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A proposed treatment for malaria is a combination of fosmidomycin and clindamycin. Both compounds inhibit the methylerythritol 4-phosphate (MEP) pathway, the parasitic source of farnesyl and geranylgeranyl pyrophosphate (FPP and GGPP, respectively). Both FPP and GGPP are crucial for the biosynthesis of several essential metabolites such as ubiquinone and dolichol, as well as for protein prenylation. Dietary prenols, such as farnesol (FOH) and geranylgeraniol (GGOH), can rescue parasites from MEP inhibitors, suggesting the existence of a missing pathway for prenol salvage via phosphorylation. In this study, we identified a gene in the genome of P. falciparum, encoding a transmembrane prenol kinase (PolK) involved in the salvage of FOH and GGOH. The enzyme was expressed in Saccharomyces cerevisiae, and its FOH/GGOH kinase activities were experimentally validated. Furthermore, conditional knockout parasites (Δ-PolK) were created to investigate the biological importance of the FOH/GGOH salvage pathway. Δ-PolK parasites were viable but displayed increased susceptibility to fosmidomycin. Their sensitivity to MEP inhibitors could not be rescued by adding prenols. Additionally, Δ-PolK parasites lost their capability to utilize prenols for protein prenylation. Experiments using culture medium supplemented with whole/delipidated human plasma in transgenic parasites revealed that human plasma has components that can diminish the effectiveness of fosmidomycin. Mass spectrometry tests indicated that both bovine supplements used in culture and human plasma contain GGOH. These findings suggest that the FOH/GGOH salvage pathway might offer an alternate source of isoprenoids for malaria parasites when de novo biosynthesis is inhibited. This study also identifies a novel kind of enzyme related to isoprenoid metabolism. Author summary: Falciparum malaria is a potentially fatal disease caused by the parasite Plasmodium falciparum. Antimalarials such as fosmidomycin and clindamycin target a critical pathway in the parasite, crucial for producing certain substances essential for the parasite's survival, particularly phosphorylated isoprenoids. However, the limited effectiveness of these drugs in clinical trials for malaria treatment underscores the need for further related studies. Previous in vitro experiments have demonstrated that the parasite can utilize unphosphorylated isoprenoids, namely farnesol and geranylgeraniol, if they are present in the external environment. Thus, these substances act as antidotes, rendering the parasite resistant to both fosmidomycin and clindamycin. This study reveals for the first time that geranylgeraniol naturally occurs in the human body. Additionally, we have identified a novel enzyme, prenol kinase, which enables the parasite to use these unphosphorylated isoprenoids by converting them into their metabolically active phosphorylated counterparts. Parasites lacking the prenol kinase gene remain viable but become more susceptible to the effects of fosmidomycin, even in the presence of farnesol or geranylgeraniol. These findings suggest that the scavenging of unphosphorylated isoprenoids by the parasite might supplement its isoprenoid needs when the endogenous production is inhibited by drugs like fosmidomycin or clindamycin. [ABSTRACT FROM AUTHOR]

Ubiquinone (UQ) is a fundamental mitochondrial electron transport chain component. This compound is synthesized as the condensation of a p -substituted benzoic acid and a polyisoprenic moiety catalyzed by the enzyme 4-hydroxybenzoate polyprenyltransferase (EC 2.5.1.39). In Plasmodium spp. this enzyme is still uncharacterized. In this work, we expressed the sequence of the Plasmodium falciparum PF3D7_0607500 gene (abbreviated as PfCOQ2) in a coq2Δ mutant strain of Saccharomyces cerevisiae , and studied the functionality of its gene product. This open reading frame could complement S. cerevisiae coq2Δ mutant growth defect on media with glycerol as a carbon source. Further, UQ was unequivocally identified in lipid extracts from this coq2Δ mutant when expressing PfCOQ2. Remarkably, UQ was detected under those conditions when S. cerevisiae cells were metabolically labeled with either [ring-14C(U)]- p -aminobenzoic acid or [ring-14C(U)]-4-hydroxybenzoic acid. However, no UQ was detected in P. falciparum if labeled with p -aminobenzoic acid. These results indicate that PfCOQ2 is a 4-hydroxybenzoate polyprenyltransferase. Further, its substrate profile seems not dissimilar to that of S. cerevisiae , but, as in other organisms, p -aminobenzoic acid does not act as an aromatic precursor in UQ biosynthesis in P. falciparum. The reason for this last feature remains to be established, but may lie upstream of PfCOQ2. [ABSTRACT FROM AUTHOR]

Malaria is one of the most widespread parasitic diseases, especially in Africa, Southeast Asia and South America. One of the greatest problems for control of the disease is the emergence of drug resistance, which leads to a need for the development of new antimalarial compounds. The biosynthesis of isoprenoids has been investigated as part of a strategy to identify new targets to obtain new antimalarial drugs. Several isoprenoid quinones, including menaquinone-4 (MK-4/vitamin K2), α- and γ-tocopherol and ubiquinone (UQ) homologs UQ-8 and UQ-9, were previously detected in in vitro cultures of Plasmodium falciparum in asexual stages. Herein, we described for the first time the presence of phylloquinone (PK/vitamin K1) in P. falciparum and discuss the possible origins of this prenylquinone. While our results in metabolic labeling experiments suggest a biosynthesis of PK prenylation via phytyl pyrophosphate (phytyl-PP) with phytol being phosphorylated, on the other hand, exogenous PK attenuated atovaquone effects on parasitic growth and respiration, showing that this metabolite can be transported from extracellular environment and that the mitochondrial electron transport system (ETS) of P. falciparum is capable to interact with PK. Although the natural role and origin of PK remains elusive, this work highlights the PK importance in plasmodial metabolism and future studies will be important to elucidate in seeking new targets for antimalarial drugs. [ABSTRACT FROM AUTHOR]