Дисертації: "Enzyme"

1

Ekici, Ozlem Dogan. "Design, synthesis, and evaluation of novel irreversible inhibitors for caspases." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/5333.

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2

Finnigan, William John Andrew. "The exploitation of thermophiles and their enzymes for the construction of multistep enzyme reactions from characterised enzyme parts." Thesis, University of Exeter, 2016. http://hdl.handle.net/10871/27323.

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Biocatalysis is a field rapidly expanding to meet a demand for green and sustainable chemical processes. As the use of enzymes for synthetic chemistry becomes more common, the construction of multistep enzyme reactions is likely to become more prominent providing excellent cost and productivity benefits. However, the design and optimisation of multistep reactions can be challenging. An enzyme toolbox of well-characterised enzyme parts is critical for the design of novel multistep reactions. Furthermore, while whole-cell biocatalysis offers an excellent platform for multistep reactions, we are limited to the use of mesophilic host organisms such as Escherichia coli. The development of a thermophilic host organism would offer a powerful tool allowing whole-cell biocatalysis at elevated temperatures. This study aimed to investigate the construction of a multistep enzyme reaction from well-characterised enzyme parts, consisting of an esterase, a carboxylic acid reductase and an alcohol dehydrogenase. A novel thermostable esterase Af-Est2 was characterised both biochemically and structurally. The enzyme shows exceptional stability making it attractive for industrial biocatalysis, and features what is likely a structural or regulatory CoA molecule tightly bound near the active site. Five carboxylic acid reductases (CARs) taken from across the known CAR family were thoroughly characterised. Kinetic analysis of these enzymes with various substrates shows they have a broad but similar substrate specificity and that electron rich acids are favoured. The characterisation of these CARs seeks to provide specifications for their use as a biocatalyst. The use of isolated enzymes was investigated as an alternative to whole-cell biocatalysis for the multistep reaction. Additional enzymes for the regeneration of cofactors and removal of by-products were included, resulting in a seven enzyme reaction. Using characterised enzyme parts, a mechanistic mathematical model was constructed to aid in the understanding and optimisation of the reaction, demonstrating the power of this approach. Thermus thermophilus was identified as a promising candidate for use as a thermophilic host organism for whole-cell biocatalysis. Synthetic biology parts including a BioBricks vector, custom ribosome binding sites and characterised promoters were developed for this purpose. The expression of enzymes to complete the multistep enzyme reaction in T. thermophilus was successful, but native T. thermophilus enzymes prevented the biotransformation from being completed. In summary, this work makes a number of contributions to the enzyme toolbox of well-characterised enzymes, and investigates their combination into a multistep enzyme reaction both in vitro and in vivo using a novel thermophilic host organism.

3

Müller, Roger. "Artificial enzymes: from catalytic antibodies toward de novo enzyme design /." Zürich : ETH, 2008. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17897.

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4

Reichstädter, Marek. "Imobilizace vybraných glykanohydroláz." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2015. http://www.nusl.cz/ntk/nusl-217152.

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The theoretical part of this thesis deals with cellulolytic enzymes, their microbial producers, the possibilities of using such enzymes in the industry and how can be enzymes - not only cellulolytic - immobilized. Experimental part examines the preparations created by immobilizing various amounts of the commercially used cellulolytic complex Cellulast 1.5L onto various synthetic carriers made of polyethylene terephthalate - commercially used Sorsilen, PET carrier and glutaraldehyde-treated PET carrier. Enzyme activity of these preparations was determined by Somogyi - Nelson method by spectrophotometry. For the highest activity immobilized preparation was determined the temperature- and the pH-optimum. The difference in effects change between the free and immobilized enzyme by measuring viscosity decrease of the substrate depending on the degradation of glycosidic bonds was also studied.

5

Ekici, Özlem Doğan. "Design, synthesis, and evaluation of novel irreversible inhibitors for caspases." Available online, Georgia Institute of Technology, 2004:, 2003. http://etd.gatech.edu/theses/available/etd-04062004-164633/unrestricted/ekici%5Fozlem%5Fd%5F200312%5Fphd.pdf.

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6

Obrecht, Lorenz. "Artificial metalloenzymes in catalysis." Thesis, University of St Andrews, 2015. http://hdl.handle.net/10023/7248.

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This thesis describes the synthesis, characterisation and application of artificial metalloenzymes as catalysts. The focus was on two mutants of SCP-2L (SCP-2L A100C and SCP-2L V83C) both of which possess a hydrophobic tunnel in which apolar substrates can accumulate. The crystal structure of SCP-2L A100C was determined and discussed with a special emphasis on its hydrophobic tunnel. The SCP-2L mutants were covalently modified at their unique cysteine with two different N-ligands (phenanthroline or dipicolylamine based) or three different phosphine ligands (all based on triphenylphosphine) in order to increase their binding capabilities towards metals. The metal binding capabilities of these artificial proteins towards different transition metals was determined. Phenanthroline modified SCP-2L was found to be a promising scaffold for Pd(II)-, Cu(II)-, Ni(II)- and Co(II)-enzymes while dipicolylamine-modified SCP-2L was found to be a promising scaffold for Pd(II)-enzymes. The rhodium binding capacity of two additional phosphine modified protein scaffolds was also investigated. Promising scaffolds for Rh(I)- and Ir(I)-enzymes were identified. Rh-enzymes of the phosphine modified proteins were tested in the aqueous-organic biphasic hydroformylation of linear long chain 1-alkenes and compared to the Rh/TPPTS reference system. Some Rh-enzymes were found to be several orders of magnitude more active than the model system while yielding comparable selectivities. The reason for this remarkable reactivity increase could not be fully elucidated but several potential modes of action could be excluded. Cu-, Co-, and Ni-enzymes of N-ligand modified SCP-2L A100C were tested in the asymmetric Diels-Alder reaction between cyclopentadiene and trans-azachalcone. A promising 29% ee for the exo-product was found for the phenanthroline modified protein in the presence of nickel. Further improvement of these catalyst systems by chemical means (e.g. optimisation of ligand structure) and bio-molecular tools (e.g. optimisation of protein environment) can lead to even more active and (enantio)selective catalysts in the future.

7

Bodhe, A. M. "Enzyme inhibitors." Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 1988. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/3302.

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8

Qian, Yuhui. "Study of Basic Wood Decay Mechanisms and Their Biotechnological Applications." Fogler Library, University of Maine, 2008. http://www.library.umaine.edu/theses/pdf/QianY2008.pdf.

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9

Zhao, Xueyan. "Nanoscale biocatalysts for bioelectrochemical applications." Akron, OH : University of Akron, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=akron1164149161.

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Thesis (M.S.)--University of Akron, Dept. of Chemical Engineering, 2006.
"December, 2006." Title from electronic thesis title page (viewed 06/27/2007) Advisor, Ping Wang; Committee members, Lu-Kwang Ju, Steven S. C. Chuang; Department Chair, Lu-Kwang Ju; Dean of the College, George K. Haritos; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.

10

Moore, Robert Goodwin Douglas C. "Towards the understanding of complex biochemical systems the significance of global protein structure and thorough parametric analysis /." Auburn, Ala, 2009. http://hdl.handle.net/10415/1766.

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11

Astier, Yann. "Enzyme kinetics and electrochemical polymer transistor detection of enzyme reactions." Thesis, University of Southampton, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.273800.

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12

Ewing, Erin. "In vacuo glycation of enzymes: A novel approach for increasing enzyme stability." Thesis, University of Ottawa (Canada), 2006. http://hdl.handle.net/10393/27129.

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A novel approach for the thermostabilization of proteins was investigated. It is well established that proteins that are naturally highly glycosylated show an increased resistance to inactivation at high temperatures. However, non-enzymatic attachment of carbohydrate to proteins, otherwise known as protein glycation, under aqueous conditions is very difficult and has not been used as a general approach for increasing the thermostability of proteins. In the present study, advantage was taken of the in vacuo protein glycation procedure recently developed by Kaplan and his co-workers by which proteins can be extensively glycated in the absence of water and chemical reagents. In this procedure, reducing sugars react with the epsilon-amino groups of lysine side-chains to form a stable ketoamine derivative. The primary objective of the research presented in this thesis, was to determine the extent to which the thermostability of proteins can be increased by in vacuo glycation with reducing monosaccharides such as glucose. Another objective of this study was to investigate possible practical applications of this thermostabilization technology. (Abstract shortened by UMI.)

13

Robertson, Graeme. "Enzyme pesticide biosensors." Thesis, University of Strathclyde, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366815.

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14

Birkin, Peter Robert. "Microelectrochemical enzyme transistors." Thesis, University of Southampton, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240628.

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15

Wilson, Robert. "Enzyme amplified immunoassays." Thesis, Cranfield University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.237805.

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16

Al-Lolage, Firas Ahmed Thanon. "Amperometric enzyme electrodes." Thesis, University of Southampton, 2018. https://eprints.soton.ac.uk/419053/.

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This thesis studies the conditions required to achieve direct electron transfer and the experimental tests needed to unequivocally demonstrate that it occurs. Many publications claim to observe direct electron transfer to redox enzymes (for example in the case of glucose oxidase) but the evidence presented is often incomplete and unconvincing. The first part of this thesis argues that the vast majority, if not all, of these claims of DET for GOx are incorrect. It presents results for glucose oxidase (GOx) adsorbed on multi‐walled carbon nanotubes (MWCNTs), a typical nanostructured GOx electrode, that clearly show that the surface redox peaks usually observed in these cases are due to free, adsorbed flavin and not due, as claimed, to DET to flavin within the enzyme. Also, the results can be explained by adsorption of enzymatically active GOx at the electrode surface and the detection of the decrease in the oxygen concentration at the electrode surface due to the enzyme catalysed oxidation of D‐glucose. The second part of this thesis establishes a flexible and structured method based on the use of site‐directed mutagenesis to introduce cysteine residues at specific locations on the enzyme surface followed by the reaction between the free thiol group and maleimide groups formed on the electrode surface to immobilise the mutated enzymes. It is preferable to immobilise redox proteins and enzymes in a specific orientation, but still with some flexibility to optimise reaction kinetics. Using cellobiose dehydrogenase (CDH) as a model system, multiwall carbon nanotube electrodes were first covalently modified with maleimide groups following a modular approach combining electrochemical surface attachment and solid phase synthesis methodology. Five CDH variants were used in this study, the CDH‐modified electrodes were tested for direct electron transfer (DET), showing high catalytic currents and excellent long‐term storage stability. A potential‐dependent Michaelis‐Menten model for the CDH modified GC/MWCNT has been constructed and a master equation employed to simulate the DET and MET experimental results. Several mechanisms were suggested to explain the DET and MET for CDH. The internal electron transfer (IET) has been shown to be the rate determining step in the proposed mechanism. This was confirmed by the simulated data along with the experimental results. The simulated data suggests the presence of two populations of immobilised enzymes, MET and DET enzyme. The validity of the aforementioned immobilisation method, was further examined. Three bilirubin oxidase (BOD) variants were used in this study, which were modified to bear a free cysteine residue in different positions at the surface of the enzyme, allowing fast and selective attachment to maleimide‐modified GC/MWCNT electrodes. The catalytic mechanism of O2 reduction by the Magnaporthe oryzae BOD covalently immobilized on multiwall carbon nanotube (MWCNT) electrodes, in the presence of Cl ̅ and at different pH, was electrochemically investigated. The results highlight for the first time the influence of chloride ions on the direct oxygen reduction by MoBOD as a function of pH.

17

Bolon, Daniel N. Goddard William A. "Computational enzyme design /." Diss., Pasadena, Calif. : California Institute of Technology, 2002. http://resolver.caltech.edu/CaltechETD:etd-01252002-100801.

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18

Mao, Wei. "Etude biochimique et sélection d'inhibiteurs spécifiques d'une cible thérapeutique leishmanienne : la GDP-Mannose-Pyrophosphorylase." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS481.

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Les leishmanioses sont des maladies tropicales négligées provoquées par un protozoaire parasite du genre Leishmania, et transmises par un insecte vecteur, le phlébotome. Les leishmanioses menacent 310 millions de personnes dans 98 pays à travers le monde. Les traitements antileishmaniens actuels sont limités et présentent des problèmes majeurs de toxicité et d'émergence de chimiorésistance. Dans ce contexte, il est nécessaire de développer de nouveaux agents antileishmaniens spécifiquement dirigés contre une cible thérapeutique chez le parasite. La GDP-Mannose Pyrophosphorylase (GDP-MP) est une cible thérapeutique essentielle à la survie du parasite à la fois in vitro et in vivo. Plusieurs différences ont été identifiées dans le site actif de GDP-MPs leishmaniennes par rapport à l'enzyme humaine, montrant ainsi l'intérêt de cette cible thérapeutique dans le développement de nouveaux traitements contre la leishmaniose. La GDP-MP catalyse la synthèse du GDP-mannose, la forme activée du mannose, brique moléculaire importante dans les processus de glycosylation et la synthèse de glycoconjugués essentiels à la reconnaissance hôte-parasite. Ce travail de thèse a consisté à produire et purifier les GDP-MPs de 3 espèces de parasites (Leishmania infantum, Leishmania donovani et Leishmania mexicana) ainsi que l'homologue humaine dans le but de comparer leurs propriétés enzymatiques. A partir d'inhibiteurs potentiels conçus et synthétisés sur la base de modèles moléculaires de GDP-MPs leishmaniennes et humaine, 100 composés ont été évalués sur les enzymes purifiées et sur les parasites in vitro. Cette analyse nous a permis de sélectionner des composés spécifiquement dirigés contre la cible du parasite et présentant une activité antileishmanienne. Nous avons également initié une étude de l'expression et de la localisation de la GDP-MP après traitement par les composés les plus intéressants. Ces composés pourront par la suite être utilisés comme outils pharmacologiques pour le développement de nouveaux agents antileishmaniens spécifiques
Leishmaniases are Neglected Tropical Disease (NTD)caused by a protozoan parasite of the genus Leishmania and transmitted by an insect vector, the phlebotomine sandfly. Leishmaniases threaten 310 millions people in 98 countries around the world. Current antileishmanial treatments are limited and present major issues of toxicity and drug resistance emergence. In this context, it is necessary to develop new specific antileishmanial drugs specifically directed against a therapeutic target in the parasite.The GDP-Mannose Pyrophosphorylase (GDP-MP) is a therapeutic target which has been described to be essential for parasite survival both in vitro and in vivo. Several differences have been identified in the active site of leishmanial GDP-MPs compared to the human counterpart, showing the prominence of this therapeutic target in the development of new treatments against leishmaniasis. The GDP-MP catalyzes the synthesis of GDP-Mannose,the activated form of mannose, an important molecular constituent of the glycosylation processes involved in the biosynthesis of glycoconjugates which are essential for host-parasite recognition. My thesis work consisted in the production and purification of GDP-MPs from 3 Leishmania species (Leishmania donovani,Leishmania infantum and Leishmania mexicana)and from humanin order to compare their enzymatic properties. From potential inhibitors designed and synthesized on the basis of leishmanial and human GDP-MP molecular models, 100 compounds were evaluated on purified enzymes and on parasites in vitro. These analyses allowed us to select some compounds which are specifically directed against the parasite target and presenting antileishmanial activities. We have also initiated a study of expression and localization of GDP-MP after treatment with the most potent compounds. These compounds will be used as pharmacological tools for the development of new specific antileishmanial drugs

19

SILVA, JOSE A. A. da. "Aspectos de atividade biologica da giroxina (enzima trombina simile) isolada do veneno da cascavel brasileira, Crotalus durissus terrificus." reponame:Repositório Institucional do IPEN, 2004. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11191.

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Made available in DSpace on 2014-10-09T12:49:21Z (GMT). No. of bitstreams: 0
Made available in DSpace on 2014-10-09T14:02:30Z (GMT). No. of bitstreams: 1 09994.pdf: 3905779 bytes, checksum: 7cdc8d8ae9585729a6a818ed202c59c8 (MD5)
Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

20

Epstein, Todd Matthew. "Structural and kinetic studies of two enzymes catalyzing phospholipase A2 activity." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 2.39 Mb., 186 p, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3200538.

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21

Snider, Catherine E. "Synthesis and biochemical evaluation of irreversible inhibitors of aromatase /." The Ohio State University, 1986. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487266362338344.

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22

Haileselassie, Seble Sereke Berhan. "Production of enzyme-modified cheese and bioactive peptides by Lactobacillus and commercial enzymes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ50782.pdf.

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23

Dong, Liang-Chang. "Thermally reversible hydrogels for controlled drug delivery and enzyme immobilization /." Thesis, Connect to this title online; UW restricted, 1990. http://hdl.handle.net/1773/8009.

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24

O'Neil, Crystal L. "Enzyme Exploitation: Manipulating Enzyme Function for Therapy, Synthesis and Natural Product Modification." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1293722936.

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25

Friemann, Rosmarie. "Structure-function studies of iron-sulfur enzyme systems /." Uppsala : Dept. of Molecular Biology, Swedish Univ. of Agricultural Sciences, 2005. http://epsilon.slu.se/a504.pdf.

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26

Williams, Simon-Peter. "Studies of enzyme kinetics and aspects of enzyme structure in vivo using NMR and molecular genetics." Thesis, University of Oxford, 1992. http://ora.ox.ac.uk/objects/uuid:d8baa574-a5d4-45a2-95a2-c141fbf8d277.

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A quantitative understanding of metabolic control depends on a knowledge of the enzymes involved. The extrapolation of studies in vitro to the intact cell is controversial because the intracellular environment is relatively poorly characterised, particularly with respect to the interactions between weakly-associated enzymes. There is a clear need to study enzymes directly in the cell, yet there are few suitable techniques. Metabolites have been very successfully studied in cells by the non-invasive technique of nuclear magnetic resonance (NMR). NMR studies of enzymes in the cell have, however, been prevented by difficulties in assigning the resonances from the many proteins within the cell. A method for studying a specific enzyme in the cell has been developed, using Saccharomyces cerevisiae and phosphoglycerate kinase (PGK) as a model system. Using an inducible expression system, PGK was synthesised in the cell without significant synthesis of other proteins. With 5-fluorotryptophan in the growth medium, fluorine-labelled PGK was formed in situ. Fluorine is an excellent label for NMR since it is absent from most cells and has a high receptivity to NMR detection. ¹⁹ F NMR was used to study PGK in the intact cell. Comparisons with measurements in vitro showed that PGK was exposed to only a small fraction of the total intracellular [ADP], implying some form of compartmentalisation. The NMR relaxation properties observed in vivo and in vitro were compared with theoretical predictions. This showed that PGK was not part of a complex in the cell and that the viscosity of the cytoplasm, relative to water, was c. 4 at 30 °C. Fluorine-labelled pyruvate kinase and hexokinase have also been prepared; the spectra of these proteins in vitro are responsive to their ligands, and further work will study these proteins in vivo. NMR techniques were also applied to study the kinetics of PGK in the cell. PGK and GAPDH catalyse an ATP↔P_i exchange which is near-equilibrium in wild-type cells. ³¹P magnetisation transfer experiments in genetically manipulated cells showed that the reaction becomes unidirectional if the PGK activity is reduced by 95 %. Net flux is reduced by less than 30 %. In low-PGK cells, the ATP↔P_i exchange from oxidative phosphorylation can be isolated from that of glycolysis, facilitating direct measurements of the P:O ratio. In the cells studied, the P:O ratio was 2 to 3.

27

Peters, Thilo. "Extrazelluläre Enzyme aus Basidiomyceten." [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=97236191X.

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28

YAMANE, Tsuneo. "Enzyme Engineering for Lipids." 名古屋大学農学国際教育協力研究センター, 2004. http://hdl.handle.net/2237/8930.

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29

Williams, Richard James. "Enzyme assisted self-assembly." Thesis, University of Manchester, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.496231.

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Self-assembling peptide systems provide a pathway for the formation of complex molecular assemblies from relatively simple designed molecules. Stimuli which have been used to trigger the self-assembly (SA) process in aqueous conditions include temperature, pH, ionic strength, and solvent exchange. Additionally, enzymes may be used to selectively control the self-assembly process; enzymes are uniquely chemo-, regio-, and enantioselective, and work naturally under mild conditions without disrupting biological Interactions.

30

Beh, Seng Kee. "Membranes for enzyme electrodes." Thesis, Cardiff University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305091.

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31

Zaman, Flora. "Kinetics of enzyme models." Thesis, University of Kent, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263701.

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32

Parratt, Julian Simon. "Enzyme catalysed nitrile hydrolysis." Thesis, University of Exeter, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357898.

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33

Dennison, Manus. "Gas-phase enzyme biosensors." Thesis, Cranfield University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309584.

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34

Hall, Geoffrey F. "Organic phase enzyme electrodes." Thesis, Cranfield University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278720.

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35

Saini, S. "Organic phase enzyme electrodes." Thesis, Cranfield University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.332925.

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36

Kalia, Yogeshvar Nath. "Development of enzyme electrodes." Thesis, Imperial College London, 1991. http://hdl.handle.net/10044/1/46856.

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37

Coote, Alexander Stuart. "Polyurethanes for enzyme immobilisation." Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/47386.

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38

Sutar, I. I. "Studies on proteolytic enzyme." Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 1987. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/3285.

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39

Lee, Charles Kai-Wu. "Eurythermalism of a deep-sea symbiosis system from an enzymological aspect." The University of Waikato, 2007. http://hdl.handle.net/10289/2588.

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The recently proposed and experimentally validated Equilibrium Model provides the most detailed description of temperature's effect on enzyme catalytic activity to date. By introducing an equilibrium between Eact, the active form of enzyme, and Einact, a reversibly inactivated form of enzyme, the Equilibrium Model explains apparent enzyme activity loss at high temperatures that cannot be accounted for by irreversible thermal denaturation. The Equilibrium Model describes enzyme behavior in the presence of substrates and under assay conditions; thus its associated parameters, deltaHeq and Teq, may have physiological significance. The Equilibrium Model parameters have been determined for twenty-one enzymes of diverse origins. The results demonstrated the wide applicability of the Equilibrium Model to enzymes of different types and temperature affinity. The study has also established deltaHeq as the first quantitative measure of enzyme eurythermalism and demonstrated the relationship between Teq and optimal growth temperature of organisms. The Equilibrium Model is therefore a useful tool for studying enzyme temperature adaptation and its role in adaptations to thermophily and eurythermalism. Moreover, it potentially enables a description of the originating environment from the properties of the enzymes. The Equilibrium Model has been employed to characterize enzymes isolated from bacterial episymbionts of Alvinella pompejana. A. pompejana inhabits one of the most extreme environments known to science and has been proposed as an extremely eurythermal organism. A metagenomic study of the A. pompejana episymbionts has unveiled new information related to the adaptive and metabolic properties of the bacterial consortium; the availability of metagenomic sequences has also enabled targeted retrieval and heterologous expression of A. pompejana episymbiont genes. By inspecting enzymes derived from the unique episymbiotic microbial consortium intimately associated with A. pompejana, the study has shed light on temperature adaptations in this unique symbiotic relationship. The findings suggested that eurythermal enzymes are one of the mechanisms used by the microbial consortium to achieve its adaptations. By combining metagenomic and enzymological studies, the research described in this thesis has lead to insights on the eurythermalism of a complex microbial system from an enzymological aspect. The findings have enhanced our knowledge on how life adapts to extreme environments, and the validation of the Equilibrium Model as a tool for studying enzyme temperature adaptation paves the way for future studies.

40

Gavva, Sandhya Reddy. "Alternate Substrates and Isotope Effects as a Probe of the Malic Enzyme Reaction." Thesis, University of North Texas, 1988. https://digital.library.unt.edu/ark:/67531/metadc330840/.

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Dissociation constants for alternate dirmcleotide substrates and competitive inhibitors suggest that the dinucleotide binding site of the Ascaris suum NAD-malic enzyme is hydrophobic in the vicinity of the nicotinamide ring. Changes in the divalent metal ion activator from Mg^2+ to Mn^2+ or Cd^2+ results in a decrease in the dinucleotide affinity and an increase in the affinity for malate. Primary deuterium and 13-C isotope effects obtained with the different metal ions suggest either a change in the transition state structure for the hydride transfer or decarboxylation steps or both. Deuterium isotope effects are finite whether reactants are maintained at saturating or limiting concentrations with all the metal ions and dinucleotide substrates used. With Cd^2+ as the divalent metal ion, inactivation of the enzyme occurs whether enzyme alone is present or is turning over. Upon inactivation only Cd^2+ ions are bound to the enzyme which becomes denatured. Modification of the enzyme to give an SCN-enzyme decreases the ability of Cd^2+ to cause inactivation. The modified enzyme generally exhibits increases in K_NAD and K_i_metai and decreases in V_max as the metal size increases from Mg^2+ to Mn^2+ or Cd^2+, indicative of crowding in the site. In all cases, affinity for malate greatly decreases, suggesting that malate does not bind optimally to the modified enzyme. For the native enzyme, primary deuterium isotope effects increase with a concomitant decrease in the 13-C effects when NAD is replaced by an alternate dinucleotide substrate different in redox potential. This suggests that when the alternate dinucleotides are used, a switch in the rate limitation of the chemical steps occurs with hydride transfer more rate limiting than decarboxylation. Deuteration of malate decreases the 13-C effect with NAD for the native enzyme, but an increase in 13-C effect is obtained with alternate dinucleotides. These suggest the presence of a secondary 13-C effect in the hydride transfer step. This phenomenon is also applicable to the modified enzyme with NAD as the substrate.

41

Oudshoorn, Matthew Leslie. "Tests of predictions made by the Equilibrium Model for the effect of temperature on enzyme activity." The University of Waikato, 2008. http://hdl.handle.net/10289/2418.

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The Classical Model describing the effects of temperature on enzyme activity consists of two processes: the catalytic reaction defined by ΔG cat and irreversible inactivation defined by ΔG inact, this model however, does not account for the observed temperature- dependant behaviour of enzymes. The recent development of the Equilibrium Model is governed not only by ΔG cat and ΔG inact but also by two new intrinsic parameters ΔHeq and Teq, which describe the enthalpy and the temperature of the midpoint, respectively, of a active and reversibly inactive enzyme transition. Teq is central to the physiological adaptation of an enzyme to its environmental temperature and links the molecular, physiological and environmental aspects of life to temperature in a way that has not been previously possible. The Equilibrium Model is therefore a more complete and accurate description of the effects of temperature on enzymes, it has provided new tools for describing and investigating enzyme thermal adaptation and possibly new biotechnological tools. The effects of the incorporating in the new Model of the parameters Teq and ΔH eq yield major differences from the Classical Model, with simulated data calculated according to the Equilibrium Model fitting well to experimental data and showing an initial rate temperature optimum that is independent of assay duration. Simulated data simulated according to the Classical Model can not be fitted to experimental data. All enzymes so far studied (gt30) display behaviour predicted by the Equilibrium Model. The research described here has set out to: experimentally test observations made by Eisenthal et al., on the basis of enzyme reactor data simulated according to the Equilibrium Model; to test the Equilibrium Model using an unusual (rapidly renaturable) enzyme, RNAase; and to test the proposed molecular basis of the Equilibrium Model by examining the effect of a change at the enzymes active site. The experimental results gathered here on the effect of time and temperature on enzyme reactor output confirm the predictions made by Eisenthal et al. (2006) and indicate that the Equilibrium Model can be a useful aid in predicting reactor performance. The Equilibrium Model depends upon the acquisition of data on the variation of the Vmax of an enzyme with time and temperature, and the non-ideal behaviour of RNase A made it impossible to collect such data for this enzyme, as a result the Equilibrium Model could not be applied. The disulfide bond within the active site cleft of A.k 1 protease was cleaved as a probe of the mechanism of the Equilibrium Model, which is proposed to arise from molecular changes at the enzymes active site. Support for the proposed mechanism was gained through the comparison of experimentally determined temperature dependence of the native and reduced forms of the enzyme and application of this data to the Equilibrium Model.

42

Silveira, Alvito J. "Synthesis of 6-guanidinobenzoxazinones as potential inhibitors of trypsin-like enzymes." Thesis, Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/26914.

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43

Garrett, Mark Denis. "A study on selectivity in microbial biotransformations of substituted arenes." Thesis, Queen's University Belfast, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287620.

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44

Sha, Zhou. "A Chemical Approach to Detect and Characterize The Activities of Mitochondrial ATP-dependent Protease Lon and ClpXP." Case Western Reserve University School of Graduate Studies / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=case1595239191845497.

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45

Fisher, Oriana. "Subcloning, enzymatic characterization, and in silico docking of transglutaminase 2." Waltham, Mass. : Brandeis University, 2009. http://dcoll.brandeis.edu/handle/10192/23253.

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46

Vögeli, Bastian [Verfasser], and Tobias [Akademischer Betreuer] Erb. "Control of reactive intermediates in enzymes and enzyme complexes / Bastian Vögeli ; Betreuer: Tobias Erb." Marburg : Philipps-Universität Marburg, 2019. http://d-nb.info/1185068716/34.

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47

Maheshwari, Sweta. "Caractérisation biochimique et cellulaire des enzymes clés du métabolisme des phospholipides chez Plasmodium falciparum." Thesis, Montpellier 2, 2012. http://www.theses.fr/2012MON20004.

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Le développement du parasite Plasmodium falciparum, responsable du paludisme, nécessite la synthèse de phospholipides et plus particulièrement de phosphatidylcholine (PC) et phosphaditylethanolamine (PE) qui représentent environ 85% de la totalité des phospholidipes du parasite. Leur synthèse s'effectue principalement par les voies métaboliques de novo, voies de Kennedy, en trois étapes enzymatiques. Les enzymes CTP: phosphoethanolamine cytidylyltransferase (ECT) et CTP: phosphocholine cytidylyltransferase (CCT) catalysent les étapes limitantes des deux voies de biosynthèse de la PE et de la PC, respectivement. Ces deux enzymes sont essentielles à la survie du parasite murin, P. berghei et représentent ainsi des cibles thérapeutiques potentielles. La PfCCT est constituée de deux domaines cytidylyltranférases (CT) répétés alors que l'enzyme homologue chez l'homme est composée d'un seul domaine. En revanche, pour la ECT, la présence de deux domaines CT est retrouvée chez toutes les espèces mais les analyses de séquences et de structures ont montré que des résidus importants du site catalytique liant le substrat n'étaient pas conservés dans le domaine CT C-terminal de la PfECT. Ce travail a eu pour but de déterminer les propriétés enzymatiques et les caractéristiques cellulaires de la PfECT et de la PfCCT. Les paramètres cinétiques de ces enzymes ont été quantifiés in vitro à l'aide protéines recombinantes ainsi que sur les enzymes endogènes à l'aide d'extraits parasitaires. Grâce à l'utilisation de protéines recombinantes ponctuellement mutées, nous avons montré que seul le domaine CT N-terminal de la PfECT est catalytiquement actif. Chez P. falciparum, la PfECT et la PfCCT sont exprimées tout au long du cycle intra-érythrocytaire du parasite. La PfECT est présente dans la fraction soluble du parasite alors que la PfCCT apparait aussi bien dans la fraction soluble qu'insoluble. Des expériences d'immunofluorescence ont montré que la PfECT est cytosolique. L'ensemble des résultats présentés apportent un éclairage important sur les fonctions et les propriétés de ces deux cibles potentielles et constituent les premières étapes indispensables à l'élaboration d'une approche thérapeutique
Phospholipids are essential for the growth and development of Plasmodium falciparum malaria parasite. Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) are its major structural phospholipids. This study focused on CTP: phosphoethanolamine cytidylyltransferase (ECT) and CTP: phosphocholine cytidylyltransferase (CCT) that catalyzes the rate-limiting steps of the de novo Kennedy pathways for PE and PC biosynthesis respectively. Both ECT and CCT are essential in the rodent malaria parasite P. berghei and constitute potential chemotherapeutic targets to fight against malaria. PfCCT consists of two very similar cytidylyltransferase (CT) domains whereas the human enzyme consists of only one CT domain. The presence of two CT domains in ECT seems to be widespread in all the organisms. Sequence and structural analysis showed that the C-terminal CT domain of ECT lacks key residues in the substrate binding motif. This study aimed at unravelling the enzymatic properties and cellular characteristics of PfECT and PfCCT enzymes. In addition, these studies addressed the key question if C-terminal CT domain of PfECT is catalytically active. Kinetic parameters of the enzymes were evaluated in vitro on native proteins as well as on recombinant proteins, the latter being produced in bacterial system. Cellular characterisation studies using polyclonal antisera showed that PfECT and PfCCT are expressed throughout the intra-erythrocytic life cycle of the parasite. PfECT is found mainly in soluble form in the parasite while PfCCT is present in soluble as well as insoluble forms in the parasite. Furthermore, immunofluorescence studies for PfECT revealed that it is mainly cytosolic. To assess the contribution of each CT domain to overall PfECT enzyme activity, recombinant PfECT mutants were generated by site-directed mutagenesis. Kinetic studies on these mutants indicated that the N-terminal CT domain was the only active domain of PfECT. Collectively, these results bring new insights into the kinetic and cellular properties of the enzymes and will pave the way in developing a future pharmacological approach

48

Chiu, May Leung. "Investigation and characterization of analyte-reporter enzyme conjugates for the enzyme-multiplied immunoassay technique." Diss., Restricted to subscribing institutions, 2009. http://proquest.umi.com/pqdweb?did=1930910331&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.

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49

Fedatto, Luciana Maria. "Caracterização de proteases extracelulares produzidas por Xylella fastidiosa de citros e videira." Universidade de São Paulo, 2005. http://www.teses.usp.br/teses/disponiveis/91/91131/tde-21062005-134055/.

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Xylella fastidiosa é uma bactéria patogênica encontrada em várias plantas. Esta bactéria secreta proteases extracelulares detectadas em gel de eletroforese, sendo a gelatina usada como substrato co-polimerizado. Três principais bandas protéicas foram detectadas com massa molar (MM) de 122, 84 e 65 kDa produzidas pelo isolado de citros (X0) e duas bandas de aproximadamente 84 e 65 kDa de isolado de videira (9713). Estas bactérias produziram zonas de hidrólise em meio sólido contendo gelatina, caseína e hemoglobina. Os resultados usando a gelatina como substrato foram os melhores para a atividade das proteases. A atividade enzimática das proteases de X. fastidiosa de citros e videira foi completamente inibida por PMSF e parcialmente inibida por EDTA, podendo ser visualizado em gel de eletroforese nativo. A temperatura ótima de atividade protéica foi de 30oC e o pH ótimo de 7,0. Além das proteases secretadas por este fitopatógeno, quitinase e β-1,3-glucanase foram também detectadas no sobrenadante das culturas. Os resultados sugeriram que estas proteases produzidas pela X. fastidiosa de citros e videira pertencem ao grupo das serina e metalo proteases.
Xylella fastidiosa is a pathogenic bacterium found in several plants. These bacteria secrete extracellular proteases into the culture broth as visualized in sodium-dodecyl-sulfate polyacrylamide activity gels containing gelatin as a co-polymerized substrate. Three major protein bands were produced by strain X0 (citrus) with molar masses (MM) of 122, 84 and 65 kDa. Grape strain 9713 produced two bands of approximately 84 and 64 kDa. These organisms produced zones of hydrolysis in agar plates amended with gelatin, casein and hemoglobin. Gelatin was the best substrate for these proteases. SDS-PAGE activity gel indicated that the protease activities of X. fastidiosa from citrus and grape were completely inhibited by PMSF and partially inhibited by EDTA. The optimal temperature for protease activity was 30oC with an optimal pH of 7.0. Among the proteolytic enzymes secreted by the phytopathogen, chitinase and β-1,3-glucanase activities were also detected in cultures of X. fastidiosa (citrus). From these results, it is suggested that these proteases produced by strains of X. fastidiosa from citrus and grape, belong to the serine- and metallo-protease group.

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Preneta, A. Z. "Studies on lactate oxidising enzymes and their application to ferrocene-based enzyme electrodes for lactate." Thesis, Cranfield University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376191.

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