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Bluth T, Kiss T, Kircher M, Braune A, Bozsak C, Huhle R, Scharffenberg M, Herzog M, Roegner J, Herzog P, Vivona L, Millone M, Dössel O, Andreeff M, Koch T, Kotzerke J, Stender B, Gama de Abreu M. Measurement of relative lung perfusion with electrical impedance and positron emission tomography: an experimental comparative study in pigs. Br J Anaesth 2019; 123:246-254. [PMID: 31160064 DOI: 10.1016/j.bja.2019.04.056] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Revised: 04/08/2019] [Accepted: 04/09/2019] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND Electrical impedance tomography (EIT) with indicator dilution may be clinically useful to measure relative lung perfusion, but there is limited information on the performance of this technique. METHODS Thirteen pigs (50-66 kg) were anaesthetised and mechanically ventilated. Sequential changes in ventilation were made: (i) right-lung ventilation with left-lung collapse, (ii) two-lung ventilation with optimised PEEP, (iii) two-lung ventilation with zero PEEP after saline lung lavage, (iv) two-lung ventilation with maximum PEEP (20/25 cm H2O to achieve peak airway pressure 45 cm H2O), and (v) two-lung ventilation under unilateral pulmonary artery occlusion. Relative lung perfusion was assessed with EIT and central venous injection of saline 3%, 5%, and 10% (10 ml) during breath holds. Relative perfusion was determined by positron emission tomography (PET) using 68Gallium-labelled microspheres. EIT and PET were compared in eight regions of equal ventro-dorsal height (right, left, ventral, mid-ventral, mid-dorsal, and dorsal), and directional changes in regional perfusion were determined. RESULTS Differences between methods were relatively small (95% of values differed by less than 8.7%, 8.9%, and 9.5% for saline 10%, 5%, and 3%, respectively). Compared with PET, EIT underestimated relative perfusion in dependent, and overestimated it in non-dependent, regions. EIT and PET detected the same direction of change in relative lung perfusion in 68.9-95.9% of measurements. CONCLUSIONS The agreement between EIT and PET for measuring and tracking changes of relative lung perfusion was satisfactory for clinical purposes. Indicator-based EIT may prove useful for measuring pulmonary perfusion at bedside.
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Affiliation(s)
- T Bluth
- Pulmonary Engineering Group Dresden, Department of Anesthesiology and Intensive Care Medicine, Pulmonary Engineering Group, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | - T Kiss
- Pulmonary Engineering Group Dresden, Department of Anesthesiology and Intensive Care Medicine, Pulmonary Engineering Group, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | - M Kircher
- Institute of Biomedical Engineering, Karlsruhe Institute of Technology, Karlsruhe, Germany
| | - A Braune
- Pulmonary Engineering Group Dresden, Department of Anesthesiology and Intensive Care Medicine, Pulmonary Engineering Group, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | - C Bozsak
- Drägerwerk AG & Co. KGaA, Lübeck, Germany
| | - R Huhle
- Pulmonary Engineering Group Dresden, Department of Anesthesiology and Intensive Care Medicine, Pulmonary Engineering Group, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | - M Scharffenberg
- Pulmonary Engineering Group Dresden, Department of Anesthesiology and Intensive Care Medicine, Pulmonary Engineering Group, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | - M Herzog
- Pulmonary Engineering Group Dresden, Department of Anesthesiology and Intensive Care Medicine, Pulmonary Engineering Group, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | - J Roegner
- Pulmonary Engineering Group Dresden, Department of Anesthesiology and Intensive Care Medicine, Pulmonary Engineering Group, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | - P Herzog
- Pulmonary Engineering Group Dresden, Department of Anesthesiology and Intensive Care Medicine, Pulmonary Engineering Group, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | - L Vivona
- Pulmonary Engineering Group Dresden, Department of Anesthesiology and Intensive Care Medicine, Pulmonary Engineering Group, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany; Department of Neurosciences, Reproductive and Odontostomatological Sciences, University of Naples Federico II, Naples, Italy
| | - M Millone
- Pulmonary Engineering Group Dresden, Department of Anesthesiology and Intensive Care Medicine, Pulmonary Engineering Group, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany; IRCCS AOU San Martino IST, Department of Surgical Sciences and Integrated Diagnostics, University of Genoa, Genoa, Italy
| | - O Dössel
- Institute of Biomedical Engineering, Karlsruhe Institute of Technology, Karlsruhe, Germany
| | - M Andreeff
- Department of Nuclear Medicine, University Hospital Carl Gustav Carus, Dresden, Germany
| | - T Koch
- Pulmonary Engineering Group Dresden, Department of Anesthesiology and Intensive Care Medicine, Pulmonary Engineering Group, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | - J Kotzerke
- Department of Nuclear Medicine, University Hospital Carl Gustav Carus, Dresden, Germany
| | - B Stender
- Drägerwerk AG & Co. KGaA, Lübeck, Germany
| | - M Gama de Abreu
- Pulmonary Engineering Group Dresden, Department of Anesthesiology and Intensive Care Medicine, Pulmonary Engineering Group, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany.
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Spieth P, Güldner A, Uhlig C, Bluth T, Kiss T, Conrad C, Bischlager K, Braune A, Huhle R, Insorsi A, Tarantino F, Ball L, Schultz M, Abolmaali N, Koch T, Pelosi P, Gama de Abreu M. Variable versus conventional lung protective mechanical ventilation during open abdominal surgery (PROVAR): a randomised controlled trial. Br J Anaesth 2018; 120:581-591. [DOI: 10.1016/j.bja.2017.11.078] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Revised: 07/31/2017] [Accepted: 09/18/2017] [Indexed: 10/18/2022] Open
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Braune A, Blaut M. Evaluation of inter-individual differences in gut bacterial isoflavone bioactivation in humans by PCR-based targeting of genes involved in equol formation. J Appl Microbiol 2017; 124:220-231. [PMID: 29055162 DOI: 10.1111/jam.13616] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Revised: 09/26/2017] [Accepted: 10/17/2017] [Indexed: 02/06/2023]
Abstract
AIM To identify human subjects harbouring intestinal bacteria that bioactivate daidzein to equol using a targeted PCR-based approach. METHODS AND RESULTS In a pilot study including 17 human subjects, equol formation was determined in faecal slurries. In parallel, faecal DNA was amplified by PCR using degenerate primers that target highly conserved regions of dihydrodaidzein reductase and tetrahydrodaidzein reductase genes. PCR products of the expected size were observed for six of the eight subjects identified as equol producers. Analysis of clone libraries revealed the amplification of sequences exclusively related to Adlercreutzia equolifaciens in four of the subjects tested positive for equol formation, whereas in three of the equol producers, only sequences related to Slackia isoflavoniconvertens were observed. No amplicons were obtained for one equol-forming subject, thus suggesting the presence of nontargeted alternative genes. Amplicons were only sporadically observed in the nonequol producers. CONCLUSION The majority of human subjects who produced equol were also detected with the developed PCR-based approach. SIGNIFICANCE AND IMPACT OF THE STUDY The obtained results shed light on the distribution and the diversity of known equol-forming bacterial species in the study group and indicate the presence of as yet unknown equol-forming bacteria.
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Affiliation(s)
- A Braune
- Department of Gastrointestinal Microbiology, German Institute of Human Nutrition Potsdam-Rehbruecke, Nuthetal, Germany
| | - M Blaut
- Department of Gastrointestinal Microbiology, German Institute of Human Nutrition Potsdam-Rehbruecke, Nuthetal, Germany
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Leary D, Winkler T, Braune A, Maksym GN. Effects of airway tree asymmetry on the emergence and spatial persistence of ventilation defects. J Appl Physiol (1985) 2014; 117:353-62. [PMID: 24947031 DOI: 10.1152/japplphysiol.00881.2013] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Asymmetry and heterogeneity in the branching of the human bronchial tree are well documented, but their effects on bronchoconstriction and ventilation distribution in asthma are unclear. In a series of seminal studies, Venegas et al. have shown that bronchoconstriction may lead to self-organized patterns of patchy ventilation in a computational model that could explain areas of poor ventilation [ventilation defects (VDefs)] observed in positron emission tomography images during induced bronchoconstriction. To investigate effects of anatomic asymmetry on the emergence of VDefs we used the symmetric tree computational model that Venegas and Winkler developed using different trees, including an anatomic human airway tree provided by M. Tawhai (University of Auckland), a symmetric tree, and three trees with intermediate asymmetry (Venegas JG, Winkler T, Musch G, Vidal Melo MF, Layfield D, Tgavalekos N, Fischman AJ, Callahan RJ, Bellani G, Harris RS. Nature 434: 777-782, 2005 and Winkler T, Venegas JG. J Appl Physiol 103: 655-663, 2007). Ventilation patterns, lung resistance (RL), lung elastance (EL), and the entropy of the ventilation distribution were compared at different levels of airway smooth muscle activation. We found VDefs emerging in both symmetric and asymmetric trees, but VDef locations were largely persistent in asymmetric trees, and bronchoconstriction reached steady state sooner than in a symmetric tree. Interestingly, bronchoconstriction in the asymmetric tree resulted in lower RL (∼%50) and greater EL (∼%25). We found that VDefs were universally caused by airway instability, but asymmetry in airway branching led to local triggers for the self-organized patchiness in ventilation and resulted in persistent locations of VDefs. These findings help to explain the emergence and the persistence in location of VDefs found in imaging studies.
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Affiliation(s)
- D Leary
- Dalhousie University, Halifax, Nova Scotia, Canada; and
| | - T Winkler
- Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - A Braune
- Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - G N Maksym
- Dalhousie University, Halifax, Nova Scotia, Canada; and
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Schranz C, Riedlinger A, Huhle R, Braune A, Gama de Abreu M, Koch E, Möller K. Selection Criteria for Competing Models of Respiratory Mechanics. BIOMED ENG-BIOMED TE 2013; 58 Suppl 1:/j/bmte.2013.58.issue-s1-N/bmt-2013-4326/bmt-2013-4326.xml. [PMID: 24043038 DOI: 10.1515/bmt-2013-4326] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Arzt M, Hetzenecker A, Greimel T, Satzl A, Luchner A, Hamer OW, Debl K, Brandl-Novak AM, Braune A, Luitgart R, Riegger G, Pfeifer M, Buchner S. Auswirkungen der Schlafapnoe auf pektanginöse Beschwerden vor und nach akutem Myokardinfarkt. Pneumologie 2012. [DOI: 10.1055/s-0032-1302781] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Hetzenecker A, Buchner S, Greiml T, Satzl A, Luchner A, Hamer OW, Debl K, Brandl-Novak AM, Braune A, Obermeier R, Riegger G, Pfeifer M, Arzt M. Auswirkungen der Schlafapnoe auf den arteriellen Blutdruck in der Frühphase nach akutem Myokardinfarkt. Pneumologie 2011. [DOI: 10.1055/s-0031-1273033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Arzt M, Satzl A, Greimel T, Debl K, Luchner A, Hamer OW, Poschenrieder F, Brandl-Novak A, Braune A, Obermeier R, Pfeifer M, Riegger G, Buchner S. Schlafapnoe ist ein Prädiktor für die Größe der Infarktnarbe nach akutem Myokardinfarkt. Pneumologie 2011. [DOI: 10.1055/s-0031-1273032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Arzt M, Obermeier R, Weber SAT, Braune A, Beinkofer D, Riegger GA, Pfeifer M. Effekte einer dynamischen positiven Druckunterstützung mit BiPAP auto SV auf den PCO2 bei Patienten mit Herzinsuffizienz und zentraler Schlafapnoe. Pneumologie 2008. [DOI: 10.1055/s-0028-1083122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Montalván Dobmayr SL, Gloger G, Schichtl T, Braune A, Blumberg FC, Pfeifer M. Korrelation zwischen Vorhandensein einer schlafbezogenen Atmungsstörung, der Schläfrigkeit und der krankheitsspezifischen Lebensqualität bei Patienten mit chronischer Herzinsuffizienz. Pneumologie 2004. [DOI: 10.1055/s-2004-819633] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Grunert RR, Braune A, Schnackenberg E, Schloot W, Krause HR. [Genetic differences in enzymes of folic acid metabolism in patients with lip-jaw-palate clefts and their relatives]. Mund Kiefer Gesichtschir 2002; 6:131-3. [PMID: 12143122 DOI: 10.1007/s10006-001-0361-4] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
BACKGROUND The effectiveness of folic acid supplementation in the periconceptional period for the prevention of cleft lip/cleft lip and palate (CLP) is contradictorily discussed. Genetically determined variants of enzymes of the folic acid metabolism could be part of the key to success or failure of folate supplementation. A mutation of the methylenetetrahydrofolate reductase (MTHFR) gene is suspected to be a risk factor for CLP. METHODS The blood samples of 66 CLP patients, their 88 relatives (without CLP), and 184 healthy controls were searched by polymerase chain reaction for mutations of MTHFR 677 C:T, MTHFR 1298 A:C and of the arylamine N-acetyltransferase (NAT1) gene [gene type NAT1 degree 4 (wild type) or not]. RESULTS There was no significant difference in the number of MTHFR gene mutations (for 677 C:T and 1298 A:C) between the three groups (p approximately 0.3), but for the NAT1 genes (p = 0.033). The homozygote mutation was found more than twice as often in CLP patients (10.5%) and their relatives (10.6%) than in the healthy controls (4.35%). DISCUSSION Our results provide no evidence that the above MTHFR gene mutations are a risk factor for CLP.A NAT1 gene mutation instead could be a risk factor for CLP.
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Affiliation(s)
- R R Grunert
- Klinik für MKG-Chirurgie, Zentralkrankenhaus, St.-Jürgen-Strasse, 28205 Bremen.
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Abstract
The degradation of the flavonol quercetin and the flavone luteolin by Eubacterium ramulus, a strict anaerobe of the human intestinal tract, was studied. Resting cells converted these flavonoids to 3,4-dihydroxyphenylacetic acid and 3-(3,4-dihydroxyphenyl)propionic acid, respectively. The conversion of quercetin was accompanied by the transient formation of two intermediates, one of which was identified as taxifolin based on its specific retention time and UV and mass spectra. The structure of the second intermediate, alphitonin, was additionally elucidated by (1)H and (13)C nuclear magnetic resonance analysis. In resting-cell experiments, taxifolin in turn was converted via alphitonin to 3,4-dihydroxyphenylacetic acid. Alphitonin, which was prepared by enzymatic conversion of taxifolin and subsequent purification, was also transformed to 3,4-dihydroxyphenylacetic acid. The coenzyme-independent isomerization of taxifolin to alphitonin was catalyzed by cell extract or a partially purified enzyme preparation of E. ramulus. The degradation of luteolin by resting cells of E. ramulus resulted in the formation of the intermediate eriodictyol, which was identified by high-performance liquid chromatography and mass spectrometry analysis. The observed intermediates of quercetin and luteolin conversion suggest that the degradation pathways in E. ramulus start with an analogous reduction step followed by different enzymatic reactions depending on the additional 3-hydroxyl group present in the flavonol structure.
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Affiliation(s)
- A Braune
- Abteilung Gastrointestinale Mikrobiologie, D-14558 Bergholz-Rehbrücke, Germany.
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Abstract
The degradation of the flavonol quercetin and the flavone luteolin by Eubacterium ramulus, a strict anaerobe of the human intestinal tract, was studied. Resting cells converted these flavonoids to 3,4-dihydroxyphenylacetic acid and 3-(3,4-dihydroxyphenyl)propionic acid, respectively. The conversion of quercetin was accompanied by the transient formation of two intermediates, one of which was identified as taxifolin based on its specific retention time and UV and mass spectra. The structure of the second intermediate, alphitonin, was additionally elucidated by (1)H and (13)C nuclear magnetic resonance analysis. In resting-cell experiments, taxifolin in turn was converted via alphitonin to 3,4-dihydroxyphenylacetic acid. Alphitonin, which was prepared by enzymatic conversion of taxifolin and subsequent purification, was also transformed to 3,4-dihydroxyphenylacetic acid. The coenzyme-independent isomerization of taxifolin to alphitonin was catalyzed by cell extract or a partially purified enzyme preparation of E. ramulus. The degradation of luteolin by resting cells of E. ramulus resulted in the formation of the intermediate eriodictyol, which was identified by high-performance liquid chromatography and mass spectrometry analysis. The observed intermediates of quercetin and luteolin conversion suggest that the degradation pathways in E. ramulus start with an analogous reduction step followed by different enzymatic reactions depending on the additional 3-hydroxyl group present in the flavonol structure.
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Affiliation(s)
- A Braune
- Abteilung Gastrointestinale Mikrobiologie, D-14558 Bergholz-Rehbrücke, Germany.
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Abstract
A novel fluorescence quenching test for the detection of flavonoid degradation by microorganisms was developed. The test is based on the ability of the flavonoids to quench the fluorescence of 1,6-diphenyl-1,3,5-hexatriene (DPH). Several members of the anthocyanidins, flavones, isoflavones, flavonols, flavanones, dihydroflavanones, chalcones, dihydrochalcones and catechins were tested with regard to their quenching properties. The anthocyanidins were the most potent quenchers of DPH fluorescence, while the flavanones, dihydroflavanones and dihydrochalcones, quenched the fluorescence only weakly. The catechins had no visible impact on DPH fluorescence. The developed test allows a quick and easy differentiation between flavonoid-degrading and flavonoid-non-degrading bacteria. The investigation of individual reactions of flavonoid transformation with the developed test system is also possible.
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Affiliation(s)
- L Schoefer
- Institute of Nutritional Science, University of Potsdam, Berghol-Rehbrücke, Germany
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Westenberg DJ, Braune A, Ruppert C, Müller V, Herzberg C, Gottschalk G, Blaut M. The F420H2-dehydrogenase from Methanolobus tindarius: cloning of the ffd operon and expression of the genes in Escherichia coli. FEMS Microbiol Lett 1999; 170:389-98. [PMID: 9933933 DOI: 10.1111/j.1574-6968.1999.tb13399.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
The membrane-bound F420H2-dehydrogenase from the methylotrophic methanogen Methanolobus tindarius oxidizes reduced coenzyme F420 and feeds the electrons into an energy-conserving electron transport chain. Based on the N-terminal amino acid sequence of the 40-kDa subunit of F420H2-dehydrogenase the corresponding gene ffdB was detected in chromosomal DNA of M. tindarius. Sequence analysis, primer extension, and RT-PCR experiments indicated that ffdB is part of an operon harboring three additional open reading frames (ffdA, ffdC, ffdD). The corresponding mRNA transcript and transcription start sites were determined. All four genes could be heterologously expressed in Escherichia coli.
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Affiliation(s)
- D J Westenberg
- Institut für Mikrobiologie und Genetik, Georg-August-Universität Göttingen, Germany
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Braune A, Bendrat K, Rospert S, Buckel W. The sodium ion translocating glutaconyl-CoA decarboxylase from Acidaminococcus fermentans: cloning and function of the genes forming a second operon. Mol Microbiol 1999; 31:473-87. [PMID: 10027965 DOI: 10.1046/j.1365-2958.1999.01189.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Glutaconyl-CoA decarboxylase from Acidaminococcus fermentans (clostridal cluster IX), a strict anaerobic inhabitant of animal intestines, uses the free energy of decarboxylation (delta G(o) approximately -30 kJ mol-1) in order to translocate Na+ from the inside through the cytoplasmic membrane. The proton, which is required for decarboxylation, most probably comes from the outside. The enzyme consists of four different subunits. The largest subunit, alpha or GcdA (65 kDa), catalyses the transfer of CO2 from glutaconyl-CoA to biotin covalently attached to the gamma-subunit, GcdC. The beta-subunit, GcdB, is responsible for the decarboxylation of carboxybiotin, which drives the Na+ translocation (approximate K(m) for Na+ 1 mM), whereas the function of the smallest subunit, delta or GcdD, is unclear. The gene gcdA is part of the 'hydroxyglutarate operon', which does not contain genes coding for the other three subunits. This paper describes that the genes, gcdDCB, are transcribed in this order from a distinct operon. The delta-subunit (GcdD, 12 kDa), with one potential transmembrane helix, probably serves as an anchor for GcdA. The biotin carrier (GcdC, 14 kDa) contains a flexible stretch of 50 amino acid residues (A26-A75), which consists of 34 alanines, 14 prolines, one valine and one lysine. The beta-subunit (GcdB, 39 kDa) comprising 11 putative transmembrane helices shares high amino acid sequence identities with corresponding deduced gene products from Veillonella parvula (80%, clostridial cluster IX), Archaeoglobus fulgidus (61%, Euryarchaeota), Propionigenium modestum (60%, clostridial cluster XIX), Salmonella typhimurium (51%, enterobacteria) and Klebsiella pneumoniae (50%, enterobacteria). Directly upstream of the promoter region of the gcdDCB operon, the 3' end of gctM was detected. It encodes a protein fragment with 73% sequence identity to the C-terminus of the alpha-subunit of methylmalonyl-CoA decarboxylase from V. parvula (MmdA). Hence, it appears that A. fermentans should be able to synthesize this enzyme by expression of gctM together with gdcDCB, but methylmalonyl-CoA decarboxylase activity could not be detected in cell-free extracts. Earlier observations of a second, lower affinity binding site for Na+ of glutaconyl-CoA decarboxylase (apparent K(m) 30 mM) were confirmed by identification of the cysteine residue 243 of GcdB between the putative hellces VII and VIII, which could be specifically protected from alkylation by Na+. The alpha-subunit was purified from an overproducing Escherichia coli strain and was characterized as a putative homotrimer able to catalyse the carboxylation of free biotin.
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Affiliation(s)
- A Braune
- Laboratorium für Mikrobiologie, Philipps-Universität, Marburg, Germany
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