The L.donovani Hypoxanthine-guanine phosphoribosyl transferase (HGPRT) oligomer is distinct from the human homolog

Development of Novel Anti-Leishmanials: The Case for Structure-Based Approaches

The neglected tropical disease (NTD) leishmaniasis is the collective name given to a diverse group of illnesses caused by ~20 species belonging to the genus Leishmania, a majority of which are vector borne and associated with complex life cycles that cause immense health, social, and economic burdens locally, but individually are not a major global health priority. Therapeutic approaches against leishmaniasis have various inadequacies including drug resistance and a lack of effective control and eradication of the disease spread. Therefore, the development of a rationale-driven, target based approaches towards novel therapeutics against leishmaniasis is an emergent need. The utilization of Artificial Intelligence/Machine Learning methods, which have made significant advances in drug discovery applications, would benefit the discovery process. In this review, following a summary of the disease epidemiology and available therapies, we consider three important leishmanial metabolic pathways that can be attractive targets for a structure-based drug discovery approach towards the development of novel anti-leishmanials. The folate biosynthesis pathway is critical, as Leishmania is auxotrophic for folates that are essential in many metabolic pathways. Leishmania can not synthesize purines de novo, and salvage them from the host, making the purine salvage pathway an attractive target for novel therapeutics. Leishmania also possesses an organelle glycosome, evolutionarily related to peroxisomes of higher eukaryotes, which is essential for the survival of the parasite. Research towards therapeutics is underway against enzymes from the first two pathways, while the third is as yet unexplored.

The Correlation Between Children’s Acute Lymphoblastic Leukemia Drug Resistance System Induced by Metabolomics-Based 6-Mercaptopurine and Hypoxanthine-Guanine Phosphoribosyl Transferase 1 Protein

This study aimed to explore 6-mercaptopurine (MP)-induced children’s acute lymphoblastic leukemia (ALL) drug resistance system and leukemia hypoxanthine-guanine phosphoribosyl transferase 1 (HPRT1) protein. Based on metabonomics, drug resistance of 6MP-Reh cell line was established by increasing concentration administration method, and the degree of drug resistance of 6MP-Reh was verified by apoptosis test, western blotting (WB) test, and drug sensitivity test. The changes of tissue inhibitor of matrix metalloproteinase (TIMP) and thioguanosine monophosphate (TGMP) in drug-resistant cells were detected through liquid chromatograph (LC)/mass spectrometer (MS). The 6MP-Reh-wt cell line was established by lentivirus infection, so as to verify the correlation between HPRT1 and drug resistance mechanism. The results showed that the inhibition concentration (IC50) value, cell vitality (CV), apoptosis rate, and 6-MP content of 6MP-Reh were higher hugely than those of Reh (P < 0.05). The contents of HPRT1, TIMP, and TGMP in 6MP-Reh cells were lower sharply than the contents of Reh cells (P < 0.001). The IC50 value of 6MP-Reh-wt was also lower steeply than the value of 6MP-Reh (P < 0.001), and the concentrations of TIMP and TGMP increased obviously (P < 0.05). Therefore, it indicated that the mutation of HPRT1 in drugresistant cell lines could lead to a decrease in their viability and cause leukemia cells to develop resistance to 6-MP. In addition, HPRT1 gene could improve their resistance to 6-MP.

Ile209 of Leishmania donovani xanthine phosphoribosyltransferase plays a key role in determining its purine base specificity

Xanthine phosphoribosyltransferase (XPRT) and hypoxanthine-guanine phosphoribosyltransferase (HGPRT) are purine salvaging enzymes of Leishmania donovani with distinct 6-oxopurine specificities. LdXPRT phosphoribosylates xanthine, hypoxanthine, and guanine, with preference toward xanthine, whereas LdHGPRT phosphoribosylates only hypoxanthine and guanine. In our study, LdXPRT was used as a model to understand these purine base specificities. Mutating I209 to V, the conserved residue found in HGPRTs, reduced the affinity of LdXPRT for xanthine, converting it to an HGXPRT-like enzyme. The Y208F mutation in the active site indicated that aromatic residue interactions with the purine ring are limited to pi-pi binding forces and do not impart purine base specificity. Deleting the unique motif (L55-Y82) of LdXPRT affected enzyme activity. Our studies established I209 as a key residue determining the 6-oxopurine specificity of LdXPRT.