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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
311

The role of DOA10 in ubiquitin-mediated degradation /

Swanson, Robert John. January 2001 (has links)
Thesis (Ph. D.)--University of Chicago, Department of Molecular Genetics and Cell Biology, June 2001. / Includes bibliographical references. Also available on the Internet.
312

Studies on human erythrocyte cholinesterase : (Acetylcholine acetyl hydrolase E.C.3.1.1.7.).

Lo, Hong-min, Edward, January 1975 (has links)
Thesis (M. Phil.)--University of Hong Kong, 1975. / Photocopy of typewcript.
313

Release of mitochondrial enzymes under the influence of ions, detergents, and sonication : comparison between normal and hepatopathological states /

Rahmatullah, Rownak. January 1981 (has links)
Thesis (M. Phil.)--University of Hong Kong, 1982.
314

Enantiomeric resolution of cyclobutanones and their photochemical ring expansion products by selective enzyme acylation and hydrolysis

Salehzadeh-Asl, Reza. January 2001 (has links)
Thesis (M. Sc.)--York University, 2001. Graduate Programme in Chemistry. / Typescript. Includes bibliographical references (leaves 56-59). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pMQ66404.
315

On the reactions of trans-3-chloroacrylic acid dehalogenase and a cis-3-chloroacrylic acid dehalogenase homologue, Cg10062 : mechanistic and evolutionary implications

Huddleston, Jamison Parker 03 September 2015 (has links)
The tautomerase superfamily (TSF) provides an excellent model system to study enzyme specificity, catalysis, and divergent evolution. trans-3-Cholroacrylic acid dehalogenase (CaaD), cis-3-chloroacrylic acid dehalogenase (cis-CaaD), and malonate semialdehyde decarboxylase (MSAD) are three TSF members that catalyze the final reactions in the degradation of the nematocide, 1,3-dichloropropene. All three enzymes have the TSF characteristic beta-alpha-beta fold and catalytic amino terminal proline (Pro-1). Both CaaD and cis-CaaD dehalogenate their respective isomers of 3-chloroacrylic acid yielding malonate semialdehyde. Subsequently, MSAD decarboxylates malonate semialdhyde resulting in acetaldehyde and CO2. Their catalytic and substrate specificities are exquisite considering they share three key and positionally conserved residues. As part of an effort to understand how such specificity evolved, a pre-steady-state kinetic analysis of CaaD was carried out. Alongside a similar study on cis-CaaD, a fluorescent mutant of CaaD was constructed that had minimal kinetic differences from the wild-type. The mutant was validated as an accurate fluorescent reporter of change in enzyme state that allowed for the reaction to be followed using stopped-flow methods. Stopped-flow fluorescence, rapid chemical quench data and ultraviolet spectroscopy were globally fit by computational simulation. The fit resulted in a kinetic mechanism for CaaD affording detailed information about the reaction, including measuring the rate of product release, the rate of chemistry, a previously unknown partially rate-limiting step associated with a conformational change, and the definition of binding constants for both products (MSA and Br-). In addition to the dehalogenation reaction, the reaction of the fluorescent mutant with a mechanism-based inhibitor, 3-bromopropiolate, was characterized. The values for the apparent rate of inhibition and potency were defined and estimates were determined for the values of the rate of chemistry and the release of bromide. The information gathered during these inhibition experiments was used to further refine the CaaD dehalogenation mechanism eliminating ambiguities present in the initial data set. Finally, the reactions of a cis-CaaD homologue, Cg10062 from Corynebacterium glutamicum were characterized. Cg10062 shares high sequence similarity (53%) and the same six critical active site residues as cis-CaaD, but Cg10062 has poor cis-CaaD activity. Moreover, Cg10062 dehalogenates both 3-chloroacrylic acid isomers. The reactions of Cg10062 with propiolate, 2-butynoate, and 2,3 butadienoate were investigated. Cg10062 functions as a hydratase/decarboxylase using propiolate generating malonate semialdehyde and acetaldehyde. Cg10062 catalyzes a hydration-dependent decarboxylation of propiolate as exogenously added malonate semialdehyde is not decarboxylated. With 2,3 butadienoate and 2-butynoate, Cg10062 functions as a hydratase and yields only acetoacetate. Mutations to the activating residues Glu114 and Tyr103 produced a range of results from a reduction in wild-type activity to a switch of activity. Possible intermediates for the hydration and decarboxylation products can be trapped as covalent adducts to Pro-1 when NaCNBH3 is incubated with certain combinations of substrate and mutant enzymes. Three mechanisms are presented to explain these findings along with the strengths and weaknesses of each mechanism in terms of being able to account for experimental observations. / text
316

Studies of bacterial catabolic enzymes: implications for the evolution of enzymes and metabolic pathways

Wang, Susan C. 28 August 2008 (has links)
Not available / text
317

Engineering highly active enzymes with altered substrate selectivities

Griswold, Karl Edwin 28 August 2008 (has links)
Not available / text
318

Functional and molecular characterization of piscine UDP-glucuronosyltransferases

Clarke, Douglas James January 1990 (has links)
Studies detailed in this thesis were concerned with elucidating the function and molecular properties of UDP-glucuronosyltransferase(s) involved in detoxicative metabolism in the piscine species, Pleuronectes platessa. This study represents the first detailed investigation of such a system in a non-mammalian species. Comparative studies on UDPGT expression in the mammalian and piscine used in this investigation indicated that a number of marked species differences were apparent which were of potential toxicological significance. Analysis of piscine UDPGT activities in liver, kidney, intestine and gill demonstrated that the phenol UDPGT activity was ubiquitous to different degrees in all tissues whereas activities to endogenous substrates were more restricted. UDPGT expression in piscine microsomes was relatively non-latent compared to its mammalian counterpart, a possible reason for this being the marked species differences observed by microsomal lipid composition analysis. Assay of hepatic microsomal fractions indicated that glucuronidation of planar phenolic xenobiotics was actively catalysed in the piscine species, whilst there was low UDPGT activity towards several steroids and bilirubin, compared to the rat. Aglycone specificity for several bulky non-planar substrates was either very low or absent in the piscine species in contrast to rats. The metabolism of the proximate carcinogen benzo(a)pyrene was also investigated in isolated hepatocytes derived from plaice. The major metabolites formed were glucuronides of benzo(a)pyrene phenols, diols and quinols, indicating that glucuronidation plays an important role in the prevention of formation of cytotoxic and carcinogenic intermediates in these animals. Administration of various xenobiotic agents indicated that polychlorinated biphenyls specifically induced phenol UDPGT activity in hepatic and renal tissue, whilst the carcinogen, 3-methylcholanthrene induced this activity solely in hepatic tissue. A procedure for the purification of hepatic UDPGTs was reported that enabled the physical separation of different UDPGT isoforms from this species indicating that they are polymorphic. One isoform that catalysed the glucuronidation of the phenolic heterocyclic compound, L-naphthol was purified 380 fold over solubilised hepatic microsomes' to apparent homogeneity with a subunit molecular weight of 55kDa. A purified UDPGT preparation was used to raise polyclonal antibodies which were applied to investigating the aforementioned biological variations in UDPGT expression at the molecular level. Such immunoblot analysis indicated that differential expression was due to varied complements of UDPGT isoenzymes. Molecular biological analysis was also employed to give an insight into the evolution of the enzyme. This work indicated that UDPGT isoforms in this piscine species had epitopes in common with their mammalian counterparts, however preliminary studies indicated no such similarity between UDPGT genes in the respective species. The relevance of these data to interspecies toxicity and evolution of detoxication enzyme systems is discussed.
319

BIOLOGICAL ROLES OF T4 BACTERIOPHAGE CODED ENZYMES AS VIRION PROTEINS

Mosher, Richard Arthur January 1978 (has links)
No description available.
320

Group I aptazymes as genetic regulatory switches

Marshall, Kristin Ann 28 March 2011 (has links)
Not available / text

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