania major PTR1 (LmPTR1) show the enzyme in its unbound, unconjugated substrate-bound (with biopterin derivatives) and inhibitor-bound forms. However, no structure has yet been determined of LmPTR1 bound to a conjugated substrate. Here, the high-resolution crystal structure of LmPTR1 in complex with folic acid is presented and the intermolecular forces that drive the binding of the substrate in the catalytic pocket are described. By expanding the collection of LmPTR1 structures in complex with process intermediates, additional insights into the active-site rearrangements that occur during the catalytic process are provided. In contrast to previous structures with biopterin derivatives, a small but significant difference in the orientation of Asp181 and Tyr194 of the catalytic triad is found. This feature is shared by PTR1 from T. brucei (TbPTR1) in complex with the same substrate molecule and may be informative in deciphering the importance of such residues at the beginning of the catalytic process.

Examination of multiple Trypanosoma cruzi targets in a new drug discovery approach for Chagas disease.

Chagas disease (CD) is a centenarian neglected parasitosis caused by the protozoan Trypanosoma cruzi (T. cruzi). Despite the continuous efforts of many organizations and institutions, CD is still an important human health problem worldwide. A lack of a safe and affordable treatment has led drug discovery programmes to focus, for years, on the search for molecules enabling interference with enzymes that are essential for T. cruzi survival. In this work, the authors want to offer a brief overview of the different validated targets that are involved in diverse parasite pathways: glycolysis, sterol synthesis, the de novo biosynthesis of pyrimidine nucleotides, the degradative processing of peptides and proteins, oxidative stress damage and purine salvage and nucleotide synthesis and metabolism. Their structural aspects, function, active sites, etc. were studied and considered with the aim of defining molecular bases in the search for new effective treatments for CD. This review also compiles, as much as possible, all the inhibitors reported to date against these T. cruzi targets, serving as a reference for future research in this field.

Efficient Synthesis and Biological Evaluation of 6-Trifluoroethoxy Functionalized Pteridine Derivatives as EGFR Inhibitors.

BACKGROUND: Pteridine-based scaffolds have been widely prevalent in pharmaceuticals, such as kinase inhibitors targeting EGFR, FLT3 and PI3K/mTOR which are attractive targets for the anticancer therapy. OBJECTIVE: This work aimed at designing and synthesizing 6-2,2,2-trifluoroethoxy functionalized pteridine-based derivatives for investigation of their anti-cancer activities as EGFR inhibitor. METHODS: Pteridine-based derivatives were synthesized in 6 steps involving amination, bromination, cyclization, alkoxylation, chlorination and coupling reactions. Cellular anti-proliferative activities and inhibition activities on EGFR signaling of these pteridine derivatives in vitro were determined by the MTT assay and western blot analysis, respectively. Molecular docking simulation studies were carried out by the crystallographic structure of the erlotinib/EGFR kinase domain [Protein Data Bank (PDB) code: 1M17]. RESULTS: The compound 7m, with IC50 values of 27.40 µM on A549 cell line, exhibited comparable anti-proliferative activity relative to the positive control. Besides, western blots showed its obvious down-regulation of p-EGFR and p-ERK expression at 0.8 µM. The molecular docking model displayed a hydrogen bond between Met-769 amide nitrogen and N-1 in pteridine motif of 7m which lied at the ATP binding site of EGFR kinase domain. CONCLUSION: The inhibition of 7m on cellular growth was comparable to that of the positive control. The inhibitory activities of 7m on EGFR phosphorylation and ERK phosphorylation in A549 cell line were relatively superior to that of the positive control. Both results suggested that the antiproliferative activity of 7m against A549 cell line was caused by inhibition of EGFR signaling pathway, providing a new perspective for the modification of pteridine-based derivatives as EGFR inhibitor.