59 research outputs found
Evolution of energy metabolism and its compartmentation in Kinetoplastida
Kinetoplastida are protozoan organisms that probably diverged early in evolution from other eukaryotes. They are characterized by a number of unique features with respect to their energy and carbohydrate metabolism. These organisms possess peculiar peroxisomes, called glycosomes, which play a central role in this metabolism; the organelles harbour enzymes of several catabolic and anabolic routes, including major parts of the glycolytic and pentosephosphate pathways. The kinetoplastid mitochondrion is also unusual with regard to both its structural and functional properties. In this review, we describe the unique compartmentation of metabolism in Kinetoplastida and the metabolic properties resulting from this compartmentation. We discuss the evidence for our recently proposed hypothesis that a common ancestor of Kinetoplastida and Euglenida acquired a photosynthetic alga as an endosymbiont, contrary to the earlier notion that this event occurred at a later stage of evolution, in the Euglenida lineage alone. The endosymbiont was subsequently lost from the kinetoplastid lineage but, during that process, some of its pathways of energy and carbohydrate metabolism were sequestered in the kinetoplastid peroxisomes, which consequently became glycosomes. The evolution of the kinetoplastid glycosomes and the possible selective advantages of these organelles for Kinetoplastida are discussed. We propose that the possession of glycosomes provided metabolic flexibility that has been important for the organisms to adapt easily to changing environmental conditions. It is likely that metabolic flexibility has been an important selective advantage for many kinetoplastid species during their evolution into the highly successful parasites today found in many divergent taxonomic groups. Also addressed is the evolution of the kinetoplastid mitochondrion, from a supposedly pluripotent organelle, attributed to a single endosymbiotic event that resulted in all mitochondria and hydrogenosomes of extant eukaryotes. Furthermore, indications are presented that Kinetoplastida may have acquired other enzymes of energy and carbohydrate metabolism by various lateral gene transfer events different from those that involved the algal- and α-proteobacterial-like endosymbionts responsible for the respective formation of the glycosomes and mitochondria
Enolase: A Key Player in the Metabolism and a Probable Virulence Factor of Trypanosomatid Parasites—Perspectives for Its Use as a Therapeutic Target
Glycolysis and glyconeogenesis play crucial roles in the ATP supply and synthesis of glycoconjugates, important for the viability and virulence, respectively, of the human-pathogenic stages of Trypanosoma brucei, Trypanosoma cruzi, and Leishmania spp. These pathways are, therefore, candidate targets for antiparasite drugs. The glycolytic/gluconeogenic enzyme enolase is generally highly conserved, with similar overall fold and identical catalytic residues in all organisms. Nonetheless, potentially important differences exist between the trypanosomatid and host enzymes, with three unique, reactive residues close to the active site of the former that might be exploited for the development of new drugs. In addition, enolase is found both in the secretome and in association with the surface of Leishmania spp. where it probably functions as plasminogen receptor, playing a role in the parasite's invasiveness and virulence, a function possibly also present in the other trypanosomatids. This location and possible function of enolase offer additional perspectives for both drug discovery and vaccination
Exploiting the 2-Amino-1,3,4-thiadiazole Scaffold To Inhibit <i>Trypanosoma brucei </i>Pteridine Reductase in Support of Early-Stage Drug Discovery
Pteridine reductase-1 (PTR1) is a promising drug target for the treatment of trypanosomiasis. We investigated the potential of a previously identified class of thiadiazole inhibitors of Leishmania major PTR1 for activity against Trypanosoma brucei (Tb). We solved crystal structures of several TbPTR1-inhibitor complexes to guide the structure-based design of new thiadiazole derivatives. Subsequent synthesis and enzyme- and cell-based assays confirm new, mid-micromolar inhibitors of TbPTR1 with low toxicity. In particular, compound 4m, a biphenyl-thiadiazole-2,5-diamine with IC50 = 16 μM, was able to potentiate the antitrypanosomal activity of the dihydrofolate reductase inhibitor methotrexate (MTX) with a 4.1-fold decrease of the EC50 value. In addition, the antiparasitic activity of the combination of 4m and MTX was reversed by addition of folic acid. By adopting an efficient hit discovery platform, we demonstrate, using the 2-amino-1,3,4-thiadiazole scaffold, how a promising tool for the development of anti-T. brucei agents can be obtained
Sleeping Sickness Pathogen (Trypanosoma brucei) and Natural Products: Therapeutic Targets and Screening Systems.
TRYPANOSOMA BRUCEI is the causative agent of human African trypanosomiasis (sleeping sickness) which is fatal if left untreated. This disease occurs in 36 African countries, south of the Sahara, where 60 million people are at risk of acquiring infection. The current chemotherapy relies on only four drugs, three of which were developed more than 60 years ago. These drugs have many limitations, ranging from oral inabsorption, acute toxicities, short duration of action and the emergence of trypanosomal resistance. Despite decades of use of most of the current trypanocides, little is known about their mode of action. That being said, African trypanosomes continue to be among the most extensively studied parasitic protists to date. Many of their intriguing biological features have been well documented and can be viewed as attractive targets for antitrypanosomal chemotherapy. A considerable number of natural products with diverse molecular structures have revealed antiparasitic potency in the laboratory and represent interesting lead compounds for the development of new and urgently needed antiparasitics. The major validated drug targets in T. BRUCEI are discussed with particular emphasis on those known to be attacked by natural compounds
La glycéraldéhyde-3-phosphate déshydrogénase : une enzyme-clé chez les Kinetoplastida
Doctorat en sciences biologiques -- UCL, 199
The evolution of kinetoplastid glycosomes
The available data on carbohydrate metabolism in Kinetoplastida have been reviewed. Based on the metabolic pattern of different kinetoplastid organisms, on the subcellular distribution of their glycolytic enzymes, and on the structural and regulatory properties of these proteins, we propose that the glycosome developed from an endosymbiont, as a specific manner to control carbohydrate and energy metabolism. It is discussed how the enzymes were subcellularly recompartmentalized during evolution as adaptation to the environment encountered by the organisms
The rational design of trypanocidal drugs: selective inhibition of the glyceraldehyde-3-phosphate dehydrogenase in Trypanosomatidae.
Within the framework of a project aimed at the structure-based design of drugs for use against sleeping sickness, selective inhibitors were designed, synthesised and tested. The target protein was glycosomal glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and the adenosine part of the NAD cofactor was chosen as lead. After one design cycle and exploiting the selectivity cleft in trypanosomal GAPDH near the C2 of the adenosine ribose, a selective inhibitor, 2'-deoxy-2'-(3-methoxybenzamido)adenosine, was obtained. This compound inhibits human GAPDH only marginally, whereas the enzymes from Trypanosoma brucei and Leishmania mexicana are inhibited by 50% at 2.2 and 0.3 mM, respectively. Moreover, the inhibition of the parasite enzyme is 45-fold (T. brucei) or 170-fold (L. mexicana) greater with this substituted analogue than that produced with adenosine
Structure, function, and biogenesis of glycosomes in kinetoplastida
Glycosomes are intracellular, microbody-like organelles found in all members of the protist order Kinetoplastida examined. Nine enzymes involved in glucose and glycerol metabolism are associated with these organelles. These enzymes are involved in pathways which, in other organisms, are usually located in the cytosol. This paper reviews our current knowledge about the glycosome and its constituent enzymes, with special reference to the organelle of Trypanosoma brucei
Comparison and evolutionary analysis of the glycosomal glyceraldehyde-3-phosphate dehydrogenase from different Kinetoplastida.
In this work, we present the sequences and a comparison of the glycosomal GAPDHs from a number of Kinetoplastida. The complete gene sequences have been determined for some species (Crithidia fasciculata, Herpetomonas samuelpessoai, Leptomonas seymouri, and Phytomonas sp), whereas for other species (Trypanosoma brucei gambiense, Trypanosoma congolense, Trypanosoma vivax, and Leishmania major), only partial sequences have been obtained by PCR amplification. The structure of all available glycosomal GAPDH genes was analyzed in detail. Considerable variations were observed in both their nucleotide composition and their codon usage. The GC content varies between 64.4% in L. seymouri and 49.5% in the previously sequenced GAPDH gene from Trypanoplasma borreli. A highly biased codon usage was found in C. fasciculata, with only 34 triplets used, whereas in T. borreli 57 codons were employed. No obvious correlation could be observed between the codon usage and either the nucleotide composition or the level of gene expression. The glycosomal GAPDH is a very well-conserved enzyme. The maximal overall difference observed in the amino acid sequences is only 25%. Specific insertions and extensions are retained in all sequences. The residues involved in catalysis, substrate, and inorganic phosphate binding are fully conserved, whereas some variability is observed in the cofactor-binding pocket. The implications of these data for the design of new trypanocidal drugs targeted against GAPDH are discussed. All available gene and amino acid sequences of glycosomal GAPDHs were used for a phylogenetic analysis. The division of the Kinetoplastida into two suborders, Bodonina and Trypanosomatina, was well supported. Within the letter group, the Trypanosoma species appeared to be monophyletic, whereas the other trypanosomatids form a second clade
Glycosomal glyceraldehyde-3-phosphate dehydrogenase of Trypanosoma brucei and Trypanosoma cruzi: expression in Escherichia coli, purification, and characterization of the enzymes.
The Trypanosoma brucei and Trypanosoma cruzi glycosomal glyceraldehyde-3-phosphate dehydrogenases have been overexpressed in Escherichia coli using a T7 expression system. These enzymes have been highly purified by ammonium sulfate precipitation, followed by phenyl-Sepharose and phospho-ultrogel chromatography. From 1 liter of bacterial culture, we obtained 4.4 mg of T. brucei enzyme, with a specific activity of 147 units/mg, and 26.6 mg of T. cruzi enzyme, with a specific activity of 122 units/mg. Both proteins have a similar subunit mass of 38 kDa. Some physicochemical and kinetic properties have been determined and compared with those reported for the authentic T. brucei enzyme. The two enzymes appear to be very similar, except for the dependence of their activity on ionic strength
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