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Updated: Jan 8, 2026
Author Spotlight: Identifying Compensatory Pathways in Malaria Parasites Containing Hypomorphic Allele of Essential Protein Kinases
Published on: November 22, 2024
Genetic analysis of pyrimidine biosynthetic enzymes in Plasmodium falciparum
Krithika Rajaram1,2, Montana L Sievert1, Rubayet Elahi1
1Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD.
Abstract:
The malaria parasite Plasmodium falciparum depends entirely on de novo pyrimidine synthesis, as it is unable to salvage these essential nucleotides. This reliance makes the pyrimidine biosynthesis pathway a compelling target for antimalarial drugs, with several inhibitors targeting its rate-limiting enzyme, dihydroorotate dehydrogenase (PfDHODH), already in clinical development. In this study, we investigated the roles of three other pathway enzymes - aspartate transcarbamoylase (PfATC), carbamoyl phosphate synthetase II (PfCPSII), and dihydroorotase (PfDHO). PfATC features a unique N-terminal extension predicted to serve as an apicoplast trafficking peptide. However, using antibodies against the native protein and an epitope-tagged version, we found no evidence of apicoplast localization. Knockdown of PfATC expression proved lethal and could not be rescued by an apicoplast metabolic bypass. Complementation assays further revealed that truncation of the N-terminal domain impaired parasite growth, suggesting that this region is important for PfATC function or stability in vivo. PfCPSII, which harbors large Plasmodium-specific insertions between its catalytic domains, was likewise found to be essential for parasite proliferation. To assess the role of PfDHO, we engineered parasites to salvage uracil via heterologous expression of a yeast enzyme. Deletion of PfDHO in this parasite line resulted in uracil auxotrophy, confirming the enzyme's essential function in pyrimidine synthesis. Together, these findings reveal multiple vulnerable nodes within the pyrimidine biosynthesis pathway.
Insights
The malaria parasite Plasmodium falciparum requires de novo pyrimidine synthesis, making its biosynthesis pathway a drug target. This study confirms essential roles for three key enzymes, revealing new vulnerabilities for antimalarial drug development.
Area of Science:
- Parasitology
- Biochemistry
- Drug Discovery
Background:
- Plasmodium falciparum, the malaria parasite, relies on de novo pyrimidine synthesis due to its inability to salvage nucleotides.
- The pyrimidine biosynthesis pathway is a validated target for antimalarial drugs, with inhibitors of dihydroorotate dehydrogenase (PfDHODH) in clinical trials.
Purpose of the Study:
- To investigate the essentiality and function of three other Plasmodium falciparum pyrimidine biosynthesis enzymes: aspartate transcarbamoylase (PfATC), carbamoyl phosphate synthetase II (PfCPSII), and dihydroorotase (PfDHO).
- To identify novel targets within the pyrimidine biosynthesis pathway for antimalarial drug development.
Main Methods:
- Utilized antibody-based detection and epitope-tagged protein analysis to assess PfATC localization.
- Performed gene knockdown experiments and complementation assays to evaluate PfATC function and the importance of its N-terminal domain.
- Engineered parasites for uracil salvage via heterologous enzyme expression to assess PfDHO essentiality.
Main Results:
- PfATC knockdown was lethal, and its N-terminal domain was crucial for parasite growth, despite not localizing to the apicoplast as predicted.
- PfCPSII, with unique Plasmodium-specific insertions, was also found to be essential for parasite proliferation.
- PfDHO was confirmed as essential for pyrimidine synthesis, as its deletion led to uracil auxotrophy.
Conclusions:
- The study validates PfATC, PfCPSII, and PfDHO as essential enzymes in Plasmodium falciparum pyrimidine biosynthesis.
- These enzymes represent critical and vulnerable nodes within the pathway, offering new opportunities for antimalarial drug targeting beyond PfDHODH.
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