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

A New Thermophilic Heterolobosean Amoeba, Fumarolamoeba ceborucoi, gen. nov., sp. nov., Isolated Near a Fumarole at a Volcano in Mexico

An amoeba was isolated from a soil sample collected at the edge of a fumarole of the volcano Ceboruco in the state of Nayarit, Mexico. The trophozoites of this new isolate have eruptive pseudopodes and do not transform into flagellates. The strain forms cysts that have a double wall. This thermophilic amoeba grows at temperatures up to 50°C. Molecular phylogenetic analysis of the small subunit ribosomal DNA (SSU rDNA) places the amoeba into the Heterolobosea. The closest relatives are Paravahlkampfia spp. Like some other heterolobosean species, this new isolate has a group I intron in the SSU rDNA. Because of its position in the molecular phylogenetic tree, and because there is no species found in the literature with similar morphological and physiological characteristics, this isolate is described as a new genus and a new species, Fumarolamoeba ceborucoi gen. nov., sp. nov

The presence of four iron-containing superoxide dismutase isozymes in Trypanosomatidae : characterization, subcellular localization, and phylogenetic origin in Trypanosoma brucei

Author Posting. © The Authors, 2005. This is the author's version of the work. It is posted here by permission of Elsevier B. V. for personal use, not for redistribution. The definitive version was published in Free Radical Biology and Medicine 40 (2006): 210-225, doi:10.1016/j.freeradbiomed.2005.06.021.Metalloenzymes such as the superoxide dismutases (SODs) form part of a defense mechanism that helps protect obligate and facultative aerobic organisms from oxygen toxicity and damage. Here, we report the presence in the trypanosomatid genomes of four SOD genes: soda, sodb1 and sodb2 and a newly identified sodc. All four genes of Trypanosoma brucei have been cloned (Tbsods), sequenced and overexpressed in Escherichia coli and shown to encode active dimeric FeSOD isozymes. Homology modelling of the structures of all four enzymes using available X-ray crystal structures of homologs showed that the four TbSOD structures were nearly identical. Subcellular localization using GFP-fusion proteins in procyclic insect trypomastigotes shows that TbSODB1 is mainly cytosolic, with a minor glycosomal component, TbSODB2 is mainly glycosomal with some activity in the cytosol and TbSODA and TbSODC are both mitochondrial isozymes. Phylogenetic studies of all available trypanosomatid SODs and 106 dimeric FeSODs and closely related cambialistic dimeric SOD sequences suggest that the trypanosomatid SODs have all been acquired by more than one event of horizontal gene transfer, followed by events of gene duplication.This work was supported by Interuniversity Attraction Pole programme of the Belgian Government P5/29 (to F.R.O.), the Institut National de la Santé et de la Recherche Médicale, the Institut Pasteur de Lille, and the Centre National de la Recherche Scientifique (to E.V.). F.D. was supported by a grant from the Ministère Français de l’Education Nationale, de la Recherche et de la Technologie. D.G. was supported by an ICP postdoctoral fellowship

What controls glycolysis in bloodstream form Trypanosoma brucei?

On the basis of the experimentally determined kinetic properties of the trypanosomal enzymes, the question is addressed of which step limits the glycolytic flux in bloodstream form Trypanosoma brucei. There appeared to be no single answer; in the physiological range, control shifted between the glucose transporter on the one hand and aldolase (ALD), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), phosphoglycerate kinase (PGK), and glycerol-3-phosphate dehydrogenase (GDH) on the other hand. The other kinases, which are often thought to control glycolysis, exerted little control; so did the utilization of ATP. We identified potential targets for anti-trypanosomal drugs by calculating which steps need the least inhibition to achieve a certain inhibition of the glycolytic flux in these parasites. The glucose transporter appeared to be the most promising target, followed by ALD, GDH, GAPDH, and PGK. By contrast, in erythrocytes more than 95% deficiencies of PGK, GAPDH, or ALD did not cause any clinical symptoms (Schuster, R. and Holzhütter, H.-G. (1995) Eur. J. Biochem. 229, 403-418). Therefore, the selectivity of drugs inhibiting these enzymes may be much higher than expected from their molecular effects alone. Quite unexpectedly, trypanosomes seem to possess a substantial overcapacity of hexokinase, phosphofructokinase, and pyruvate kinase, making these "irreversible" enzymes mediocre drug targets

The streamlined genome of Phytomonas spp. relative to human pathogenic kinetoplastids reveals a parasite tailored for plants

Members of the family Trypanosomatidae infect many organisms, including animals, plants and humans. Plant-infecting trypanosomes are grouped under the single genus Phytomonas, failing to reflect the wide biological and pathological diversity of these protists. While some Phytomonas spp. multiply in the latex of plants, or in fruit or seeds without apparent pathogenicity, others colonize the phloem sap and afflict plants of substantial economic value, including the coffee tree, coconut and oil palms. Plant trypanosomes have not been studied extensively at the genome level, a major gap in understanding and controlling pathogenesis. We describe the genome sequences of two plant trypanosomatids, one pathogenic isolate from a Guianan coconut and one non-symptomatic isolate from Euphorbia collected in France. Although these parasites have extremely distinct pathogenic impacts, very few genes are unique to either, with the vast majority of genes shared by both isolates. Significantly, both Phytomonas spp. genomes consist essentially of single copy genes for the bulk of their metabolic enzymes, whereas other trypanosomatids e.g. Leishmania and Trypanosoma possess multiple paralogous genes or families. Indeed, comparison with other trypanosomatid genomes revealed a highly streamlined genome, encoding for a minimized metabolic system while conserving the major pathways, and with retention of a full complement of endomembrane organelles, but with no evidence for functional complexity. Identification of the metabolic genes of Phytomonas provides opportunities for establishing in vitro culturing of these fastidious parasites and new tools for the control of agricultural plant disease. © 2014 Porcel et al

Part II : aerobic protists - trypanosomatidae

This chapter focuses on the carbohydrate metabolism of the Trypanosomatidae, protozoan parasites responsible for a number of important diseases of man. Many enzymes of glycolysis and related pathways in trypanosomatids are sequestered inside microbodies, which makes them usefulnot only as a drug target but also for basic research. The potential for chemotherapeutic exploitation of carbohydrate metabolism is significant. The biochemistry of trypanosomes is studied in great detail, because these organisms harbor many peculiarities that have attracted biochemists interested in fundamental aspects of these organisms. The fact that trypanosomes are among the few parasitic organisms that can easily be grown in large numbers in the blood of infected rodents has facilitated their study. The chapter concludes that the advent of molecular biology where the number of cells available for research is no longer a limiting factor, has led to an enormous growth of the literature over recent years. Through the combined efforts of many researchers in various disciplines over many years, a good understanding of the glycolytic pathway of the African trypanosome is obtained. These efforts have led to the cloning, sequencing, and over expression of all the enzymes of the pathway and the resolution of the crystal structure of many

Naegleria gruberi metabolism.

The completion of the genome project for Naegleria gruberi provides a unique insight into the metabolic capacities of an organism, for which there is an almost complete lack of experimental data. The metabolism of Naegleria seems to be extremely versatile, as can be expected for a free-living amoeboflagellate, but although considered to be fully aerobic, its genome also predicts important anaerobic traits. Other predictions are that carbohydrates are oxidised to carbon dioxide and water when oxygen is not limiting and that in the absence of oxygen the end-products will be succinate, acetate and minor quantities of ethanol and D-lactate. The hybrid mitochondrion/hydrogenosome has both cytochromes and an [Fe] hydrogenase, but seems to lack pyruvate-ferredoxin oxidoreductase. Genomic information also provides the possibility to identify drugs with a possible mode of action in the fatal primary amoebic meningoencephalitis caused by the closely related opportunistic pathogen Naegleria fowleri