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1
Förster, Anke. "Quantitative Studien zu Vorkommen und metabolischem Transit alimentärer Maillard-Reaktions-Produkte." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2007. http://nbn-resolving.de/urn:nbn:de:swb:14-1168006117145-39700.
Full textAbstract:
Die Maillard-Reaktion und ihre Produkte (MRPs) sind aus der Lebensmittelchemie bekannt. Der Nachweis der Derivate in physiologischen Medien und die Beobachtung erhöhter Gehalte im Zusammenhang mit Alterungsgeschehen und Stoffwechselerkrankungen führte zur Diskussion möglicher pathophysiologischer Konsequenzen in vivo. Auf diesem Hintergrund stellt sich die Frage nach der Relevanz der täglichen Nahrung als MRP-Quelle. Grundlage zur Beurteilung sind quantitative Daten zum Vorkommen der Verbindungen in Lebensmitteln. Heterogenität und Vielzahl der Produkte machen die Betrachtung individueller und die Berücksichtigung noch unbekannter Derivate notwendig. Durch Bestimmung von Lysin, dem Amadori-Produkt (AP) Ne-Desoxylactulosyl-1-lysin, Pyrralin, Ne-Carboxymethyllysin (CML), Glyoxal- und Methylglyoxal-Lysin-Dimer (GOLD, MOLD) und 2-Amino-6-(3-hydroxy-2-methyl-4-oxo-4H-pyridin-1-yl)-hexansäure (Maltosin) in verschiedenen Milchprodukten konnte gezeigt werden, dass AP das Hauptprodukt der Lysinderivatisierung in diesen Proben darstellt. CML und Pyrralin gewannen mit zunehmender Erhitzung an Bedeutung, wobei Pyrralin auch in den stark thermisch behandelten Proben nur in relativ geringen Mengen gebildet wird. GOLD und MOLD waren nicht nachweisbar. Mit den erfassten Derivaten konnte nur ein Teil, 40-50 % in flüssigen Proben, der Lysinmodifizierung erklärt werden. Es kommt demnach in erheblichem Maße zur Bildung weiterer in Nahrungsmitteln noch nicht erfasster Derivate. Das hier erstmals in Lebensmitteln quantifizierte Maltosin leistet keinen relevanten Beitrag zur weiteren Aufklärung der Lysinmodifizierung, da es erst in sehr stark erhitzten Produkten und in deutlich geringeren Mengen als Pyrralin entsteht. Zur Beurteilung der ernährungsphysiologischen Relevanz alimentärer MRPs sind neben der zugeführten Menge deren Resorbierbarkeit und Elimination aus dem Körper von Interesse. Anhand der renalen Exkretion definierter Lysinderivate in Abhängigkeit von der nahrungsbedingten Zufuhr sollten Aussagen zu deren metabolischem Transit getroffen werden. Es wurde eine Ernährungsstudie durchgeführt, in der die Probanden zunächst auf MRP-haltige Lebensmittel verzichteten, dann, bis auf eine Kontrollgruppe, Mahlzeiten mit bekannten Gehalten verzehrten und im Anschluss wieder MRPfrei lebten. Die 24h-Urinproben der Teilnehmer wurden hinsichtlich der Gehalte an freiem AP, Pyrralin, CML und Pentosidin untersucht. Die Gehalte lagen für AP, Pyrralin und CML in der Größenordnung weniger mg pro Tag, für Pentosidin dagegen nur bei wenigen µg pro Tag. Der Verzicht auf MRP-haltige Nahrung führte innerhalb von 48 bis 72 h zum Absinken der Gehalte auf ein Basislevel. Es zeigte sich, dass mehr als 85 % des AP, ca. 90 % des Pyrralins aber nur 30 bis 40 % des Pentosidins im Urin aus alimentären Quellen stammen. AP, Pyrralin und Pentosidin werden demnach grundsätzlich aus der Nahrung resorbiert und über die Nieren eliminiert. Im Gegensatz zu Literaturberichten waren die im Urin messbaren CML-Gehalte durch die MRP-freie Diät nicht beeinflussbar, was auf eine geringe oder fehlende proteolytische Freisetzung und/oder schlechtere Resorbierbarkeit der Verbindung hindeutet. Nach Verzehr definierter MRP-Mengen zeigten sich stark unterschiedliche Wiederfindungen. Während freies Pentosidin und proteingebundenes Pyrralin nahezu vollständig bzw. zum überwiegenden Teil (50 bis 60 %) über den Urin eliminiert werden, trifft dies nur auf einen geringen Prozentsatz des proteingebundenen Pentosidins (2 %) und des AP (<3 %) zu. Eine ernährungsphysiologische Beurteilung kann demnach nur nach Kenntnis der im Lebensmittel enthaltenen Derivate und deren individuellen metabolischen Transits erfolgen. Ausgehend von der vorliegenden Arbeit und der Literatur ist das von der Nahrung ausgehende Gefährdungspotential als gering anzusehen. Zu berücksichtigen bleibt, dass ein großer Teil der MRPs noch immer unbekannt ist, ernährungsphysiologische Konsequenzen damit nicht abschließend einzuschätzen sind.
2
Förster, Anke. "Quantitative Studien zu Vorkommen und metabolischem Transit alimentärer Maillard-Reaktions-Produkte." Doctoral thesis, Technische Universität Dresden, 2006. https://tud.qucosa.de/id/qucosa%3A24947.
Full textAbstract:
Die Maillard-Reaktion und ihre Produkte (MRPs) sind aus der Lebensmittelchemie bekannt. Der Nachweis der Derivate in physiologischen Medien und die Beobachtung erhöhter Gehalte im Zusammenhang mit Alterungsgeschehen und Stoffwechselerkrankungen führte zur Diskussion möglicher pathophysiologischer Konsequenzen in vivo. Auf diesem Hintergrund stellt sich die Frage nach der Relevanz der täglichen Nahrung als MRP-Quelle. Grundlage zur Beurteilung sind quantitative Daten zum Vorkommen der Verbindungen in Lebensmitteln. Heterogenität und Vielzahl der Produkte machen die Betrachtung individueller und die Berücksichtigung noch unbekannter Derivate notwendig. Durch Bestimmung von Lysin, dem Amadori-Produkt (AP) Ne-Desoxylactulosyl-1-lysin, Pyrralin, Ne-Carboxymethyllysin (CML), Glyoxal- und Methylglyoxal-Lysin-Dimer (GOLD, MOLD) und 2-Amino-6-(3-hydroxy-2-methyl-4-oxo-4H-pyridin-1-yl)-hexansäure (Maltosin) in verschiedenen Milchprodukten konnte gezeigt werden, dass AP das Hauptprodukt der Lysinderivatisierung in diesen Proben darstellt. CML und Pyrralin gewannen mit zunehmender Erhitzung an Bedeutung, wobei Pyrralin auch in den stark thermisch behandelten Proben nur in relativ geringen Mengen gebildet wird. GOLD und MOLD waren nicht nachweisbar. Mit den erfassten Derivaten konnte nur ein Teil, 40-50 % in flüssigen Proben, der Lysinmodifizierung erklärt werden. Es kommt demnach in erheblichem Maße zur Bildung weiterer in Nahrungsmitteln noch nicht erfasster Derivate. Das hier erstmals in Lebensmitteln quantifizierte Maltosin leistet keinen relevanten Beitrag zur weiteren Aufklärung der Lysinmodifizierung, da es erst in sehr stark erhitzten Produkten und in deutlich geringeren Mengen als Pyrralin entsteht. Zur Beurteilung der ernährungsphysiologischen Relevanz alimentärer MRPs sind neben der zugeführten Menge deren Resorbierbarkeit und Elimination aus dem Körper von Interesse. Anhand der renalen Exkretion definierter Lysinderivate in Abhängigkeit von der nahrungsbedingten Zufuhr sollten Aussagen zu deren metabolischem Transit getroffen werden. Es wurde eine Ernährungsstudie durchgeführt, in der die Probanden zunächst auf MRP-haltige Lebensmittel verzichteten, dann, bis auf eine Kontrollgruppe, Mahlzeiten mit bekannten Gehalten verzehrten und im Anschluss wieder MRPfrei lebten. Die 24h-Urinproben der Teilnehmer wurden hinsichtlich der Gehalte an freiem AP, Pyrralin, CML und Pentosidin untersucht. Die Gehalte lagen für AP, Pyrralin und CML in der Größenordnung weniger mg pro Tag, für Pentosidin dagegen nur bei wenigen µg pro Tag. Der Verzicht auf MRP-haltige Nahrung führte innerhalb von 48 bis 72 h zum Absinken der Gehalte auf ein Basislevel. Es zeigte sich, dass mehr als 85 % des AP, ca. 90 % des Pyrralins aber nur 30 bis 40 % des Pentosidins im Urin aus alimentären Quellen stammen. AP, Pyrralin und Pentosidin werden demnach grundsätzlich aus der Nahrung resorbiert und über die Nieren eliminiert. Im Gegensatz zu Literaturberichten waren die im Urin messbaren CML-Gehalte durch die MRP-freie Diät nicht beeinflussbar, was auf eine geringe oder fehlende proteolytische Freisetzung und/oder schlechtere Resorbierbarkeit der Verbindung hindeutet. Nach Verzehr definierter MRP-Mengen zeigten sich stark unterschiedliche Wiederfindungen. Während freies Pentosidin und proteingebundenes Pyrralin nahezu vollständig bzw. zum überwiegenden Teil (50 bis 60 %) über den Urin eliminiert werden, trifft dies nur auf einen geringen Prozentsatz des proteingebundenen Pentosidins (2 %) und des AP (<3 %) zu. Eine ernährungsphysiologische Beurteilung kann demnach nur nach Kenntnis der im Lebensmittel enthaltenen Derivate und deren individuellen metabolischen Transits erfolgen. Ausgehend von der vorliegenden Arbeit und der Literatur ist das von der Nahrung ausgehende Gefährdungspotential als gering anzusehen. Zu berücksichtigen bleibt, dass ein großer Teil der MRPs noch immer unbekannt ist, ernährungsphysiologische Konsequenzen damit nicht abschließend einzuschätzen sind.
3
Laba, Marija. "Optimalizace metody HPLC-ELSD pro stanovení sacharidů v potravinách." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2017. http://www.nusl.cz/ntk/nusl-295706.
Full textAbstract:
This master's thesis deals with the optimalization of HPLC-ELSD method for the determination of carbohydrates in food. The theoretical part focuses on the classification and characterization of carbohydrates, the occurrence of carbohydrates in food and their physiological importance. There was targeted mainly glucose, fructose, sucrose and maltose. There is a brief summary of the analytical methods that can be used to determine carbohydrates. Experimental part is based on a literary review. It also deals with high performance liquid chromatography with evaporative light scattering detector. The main content in this part is the optimalization of condition for reliable and rapid separation of the most frequently occurring carbohydrates in foods. The carbohydrates were identified and quantified under optimum condition in real samples specifically in fruit juice, beer, ketchup and red pepper powder. The result is commented in conclusion.
4
Duda, Štěpán. "Studium budičů anhydritových maltovin." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2018. http://www.nusl.cz/ntk/nusl-371821.
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Presented diploma thesis is dealing with study of exciters of anhydrite binders. Theoretical part is dedicated to study of available domestic and foreign literature on a given topic. Attention is also paid to the study of the current research at the institute of THD. In the experimental part is developed a proposal of potential exciters of hydration on the basis of literature and according to the results of the research at the institute of THD. Next is proposed the methodological concept of the work. Testing of the monitored technological features follows. The study of the hydration process was recorded using XRD analysis and thermal analysis. Evaluation of the results was implemented by the mutual comparing of prepared recipes.
5
Verner, Filip. "Studium hydratačního procesu anhydritových maltovin." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2017. http://www.nusl.cz/ntk/nusl-265222.
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The presented work deals with the study of hydration processes anhydrite binders with external exciters. Work is divided into two parts. Conceptually is this work divided into two parts The theoretical part of study contains general theory of gypsum binders, anhydrite binders and research at the institude THD. In the experimental part deals with proposal of recipes, making of samples and subsequent determination of main technological tests and monitoring hydration process by the XRD and DTA analysis.
6
Ciencialová, Zuzana. "Vliv modifikujících přísad na dosahované vlastnosti anhydritových maltovin." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2017. http://www.nusl.cz/ntk/nusl-265351.
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This diploma thesis deals with influence of modifying additives on achieved properties of anhydrite binders. The first part is focused on funamentals of anhydrite binders. Ist second part introduces anhydrite under-layments and their standard requirements. The experimental part is dedicated to anhydrite binders modyfyied by plasticizers, while their final properties are compared.
7
Seifert, Steffen. "Synthese und Komplexbildungseigenschaften ausgewählter Maillard-Reaktionsprodukte." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1232923513056-87374.
Full textAbstract:
Zahlreiche Studien belegen, dass Maillard-Reaktionsprodukte (MRP) in vivo einen Einfluss auf den physiologischen Metallionenhaushalt haben können. Da bisher noch keine Korrelation zwischen dem Entstehen von definierten MRP und einem erhöhten Metallionenbindungsvermögen ermittelt werden konnte, war es das Ziel dieser Arbeit, die Komplexbildungseigenschaften der ausgewählten MRP Nε-Carboxymethyllysin, Isomaltol und Maltosin sowie deren Strukturanaloga Maltol, Deferipron, Mimosin und Pyridosin mit den physiologisch relevanten Metallionen Cu(II), Zn(II), Fe(III), Al(III) und Mn(II) zu untersuchen. Dazu wurden die MRP Nε-Carboxymethyllysin und Maltosin sowie die parallel untersuchten Substanzen Pyridosin, Maltosin-3-benzylether, Nα-Hippuryl- und Nα-Acetylmaltosin in ausreichender Menge und Reinheit synthetisiert. Dabei gelang es, für Maltosin und Pyridosin neue und effiziente Synthesewege zu entwickeln, bei welchen zum ersten Mal beide Substanzen gezielt aufgebaut wurden. Die Komplexbildungskonstanten der Liganden mit den Metallionen wurden pH-potentiometrisch bestimmt (I[KNO3] = 0,15 M; θ = 25 °C). Durch die Auswertung der Protonierungskonstanten der gebildeten Komplexe und das Vermessen geeigneter Derivate konnten für die untersuchten Komplexe zusätzlich die Koordinationsstellen der Liganden aufgeklärt werden. Die Untersuchungen zu den Komplexbildungseigenschaften bestätigten erstmals die Vermutung, dass MRP in der Lage sind, Metallionen zu binden. Dabei wurde weiterhin ermittelt, dass die Bindung von Cu(II) durch Nε-Carboxymethyllysin und von Fe(III), Al(III) und Cu(II) durch Maltosin durchaus von physiologischer Relevanz sind. Die Bedeutung der Ergebnisse wurde qualitativ durch Versuche mit Maltosin-derivatisiertem Rinderserumalbumin unterstrichen. Als besonderes Ergebnis der Arbeit ist herauszustellen, dass das MRP Maltosin und die Verbindung Pyridosin deutlich stabilere Komplexe mit Fe(III) bilden als das zur Fe(III)-Chelattherapie eingesetzte Medikament Deferipron. Diese festgestellte Eigenschaft bietet interessante Perspektiven für zukünftige Studien zur möglichen Anwendung von z. B. Maltosin als PharmakonSeveral studies show that Maillard reaction products (MRP) may influence the physiological metal ion balance. But none of these studies prove a correlation between the formation of defined MRP and an enhanced metal ion binding. Therefore it was the aim of this work to investigate the complex formation characteristics of the selected MRP Nε-carboxymethyllysine, isomaltol and maltosine as well as the structural analogues maltol, deferiprone, mimosine and pyridosine with the physiological relevant metal ions Cu(II), Zn(II), Fe(III), Al(III) and Mn(II). For that purpose the MRP Nε-carboxymethyllysine and maltosine plus the parallel analysed substances pyridosine, maltosine-3-benzylether, Nα-hippuryl- and Nα-acetylmaltosine were synthesised. Thereby new and efficient syntheses for maltosine and pyridosine were developed. The stability constants of the ligands with the metal ions were determined by pH-potentiometry (I(KNO3) = 0,15 M; θ = 25 °C). Furthermore the donor atoms within the formed complexes were determined by the evaluation of the protonation constants of the formed complexes and by the analysis of adequate derivatives. The studies to the complex formation characteristics confirm for the first time the assumption, that MRP are able to form stable complexes with metal ions. Withal it was ascertained that the coordination of Cu(II) by Nε-carboxymethyllysine and of Fe(III), Al(III) and Cu(II) by maltosine may be of physiological relevance. The significance of the results was pointed out by experiments with maltosine derivatised bovine serum albumine. The fact that the MRP maltosine and the compound pyridosine form more stable complexes with Fe(III) as the medicament for the Fe(III) chelate therapy deferiprone is a particular result of this work. This property affords interesting perspectives for future studies about a possible appliance of e.g. maltosine as pharmaceutical
8
Dalgleish, Pamela Weir. "The yeast maltose transporter." Thesis, Heriot-Watt University, 1997. http://hdl.handle.net/10399/678.
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9
Seifert, Steffen. "Synthese und Komplexbildungseigenschaften ausgewählter Maillard-Reaktionsprodukte." Doctoral thesis, Technische Universität Dresden, 2008. https://tud.qucosa.de/id/qucosa%3A23758.
Full textAbstract:
Zahlreiche Studien belegen, dass Maillard-Reaktionsprodukte (MRP) in vivo einen Einfluss auf den physiologischen Metallionenhaushalt haben können. Da bisher noch keine Korrelation zwischen dem Entstehen von definierten MRP und einem erhöhten Metallionenbindungsvermögen ermittelt werden konnte, war es das Ziel dieser Arbeit, die Komplexbildungseigenschaften der ausgewählten MRP Nε-Carboxymethyllysin, Isomaltol und Maltosin sowie deren Strukturanaloga Maltol, Deferipron, Mimosin und Pyridosin mit den physiologisch relevanten Metallionen Cu(II), Zn(II), Fe(III), Al(III) und Mn(II) zu untersuchen. Dazu wurden die MRP Nε-Carboxymethyllysin und Maltosin sowie die parallel untersuchten Substanzen Pyridosin, Maltosin-3-benzylether, Nα-Hippuryl- und Nα-Acetylmaltosin in ausreichender Menge und Reinheit synthetisiert. Dabei gelang es, für Maltosin und Pyridosin neue und effiziente Synthesewege zu entwickeln, bei welchen zum ersten Mal beide Substanzen gezielt aufgebaut wurden. Die Komplexbildungskonstanten der Liganden mit den Metallionen wurden pH-potentiometrisch bestimmt (I[KNO3] = 0,15 M; θ = 25 °C). Durch die Auswertung der Protonierungskonstanten der gebildeten Komplexe und das Vermessen geeigneter Derivate konnten für die untersuchten Komplexe zusätzlich die Koordinationsstellen der Liganden aufgeklärt werden. Die Untersuchungen zu den Komplexbildungseigenschaften bestätigten erstmals die Vermutung, dass MRP in der Lage sind, Metallionen zu binden. Dabei wurde weiterhin ermittelt, dass die Bindung von Cu(II) durch Nε-Carboxymethyllysin und von Fe(III), Al(III) und Cu(II) durch Maltosin durchaus von physiologischer Relevanz sind. Die Bedeutung der Ergebnisse wurde qualitativ durch Versuche mit Maltosin-derivatisiertem Rinderserumalbumin unterstrichen. Als besonderes Ergebnis der Arbeit ist herauszustellen, dass das MRP Maltosin und die Verbindung Pyridosin deutlich stabilere Komplexe mit Fe(III) bilden als das zur Fe(III)-Chelattherapie eingesetzte Medikament Deferipron. Diese festgestellte Eigenschaft bietet interessante Perspektiven für zukünftige Studien zur möglichen Anwendung von z. B. Maltosin als Pharmakon.Several studies show that Maillard reaction products (MRP) may influence the physiological metal ion balance. But none of these studies prove a correlation between the formation of defined MRP and an enhanced metal ion binding. Therefore it was the aim of this work to investigate the complex formation characteristics of the selected MRP Nε-carboxymethyllysine, isomaltol and maltosine as well as the structural analogues maltol, deferiprone, mimosine and pyridosine with the physiological relevant metal ions Cu(II), Zn(II), Fe(III), Al(III) and Mn(II). For that purpose the MRP Nε-carboxymethyllysine and maltosine plus the parallel analysed substances pyridosine, maltosine-3-benzylether, Nα-hippuryl- and Nα-acetylmaltosine were synthesised. Thereby new and efficient syntheses for maltosine and pyridosine were developed. The stability constants of the ligands with the metal ions were determined by pH-potentiometry (I(KNO3) = 0,15 M; θ = 25 °C). Furthermore the donor atoms within the formed complexes were determined by the evaluation of the protonation constants of the formed complexes and by the analysis of adequate derivatives. The studies to the complex formation characteristics confirm for the first time the assumption, that MRP are able to form stable complexes with metal ions. Withal it was ascertained that the coordination of Cu(II) by Nε-carboxymethyllysine and of Fe(III), Al(III) and Cu(II) by maltosine may be of physiological relevance. The significance of the results was pointed out by experiments with maltosine derivatised bovine serum albumine. The fact that the MRP maltosine and the compound pyridosine form more stable complexes with Fe(III) as the medicament for the Fe(III) chelate therapy deferiprone is a particular result of this work. This property affords interesting perspectives for future studies about a possible appliance of e.g. maltosine as pharmaceutical.
10
Wagner, Štěpán. "Využití fluidních popílků k přípravě hydraulické maltoviny." Doctoral thesis, Vysoké učení technické v Brně. Fakulta stavební, 2012. http://www.nusl.cz/ntk/nusl-392282.
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FBC-ashes, as a waste product of a relatively new technology of combustion, so-called fluidized bed combustion, cannot be used for building materials production in contrast to fly-ashes. Problem rests in their chemical as well as their mineralogical composition. Thought it can be admitted that FBC-ash may be used for preparation of the hydraulic binder with a similar chemical and mineralogical composition, but only in a certain limit of concentration. The first part of this thesis was focused on the potentialities of fluid fly ashes utilization as hydraulic bonding material in preparation of dry mortar mixtures and the second part of works was engaged in research development of burned hydraulic binder of FBC ash. The thesis explores the conjunction between parameters of burning mode and hydraulic binder characteristics.
11
Schönert, Stefan. "Maltose- und Maltodextrin-Verwertung in Bacillus subtilis." [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=973091967.
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12
Bao, Huan. "The regulatory mechanisms of the maltose transporter." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/46285.
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ATP-binding cassette (ABC) transporters couple ATP hydrolysis to import and export of a large array of substances across cell membranes in all kingdoms of life. Since the transport reaction consumes cellular energy, substrate translocation mediated by ABC transporters must be regulated according to the requirements of the cell. This thesis uses the Escherichia coli maltose transporter MalFGK2 to understand the regulatory mechanisms of ABC importers. Biochemical and biophysical approaches were employed to investigate how this transport process is modulated by maltose, the maltose-binding protein MalE and the glucose-specific enzyme EIIAGlc. First, I show that ATP facilitates MalE binding to MalFGK2, which forms the complex of MalE-MalFGK2 for efficient maltose transport. In addition, when the external maltose level exceeds that required, maltose is able to limit the maximal transport rate by promoting dissociation of MalE from MalFGK2. Finally, I find that the N-terminal tail of EIIAGlc and acidic phospholipids are essential for the binding of the protein to the MalK dimer, so that cleavage of ATP by MalFGK2 is inhibited. These results, combined with previous genetic, biochemical and structural work, provide valuable insights into our understanding of the regulatory mechanisms of the maltose transport system.
13
Hamid, Mas Rina Wati Haji Abdul. "Maltose metabolism in Bacillus licheniformis NCIB 6346." Thesis, Heriot-Watt University, 1992. http://hdl.handle.net/10399/801.
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14
Hollingsworth, Kristian. "The synthesis of a maltose responsive switch." Thesis, University of Leeds, 2015. http://etheses.whiterose.ac.uk/12160/.
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A cells interaction with its surroundings is governed by the flora of the cell surface. This complex landscape of structures provides an opportunity for the re-engineering of the surface and so the cells properties without the use of genetic modification. Applying the principles of supramolecular chemistry; surface proteins can be targeted with carbohydrate based ligands to form both stable and metabolite-responsive non-covalent complexes. This redecoration of the surfaces of bacteria will make it possible to control the interactions that a bacterium makes with its environment, whether in a patient or a bioreactor. In this project the transport protein maltoporin and maltose binding protein (MBP) will be utilised in the construction of a maltose responsive switch. Both proteins will be targeted with a maltose-based polymer which can thread through maltoporin on the cell surface to interact with MBP in the periplasm. In addition, the synthesis of molecules to probe the binding of maltoporin through biophysical experiments will be investigated.
15
Luo, Xing. "Roles of regulatory RNAs in Vibrio pathogenic to species of aquaculture interest." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS226.
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Les petits ARN régulateurs bactériens, généralement de 50 à 300 nt de long, agissent en appariant les bases avec des cibles d'ARNm spécifiques, affectant ainsi leur traduction et/ou leur stabilité, sont des éléments importants qui régulent divers processus. V. tasmaniensis LGP32 est un pathogène de l'huître facultatif. Un ARNs Vsr217 s'est révélé être conservé dans les vibrions et fortement régulé à la hausse lors de l'infection des huîtres. J'ai trouvé que vsr217 et le gène en aval malK (codant pour une sous-unité du transporteur principal de maltose) sont tous deux exprimés à partir d'un promoteur en amont régulé par l'activateur de maltose MalT, Vsr217 étant généré à partir de la longue 5' UTR de l'ARNm de malK. Outre un effet cis sur l’expression du malK, qui diminue chez le mutant Δvsr217, nous avons constaté que l’absence de cet ARNs entraînait, lors de la croissance de cellules dans du maltose, l’augmentation de deux enzymes importantes impliquées dans la voie de la glycolyse/néoglucogenèse, Fbp et PpsA et cet ARNm de fbp étaient une cible directe de Vsr217. J'ai également exploré la régulation de la biosynthèse des acides aminés à chaîne ramifiée (BCAA: Leucine, Valine et Isoleucine) chez V. alginolyticus, un agent pathogène des poissons et mollusques et des poissons de mer et un agent pathogène humain émergent opportuniste. Nous avons constaté que l'opéron ilvGMEDA (codant la voie principale pour la biosynthèse des BCAAs) est régulé par un peptide leader traduit. Ainsi, la traduction d'un peptide riche en BCAA codé en amont des gènes de structure fournit une réponse adaptative par un mécanisme similaire au modèle canonique de E. coli. Cette étude portant sur un organisme non modèle à Gram-négatif met en évidence la conservation mécanistique de l'atténuation de la transcription malgré l'absence de conservation de la séquence primaireBacterial regulatory small RNAs, usually 50-300 nt long, act by base-pairing with specific mRNA targets, affecting their translation and/or stability, are important elements which regulate a variety of processes. V. tasmaniensis LGP32 is a facultative oyster pathogen. A sRNA Vsr217 was found to be conserved within vibrios and highly upregulated during oyster infection. I found that vsr217 and the downstream gene malK (encoding a subunit of the major maltose transporter) are both expressed from an upstream promoter regulated by the maltose activator MalT with Vsr217 being generated from the long 5' UTR of the malK mRNA. Beside a cis-effect on malK expression, which decreases in the Δvsr217 mutant, we found that the absence of this sRNA resulted, when cells grown in maltose, in the increase of two important enzymes involved in the glycolysis/neoglucogenesis pathway, Fbp and PpsA and that fbp mRNA was a direct target of Vsr217. I also explored the regulation of the biosynthesis of branched-chain amino acids (BCAAs: Leucine, Valine and Isoleucine) in V. alginolyticus, a marine fish and shellfish pathogen and an emerging opportunistic human pathogen. We found that the ilvGMEDA operon (encoding the main pathway for biosynthesis of BCAAs) is regulated by a translated leader peptide. Thus, the translation of a BCAA rich peptide encoded upstream of the structural genes provides an adaptive response by a mechanism similar to the E. coli canonical model. This study with a non-model Gram-negative organism highlights the mechanistic conservation of transcription attenuation despite the absence of primary sequence conservation
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Yip, Hopi. "Genetic manipulation of baker's yeast for improved maltose utilisation /." [Richmond, N.S.W.] : Centre for Biostructural and Biomolecular Resarch, Faculty of Science and Technolocy, University of Western Sydney, Hawkesbury, 1999. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20030625.100807/index.html.
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Yip, Hopi, of Western Sydney Hawkesbury University, and Faculty of Science and Technology. "Genetic manipulation of baker's yeast for improved maltose utilisation." THESIS_FSTA_SFS_Yip_H.xml, 1999. http://handle.uws.edu.au:8081/1959.7/223.
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Two yeast/E.coli shuttle vector plasmids were studied in 1994, termed pIBIDB and pBP33. According to this study, each plasmid should contain at least one ADH2UAS (upstream activation sequence in the alcohol dehydrogenase 2 gene) insert. In the present study, the constructed plasmids were analysed and transformed into laboratory strain yeast. The aim of this project was to identify the orientation, quantity and quality of the insert in the selected plasmids. Methods such as restriction analysis, polymerase chained reaction (PCR), sequencing, plate assays and enzyme assays were used to identify and evaluate the novel inserts. The data presented in this thesis suggest the inserted ADH2UAS fragment did enhance the production of maltose permease and maltase when the transformants were cultivated in maltose and ethanol-glycerol medium. The results suggested that transformants containing two inserts of ADH2UAS had a greater influence on the transformants than a single insert. But the inserts within the vectors and in transformed laboratory stain yeast appeared unstable. This could be due to the method used for plasmid construction and the storage condition of the transformantsMaster of Science (Hons)
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Scott, Peter. "The metabolism of sucrose and maltose by barley microspores." Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239199.
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Jensen, Ulla Helene. "Studies on the properties of the yeast maltose transporter." Thesis, Heriot-Watt University, 1998. http://hdl.handle.net/10399/627.
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Shahir, Shafinaz. "Engineering and the maltose binding protein for metal ions sensing." Thesis, Imperial College London, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.434921.
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Ruzanski, Christian. "The metabolism of maltose in Arabidopsis thaliana leaves at night." Thesis, University of East Anglia, 2011. https://ueaeprints.uea.ac.uk/36357/.
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Al-Basheri, Khalid Ali. "The biochemistry and genetics of maltose metabolism in clostridium acetobutylicum." Thesis, Heriot-Watt University, 1994. http://hdl.handle.net/10399/1383.
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Hollatz, Cláudia. "Análise da fermentação de maltose e maltotriose por saccharomyces cerevisiae." Florianópolis, SC, 2004. http://repositorio.ufsc.br/xmlui/handle/123456789/87074.
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A fermentação da maltose e maltotriose por Saccharomyces cerevisiae é de fundamental importância para diversas aplicações industriais desta levedura. No presente trabalho foi analisado aspectos do metabolismo destes açúcares relevantes para os processos de panificação e cervejaria. Por exemplo, células de leveduras continuam fermentando a massa do pão mesmo quando submetidas a refrigeração, sendo esta uma característica indesejável nas cepas de panificação. Uma vez que a maltose é o principal açúcar encontrado na massa do pão, a influência do frio (10ºC) na fermentação deste açúcar foi analisada em uma cepa selvagem de S. cerevisiae, e numa cepa csf1. mutante incapaz de transportar glicose e leucina a baixas temperaturas. A baixa temperatura afeta a cinética da fermentação por diminuir a velocidade de crescimento e rendimento celular final, com quase nenhum etanol produzido a partir de maltose pelas células selvagens a 10oC. A cepa csf1. foi incapaz de crescer em maltose a 10oC, indicando que o gene CSF1 é também necessário para a utilização de maltose a baixas temperaturas. Entretanto, o mutante csf1. também mostrou inibição acentuada da fermentação de glicose e maltose por estresse salino, além de uma significativa sensibilidade a uma série de compostos tóxicos, incluindo higromicina B, Ca2+, tetrametilamônio e pH ácido, mas não a altas concentrações de K+. Estes resultados indicam que o gene CSF1 estaria também envolvido na regulação de outros processos fisiológicos, incluindo a homeostase iônica. Em cervejaria a otimização do processo fermentativo depende da eficiente utilização de maltose e maltotriose pelas células de S. cerevisiae. Entretanto, as leveduras têm dificuldade de fermentar a maltotriose, e a incompleta utilização deste açúcar resulta, por exemplo, em uma cerveja de baixa qualidade, com um elevado extrato filtrável e sabor atípico. Para tentar compreender melhor a metabolização da maltotriose, a utilização deste açúcar foi analisada em cepas de S. cerevisiae com genótipos definidos e deletadas, ou não, em permeases específicas. A cepa selvagem analisada cresce lentamente em maltotriose, somente após uma extensa fase lag, sem produzir etanol durante o crescimento. Este fenótipo (crescimento lento e não fermentativo) não foi alterado pela deleção do gene AGT1, indicando que outro(s) transportador(es) estaria(m) provavelmente envolvido(s) na lenta utilização da maltotriose. Por outro lado uma cepa deletada nos transportadores de hexoses (hxt1-7. gal2.) fermentou eficientemente a maltotriose, mas quando o gene AGT1 foi deletado do genoma a cepa voltou a respirar este açúcar, indicando que a permease codificada pelo AGT1 é fundamental para a fermentação da maltotriose. Uma vez que a expressão constitutiva dos genes MAL é uma característica altamente desejável em cepas de panificação e cervejaria, decidiu-se analisar a contribuição que um gene regulador constitutivo teria na fermentação da maltotriose. Enquanto que algumas cepas MAL constitutivas foram capazes de fermentar eficientemente a maltotriose, a transformação de uma cepa selvagem incapaz de fermentar este açúcar com um plasmídeo contendo o gene MAL63c não melhorou a produção de etanol a partir de maltotriose. Estes resultados indicam a existência de outros fatores necessários para a eficiente fermentação de maltotriose por Saccharomyces cerevisiae. and maltotriose fermentation by Saccharomyces cerevisiae is of prime importance for several industrial applications of this yeast. In this work we have analyzed several aspects of the metabolism of these sugars relevant to the brewing and baking processes. For example, yeast cells still ferment the dough under refrigerated conditions, a characteristic highly undesirable for backing strains. Since maltose is the most abundant sugar in backing dough, we have studied the influence of cold temperature (10oC) on the fermentation of maltose by a S. cerevisiae wild-type strain, and a csf1. mutant impaired in glucose and leucine uptake at low temperatures. Cold temperature affected the fermentation kinetics by decreasing the growth rate and the final cell yield, with almost no ethanol been produced from maltose by the wild-type cells at 10oC. The csf1. strain did not grew on maltose when cultured at 10oC, indicating that the CSF1 gene is also required for maltose consumption at low temperatures. However, this mutant also showed increased inhibition of glucose and maltose fermentation under salt stress, and an increased sensitivity to several toxic compounds, including hygromycin B, Ca2+, tetramethylammonium and acidic pH, but not to high K+ concentrations. These results indicate that the CSF1 gene is probably involved in the regulation of other physiological processes, including ion homeostasis. Fermentation process optimization in the brewing industry depends on the efficient utilization of maltose and maltotriose by S. cerevisiae. However, yeasts have a difficulty to ferment maltotriose, and the incomplete utilization of this sugar results, for example, in a low quality beer with high content of fermentable sugars and atypical flavor profiles. To further understand the utilization of maltotriose, we analyzed the uptake of this sugar in yeasts strains with defined genotypes, deleted or not in specific transporters. The wild-type strain analyzed grows slowly in maltotriose, only after an extensive lag phase, and no ethanol was produce during growth. This phenotype (slow growth with no fermentation) was not affected by deletion of the AGT1 gene, indicating that probably other transporters may be involved in the slow utilization of maltotriose. On the other hand, a strain that was deleted in the hexose transporters (hxt1-7. gal2.) fermented maltotriose efficiently, but when the AGT1 gene was disrupted from the genome the strain started to respired the sugar, indicating that the AGT1 permease is required for maltotriose fermentation. Since the constitutive expression of MAL genes is a desired property of baker#s and brewery#s strains, we analyzed the contribution that a constitutive regulatory gene would have in maltotriose fermentation. While some MAL constitutive strains were capable to efficiently ferment maltotriose , the transformation of a wild-type strain incapable to ferment this sugar with a plasmid harboring the MAL63c gene did not improve ethanol production from maltotriose. These results indicate the existence of other factors required for the efficient fermentation of maltotriose by Saccharomyces.
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Liu, Mei-Ling. "Plasmid-Linked Maltose Utilization in Lactobacillus spp. Isolated from Meat." DigitalCommons@USU, 1987. https://digitalcommons.usu.edu/etd/5342.
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Five strains of Lactobacillus plantarum and four strains of Lactobacillus species isolated from fresh meat were examined for the presence of plasmid DNA. All strains examined contained between one and five plasmids ranging in molecular mass from 1.3 to 51.6 (Mdal). Plasmid-curing experiments suggest that maltose utilization is associated with a 51 Mdal plasmid in Lactobacillus sp. DB29 and 42 Mdal plasmids in Lactobacillus spp. DB27, DB28, DB31. Southern blot DNA-DNA hybridization showed homology between the maltose plasmid from Lactobacillus sp. DB29 and several plasmids from the other Lactobacillus spp.
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Kirsch, Monika. "Low temperature induces raffinose family oligosaccharide and maltose accumulation in plants." Göttingen Cuvillier, 2009. http://d-nb.info/999186418/04.
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Day, Matthew. "Production and analysis of escherichia coli groE chaperonins." Thesis, Birkbeck (University of London), 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243960.
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Seibold, Gerd Michael. "Charakterisierung des Glycogen- und Maltosestoffwechsels von Corynebacterium glutamicum." [S.l. : s.n.], 2008. http://nbn-resolving.de/urn:nbn:de:bsz:289-vts-63818.
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Machado, Fernando de Almeida. "Esvaziamento gastrico de soluções de açucares e de leite de vaca sem e com acrescimo de carboidratos em ratos adultos." [s.n.], 1995. http://repositorio.unicamp.br/jspui/handle/REPOSIP/308877.
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Orientador: Edgard Ferro CollaresTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Ciencias Medicas
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Resumo: O presente trabalho teve como objetivo, numa primeira etapa, verificar, em ratos adultos, as retenções gástricas (RG) de soluções aqüosas de lactose, sacarose e maltose, todas na concentração a 10% (p/v), e a influência da associação combinada entre dois desses açúcares sobre o esvaziamento gástrico e, numa segunda etapa, verificar se essa influência se mantém quando se adiciona sacarose ou maltose ao leite de vaca integral. Foram utilizados 120 ratos Wistar machos com idade entre 8 a 10 semanas, que receberam suas respectivas refeições de prova por via oro gástrica, através de uma sonda metálica, no volume de 2 ml/l00 g de peso. As soluções de açúcares foram marcadas com fenol vermelho (6 mg/dl) e os leites foram marcados com PEG 4000 (2 g/dl). As RG foram determinadas calculando-se a quantidade de marcado retido no estômago, após leitura espectrofotométrica. Na primeira etapa do experimento, foram utilizados 48 animais, divididos eqüitativamente em 6 subgrupos, de acordo com a refeição de prova utilizada: lactose 10% (L), sacarose 10% (S), maltose 10% (M), lactose 5% + sacarose 5% (LS), lactose 5% + , maltose 5% (LM) e sacarose 5% + maltose 5% (SM) (p/v). A RG foi avaliada após 15 minutos da infusão orogástrica da refeição de prova. Na segunda etapa do estudo, foram utilizados 72 animais divididos em 3 subgrupos eqüitativos, de acordo com a refeição-de prova: leite de vaca integral sem acréscimo de açúcar, leite de vaca com sacarose 5% (p/v) e leite de vaca com maltose 5% (p/v). Para cada refeição de prova, foi avaliada a RG ao tempo de 15, 30 e 45 minutos, utilizando-se, em cada momento, 8 animais em cada subgrupo. Foram utilizados os testes estatísticos não paramétricos de Kruskal- W allis, com níveis de significância de 10%. Em seguida, foram feitos os testes de comparações múltiplas, com níveis de significância de 1% e 2%, respectivamente. Os resultados do estudo mostram que são significativas as diferenças entre as RG das soluções de L e M, SeM, S e SM, L e LM, L e SM. A maltose, associada à lactose ou à sacarose, promoveu retenção gástrica significativamente maior que a de solução de lactose ou sacarose isoladas, mantendo-se a densidade energética
Abstract: This study has the goals of establishing the gastric retentions of aqueous solutions of lactose, sucrose and maltose, all of them at 10% (w/v), and also the influence of associations between two of these sugars on the gastric retentions. Later on, it was studied this influence on gastric retention using sucrose or maltose on whole cow's milk. It was used 120 Wistar male rats, aged from 8 to 10 weeks. The rats received a test meal (2 rnl/l00g weight) with a marker by orogastric route through a metal tube. The markers used were phenol red (6 mg/dl) in the sugars aqueous solutions and polyethylene glycol (PEG) 4000 (2 g/dl) in the cow's milk test meal. The gastric retention was measured by determining the amount ofthe marker staying in the stomach by spectrophotometry. During the first phase of the study, 48 rats were distributed in 6 subgroups, each of them received test meal of aqueous solution of lactose 10% (L), sucrose 10% (S), maltose 10% (M), lactose 5% + sucrose 5% (LS), lactose 5% + maltose 5% (LM) and sucrose 5% + maltose 5% (SM) (w/v). The gastric retentions were determined 15 minutes after the infusion of test meal. In the second phase it was used 72 rats which were equaly distributed in 3 subgroups, according to the test meal: whole cow's milk without sugar addition, cow's milk plus suciose 5% (w/v) and cow's milk plus maltose 5% (w/v). The determinations of gastric retentions were performed at 15, 30 and 45 minutes after the orogastric infusion, being 8 animals used for each time and each test meal. In both phases of the study it was utilized the Kruskal- Wallis test, being a. = 10%. Later, the multiple comparisions were calculated with a. = 1 % and 2%, respectively, to first and second phases. There are significant differences between gastric retention of aqueous solutions of lactose and maltose (L x M), sucrose and maltose (S x M), sucrose and sucrose + maltose (S x SM), lactose and lactose + maltose (L x LM), lactose and sucrose + maltose (L x SM). The gastric retention of maltose plus lactose or maltose plus sucrose was significantly larger than those oflactose or sucrose at the same energetic density
Doutorado
Doutor em Saude da Criança e do Adolescente
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Engström, Henrik. "Development of Flourescence-based Immunosensors for Continous Carbohydrate Monotoring : Applications for Maltose and Glucose." Doctoral thesis, Högskolan i Kalmar, Naturvetenskapliga institutionen, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:hik:diva-45.
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Weak affinity interaction of monoclonal antibodies and carbohydrate antigens can be detected and quantified by alterations in the antibodies' intrinsic tryptophan fluorescence. These weak/transient binding events have been monitored by total internal reflection fluorescence (TlRF) by facilitating the change in intrinsic tryptophan fluorescence. This immunosensor followed instant changes in the antigen concentration with rapid association- and dissociation rate constants reaching equilibrium in a short time, without the need for regeneration. Furthermore, in a competition assay with extrinsic fluorescence labeling, it was established that Förster/fluorescence resonance energy transfer (FRET) can be applied for weak and transient interactions. By entrapping components in small semipermeable capsules, aconvenient flow system was fabricated allowing on-line measurements of maltose. Quantification of maltose concentration was achievable in the mM-range without need for regeneration.High specificty for maltose was exhibited in crude food-samples with quantification in accordance with batch analysis. Furthermore, a monoclonal antibody was developed for potential use as a glucose immunosensor for diabetes. Its ability to interact with glucose was determined by competitive weak affinity chromatography (WAC) to approximately 19 mM in dissociation constant. This antibody was developed to bind monosaccharides, especially glucose, by utilizing crossreation with a carbohydrate dextran polymer. Selectivity for glucose was greater than for the similar monosaccharides, mannose and galactose. This antibody, or a fragment, in a fluorescence platform is an alternative to monitor glucose in vivo where other glucose-binders might fail.Att känna igen en motståndare är viktigt i många sammanhang, inte minst i kroppens immunförsvar som är utvecklat för att angripa främmande ämnen i kroppen. Antikroppen spelar en central roll i immunförsvaret där den lär sig att känna igen sin motståndare (antigen) och därmed binda sitt antigen. De antikroppsproducerande cellerna kan användas i laboratoriet för att producera antikroppar som härstammar från försöksdjur. I denna avhandling har antikroppar använts som binder betydligt svagare till antigenet än vad man i de flesta analyser använder sig av för att t.ex. detektera sjukdomar. Antikroppar som binder till olika typer av socker, däribland maltsocker (maltos) och blodsocker (glukos) har studerats. Dessa antikroppar har använts för att undersöka hur hårt de binder till sitt antigen beroende på temperatur och om antikropparna kan känna igen liknande motståndare (korsreaktivitet). Fördelen med dessa svaga bindningar är att antikroppen snabbt kan binda in och släppa sitt antigen istället för att nästan permanent sitta på sitt antigen, som vid starka bindningar. Bindningens styrka (affinitet) har i avhandlingen studerats med hjälp av fluorescensteknik och affinitets-separation. Den maltosbindande antikroppen har använts tillsammans med fluorescensteknik för att designa två olika biosensorer (immunosensorer). Immunosensorerna kan mäta förändringen av maltoskoncentration över tid, vilket är attraktivt i t.ex. livsmedelsindustrin när man vill mäta maltoshalten kontinuerligt under tillverkningen. Den glukosbindande antikroppen har använts i affinitets-separation för att bestämma dess affinitet mot glukos och olika polymerer av glukos. En glukosbindande antikropp är åtråvärt för att t.ex. kontinuerligt mäta koncentrationen av blodsocker genom huden hos diabetiker och därmed minska antalet blodprover man idag behöver ta.
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Cerqueira, Vanessa Cassoni [UNESP]. "Produção de frutose a partir de hidrolisado enzimático de amido de mandioca." Universidade Estadual Paulista (UNESP), 2012. http://hdl.handle.net/11449/101731.
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Universidade Estadual Paulista (UNESP)
Os produtos das hidrólises de amido são glicose, maltose e uma série de oligossacarídeos e polissacarídeos que encontram utilização principalmente na indústria de alimentos. Neste grupo enquadram-se os adoçantes que aditam sabores a produtos que são demandados por consumidores específicos. Atualmente o açúcar mais utilizado no Brasil é a sacarose, produto extraído da cana-de-açúcar, e o mais utilizado mundialmente é a frutose obtida a partir da hidrólise do milho e posterior isomerização da glicose para frutose. A frutose apresenta capacidade edulcorante 30% maior que a sacarose, 2,5 vezes maior que a glicose e 2 vezes mais solúvel que a glicose, com isso, pode ser utilizada em menor quantidade, diminuindo o poder calórico do alimento e viabilizando sua utilização no tratamento da obesidade. Levando em consideração a importância dos adoçantes para o mercado de alimentos, o presente trabalho teve como objetivo realizar estudos sobre o processo de obtenção da frutose a partir de amido de mandioca. Para a execução dos ensaios utilizou-se fontes comerciais de α– amilase e amiloglucosidase, Liquozyme Supra 2.2X e Saczyme 750 AGUg-1, respectivamente, aplicadas em substrato de amido de mandioca em reator agitado com temperatura controlada. Após o processo de hidrólise enzimática, o hidrolisado passou por um processo de purificação utilizando terra diatomácea e carvão ativado em quatro temperaturas (30, 40, 50 e 60°C), com a finalidade de remoção de contaminantes originários da matéria prima, que levam a odor, cor e sabores indesejáveis. Após o tratamento com carvão ativo e terra diatomácea foram realizados ensaios para estabelecer os melhores parâmetros para a realização do processo de isomerização, buscando a conversão de parte da glicose à frutose, utilizando a enzima...
The products of starch hydrolyses are glucose, maltose and a series of oligosaccharides and polysaccharides which have their main utilization in food industry. This group comprises sweeteners that add flavor to products demanded by specific consumers. Currently the most used sugar in Brazil is sucrose, a product extracted from sugarcane, while the most used sugar worldwide is fructose obtained from maize hydrolysis and subsequent glucose isomerization to fructose. The sweetening capacity of fructose is 30% higher than that of sucrose and 2.5-fold higher than that of glucose; in addition, fructose is 2-fold more soluble than glucose and thus can be used in smaller quantities, decreasing the food’s caloric potential and making its use viable in obesity treatment. Considering the importance of sweeteners for the food market, the present study aimed to investigate the process of fructose production from cassava starch. The assays were performed by using commercial sources of α–amylase and amyloglucosidase, Liquozyme Supra 2.2X and Saczyme 750 AGUg-1, respectively, applied to cassava starch substrate in an agitated reactor at controlled temperature. Following the process of enzymatic hydrolysis, the hydrolysate underwent a purification process using diatomaceous earth and activated charcoal at four temperatures (30, 40, 50 and 60°C), in order to remove contaminants originated from the raw material, which lead to undesirable smell, color and flavor. After the treatment with activated charcoal and diatomaceous earth, assays were carried out to establish the best parameters for the isomerization process, aiming at the conversion of part of glucose into fructose, using the enzyme isomerase. The process selected for the studies was in a continuous system where the glucose syrup, previously purified, was continuously pumped... (Complete abstract click electronic access below)
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Dodsworth, Steven James. "Cloning, sequencing and expression of the Aeromonas salmonicida maltose-inducible porin gene." Thesis, University of Nottingham, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359863.
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Kaplan, Fatma. "Beta-amylase induction and the protective role of maltose during temperature shock." [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0008330.
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Rodrigues, Sueli. "Estudo da sintese enzimatica de dextrana na presença de maltose como aceptor." [s.n.], 2003. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266523.
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Orientadores: Liliane M. F. Lona, Telma F. FrancoTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica
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Doutorado
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LEMEE, LENAICK. "Le maltose en synthese glycosidique acylation d'oligomeres de l'amylose et de l'amidon." Rennes 1, 2000. http://www.theses.fr/2000REN10095.
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L'amidon est une ressource agricole, renouvelable, bon marche et disponible en quantite importante. L'utilisation de l'amidon en tant que materiau devient un sujet d'autant plus interessant que le recyclage des matieres plastiques d'origine petrochimique reste problematique et que la demande en materiaux biodegradables augmente rapidement. L'hydrophilie naturelle de ce polysaccharide est une contrainte majeure qui limite le developpement des materiaux a base d'amidon. Une alternative consiste a utiliser des esters d'amidon moins hydrophiles mais dont la preparation necessite jusqu'ici la presence de solvant. La mise au point d'une reaction d'esterification transposable en machine selon un procede continu ou discontinu permettrait de developper l'utilisation industrielle des esters d'amidon par exemple dans le domaine de l'emballage et des polymeres biodegradables. Par ailleurs l'hydrolyse chimique et/ou enzymatique de l'amidon fournit egalement le maltose qui est un substrat de depart particulierement interessant en synthese glycosidique et qui peut etre utilise pour la preparation de molecules a haute valeur ajoutee. Dans un premier chapitre, apres une rapide mise au point sur la synthese glycosidique, nous decrivons la preparation des -maltoside et -maltotrioside de methyle ces deux oligosaccharides modeles de l'amylose ainsi que l'-d-glucopyranoside de methyle ont ensuite ete partiellement et regioselectivement acyles en utilisant une reaction de transesterification avec des esters de glycidyle ou de vinyle. La deuxieme partie de cette these est consacree a la preparation du motif trisaccharidique de l'acarbose qui est un principe actif utilise dans le traitement du diabete. Notre approche s'appuie sur une strategie 1 + 2 utilisant un donneur de fucopyranosyle et un accepteur maltosidique prepares respectivement a partir du d-galactose et du maltose. Au cours de ce travail nous avons montre les influences respectives du solvant et du groupe protecteur introduit sur la position 4 du donneur de glycosyle sur la stereoselectivite du couplage glycosidique. Enfin, au cours du troisieme chapitre, nous avons transpose les reactions d'acylation decrites dans le chapitre 1 a des polymeres synthetiques puis a l'amidon. Nous avons egalement etudie la reaction de formiatation de l'amidon et montre que certains formiates d'amidon peuvent etre utilises comme substrats des reactions de transesterification.
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Eduardo, Mariana de Paula. "Hidrólise enzimática de mandioca e puba para a obtenção de xarope de maltose." Universidade de São Paulo, 2003. http://www.teses.usp.br/teses/disponiveis/11/11141/tde-07042003-142026/.
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Atualmente o consumo de xarope de maltose vem crescendo devido ao seu uso em cervejarias e está substituindo progressivamente os adjuntos amiláceos. O xarope de maltose é, tradicionalmente, produzido por meio da hidrólise ácida e/ou enzimática de amido ou flocos de milho. Este trabalho teve como objetivo analisar a possibilidade de obtenção de maltose a partir de outras matérias-primas amiláceas como a mandioca e a puba (produto derivado da fermentação da mandioca) pela ação da a-amilase bacteriana e da a-amilase fúngica sem que fosse necessária a extração do amido. Amostras de mandioca e puba com 10, 20 e 30% de sólidos foram incubadas com a-amilase bacteriana termoestável durante 10, 20 e 30 minutos a 80 0 C, adicionando-se em seguida, µ-amilase fúngica e incubando-se as amostras durante 48 horas a 55 0 C. O grau de sacarificação, expresso em dextrose equivalente (DE), foi determinado pelo método DNS em vários intervalos de tempo. Glicose e maltose foram determinadas por HPLC após 48 horas de sacarificação. Os resultados mostraram que o tempo de ação da a-amilase bacteriana não causou diferenças significativas no grau de hidrólise entre as amostras, mas a concentração de sólidos influiu significativamente no grau da liquefação das amostras. O comportamento das curvas do grau de sacarificação foi semelhante para todos os tratamentos tanto da mandioca quanto da puba. O conteúdo de maltose nas amostras variou entre 30-60% e a glicose entre 0-10% caracterizando um xarope com alto teor de maltose. A eficiência de hidrólise ficou abaixo do esperado. Entretanto, esse fato pode ser explicado pela utilização da mandioca sem extração prévia do amido e pelas dificuldades na extração dos sólidos por centrifugação. Pode-se afirmar que tanto a mandioca quanto à puba podem ser utilizadas como matéria prima em substituição ao milho na obtenção de xarope de maltose através da hidrólise enzimática. A puba, porém, é de mais fácil manuseio sendo que o tratamento com 20% de sólidos, exposto durante 10 minutos a a-amilase bacteriana proporcionou maior rendimento, atingindo 4,2 kg de maltose e 0,3 kg de glicose por 100 kg de mandioca fresca além de proporcionar menor quantidade de resíduo sólidos de 13,7 kg.Nowadays the consumption of maltose syrups is increasing due to its utilization in breweries where it replaces starch adjuncts. Traditionally maltose syrup has been produced from cornstarch or pellets using acid and/or enzymatic hydrolysis. The objective of this work was to evaluate the possibility of obtaining maltose from starch sources other than maize, such as cassava roots or puba, a fermented cassava product, without extraction of the starch, using bacterial a-amylase and fungal a-amylase for starch hydrolysis. Cassava and puba samples with 10, 20 and 30% dry matter were incubated with termostable bacterial a-amylase for 10, 20 and 30 minutes at 80 0 C, followed by the addition of fungal a-amylase. The samples were incubated for 48 hours at 55 0 C. The degree of saccharification, expressed as dextrose equivalent (DE), was determined by the DNS method. The glucose and maltose contents of the hydrolysate were determined after 48 hours by HPLC. The results showed that the time of action of a-amylase did not influence the degree of saccharification of the samples but the solids concentration significantly affected the hydrolysis degree. The saccharification degree curves were similar for both cassava and puba. The maltose content of the samples varied between 30-60% and the glucose content between 0-10%, which characterized them as "High maltose syrups". The hydrolysis efficiency was lower than expected. However, this fact could be explained by the use of cassava without extraction of the starch and by the difficulty of extracting the solids by centrifugation. It was concluded that for replacement of corn starch, both cassava roots and puba could be used as raw materials for maltose syrup production by enzymatic hydrolysis. However the puba was easier to handle than cassava. The puba treatment consisting of 20% of solids and 10 minutes exposure to a-amylase gave the highest yield reaching 4.2 kg of maltose and 0.3 kg of glucose per 100 kg of raw cassava, in addition to a lower solids residue of 13.7 kg.
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Derkaoui, Meriem. "Métabolisme du carbone et virulence chez Neisseria meningitidis." Thesis, Paris, AgroParisTech, 2015. http://www.theses.fr/2015AGPT0047/document.
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Neisseria meningitidis possède un PTS incomplet. Constitué des composants générales EI et HPr et de deux EIIAs (EIIANtr et EIIAMan), ce système ne permet pas le transport des sucres chez cette bactérie. Cependant, nous avons confirmé que la cascade de phosphorylation (EI HPr EIIANtr) est fonctionnelle et que HPr est aussi phosphorylée sur sa Ser-46 par une HprK/P.Dans l’objectif d’étudier l’effet de HPr sur la virulence de N. meningitidis, nous avons construit un mutant ΔptsH chez N. meningitidis 2C4-3. Le mutant ΔptsH a montré une faible survie chez la souris, une faible production de la capsule, une meilleure adhérence aux cellules épithéliales et un niveau élevé de cellules apoptotiques, par rapport à la souche sauvage. HPr semble intervenir dans la virulence de N. meningitidis en interagissant avec la protéine CrgA. L’interaction HPr/CrgA est plus forte quand HPr est phosphorylée sur sa Ser-46 par HprK/P.N. meningitidis utilise le glucose et le maltose comme seuls sucres. Nous avons identifié une perméase à glucose (GlcP) et une perméase à maltose (MalY), responsables du transport de ces sucres. Une perméase putative à gluconate (GntP) a été également identifiée chez N. meningitidis 2C4-3. Cette perméase n’assure pas le transport du gluconate, dans les conditions testées. La délétion de gntP chez N. meningitidis 2C4-3 induit une meilleure croissance sur glucose et une bonne survie du mutant ΔgntP chez la souris, par rapport à la souche sauvage. La fonction réelle de la perméase GntP chez N. meningitidis reste inconnue et suscite des études ultérieuresNeisseria meningitidis has an incomplete PTS composed of general proteins EI and HPr and two EIIAs (EIIANtr and EIIAMan). This system does not allow the transport of sugars in this bacterium. However, we confirmed that the phosphorylation cascade (EI HPr EIIANtr) is functional and HPr is also phosphorylated at its Ser-46 by an HprK/P.In order to study the effect of HPr on meningococcal virulence, we constructed a ΔptsH mutant in N. meningitidis 2C4-3. Compared to the wild-type strain, the ΔptsH mutant showed poor survival in mice, low production of capsule, better adherence to epithelial cells and high levels of apoptotic cells. HPr appears to be involved in the virulence of N. meningitidis by interacting with CrgA protein. The HPr/CrgA interaction is stronger when HPr is phosphorylated at its Ser-46 by HprK/P.N. meningitidis uses glucose and maltose as the only sugars. We identified permeases for glucose (GlcP) and maltose (MalY), which catalyze the uptake of these sugars.A putative gluconate permease (GntP) has also been identified in N. meningitidis 2C4-3. Under the conditions tested, this permease did not catalyze the transport of gluconate. Compared to the wild-type strain, deletion of gntP in N. meningitidis 2C4-3 induced faster growth on glucose and a better survival of the mutant in mice. To underst and the function of the GntP permease in N. meningitidis further studies will have to be carried out
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Zhang, Xiaochen 1969. "The binding modes of maltose binding protein with different ligands studied by NMR /." Thesis, McGill University, 1997. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=27438.
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Maltose Binding Protein (MBP) of Escherichia Coli, a kind of periplasmic protein, can bind its ligands interacting predominantly either with their anomeric end (end-on binding) or with the middle of the maltodextrin chain (middle binding). Using NMR spectroscopy, we have studied the modes by which maltose, linear maltodextrin and some derivatives like $ beta$-cyclodextrin bind to MBP. 1D proton difference spectra and 2D HSQC proton-nitrogen correlation spectra were acquired of MBP in the presence of different ligands. Spectra with linear maltodextrins showed many common features and were distinctly different from those of MBP with $ beta$-cyclodextrin. 2D HSQC spectra suggest further that MBP- $ beta$-cyclodextrin adopts an open form conformation similar to that of ligand free MBP because of the surprisingly similarity of their spectra. Ligands such as $ beta$-cyclodextrin, can not be transported into the cyto-plasm but have high affinity for MBP, multiple $ alpha$(1-4) linkages and no reducing end. These ligands bind to MBP mainly by the middle binding mode. This suggests that this mode determines high affinity binding of ligand to MBP, but doesn't produce a physiologically active complex.
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Zhang, Xiaochen. "The binding modes of maltose binding protein with different ligands studied by NMR." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq29813.pdf.
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Greller, Gerhard. "Molekulare und biochemische Charakterisierung des Trehalose-Maltose-Transportsystems des hyperthermophilen Archaeons Thermococcus litoralis." [S.l. : s.n.], 2001. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB9676828.
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Baldassarri, Hilary. "A musica une e ensina: o projeto DIRE FARE MUSICARE de Raffaele Maltoni." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/9823/.
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Abstract
Il presente elaborato espone una proposta di traduzione in portoghese del libro DIRE FARE MUSICARE dell’autore italiano Raffaele Maltoni. Il libro contiene 15 canzoni che accompagnano varie attività musicali, motorie e ludiche. Charly, il simpatico mostro viola, guida i bambini durante il percorso musicale.
All’introduzione sul genere della letteratura infantile e sull’importanza della musica nell’apprendimento, segue un analisi del testo e un commento alla traduzione.
Sinopse
O presente trabalho apresenta uma proposta de tradução em português do livro DIRE FARE MUSICARE do autor italiano Raffaele Maltoni. O livro contem 15 canções que acompanham atividades musicais, motoras e lúdicas. Charly, o simpático monstro violeta, acompanha as crianças ao longo do percurso musical.
À introdução sobre o género da literatura infantil e sobre a importância da música na aprendizagem, segue uma analise do texto e um comentário à tradução.
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Merstorf, Céline. "Stabilité conformationnelle et dépliement de la protéine MalE : Étude par nanopore et par spectroscopie RMN." Thesis, Cergy-Pontoise, 2011. http://www.theses.fr/2011CERG0571/document.
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Nous avons étudié le couplage dépliement-transport de la Maltose Binding Protein (MBP ou MalE), une protéine périplasmique d'E. Coli et d'un mutant instable, le MalE219, en fonction de la concentration d'un agent dénaturant, le chlorure de guanidium (GdnHCl) à l'échelle de la molécule unique. La technique utilisée est basée sur la détection électrique du transport de macromolécules à travers un nanopore protéique (l'Aérolysine d'Aeromonas Hydrophila) inséré dans une bicouche lipidique plane. Les résultats obtenus ont été comparés à ceux obtenus lors d'une précédente étude réalisée à travers un autre nanopore protéique, l'alpha-hémolysine du Staphylocoque doré, de géométrie et de charge nette différente. Nous avons montré l'existence de temps courts et longs de blocage du courant associés à des protéines dépliées ou partiellement repliées. La fréquence des blocages du courant permet d'obtenir la fraction de protéine dépliée passant à travers le pore en fonction de la concentration en GdnHCl. Les courbes de dénaturation obtenues avec les deux pores montrent un comportement sigmoïdale très similaire. Le type de pore n'influence donc pas la dénaturation des protéines, mais uniquement leur dynamique de transport. En revanche, la courbe de dénaturation du mutant instable présente un déplacement vers les concentrations plus faibles en GdnHCl. Il a été montré également que la présence du maltose comme ligand sur le MalE219 stabilise nettement sa structure. Pour La MBP, les temps de blocages longs diminuent avec l'augmentation de la concentration de GdnHCl montrant une dynamique de transition vitreuse . Cette technique est appropriée à l'étude du dépliement et des changements de conformation de protéines, mais ne permet pas d'obtenir des informations structurales sur les états intermédiaires de repliement. Ainsi, la spectroscopie RMN a été utilisée pour tenter de caractériser ces états intermédiaires de repliement, notamment par la méthode d'échange proton-deutérium. Elle consiste à suivre les cinétiques d'échange des résidus de la protéine sur des spectres 2D 1H-15N HSQC à différentes concentrations de GdnHCl.Ainsi 180 résidus sur les 370 que compte la MBP ont été suivis lors de la dénaturation en présence de GdnHCl. Les deux hélices en C-terminal sont très accessibles au solvant et se dénaturent facilement. La MBP est composée de deux domaines globulaires, le domaine N-ter et le domaine C-ter. Les éléments de structures secondaires situés dans la zone intermédiaire entre les deux domaines (principalement des brins β) sont particulièrement affectés par l'agent dénaturant. D'autres structures secondaires dans les domaines globulaires sont très protégées et plutôt stables. Il est donc proposé que les protéines partiellement dépliées s'insèrent dans le pore par l'extrémité C-terminal et que des parties de structuration tertiaire restent stable entraînant le blocage du poreWe study the unfolding-transport mechanism of the Maltose Binding Protein (MBP or MalE), a periplasm protein of E. Coli and a destabilised variant, the MalE219, as the function of the concentration of denaturing agent, Guanidine Hydrochloride(GdnHCl) at the single molecule level. The technique is based on the electrical detection of the macromolecule transport through a nanometer-scale channel, Aerolysin channel, inserted into a planar lipid bilayer. Results obtained were compared to previous data with another channel, the alpha-Hemolysin. Both channels have different geometry and net charge.We show that we can distinguish unfolded states from partially folded ones with aerolysin pore.Unfolded proteins induce short current blockades, their duration is constant as a function of the concentration of denaturing agent. Partially folded proteins exhibit long blockades whose life times decrease as the concentration of GdnHCl increase, this indicates a possible glassy dynamics.The frequency of the short current blockades increases as the concentration of denaturing agent increases, following a sigmoidal denaturation curve.The unfolding curve of native MBP with Aerolysin pore is similar to the one previously measured with Hemolysin channel. The denaturation curve of the destabilized variant obtained with Aerolysin is shifted towards lower value of GdnHCl concentration in agreement with bulk measurements. We show also that the addition of maltose stabilizes the structure of MalE219. This nanopore recording technique is also suitable for the study of unfolding and conformation changes of proteins.In order to obtain structural informations that nanopore recording cannot provides, the structure of MBP along its denaturation curve was studied by NMR spectroscopy. The Hydrogen-exchange method known to be sensitive to folding intermediates was specially used. It consists in tracking hydrogen-deuterium exchange rates for amino on the 2D 1H-15N HSQC spectra.Thus, 180 residus of 370 for MBP was followed during denaturation in the presence of GdnHCl. The two last helices in C-terminal of MBP are accessible to the solvent and are denaturated easily. MBP is a two domains protein, N-ter domain and C-ter domain. It was found out that the C- and D-domain of MBP (mainly alpha-helices) could be relatively stable in presence of denaturing agent and that beta strands which make the link between the two domains would be affected by the denaturing agent. It was proposed that partially unfolded proteins enter the pore by the C-terminal end and that stable tertiary structure still present block the pore
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Hiller, Rebecca Marie. "Mathematical modeling of maltose uptake system in E. coli using nanodisc fluorescence quenching data." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/44253.
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Recent data measured in nanodiscs conflicts with the standard theory of maltose transport in the MalE-MalFGK₂ uptake system found in E. coli. Nanodisc fluorescence quenching data suggest an alternate pathway in which unliganded MalE binds the P-open transporter, facilitating maltose acquisition. Nanodisc data also indicate that MalE regulates maltose uptake at high concentrations. We analyzed four mathematical models of the maltose uptake system: the distinct standard and alternate models, and two integrated models. Nanodisc fluorescence quenching data and nonlinear regression analysis were used to fit equilibrium constants and kinetic rates. The flux through each pathway in an integrated model was calculated using asymptotic analysis and fit parameter values. We conclude that it is likely that transport occurs when liganded MalE associates to a P-open conformation of MalFGK₂, rather than binding to the P-closed transporter as suggested by the standard model. The standard pathway was calculated to be negative, i.e. to occur in reverse as a means of regulating maltose uptake at high concentration. This analysis conflicts with the standard model in which liganded MalE binds to a closed transporter and triggers an opening of the transporter proteins which in turn open the liganded MalE. The analysis also found that a relatively small amount of maltose transport may occur through the alternate pathway involving unliganded MalE.
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Lautenschläger, Friedrich Stefan [Verfasser]. "Einfuss von Maltose-modizierten Polyethylenimin-Nanopartikeln auf mesenchymale Stammzellen und Osteoblasten / Friedrich Stefan Lautenschläger." Gießen : Universitätsbibliothek, 2017. http://d-nb.info/1137466065/34.
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L'Hote, Hervé. "Etude génétique et enzymatique de la fermentation du maltose dans une levure de brasserie." Grenoble 2 : ANRT, 1986. http://catalogue.bnf.fr/ark:/12148/cb37599184c.
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Chapon, Christine. "De la régulation de l'expression du système maltose chez Escherichia coli et Klebsiella pneumoniae." Grenoble 2 : ANRT, 1986. http://catalogue.bnf.fr/ark:/12148/cb37596607k.
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Grand, Maxime. "Régulation des opérons Maltose/Maltodextrines et Gentiobiose induits en contexte d'infection chez Enterococcus faecalis." Thesis, Normandie, 2019. http://www.theses.fr/2019NORMC226.
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Les entérocoques sont des bactéries commensales de l'Homme majoritairement rencontrées dans le tractus digestif. En dépit du caractère bénéfique pour leur hôte, ces microorganismes sont retrouvés au deuxième rang des bactéries responsables d'infection nosocomiales en France ces dernières décennies. Diverses études tendent à montrer que le métabolisme énergétique constitue un facteur crucial pour le processus infectieux des microorganismes. Lors de ce travail, nous nous sommes intéressés à l'étude des métabolismes de différents polymères de glucoses chez Enterococcus faecalis : les maltodextrines et le gentiobiose. L'utilisation du maltose et des maltodextrines est, chez cette bactérie, directement coordonnée au niveau transcriptionnel par le répresseur MalR. L'activité de ce régulateur est rapidement modulée par le maltose qui représente l'inducteur du système et par un corépresseur protéique : la protéine P Ser HPr qui, à l'inverse, favorise la répression exercée par MalR. Le métabolisme des maltodextrines complexes, mais pas le métabolisme du maltose, est également réprimé par le régulateur pléiotrope CcpA en coordination avec son cofacteur P Ser HPr en présence de glucose. La répression catabolique de l'opéron genBA, impliqué dans le métabolisme du β glycoside gentiobiose, est aussi assurée par ce régulateur CcpA en présence de glucose. Cet opéron genBA est responsable de l'import du gentiobiose par un PTS ainsi que de son catabolisme grâce à une hydrolase. L'expression de cette structure opéronique nécessite la présence de l'activateur transcriptionnel GenR actif en présence de l'inducteur gentiobiose 6' PEnterococci are commensal bacteria of Humans predominantly encountered in the digestive tract. Despite their beneficial activity for their host, these microorganisms became the second leading bacterial cause of hospital acquired infections in France for last decades. Some studies showed that the central metabolism is a critical factor for microorganisms infection process. In this study, we worked on the characterisation of metabolisms of the different glucose polymers maltodextrins and gentiobiose in Enterococcus faecalis. The maltose and maltodextrins utilization is coordinated in this bacterium transcriptionally by the MalR repressor. The MalR activity is rapidly modulated by the inducer maltose and by the co repressor P Ser HPr which strengthens the MalR DNA binding. The metabolism of long maltodextrins is also repressed by the pleiotropic regulator CcpA in complex with its essential cofactor P Ser HPr in presence of glucose. The Catabolite repression of the operon genBA, involved in metabolism of the β glycoside gentiobiose, is assumed by CcpA in presence of glucose. This operon genBA allows the gentiobiose uptake with a PTS and its catabolism by a hydrolase. The expression of this latter operon requires both the GenR transcriptional activator and the inducer gentiobiose 6' P
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Souza, Cristiane Santos de. "Análise molecular e estrutural da proteína ligadora de maltose (MalE) de Xanthomonas axonopodis pv. citri." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/42/42132/tde-23102009-130040/.
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A captação de maltose em bactérias é feita por um sistema transportador do tipo ABC composto por uma proteína ligadora de substrato (MalE), duas proteínas transmembrana e uma ATPase. No presente trabalho descrevemos a clonagem, expressão e análise bioquímica e estrutural da proteína MalE da bactéria fitopatogênica Xanthomonas axonopodis pv citri (Xac) O gene malE de Xac foi clonado em vetor de expressão pET28a, a proteína recombinante foi expressa em Escherichia coli e purificada por cromatografia de afinidade ao níquel. Amostras da proteína solúvel foram analisadas quanto à estrutura secundária, interação com possíveis ligantes, estabilidade frente a diferentes condições físico-químicas. Ensaios de cristalização possibilitaram a obtenção de cristais em diferentes condições, um deles apresentou grupo espacial P6122, mas não foi possível resolver a estrutura. Com base nas estruturas conhecidas de ortólogos de MalE, geramos um modelo estrutural para a proteína de Xac e foram feitas análises quanto à interação com trealose e maltose. Modelos estruturais dos componentes transmembrana (LacF e LacG) e ATPase (UgpC) do sistema transportador de maltose de Xac também foram gerados. Os resultados representam uma contribuição importante para o conhecimento sobre a fisiologia e sistemas de transporte de Xac.Maltose uptake in bacteria is mediated by an ABC transporter comprising a substrate binding protein (MalE), two transmembrane proteins, and one ATPase. In the present study, we describe the cloning, expression and biochemical as well as structural analyses of the MalE protein of the phytopagen Xanthomonas axonopodis pv citri (Xac). The malE gene of Xac was cloned in the pET28a expression vector, the recombinant protein was expressed in Escherichia coli and, subsequently, purified by nickel affinity chromatography. Samples of soluble protein were analyzed regarding secondary structure, interaction with putative ligants and stability under different physico-chemical conditions. Crystallization trials were carried out under different conditions, one particular condition yielded crystal with a P6122space group, but the structure was not solved. Based on known ortholog structures, a structural model for Xac MalE was obtained allowing interaction with modeled threhalose and maltose. Structural models the transmembrane (LacF and LacG) and ATPase (UgpC) components were also obtained. The present results represent an important contribution to the knowledge of the physiology and transporter systems found in Xac.
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Duplay, Pascale. "Approche genetique de la topologie fonctionnelle de la proteine affine du maltose chez escherichia coli." Paris 7, 1987. http://www.theses.fr/1987PA077001.
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SCHREIBER, VALERIE. "Mecanismes de regulation de l'activite de malt, l'activateur transcriptionnel du regulon maltose chez escherichia coli." Paris 6, 1999. http://www.theses.fr/1999PA066465.
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Chez les enterobacteries, le regulon maltose regroupe un ensemble d'operons dont les genes codent les proteines du systeme de transport et du metabolisme des maltodextrines et, chez klebsiella oxytoca, les proteines impliquees dans la secretion de la pullulanase. L'expression de ces operons est controlee par un activateur transcriptionnel specifique du regulon maltose, la proteine malt et par un regulateur global, la proteine crp. L'activite de malt (102 kda) est regulee, au niveau de la proteine, positivement par l'atp et le maltotriose et negativement par 3 proteines, malk, maly et aes. Dans un premier temps, a l'aide d'approches biochimiques et biophysiques, nous avons caracterise la structure quaternaire de malt en solution en presence de differentes combinaisons d'effecteurs. Ainsi, nous avons montre qu'en absence d'effecteur malt est monomerique ; (ii) qu'en presence de ces effecteurs positifs, l'atp et le maltotriose, la proteine malt oligomerise en solution et (iii) que son oligomerisation est impliquee dans la fixation de malt sur les promoteurs maltose. Nous avons egalement debute une caracterisation structurale des complexes nucleoproteiques formes entre malt et les promoteurs maltose. La seconde thematique de ce memoire porte sur la repression exercee par la proteine maly sur malt. Bien que le role de maly soit connu depuis longtemps grace a des experiences genetiques, nous ignorions tout du mecanisme moleculaire a la base de cet effet represseur. Nous avons montre (i) qu'un tel mecanisme passe par des interactions directes proteine-proteine entre malt et maly et n'implique aucun autre facteur et (ii) que la fixation de maly sur malt entre en competition avec la fixation du maltotriose sur malt, regulant ainsi l'activite transcriptionnelle de cet activateur.
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Chagneau, Claudia. "Le contrôle par CRP-AMPc de l'expression du gène malT d'Escherichia coli permet d'associer la nature de la source de carbone et le pH extracellulaire." Lyon 1, 2002. http://www.theses.fr/2002LYO10205.
Full textAbstract:
Les bactéries sont capables de détecter les variations de nombreux paramètres de l'environnement et d'y répondre. Ces réponses adaptatives impliquent que les informations associées à l'environnement soient perçues par des molécules réceptrices qui génèrent un signal transmis à des régulateurs de l'expression des gènes. Une information importante pour les bactéries est le pH du milieu de culture. Chez la bactérie neutrophile Escherichia coli, plusieurs gènes ont une expression qui varie suivant la valeur du pH extracellulaire sans qu'il n'y ait de changement du pH intracellulaire. Parmi ces gènes se trouvent les gènes du régulon maltose qui codent pour des protéines impliquées dans le transport et le métabolisme du maltose et des maltodextrines. La voie de signalisation associée au pH extracellulaire et impliquée dans la régulation de l'expression du régulon maltose n'a pas été identifiée à ce jour et ce travail a eu pour objectif de contribuer à cette caractérisation. Durant cette étude, nous avons mis en évidence une relation étroite entre les mécanismes impliqués dans la transduction du signal associé au pH extracellulaire et les mécanismes mis en jeu dans l'adaptation aux sources de carbone présentes dans le milieu de culture. En effet, la régulation de l'expression du régulon maltose selon le pH dépend de la concentration de la protéine GlpK qui catalyse la phosphorylation du glycérol en glycérol-3-phosphate et nécessite la présence de glycérol dans le milieu de culture. De plus, des éléments impliqués dans la répression catabolique tels que le régulateur transcriptionnel global CRP-AMPc et la protéine IIAGlc sont nécessaires à la régulation du régulon maltose selon le pH extracellulaire. La transduction du signal généré par le pH extracellulaire modulerait d'une part la quantité de complexe CRP-AMPc en contrôlant la production d'AMPc par l'adénylate cyclase et déclencherait d'autre part, à certains pH, l'activation d'un mécanisme qui requiert la protéine IIAGlc et qui est susceptible de réprimer la transcription de certains gènes.