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https://www.readbyqxmd.com/read/29106396/purinyl-cobamide-is-a-native-prosthetic-group-of-reductive-dehalogenases
#1
Jun Yan, Meng Bi, Allen K Bourdon, Abigail T Farmer, Po-Hsiang Wang, Olivia Molenda, Andrew T Quaile, Nannan Jiang, Yi Yang, Yongchao Yin, Burcu Şimşir, Shawn R Campagna, Elizabeth A Edwards, Frank E Löffler
Cobamides such as vitamin B12 are structurally conserved, cobalt-containing tetrapyrrole biomolecules that have essential biochemical functions in all domains of life. In organohalide respiration, a vital biological process for the global cycling of natural and anthropogenic organohalogens, cobamides are the requisite prosthetic groups for carbon-halogen bond-cleaving reductive dehalogenases. This study reports the biosynthesis of a new cobamide with unsubstituted purine as the lower base and assigns unsubstituted purine a biological function by demonstrating that Coα-purinyl-cobamide (purinyl-Cba) is the native prosthetic group in catalytically active tetrachloroethene reductive dehalogenases of Desulfitobacterium hafniense...
November 6, 2017: Nature Chemical Biology
https://www.readbyqxmd.com/read/28869789/subtle-changes-in-the-active-site-architecture-untangled-overlapping-substrate-ranges-and-mechanistic-differences-of-two-reductive-dehalogenases
#2
Cindy Kunze, Gabriele Diekert, Torsten Schubert
Reductive dehalogenases (RDases) of organohalide-respiring bacteria are cobamide-containing iron-sulfur proteins that catalyze different reductive dehalogenation reactions. Here, we report a functional analysis of two recombinant RDases, the tetrachloroethene (PCE) reductive dehalogenase (PceA) of Desulfitobacterium hafniense Y51 and the 1,2-dichloroethane (1,2-DCA) reductive dehalogenase (DcaA) of Desulfitobacterium dichloroeliminans DCA1. Both enzymes share 88% protein sequence identity, but appeared to have divergent mechanisms...
October 2017: FEBS Journal
https://www.readbyqxmd.com/read/28671181/cobamide-mediated-enzymatic-reductive-dehalogenation-via-long-range-electron-transfer
#3
Cindy Kunze, Martin Bommer, Wilfred R Hagen, Marie Uksa, Holger Dobbek, Torsten Schubert, Gabriele Diekert
The capacity of metal-containing porphyrinoids to mediate reductive dehalogenation is implemented in cobamide-containing reductive dehalogenases (RDases), which serve as terminal reductases in organohalide-respiring microbes. RDases allow for the exploitation of halogenated compounds as electron acceptors. Their reaction mechanism is under debate. Here we report on substrate-enzyme interactions in a tetrachloroethene RDase (PceA) that also converts aryl halides. The shape of PceA's highly apolar active site directs binding of bromophenols at some distance from the cobalt and with the hydroxyl substituent towards the metal...
July 3, 2017: Nature Communications
https://www.readbyqxmd.com/read/28648395/the-complete-genome-of-the-tetrachloroethene-respiring-epsilonproteobacterium-sulfurospirillum-halorespirans
#4
Tobias Goris, Benjamin Schenz, Johannes Zimmermann, Mikael Lemos, Jörg Hackermüller, Torsten Schubert, Gabriele Diekert
Sulfurospirillum halorespirans is a bacterium that couples the reductive dehalogenation of chlorinated ethenes to growth. This process is called organohalide respiration (OHR), which can be of importance for bioremediation. Here, we report the complete genome of S. halorespirans, the second one of an organohalide-respiring Epsilonproteobacterium after that of Sulfurospirillum multivorans. With both genomes at hand, we were able to ascertain that the genomic region encoding OHR proteins in Epsilonproteobacteria differs from that found in organohalide-respiring bacteria (OHRB) affiliated to other phyla and that the production of a unique cobamide, norpseudo-B12, might not be limited to the model organism S...
June 22, 2017: Journal of Biotechnology
https://www.readbyqxmd.com/read/28397170/the-organohalide-respiring-bacterium-sulfurospirillum-multivorans-a-natural-source-for-unusual-cobamides
#5
REVIEW
Torsten Schubert
Cobamides ('complete' corrinoids) are essential for organohalide-respiring bacteria because they act as cofactors of reductive dehalogenases (RDases). RDases are the key enzymes in organohalide respiration, a process relevant for environmental remediation. More than a decade ago, the unusual norpseudo-B12 was identified as cofactor of the tetrachloroethene RDase (PceA) purified from the epsilonproteobacterium Sulfurospirillum multivorans. Since then, the question was raised whether or not the production of the uncommon cobamide is a specific adaptation to the requirements of PceA...
May 2017: World Journal of Microbiology & Biotechnology
https://www.readbyqxmd.com/read/27274028/the-smul_1544-gene-product-governs-norcobamide-biosynthesis-in-the-tetrachloroethene-respiring-bacterium-sulfurospirillum-multivorans
#6
Sebastian Keller, Aaron Treder, Stephan H von Reuss, Jorge C Escalante-Semerena, Torsten Schubert
UNLABELLED: The tetrachloroethene (PCE)-respiring bacterium Sulfurospirillum multivorans produces a unique cobamide, namely, norpseudo-B12, which, in comparison to other cobamides, e.g., cobalamin and pseudo-B12, lacks the methyl group in the linker moiety of the nucleotide loop. In this study, the protein SMUL_1544 was shown to be responsible for the formation of the unusual linker moiety, which is most probably derived from ethanolamine-phosphate (EA-P) as the precursor. The product of the SMUL_1544 gene successfully complemented a Salmonella enterica ΔcobD mutant...
August 15, 2016: Journal of Bacteriology
https://www.readbyqxmd.com/read/26597297/blub-cobt2-fusion-enzyme-activity-reveals-mechanisms-responsible-for-production-of-active-form-of-vitamin-b%C3%A2-%C3%A2-by-propionibacterium-freudenreichii
#7
Paulina Deptula, Petri Kylli, Bhawani Chamlagain, Liisa Holm, Risto Kostiainen, Vieno Piironen, Kirsi Savijoki, Pekka Varmanen
BACKGROUND: Propionibacterium freudenreichii is a food grade bacterium that has gained attention as a producer of appreciable amounts of cobalamin, a cobamide with activity of vitamin B12. Production of active form of vitamin is a prerequisite for attempts to naturally fortify foods with B12 by microbial fermentation. Active vitamin B12 is distinguished from the pseudovitamin by the presence of 5,6-dimethylbenzimidazole (DMBI) as the lower ligand. Genomic data indicate that P. freudenreichii possesses a fusion gene, bluB/cobT2, coding for a predicted phosphoribosyltransferase/nitroreductase, which is presumably involved in production of vitamin B12...
2015: Microbial Cell Factories
https://www.readbyqxmd.com/read/26555247/the-corrinoid-cofactor-of-reductive-dehalogenases-affects-dechlorination-rates-and-extents-in-organohalide-respiring-dehalococcoides-mccartyi
#8
Jun Yan, Burcu Şimşir, Abigail T Farmer, Meng Bi, Yi Yang, Shawn R Campagna, Frank E Löffler
Corrinoid auxotrophic organohalide-respiring Dehalococcoides mccartyi (Dhc) strains are keystone bacteria for reductive dechlorination of toxic and carcinogenic chloroorganic contaminants. We demonstrate that the lower base attached to the essential corrinoid cofactor of reductive dehalogenase (RDase) enzyme systems modulates dechlorination activity and affects the vinyl chloride (VC) RDases BvcA and VcrA differently. Amendment of 5,6-dimethylbenzimidazolyl-cobamide (DMB-Cba) to Dhc strain BAV1 and strain GT cultures supported cis-1,2-dichloroethene-to-ethene reductive dechlorination at rates of 107...
May 2016: ISME Journal
https://www.readbyqxmd.com/read/26513744/solution-structural-studies-of-gtp-adenosylcobinamide-phosphateguanylyl-transferase-coby-from-methanocaldococcus-jannaschii
#9
Kiran K Singarapu, Michele M Otte, Marco Tonelli, William M Westler, Jorge C Escalante-Semerena, John L Markley
GTP:adenosylcobinamide-phosphate (AdoCbi-P) guanylyl transferase (CobY) is an enzyme that transfers the GMP moiety of GTP to AdoCbi yielding AdoCbi-GDP in the late steps of the assembly of Ado-cobamides in archaea. The failure of repeated attempts to crystallize ligand-free (apo) CobY prompted us to explore its 3D structure by solution NMR spectroscopy. As reported here, the solution structure has a mixed α/β fold consisting of seven β-strands and five α-helices, which is very similar to a Rossmann fold...
2015: PloS One
https://www.readbyqxmd.com/read/26246619/anaerobic-biosynthesis-of-the-lower-ligand-of-vitamin-b12
#10
COMPARATIVE STUDY
Amrita B Hazra, Andrew W Han, Angad P Mehta, Kenny C Mok, Vadim Osadchiy, Tadhg P Begley, Michiko E Taga
Vitamin B12 (cobalamin) is required by humans and other organisms for diverse metabolic processes, although only a subset of prokaryotes is capable of synthesizing B12 and other cobamide cofactors. The complete aerobic and anaerobic pathways for the de novo biosynthesis of B12 are known, with the exception of the steps leading to the anaerobic biosynthesis of the lower ligand, 5,6-dimethylbenzimidazole (DMB). Here, we report the identification and characterization of the complete pathway for anaerobic DMB biosynthesis...
August 25, 2015: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/25431570/a-bioassay-for-the-detection-of-benzimidazoles-reveals-their-presence-in-a-range-of-environmental-samples
#11
Terence S Crofts, Yujie Men, Lisa Alvarez-Cohen, Michiko E Taga
Cobamides are a family of enzyme cofactors that include vitamin B12 (cobalamin) and are produced solely by prokaryotes. Structural variability in the lower axial ligand has been observed in cobamides produced by diverse organisms. Of the three classes of lower ligands, the benzimidazoles are uniquely found in cobamides, whereas the purine and phenolic bases have additional biological functions. Many organisms acquire cobamides by salvaging and remodeling cobamides or their precursors from the environment. These processes require free benzimidazoles for incorporation as lower ligands, though the presence of benzimidazoles in the environment has not been previously investigated...
2014: Frontiers in Microbiology
https://www.readbyqxmd.com/read/25412146/regiospecific-formation-of-cobamide-isomers-is-directed-by-cobt
#12
Terence S Crofts, Amrita B Hazra, Jennifer L A Tran, Olga M Sokolovskaya, Vadim Osadchiy, Omer Ad, Jeffrey Pelton, Stefan Bauer, Michiko E Taga
Cobamides, which include vitamin B₁₂ (cobalamin), are a class of modified tetrapyrroles synthesized exclusively by prokaryotes that function as cofactors for diverse biological processes. Cobamides contain a centrally bound cobalt ion that coordinates to upper and lower axial ligands. The lower ligand is covalently linked to a phosphoribosyl moiety through an alpha-glycosidic bond formed by the CobT enzyme. CobT can catalyze the phosphoribosylation of a variety of substrates. We investigated the ability of CobT to act on either of two nitrogen atoms within a single, asymmetric benzimidazole substrate to form two isomeric riboside phosphate products...
December 16, 2014: Biochemistry
https://www.readbyqxmd.com/read/25171056/supplementing-lactating-dairy-cows-with-a-vitamin-b12-precursor-5-6-dimethylbenzimidazole-increases-the-apparent-ruminal-synthesis-of-vitamin-b12
#13
RANDOMIZED CONTROLLED TRIAL
A Brito, J Chiquette, S P Stabler, R H Allen, C L Girard
Cobalamin (CBL), the biologically active form of vitamin B12, and its analogs, are produced by bacteria only if cobalt supply is adequate. The analogs differ generally by the nucleotide moiety of the molecule. In CBL, 5,6-dimethylbenzimidazole (5,6-DMB) is the base in the nucleotide moiety. The present study aimed to determine if a supplement of 5,6-DMB could increase utilization of dietary cobalt for synthesis of CBL and change ruminal fermentation, nutrient digestibility, omasal flow of nutrients and ruminal protozoa counts...
January 2015: Animal: An International Journal of Animal Bioscience
https://www.readbyqxmd.com/read/25146291/riboswitches-a-riboswitch-containing-srna-controls-gene-expression-by-sequestration-of-a-response-regulator
#14
Sruti DebRoy, Margo Gebbie, Arati Ramesh, Jonathan R Goodson, Melissa R Cruz, Ambro van Hoof, Wade C Winkler, Danielle A Garsin
The ethanolamine utilization (eut) locus of Enterococcus faecalis, containing at least 19 genes distributed over four polycistronic messenger RNAs, appears to be regulated by a single adenosyl cobalamine (AdoCbl)-responsive riboswitch. We report that the AdoCbl-binding riboswitch is part of a small, trans-acting RNA, EutX, which additionally contains a dual-hairpin substrate for the RNA binding-response regulator, EutV. In the absence of AdoCbl, EutX uses this structure to sequester EutV. EutV is known to regulate the eut messenger RNAs by binding dual-hairpin structures that overlap terminators and thus prevent transcription termination...
August 22, 2014: Science
https://www.readbyqxmd.com/read/25146272/rna-riboswitch-regulates-rna
#15
COMMENT
Jiandong Chen, Susan Gottesman
No abstract text is available yet for this article.
August 22, 2014: Science
https://www.readbyqxmd.com/read/24959550/b-vitamins-and-cognitive-performance-in-older-adults-review
#16
REVIEW
J L Reay, M A Smith, L M Riby
A copious amount of scientific scrutiny has been dedicated to documenting typical and atypical human ageing, with a substantial body of work focusing upon the impact of lifestyle choices. One such lifestyle choice is that of diet and, in particular, micronutrient ingestion. Epidemiological studies have reported positive associations between B vitamin status and cognitive function, including negative associations between biological markers (i.e., homocysteine) of dysregulated one-carbon metabolism and cognitive function...
2013: ISRN Nutrition
https://www.readbyqxmd.com/read/24846280/a-mechanochemical-switch-to-control-radical-intermediates
#17
COMPARATIVE STUDY
Elizabeth Brunk, Whitney F Kellett, Nigel G J Richards, Ursula Rothlisberger
B₁₂-dependent enzymes employ radical species with exceptional prowess to catalyze some of the most chemically challenging, thermodynamically unfavorable reactions. However, dealing with highly reactive intermediates is an extremely demanding task, requiring sophisticated control strategies to prevent unwanted side reactions. Using hybrid quantum mechanical/molecular mechanical simulations, we follow the full catalytic cycle of an AdoB₁₂-dependent enzyme and present the details of a mechanism that utilizes a highly effective mechanochemical switch...
June 17, 2014: Biochemistry
https://www.readbyqxmd.com/read/24814779/functional-heterologous-production-of-reductive-dehalogenases-from-desulfitobacterium-hafniense-strains
#18
Anita Mac Nelly, Marco Kai, Aleš Svatoš, Gabriele Diekert, Torsten Schubert
The anaerobic dehalogenation of organohalides is catalyzed by the reductive dehalogenase (RdhA) enzymes produced in phylogenetically diverse bacteria. These enzymes contain a cobamide cofactor at the active site and two iron-sulfur clusters. In this study, the tetrachloroethene (PCE) reductive dehalogenase (PceA) of the Gram-positive Desulfitobacterium hafniense strain Y51 was produced in a catalytically active form in the nondechlorinating, cobamide-producing bacterium Shimwellia blattae (ATCC 33430), a Gram-negative gammaproteobacterium...
July 2014: Applied and Environmental Microbiology
https://www.readbyqxmd.com/read/24746273/intravenous-cobinamide-versus-hydroxocobalamin-for-acute-treatment-of-severe-cyanide-poisoning-in-a-swine-sus-scrofa-model
#19
Vikhyat S Bebarta, David A Tanen, Susan Boudreau, Maria Castaneda, Lee A Zarzabal, Toni Vargas, Gerry R Boss
STUDY OBJECTIVE: Hydroxocobalamin is a Food and Drug Administration-approved antidote for cyanide poisoning. Cobinamide is a potential antidote that contains 2 cyanide-binding sites. To our knowledge, no study has directly compared hydroxocobalamin with cobinamide in a severe, cyanide-toxic large-animal model. Our objective is to compare the time to return of spontaneous breathing in swine with acute cyanide-induced apnea treated with intravenous hydroxocobalamin, intravenous cobinamide, or saline solution (control)...
December 2014: Annals of Emergency Medicine
https://www.readbyqxmd.com/read/24735254/catalytic-roles-of-substrate-binding-residues-in-coenzyme-b12-dependent-ethanolamine-ammonia-lyase
#20
Koichi Mori, Toshihiro Oiwa, Satoshi Kawaguchi, Kyosuke Kondo, Yusuke Takahashi, Tetsuo Toraya
Ethanolamine ammonia-lyase (EAL) catalyzes the adenosylcobalamin-dependent conversion of ethanolamine to acetaldehyde and ammonia. 1-OH of the substrate is hydrogen-bonded with Gluα287, Argα160, and Asnα193 and 2-NH2 with Gluα287, Glnα162, and Aspα362. The active site somewhat resembles that of diol dehydratase. All five residues were important for the high-affinity binding of the substrate and for catalysis. The -COO(-) group at residue α287 was absolutely required for activity and coenzyme Co-C bond cleavage, and there was a spatially optimal position for it, suggesting that Gluα287 contributes to Co-C bond homolysis, stabilizes the transition state for the migration of NH2 from C2 to C1 through partial deprotonation of spectator OH, and functions as a base in the elimination of ammonia...
April 29, 2014: Biochemistry
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