Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0024530 (malaria)
 44,886 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The energy metabolism of the blood stage form of the human malaria parasite Plasmodium falciparum is adapted to the host cell. Like erythrocytes, P. falciparum merozoites lack a functional citric acid cycle. Generation of ATP depends therefore fully on the glycolytic pathway. Aldolase is a key enzyme of this pathway and a high degree of sequence diversity between parasite and host makes it a potential drug target. We have expressed the enzyme in its tetrameric form in Escherichia coli and the catalytic constants Vmax and Km of the recombinant enzyme correspond to the constants of parasite-derived aldolase. Rabbit antibodies against the recombinant P. falciparum aldolase inhibit the natural enzyme and no cross-reaction with human aldolase is detectable. Both the recombinant and the natural protein bind to the cytosolic domain of the band 3 membrane protein in vitro. A 19-residue synthetic peptide corresponding to the sequence of the binding domain of band 3 is an inhibitor when included in the binding assay. In addition, this peptide inhibits the catalytic activity of recombinant P. falciparum aldolase when assayed in a buffer system devoid of anions such as chloride or phosphate. The band 3-derived peptides compete with the aldolase substrate fructose-1,6-diphosphate for binding, suggesting that both reagents have a high affinity for the substrate pocket. A similar sequence motif exists in P. falciparum actin II. A 19-residue peptide corresponding to this sequence is also an inhibitor which could suggest that the P. falciparum aldolase can associate with the cytoskeleton of the parasite or of the host.
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PMID:Expression, purification, biochemical characterization and inhibition of recombinant Plasmodium falciparum aldolase. 220 32

Aldolase of the human malaria parasite Plasmodium falciparum (PfAldo) may be a potential target for the development of novel antimalarial drugs. Using in vitro mutagenesis we analyzed the function of the carboxy-terminus of the recombinant enzyme. Deletion of the carboxy-terminus of PfAldo confirmed its critical role in catalysis; exchange of conserved residues minimally affected enzyme activity. We exchanged a pair of parasite specific lysine residues with corresponding amino acids of the host. These mutant enzymes exhibited an increased catalytic activity and reduced binding to erythrocyte band 3 protein. Homologous peptides of human band 3 protein and P. falciparum alpha-tubulin were competitive inhibitors of PfAldo. Selective inhibition of PfAldo by the alpha-tubulin peptide depends on the presence of tandem lysine residues and the fine structure of the inhibitor peptide. Our data support the concept of a matrix organisation of glycolytic enzymes in Plasmodium falciparum.
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PMID:Selective inhibition of Plasmodium falciparum aldolase by a tubulin derived peptide and identification of the binding site. 845 25

A major obstacle in the global effort to control malaria is the paucity of anti-malarial drugs. This is compounded by the continuing emergence and spread of resistance to old and new anti-malarial drugs in the malarial parasites. Here we describe the anti-malarial effect of phosphorothioate antisense (AS) oligodeoxynucleotides (ODNs) targeting the aldolase enzyme of Plasmodium falciparum, using the asexual blood stages of the parasite grown in vitro. The blood stages of P. falciparum depend almost entirely on the energy produced by their own glycolysis. Aldolase, the fourth enzyme of the glycolytic pathway, is highly upregulated during the malarial 48-h life cycle. We found that the mRNA of this enzyme can be inhibited, in a sequence specific manner, using AS-ODN to the splice sites on the pre-mRNA of malarial aldolase. At the enzyme level, both specific AS-ODNs for the splice sites, as well as for the translation initiation site on mature mRNA, can inhibit aldolase enzyme activity within the trophozoites of P. falciparum. Furthermore, this downregulation of the malarial aldolase results in a reduction in the production of ATP within the parasite. Finally, the treatment reduces parasitemia. In summary, AS-ODNs targeting the aldolase gene of P. falciparum can interfere with the blood-stage life cycle of this parasite in vitro by inhibiting the expression of the enzyme aldolase which results in decreased malarial glycolysis and energy production. Thus, we conclude that blockade of the expression of malarial glycolytic enzymes using specific AS-ODNs has the potential of a new anti-malarial strategy.
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PMID:Antisense oligonucleotides targeting malarial aldolase inhibit the asexual erythrocytic stages of Plasmodium falciparum. 1047 79

An actomyosin motor located underneath the plasma membrane drives motility and host-cell invasion of apicomplexan parasites such as Plasmodium falciparum and Plasmodium vivax, the causative agents of malaria. Aldolase connects the motor actin filaments to transmembrane adhesive proteins of the thrombospondin-related anonymous protein (TRAP) family and transduces the motor force across the parasite surface. The TRAP-aldolase interaction is a distinctive and critical trait of host hepatocyte invasion by Plasmodium sporozoites, with a likely similar interaction crucial for erythrocyte invasion by merozoites. Here, we describe 2.4-A and 2.7-A structures of P. falciparum aldolase (PfAldo) obtained from crystals grown in the presence of the C-terminal hexapeptide of TRAP from Plasmodium berghei. The indole ring of the critical penultimate Trp-residue of TRAP fits snugly into a newly formed hydrophobic pocket, which is exclusively delimited by hydrophilic residues: two arginines, one glutamate, and one glutamine. Comparison with the unliganded PfAldo structure shows that the two arginines adopt new side-chain rotamers, whereas a 25-residue subdomain, forming a helix-loop-helix unit, shifts upon binding the TRAP-tail. The structural data are in agreement with decreased TRAP binding after mutagenesis of PfAldo residues in and near the induced TRAP-binding pocket. Remarkably, the TRAP- and actin-binding sites of PfAldo seem to overlap, suggesting that both the plasticity of the aldolase active-site region and the multimeric nature of the enzyme are crucial for its intriguing nonenzymatic function in the invasion machinery of the malaria parasite.
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PMID:Aldolase provides an unusual binding site for thrombospondin-related anonymous protein in the invasion machinery of the malaria parasite. 1742 53

The objective of this study is to develop and evaluate a simple, cheap, and stable positive control for the quality control and quality assurance (QA) of rapid diagnostic tests (RDT) for the diagnosis of malaria. Plasmodium falciparum in vitro culture of known parasite concentrations was dried on a protein saver card, that is, dried blood spots (DBSs). The cards were stored at temperatures ranging from 27 to 60 degrees C from 1 day up to 6 months. Antigens were subsequently eluted from the card giving final concentrations ranging from 30 000 parasites to 300 parasites/microL and tested for stability against RDT based on the antigens parasite lactate dehydrogenase (pLDH), aldolase, and histidine-rich protein 2 (HRP-2). HRP-2 antigens were stable throughout the whole study and yielded positive results irrespective of parasite concentration, storage duration, or temperature, although band intensity differences could be observed when high parasites were compared with low parasite densities. Aldolase was able to generate positive signals for up to 4 weeks irrespective of the storage conditions. Thereafter, intensities decreased proportionally to increasing temperature and storage duration. Thirty thousand parasites per liter could give a signal up to 16 weeks when stored at a temperature of maximum 45 degrees C. However, densities of 300 parasites/microL were not able to generate a signal during the study. pLDH, the least stable of the 3 antigens, was not able to generate a signal after 1 week of storage. The DBS method yields a very stable positive control for quality control and QA of RDTs based on HRP-2. RDTs based on aldolase may also benefit from this method although to a lesser extent because that particular antigen is less stable in the DBS system.
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PMID:Development of a stable positive control to be used for quality assurance of rapid diagnostic tests for malaria. 1937 69

Aldolase has been implicated as a protein coupling the actomyosin motor and cell surface adhesins involved in motility and host cell invasion in the human malaria parasite Plasmodium falciparum. It binds to the cytoplasmic domain (CTD) of type 1 membrane proteins of the thrombospondin-related anonymous protein (TRAP) family. Other type 1 membrane proteins located in the apical organelles of merozoites, the form of the parasite that invades red blood cells, including apical membrane antigen 1 (AMA1) and members of the erythrocyte binding ligand (EBL) and reticulocyte binding homologue (RH) protein families have been implicated in host cell binding and invasion. Using a direct binding method we confirm that TRAP and merozoite TRAP (MTRAP) bind aldolase and show that the interaction is mediated by more than just the C-terminal six amino acid residues identified previously. Single amino acid substitutions in the MTRAP CTD abolished binding to aldolase. The CTDs of AMA1 and members of the EBL and RH protein families also bound to aldolase. MTRAP competed with AMA1 and RH4 for binding to aldolase, indicating overlapping binding sites. MTRAP CTD was phosphorylated in vitro by both calcium dependent kinase 1 (CDPK1) and protein kinase A, and this modification increased the affinity of binding to aldolase by ten-fold. Phosphorylation of the CTD of members of the EBL and RH protein families also increased their affinity for aldolase in some cases. To examine whether or not MTRAP expressed in asexual blood stage parasites is phosphorylated, it was tagged with GFP, purified and analysed, however no phosphorylation was detected. We propose that CTD binding to aldolase may be dynamically modulated by phosphorylation, and there may be competition for aldolase binding between different CTDs. The use and efficiency of alternate invasion pathways may be determined by the affinity of adhesins and cell invasion proteins for aldolase, in addition to their host ligand specificity.
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PMID:The Binding of Plasmodium falciparum Adhesins and Erythrocyte Invasion Proteins to Aldolase Is Enhanced by Phosphorylation. 2760 74

The World Heal Organization (WHO) has identified malaria diagnosis as being pivotal to eradicating the disease by 2030 as stipulated in the Sustainable Development Goals (SDG). The data presented here was obtained from outpatients of a hospital in the South Western Region of Nigeria from November 2016 to May 2017. The data contains malaria incidence amongst asymptomatic and symptomatic outpatients in the period under review. Malaria incidence was obtained using two diagnostic test kits, Bioline SD (HRP-2) and ACON (HRP-2/Aldolase) alongside Microscopy as gold standard. Specificity, Sensitivity and Kappa statistic of each test device is presented in the tables herewith. Data presented here could be used alongside other data sources to assess the state of malaria diagnostics.
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PMID:Data set on Rapid Diagnostic Tests (RDTs) and microscopy for diagnosing plasmodium falciparum and plasmodium vivax. 3018 42