title: Identification and characterization of a re-citrate synthase in Dehalococcoides strain CBDB1.
abstract: The genome annotations of all sequenced Dehalococcoides strains lack a citrate synthase, although physiological experiments have indicated that such an activity should be encoded. We here report that a Re face-specific citrate synthase is synthesized by Dehalococcoides strain CBDB1 and that this function is encoded by the gene cbdbA1708 (NCBI accession number CAI83711), previously annotated as encoding homocitrate synthase. Gene cbdbA1708 was heterologously expressed in Escherichia coli, and the recombinant enzyme was purified. The enzyme catalyzed the condensation of oxaloacetate and acetyl coenzyme A (acetyl-CoA) to citrate. The protein did not have homocitrate synthase activity and was inhibited by citrate, and Mn2+ was needed for full activity. The stereospecificity of the heterologously expressed citrate synthase was determined by electrospray ionization liquid chromatography-mass spectrometry (ESI LC/MS). Citrate was synthesized from [2-(13)C]acetyl-CoA and oxaloacetate by the Dehalococcoides recombinant citrate synthase and then converted to acetate and malate by commercial citrate lyase plus malate dehydrogenase. The formation of unlabeled acetate and 13C-labeled malate proved the Re face-specific activity of the enzyme. Shotgun proteome analyses of cell extracts of strain CBDB1 demonstrated that cbdbA1708 is expressed in strain CBDB1.
authors.affiliation: Department of Isotope Biogeochemistry, Helmholtz Centre for Environmental Research-UFZ, Permoserstr. 15, 04318 Leipzig, Germany.
authors.forename: Ernest
authors.initials: E
authors.lastname: Marco-Urrea
authors.forename: Steffanie
authors.initials: S
authors.lastname: Paul
authors.forename: Viola
authors.initials: V
authors.lastname: Khodaverdi
authors.forename: Jana
authors.initials: J
authors.lastname: Seifert
authors.forename: Martin
authors.initials: M
authors.lastname: von Bergen
authors.forename: Utta
authors.initials: U
authors.lastname: Kretzschmar
authors.forename: Lorenz
authors.initials: L
authors.lastname: Adrian
mesh_terms: D001426:Bacterial Proteins / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D041862:Chloroflexi / Q000201:enzymology* / Q000235:genetics; D002853:Chromatography, Liquid; D002950:Citrate (si)-Synthase / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D002951:Citrates / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D008345:Manganese / Q000494:pharmacology; D008954:Models, Biological; D010802:Phylogeny; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D001426:Bacterial Proteins; D002951:Citrates; D008345:Manganese; D002950:Citrate (si)-Synthase