title: Erythritol feeds the pentose phosphate pathway via three new isomerases leading to D-erythrose-4-phosphate in Brucella.
abstract: Erythritol is an important nutrient for several α-2 Proteobacteria, including N2-fixing plant endosymbionts and Brucella, a worldwide pathogen that finds this four-carbon polyol in genital tissues. Erythritol metabolism involves phosphorylation to L-erythritol-4-phosphate by the kinase EryA and oxidation of the latter to L-3-tetrulose 4-phosphate by the dehydrogenase EryB. It is accepted that further steps involve oxidation by the putative dehydrogenase EryC and subsequent decarboxylation to yield triose-phosphates. Accordingly, growth on erythritol as the sole C source should require aldolase and fructose-1,6-bisphosphatase to produce essential hexose-6-monophosphate. However, we observed that a mutant devoid of fructose-1,6-bisphosphatases grew normally on erythritol and that EryC, which was assumed to be a dehydrogenase, actually belongs to the xylose isomerase superfamily. Moreover, we found that TpiA2 and RpiB, distant homologs of triose phosphate isomerase and ribose 5-phosphate isomerase B, were necessary, as previously shown for Rhizobium. By using purified recombinant enzymes, we demonstrated that L-3-tetrulose-4-phosphate was converted to D-erythrose 4-phosphate through three previously unknown isomerization reactions catalyzed by EryC (tetrulose-4-phosphate racemase), TpiA2 (D-3-tetrulose-4-phosphate isomerase; renamed EryH), and RpiB (D-erythrose-4-phosphate isomerase; renamed EryI), a pathway fully consistent with the isotopomer distribution of the erythrose-4-phosphate-derived amino acids phenylalanine and tyrosine obtained from bacteria grown on (13)C-labeled erythritol. D-erythrose-4-phosphate is then converted by enzymes of the pentose phosphate pathway to glyceraldehyde 3-phosphate and fructose 6-phosphate, thus bypassing fructose-1,6-bisphosphatase. This is the first description to our knowledge of a route feeding carbohydrate metabolism exclusively via D-erythrose 4-phosphate, a pathway that may provide clues to the preferential metabolism of erythritol by Brucella and its role in pathogenicity.
authors.affiliation: Research Unit in Microorganisms Biology, University of Namur, B-5000 Namur, Belgium;
authors.forename: Thibault
authors.initials: T
authors.lastname: Barbier
authors.affiliation: Welbio and de Duve Institute, Université Catholique de Louvain, B-1200 Brussels, Belgium;
authors.forename: François
authors.initials: F
authors.lastname: Collard
authors.affiliation: Departamento de Microbiología e Instituto de Salud Tropical, Universidad de Navarra, 31008 Pamplona, Spain;
authors.forename: Amaia
authors.initials: A
authors.lastname: Zúñiga-Ripa
authors.affiliation: Departamento de Microbiología e Instituto de Salud Tropical, Universidad de Navarra, 31008 Pamplona, Spain;
authors.forename: Ignacio
authors.initials: I
authors.lastname: Moriyón
authors.affiliation: Institute of Biochemical Engineering, Technische Universität Braunschweig, 38106 Braunschweig, Germany; and.
authors.forename: Thibault
authors.initials: T
authors.lastname: Godard
authors.affiliation: Institute of Systems Biotechnology, Saarland University, 66123 Saarbrücken, Germany.
authors.forename: Judith
authors.initials: J
authors.lastname: Becker
authors.affiliation: Institute of Systems Biotechnology, Saarland University, 66123 Saarbrücken, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Wittmann
authors.affiliation: Welbio and de Duve Institute, Université Catholique de Louvain, B-1200 Brussels, Belgium; emile.vanschaftingen@uclouvain.be jean-jacques.letesson@unamur.be.
authors.forename: Emile
authors.initials: E
authors.lastname: Van Schaftingen
authors.affiliation: Research Unit in Microorganisms Biology, University of Namur, B-5000 Namur, Belgium; emile.vanschaftingen@uclouvain.be jean-jacques.letesson@unamur.be.
authors.forename: Jean-Jacques
authors.initials: JJ
authors.lastname: Letesson
mesh_terms: D053898:Biosynthetic Pathways / Q000502:physiology*; D002002:Brucella / Q000378:metabolism* / Q000472:pathogenicity; D002238:Carbohydrate Epimerases / Q000378:metabolism*; D002247:Carbon Isotopes / Q000378:metabolism; D004896:Erythritol / Q000378:metabolism*; D008401:Gas Chromatography-Mass Spectrometry; D007536:Isomerism; D010766:Phosphorylation; D013053:Spectrophotometry; D013403:Sugar Phosphates / Q000096:biosynthesis*
chemical_list: D002247:Carbon Isotopes; D013403:Sugar Phosphates; C026959:erythrose 4-phosphate; D002238:Carbohydrate Epimerases; D004896:Erythritol
keywords: Brucella; alphaproteobacteria; erythritol; pentose phosphate cycle; tetrose metabolism