Publications by authors named "Paul A M Michels"

Introduction: , an important cattle ectoparasite, is responsible for a substantial negative impact on the economy due to productivity loss. The emergence of resistance to widely used commercial acaricides has sparked efforts to explore alternative products for tick control.

Methods: To address this challenge, innovative solutions targeting essential tick enzymes, like glutathione S-transferase (GST), have gained attention.

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  • Human African trypanosomiasis, or sleeping sickness, is caused by the parasite Trypanosoma brucei and transmitted by the tsetse fly, with the study focusing on the effects of the drug suramin on this parasite.
  • The research aims to analyze how suramin alters the metabolism of T. brucei using advanced techniques like liquid chromatography-mass spectrometry and nuclear magnetic resonance spectroscopy, supported by extensive statistical analysis.
  • Results indicate significant metabolic changes in T. brucei after suramin treatment, especially in amino acid and sugar metabolism, with clear distinctions observed between treated and untreated samples through various statistical methods.
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ATP hydrolysis is required for the synthesis, transport and polymerization of monomers for macromolecules as well as for the assembly of the latter into cellular structures. Other cellular processes not directly related to synthesis of biomass, such as maintenance of membrane potential and cellular shape, also require ATP. The unicellular flagellated parasite Trypanosoma brucei has a complex digenetic life cycle.

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  • Per-ARNT-Sim (PAS) domains are found in many organisms and are crucial for regulating enzymatic activity and environmental adaptation by binding small ligands.
  • Researchers characterized a specific phosphoglycerate kinase with a PAS domain (TcPAS-PGK) from the parasite Trypanosoma cruzi, identifying it as an active enzyme localized in glycosomes.
  • The study compares the substrate affinities of two protein forms—one with the PAS domain and one without—finding differences in their activity patterns and inhibition at high substrate concentrations.
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  • Trypanosomiases are tropical diseases caused by kinetoplastids, leading to significant health and economic issues, particularly due to the lack of effective treatments.
  • The current drugs face challenges like high toxicity, limited effectiveness, and resistance, prompting the search for new therapeutic options.
  • Antimicrobial peptides (AMPs) from various organisms show promise as potential treatments due to their ability to disrupt cell membranes and combat pathogenic microorganisms, including the parasites responsible for trypanosomiases.
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Striated intracytoplasmic membranes in alphaproteobacteria are often reminiscent of millefoglie pastries. A new study reveals a protein complex homologous to that responsible for mitochondrial cristae formation drives intracytoplasmic membrane formation, thereby establishing bacterial ancestry for the biogenesis of mitochondrial cristae.

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Previously, we reported the development of novel small molecules that are potent inhibitors of the glycolytic enzyme phosphofructokinase (PFK) of and related protists responsible for serious diseases in humans and domestic animals. Cultured bloodstream-form trypanosomes, which are fully reliant on glycolysis for their ATP production, are rapidly killed at submicromolar concentrations of these compounds, which have no effect on the activity of human PFKs and human cells. Single-day oral dosing cures stage 1 human trypanosomiasis in an animal model.

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Rhipicephalus (Boophilus) microplus (Canestrini, 1887) is one of the most important ectoparasites of cattle, causing severe economic losses in tropical and subtropical regions of the world. The selection of resistance to the most commonly used commercial acaricides has stimulated the search for new products for tick control. The identification and development of drugs that inhibit key tick enzymes, such as glutathione S-transferase (GST), is a rational approach that has already been applied to other parasites than ticks.

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  • Kinetoplastea and Diplonemea, two classes in the Euglenozoa phylum, have glycolytic enzymes compartmentalized in unique organelles called glycosomes, a feature absent in the Euglenida class.
  • Recent genomic studies of various euglenozoans suggest that this compartmentalization likely emerged in a common ancestor and evolved to include additional metabolic processes specific to these groups.
  • The divergence of peroxin proteins, which are essential for glycosome formation, indicates a complex evolutionary history for the function of these organelles in kinetoplastids and diplonemids, suggesting a selective advantage for this metabolic compartmentalization.
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  • Kinetoplastea and Diplonemea have unique organelles called glycosomes that contain most enzymes from the glycolytic pathway and other metabolic pathways, in addition to lipid metabolism systems.
  • Research on glycosomes, especially in trypanosomes, has revealed their distinctive features in cell metabolism, biogenesis, and structure, which share similarities with peroxisomes in other eukaryotes but also show significant differences.
  • Despite extensive studies, many aspects of glycosomes and peroxisomes, such as their biogenesis, structural diversity, and boundary membrane properties, remain poorly understood and raise numerous questions.
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  • The TriTryp parasites, including Trypanosoma brucei, Trypanosoma cruzi, and Leishmania spp., exhibit complex life cycles with adaptive carbohydrate metabolism that is crucial for their survival across different developmental stages.
  • This review highlights recent findings on their metabolic networks, including the roles of various pathways like glycolysis and the unique compartmentalization of enzymes in different cellular regions.
  • Key differences in metabolic regulation between species and life stages, including enzyme modifications and structural variations, underscore the complexity and evolutionary divergence of these related parasites.
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The parasitic protist Trypanosoma brucei is the causative agent of Human African Trypanosomiasis, also known as sleeping sickness. The parasite enters the blood via the bite of the tsetse fly where it is wholly reliant on glycolysis for the production of ATP. Glycolytic enzymes have been regarded as challenging drug targets because of their highly conserved active sites and phosphorylated substrates.

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6-Phosphofructokinase-1-kinase (PFK) tetramers catalyse the phosphorylation of fructose 6-phosphate (F6P) to fructose 1,6-bisphosphate (F16BP). Vertebrates have three PFK isoforms (PFK-M, PFK-L, and PFK-P). This study is the first to compare the kinetics, structures, and transcript levels of recombinant human PFK isoforms.

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During its intra-erythrocytic growth phase, the malaria parasite Plasmodium falciparum relies heavily on glycolysis for its energy requirements. Pyruvate kinase (PYK) is essential for regulating glycolytic flux and for ATP production, yet the allosteric mechanism of P. falciparum PYK (PfPYK) remains poorly understood.

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  • * Recent studies show that glycosomes are multifunctional, engaging in both catabolic (breaking down molecules) and anabolic (building up molecules) processes, and they interact with other cellular compartments for coordinated metabolism.
  • * Research suggests that protein transport systems are vital for metabolite movement across glycosomal membranes, which could lead to potential new treatments for Chagas disease, a condition caused by these parasites that lacks effective current therapies.
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Trypanosomatids possess glycosome organelles that contain much of the glycolytic machinery, including phosphofructokinase (PFK). We present kinetic and structural data for PFK from three human pathogenic trypanosomatids, illustrating intriguing differences that may reflect evolutionary adaptations to differing ecological niches. The activity of Leishmania PFK - to a much larger extent than Trypanosoma PFK - is reliant on AMP for activity regulation, with 1 mm AMP increasing the L.

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African trypanosomiasis, sleeping sickness in humans or nagana in animals, is a potentially fatal neglected tropical disease and a threat to 65 million human lives and 100 million small and large livestock animals in sub-Saharan Africa. Available treatments for this devastating disease are few and have limited efficacy, prompting the search for new drug candidates. Simultaneous inhibition of the trypanosomal glycerol kinase (TGK) and trypanosomal alternative oxidase (TAO) is considered a validated strategy toward the development of new drugs.

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In response to the stress of infection, Mycobacterium tuberculosis (Mtb) reprograms its metabolism to accommodate nutrient and energetic demands in a changing environment. Pyruvate kinase (PYK) is an essential glycolytic enzyme in the phosphoenolpyruvate-pyruvate-oxaloacetate node that is a central switch point for carbon flux distribution. Here we show that the competitive binding of pentose monophosphate inhibitors or the activator glucose 6-phosphate (G6P) to MtbPYK tightly regulates the metabolic flux.

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Trypanothione (T(SH)) is the main antioxidant metabolite for peroxide reduction in Trypanosoma cruzi; therefore, its metabolism has attracted attention for therapeutic intervention against Chagas disease. To validate drug targets within the T(SH) metabolism, the strategies and methods of Metabolic Control Analysis and kinetic modeling of the metabolic pathway were used here, to identify the steps that mainly control the pathway fluxes and which could be appropriate sites for therapeutic intervention. For that purpose, gamma-glutamylcysteine synthetase (γECS), trypanothione synthetase (TryS), trypanothione reductase (TryR) and the tryparedoxin cytosolic isoform 1 (TXN1) were separately overexpressed to different levels in T.

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  • Glycosomes in Trypanosoma cruzi, which cause Chagas disease, are specialized peroxisomes that compartmentalize the first seven steps of glycolysis and other metabolic processes.
  • The study involved purifying glycosomes from the T. cruzi epimastigotes, collecting soluble and membrane fractions, and using NaCO treatment and osmotic shock to separate the proteins.
  • Proteomic analysis confirmed known enzymes in these metabolic pathways and revealed new components present in the glycosomes of the parasite.
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Entamoeba histolytica has neither Krebs cycle nor oxidative phosphorylation activities; therefore, glycolysis is the main pathway for ATP supply and provision of carbon skeleton precursors for the synthesis of macromolecules. Glucose is metabolized through fermentative glycolysis, producing ethanol as its main end-product as well as some acetate. Amoebal glycolysis markedly differs from the typical Embden-Meyerhof-Parnas pathway present in human cells: (i) by the use of inorganic pyrophosphate, instead of ATP, as the high-energy phospho group donor; (ii) with one exception, the pathway enzymes can catalyze reversible reactions under physiological conditions; (iii) there is no allosteric regulation and sigmoidal kinetic behavior of key enzymes; and (iv) the presence of some glycolytic and fermentation enzymes similar to those of anaerobic bacteria.

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Eukaryotic ATP-dependent phosphofructokinases (PFKs) are often considered unidirectional enzymes catalysing the transfer of a phospho moiety from ATP to fructose 6-phosphate to produce ADP and fructose 1,6-bisphosphate. The reverse reaction is not generally considered to occur under normal conditions and has never been demonstrated for any eukaryotic ATP-dependent PFKs, though it does occur in inorganic pyrophosphate-dependent PFKs and has been experimentally shown for bacterial ATP-dependent PFKs. The evidence is provided via two orthogonal assays that all three human PFK isoforms can catalyse the reverse reaction , allowing determination of kinetic properties.

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In the search for therapeutic targets in the intermediary metabolism of trypanosomatids the gene essentiality criterion as determined by using knock-out and knock-down genetic strategies is commonly applied. As most of the evaluated enzymes/transporters have turned out to be essential for parasite survival, additional criteria and approaches are clearly required for suitable drug target prioritization. The fundamentals of Metabolic Control Analysis (MCA; an approach in the study of control and regulation of metabolism) and kinetic modeling of metabolic pathways (a bottom-up systems biology approach) allow quantification of the degree of control that each enzyme exerts on the pathway flux (flux control coefficient) and metabolic intermediate concentrations (concentration control coefficient).

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We have tested the effect of all 20 proteinogenic amino acids on the activity of the M2 isoenzyme of pyruvate kinase (M2PYK) and show that, within physiologically relevant concentrations, phenylalanine, alanine, tryptophan, methionine, valine, and proline act as inhibitors, while histidine and serine act as activators. Size exclusion chromatography has been used to show that all amino acids, whether activators or inhibitors, stabilise the tetrameric form of M2PYK. In the absence of amino-acid ligands an apparent tetramer-monomer dissociation is estimated to be ∼0.

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