Identification of new inhibitors of Plasmodium falciparum hypoxanthine-guanine-xanthine Phosphoribosyltransferase (HG(X)PRT): An outlook towards the treatment of malaria

Laleen Hammal; Sumaira Javaid; Atia-Tul Wahab; Humaira Zafar; Noor Rahman; Aftab Ahmed; M Iqbal Choudhary

doi:10.1016/j.ijbiomac.2024.137917

Identification of new inhibitors of Plasmodium falciparum hypoxanthine-guanine-xanthine Phosphoribosyltransferase (HG(X)PRT): An outlook towards the treatment of malaria

Int J Biol Macromol. 2024 Nov 25:137917. doi: 10.1016/j.ijbiomac.2024.137917. Online ahead of print.

Authors

Laleen Hammal¹, Sumaira Javaid², Atia-Tul Wahab¹, Humaira Zafar³, Noor Rahman¹, Aftab Ahmed⁴, M Iqbal Choudhary⁵

Affiliations

¹ Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center of Chemical and Biological Sciences, University of Karachi, Karachi 75270, Pakistan.
² Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center of Chemical and Biological Sciences, University of Karachi, Karachi 75270, Pakistan. Electronic address: sumaira.javed@iccs.edu.
³ Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center of Chemical and Biological Sciences, University of Karachi, Karachi 75270, Pakistan. Electronic address: humaira.zafar@iccs.edu.
⁴ School of Pharmacy, Chapman University Irvine, CA 92618, USA.
⁵ Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center of Chemical and Biological Sciences, University of Karachi, Karachi 75270, Pakistan; H. E. J. Research Institute of Chemistry, International Center for Chemical and Biological Sciences, University of Karachi, Karachi 75270, Pakistan; Department of Biochemistry, Faculty of Sciences, King Abdulaziz University, Jeddah 22252, Saudi Arabia. Electronic address: iqbal.choudhary@iccs.edu.

PMID: 39603289
DOI: 10.1016/j.ijbiomac.2024.137917

Abstract

Plasmodium, a protozoan parasite responsible for causing malaria relies on the purine salvage pathway to synthesize purine as they are incapable of synthesizing them de novo. This pathway is crucial for the survival of the parasite and hence enzymes of this pathway can serve as antimalarial drug targets. One of the enzymes of this pathway is hypoxanthine guanine (xanthine) phosphoribosyltransferase [HG(X)PRT] that serves as novel target, potentially less prone to existing resistance mechanisms seen with the use of traditional antimalarial drugs. HGXPRT inhibition disrupts the parasite's ability to synthesize nucleotides, essential for its growth and replication. In this regard, the current study was designed to identify the inhibitors of HGXPRT. For this purpose, the enzyme was produced through recombinant technology and purified with 10 mg/ L yield. Followed this, UV-based enzyme inhibition assay was optimized and >200 fully characterized compounds were evaluated for their HGXPRT inhibitory activity. Out of them fourteen compounds 1-14 showed significant to weak inhibition of HGXPRT enzyme with IC₅₀ values in the range of 15.7 to 229.6 μM, as compared to the standard inhibitor i.e. 9-deazaguanine (IC₅₀ = 12 ± 1.0 μM). In- silico and biophysical studies were further performed on active compounds to get structural insights into enzyme-inhibitor complex at the atomic level. Docking studies predicted that these inhibitors accommodate the purine binding site of enzyme and interacted with critical residues such as Asp148, Phe197, and Val198. Biophysical studies showed that these identified inhibitors interacted with HGXPRT enzyme in a non-ambiguous manner. Furthermore, these inhibitors were found to be non-cytotoxic against human fibroblast cell lines (BJ). Hence, this study identified 14 hits that could lead to further research towards anti-malarial drug design and development.

Keywords: Anti-malarial agents; HGXPRT; Plasmodium falciparam; Purine salvage pathway; STD-NMR.