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Lactobacillus casei BL23 expresses two enzymes encoded by the genes iolG1 and iolG2. They have been putatively assigned as myo-inositol dehydrogenases by sequence comparison. The enzyme catalyzes the reversible conversion of myo-inositol to scyllo-inosose and the concurrent reduction of NAD+ to NADH. iolG1 was subsequently determined to be a myo-inositol dehydrogenase but iolG2 was determined to be a scyllo-inositol dehydrogenase. Sequence analysis and kinetics by themselves did not provide insight as to why the enzymes are functionally different. This manuscript provides a structural rationalization for the differences in stereoisomer selectivity by X- ray crystal structure analysis and comparison. High resolution apo, binary, and ternary crystal structures for iolG1 and iolG2 wild type enzymes were determined. For iolG1 the ternary structures were determined for myo-inositol and d-chiro-inositol and for iolG2 the scyllo-inositol bound structure was determined. The high resolution structure information revealed the composition of their respective active sites and showed that subtle differences in critical amino acids for each enzyme define the orientation of the inositol stereoisomer for inline transfer of a hydride to NAD+. Mutagenesis studies of a closely related myo-inositol dehydrogenase from Bacillus subtilis were carried out. The wild type structure for BsIDH had already been determined and characterized. A portion of the results in this manuscript briefly explore structures of dehydrogenase mutants which validate the structural role of residues involved in cofactor selectivity

Wong Wei-yan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 221-242). / Abstracts in English and Chinese. / Thesis committee --- p.i / Declaration --- p.ii / Acknowledgements --- p.iii / Abstract in Chinese --- p.iv / Abstract in English --- p.vi / List of abbreviations --- p.viii / List of figures --- p.xi / List of tables --- p.xv / Content: --- p.xvi / General introduction --- p.1 / Aldehyde dehydrogenase superfamily --- p.3 / Background of antiquitin --- p.5 / Plant antiqutins (ALDH7B) --- p.5 / Animal antiquitins (ALDH7A) --- p.8 / Human antiquitin information on NCBI --- p.14 / Rationale of studying the inducibility of annquitin and overexpression of it in HEK293 and HepG2 cells --- p.16 / Flowchart 1 Procedure of antiquitin expression studies in the HEK293 and HepG2 cells under stress --- p.19 / Flowchart 2 Procedure to study antiquitin expression in the HEK293 and HepG2 cells after in silico promoter search --- p.20 / Flowchart 3 Procedure to study antiquitin overexpressed HEK293 and HepG2 cells --- p.21 / Chapter Chapter 1 --- Inducibility of antiquitin in the HEK293 and HepG2 cells under hyperosmotic stress / Chapter 1.1 --- Introduction --- p.22 / Chapter 1.1.1 --- Cellular response to hyperosmotic stress --- p.22 / Chapter 1.1.2 --- Methods to study the responses of cells under hyperosmotic stress --- p.24 / Chapter 1.2 --- Materials --- p.26 / Chapter 1.2.1 --- Cell culture media --- p.26 / Chapter 1.2.2 --- Buffers for RNA use --- p.26 / Chapter 1.2.3 --- Buffers for DNA use --- p.27 / Chapter 1.2.4 --- Other chemicals --- p.27 / Chapter 1.3 --- Methods --- p.28 / Chapter 1.3.1 --- Culture of HEK293 and HepG2 cells --- p.28 / Chapter 1.3.2 --- Hyperosmotic stress on HEK293 and HepG2 cells --- p.29 / Chapter 1.3.3 --- MTT assay --- p.29 / Chapter 1.3.4 --- Total RNA extraction --- p.30 / Chapter 1.3.5 --- Reverse transcription polymerase chain reaction (RT-PCR) --- p.30 / Chapter 1.3.6 --- Polymerase chain reaction (PCR) --- p.31 / Chapter 1.3.7 --- Quantification of PCR products --- p.31 / Chapter 1.3.8 --- Statistical analysis --- p.33 / Chapter 1.4 --- Results --- p.34 / Chapter 1.4.1 --- Viability of HEK293 and HepG2 cells under hyperosmotic stress --- p.34 / Chapter 1.4.2 --- Validation of RNA quality --- p.34 / Chapter 1.4.3 --- Validation and determination of PCR conditions --- p.40 / Chapter 1.4.4 --- Inducibility of antiquitin in HEK293 cells under hyperosmotic stress / Chapter 1.4.5 --- Inducibility of antiquitin in HepG2 cells under hyperosmotic stress --- p.43 / Chapter 1.4.6 --- Inducibility of aldose reductase under hyperosmotic stress --- p.43 / Chapter Chapter 2 --- "In silico studies of human antiquitin promoter, genomics sequences and open reading frame" --- p.54 / Chapter 2.1 --- Introduction --- p.54 / Chapter 2.1.1 --- Eukaryotic promoters --- p.55 / Chapter 2.1.2 --- Key events in transcriptional initiation --- p.55 / Chapter 2.1.3 --- Alternative splicing of mRNA --- p.57 / Chapter 2.1.4 --- Bipartite nuclear localization signal (NLS) --- p.57 / Chapter 2.2 --- Methods --- p.60 / Chapter 2.2.1 --- Putative promoter studies of human antiquitin --- p.60 / Chapter 2.2.2 --- Putative promoter studies of Arabidopsis thaliana antiquitin --- p.60 / Chapter 2.2.3 --- Analysis for the alternative splicing of human antiquitin mRNA --- p.60 / Chapter 2.2.4 --- Analysis for the nuclear localization signal (NLS) of human antiquitin amino acid sequence --- p.61 / Chapter 2.2.5 --- Nucleotide / amino acid sequence analyses --- p.61 / Chapter 2.3 --- Results --- p.62 / Chapter 2.3.1 --- Computer search for the putative cis-acting elements on human antiquitin promoter --- p.62 / Chapter 2.3.2 --- Comparison of cis-acting elements found on human antiquitin promoter with those on Arabidopsis thaliana antiquitin promoter --- p.62 / Chapter 2.3.3 --- Possibilities of alternative splicing isoforms of human antiquitin / Chapter 2.3.4 --- Possibilities of bipartite nuclear localization signals on human antiquitin protein --- p.83 / Chapter Chapter 3 --- Overexpression of antiquitin in HEK293 and HepG2 cells and their characterization / Chapter 3.1 --- Introduction --- p.86 / Chapter 3.1.1 --- Cell cycle of a human somatic cell --- p.88 / Chapter 3.1.2 --- Detection of changes in the transcriptome --- p.90 / Chapter 3.1.3 --- Human genome U133 Plus 2.0 array --- p.95 / Chapter 3.1.4 --- Detection of changes in the proteome --- p.96 / Chapter 3.1.5 --- MALDI-TOF MS --- p.97 / Chapter 3.2 --- Materials --- p.99 / Chapter 3.2.1 --- Solutions for cell culture use --- p.99 / Chapter 3.2.2 --- Solutions for cloning --- p.99 / Chapter 3.2.3 --- Buffers for cell cycle analysis --- p.99 / Chapter 3.2.4 --- Buffers for two-dimensional (2D) electrophoresis --- p.100 / Chapter 3.2.5 --- Solutions for silver staining --- p.101 / Chapter 3.2.6 --- Solutions for Coomassie blue protein staining --- p.102 / Chapter 3.2.7 --- Solutions for Western blotting --- p.102 / Chapter 3.2.8 --- Solutions for mass spectrometry --- p.103 / Chapter 3.3 --- Methods --- p.104 / Chapter 3.3.1 --- Hypoosmotic stress --- p.104 / Chapter 3.3.2 --- Heat shock --- p.104 / Chapter 3.3.3 --- Oxidative stress treatment / Chapter 3.3.4 --- Chemical hypoxia --- p.104 / Chapter 3.3.5 --- Treatment of forskolin --- p.106 / Chapter 3.3.6 --- Culture of SHSY5Y cells and its differentiation --- p.106 / Chapter 3.3.7 --- Cloning of pBUDCE4.1/ATQ --- p.106 / Chapter 3.3.8 --- PCR product purification --- p.107 / Chapter 3.3.9 --- Preparation of pEGFP.N1 vector for co-transfection --- p.109 / Chapter 3.3.10 --- Transfection of HEK293 and HepG2 cells --- p.109 / Chapter 3.3.11 --- Assays to characterize transient transfected HEK293 and HepG2 cells --- p.110 / Chapter 3.3.11.1 --- Transfection efficiency monitoring --- p.110 / Chapter 3.3.11.2 --- Cell cycle analysis --- p.112 / Chapter 3.3.11.3 --- Cell doubling time measurement --- p.112 / Chapter 3.3.11.4 --- Stress responsiveness --- p.113 / Chapter 3.3.11.5 --- Oligonucleotide array analysis --- p.113 / Chapter 3.3.11.5.1 --- Total RNA extraction --- p.113 / Chapter 3.3.11.5.2 --- Oligonucleotide array preparations --- p.113 / Chapter 3.3.11.5.3 --- Data analysis --- p.114 / Chapter 3.3.11.6 --- Two-dimensional (2D) electrophoresis --- p.115 / Chapter 3.3.11.6.1 --- Total protein extraction --- p.115 / Chapter 3.3.11.6.2 --- Protein quantification --- p.115 / Chapter 3.3.11.6.3 --- First dimension electrophoresis: isoelectric focusing (IEF) --- p.115 / Chapter 3.3.11.6.4 --- Second dimension electrophoresis: SDS- --- p.116 / Chapter 3.3.11.6.5 --- Silver staining --- p.116 / Chapter 3.3.11.6.6 --- Spots detection --- p.117 / Chapter 3.3.11.7 --- Preparations of samples for MALDI-TOF MS --- p.117 / Chapter 3.3.11.7.1 --- Silver de-staining --- p.117 / Chapter 3.3.11.7.2 --- In-gel tryptic digestion --- p.118 / Chapter 3.3.11.7.3 --- Peptide extraction --- p.118 / Chapter 3.3.11.7.4 --- ZipTip® samples desalting and concentrating --- p.119 / Chapter 3.3.11.7.5 --- MALDI-TOF MS --- p.119 / Chapter 3.3.11.8 --- Western blotting --- p.119 / Chapter 3.3.11.8.1 --- Antibodies probing --- p.120 / Chapter 3.3.11.8.2 --- Enhanced chemiluminescence's (ECL) assay --- p.121 / Chapter 3.4 --- Results --- p.122 / Chapter 3.4.1 --- Inducibility of antiquitin in HEK293 cells under xenobiotic stimulus --- p.122 / Chapter 3.4.2 --- Inducibility of antiquitin in HEK293 and HepG2 cells under chemical hypoxia --- p.122 / Chapter 3.4.3 --- Inducibility of antiquitin in HEK293 and HepG2 cells under hypoosmotic stress --- p.122 / Chapter 3.4.4 --- Inducibility of antiquitin in HEK293 and HepG2 cells under heat shock --- p.122 / Chapter 3.4.5 --- Inducibility of antiquitin in HEK293 and HepG2 cells under forskolin challenge --- p.128 / Chapter 3.4.6 --- Expression of antiquitin in differentiating SHSY5Y cells by retinoic acid and N2 supplement --- p.128 / Chapter 3.4.7 --- Overexpression of antiquitin in HEK293 and HepG2 cells --- p.128 / Chapter 3.4.8 --- Viability of transfected HEK293 and HepG2 cells under hyperosmotic stress --- p.136 / Chapter 3.4.9 --- Cell doubling times of transfected HEK293 and HepG2 cells --- p.143 / Chapter 3.4.10 --- Cell cycle analysis of transfected HEK293 and HepG2 cells --- p.143 / Chapter 3.4.11 --- "Western blot analysis of cyclin D, cyclin A and cyclin B of transfected HEK293 and HepG2 cells" --- p.148 / Chapter 3.4.12 --- RNA quality control tests for oligonucleotide array analysis --- p.148 / Chapter 3.4.13 --- Oligonucleotide array analysis on transfected HEK293 and HepG2 cells --- p.155 / Chapter 3.4.14 --- Two-dimensional electrophoresis of transfected HEK293 and HepG2 cells --- p.169 / Chapter 3.4.15 --- MALDI-TOF MS of transfected HEK293 and HepG2 cells --- p.169 / Chapter 3.4.16 --- Genes and proteins upregulnted in the antiquitin transfected HEK293 and HepG2 cells --- p.190 / Discussion --- p.197 / Reference --- p.221 / Appendix Materials used in the project --- p.243

by Tang Wai Kwan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 91-110). / Abstracts in English and Chinese. / Acknowledgements / 論文摘要 / Abstract / Abbreviations / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Aldehyde Dehydrogenase Extended Family --- p.1 / Chapter 1.1.1 --- Phylogenetic Tree --- p.2 / Chapter 1.1.2 --- Physiological Functions --- p.4 / Chapter 1.1.3 --- Structural Conservations --- p.7 / Chapter 1.2 --- ALDH-1 and ALDH-2 --- p.9 / Chapter 1.3 --- Antiquitin --- p.11 / Chapter 1.4 --- Osmoregulation --- p.14 / Chapter 1.4.1 --- Osmoprotectant --- p.14 / Chapter 1.4.2 --- Betaine Aldehyde Dehydrogenase --- p.15 / Chapter 1.5 --- Objectives of the Present Study --- p.18 / Chapter Chapter 2 --- Purification and Characterization of Seabream ALDH-2 and Antiquitin --- p.20 / Chapter 2.1 --- Introduction --- p.20 / Chapter 2.2 --- Materials --- p.21 / Chapter 2.3 --- Methodology / Chapter 2.3.1 --- Preparation of Crude Tissue Extract --- p.22 / Chapter 2.3.2 --- Synthesis of α-Cyanocinnamate Sepharose --- p.22 / Chapter 2.3.3 --- Synthesis of p-Hydroxyacetophenone Sepharose --- p.23 / Chapter 2.3.4 --- Purification of ALDH-2 --- p.23 / Chapter 2.3.5 --- Purification of Antiquitin --- p.24 / Chapter 2.3.6 --- Enzyme and Protein Assays --- p.24 / Chapter 2.3.7 --- Electrophoretic Procedures / Chapter 2.3.7.1 --- Sodium Dodecyl Sulfate Polyacrylamide Gel Electrophoresis (SDS-PAGE) --- p.26 / Chapter 2.3.7.2 --- Native PAGE --- p.27 / Chapter 2.3.7.3 --- Isoelectric focusing (IEF) --- p.27 / Chapter 2.3.8 --- N-terminal Amino Acid Sequencing --- p.28 / Chapter 2.4 --- Results / Chapter 2.4.1 --- Tissue Distribution of ALDH --- p.29 / Chapter 2.4.2 --- Purification and Molecular Properties of ALDH-2 --- p.31 / Chapter 2.4.3 --- Kinetic Properties of ALDH-2 --- p.42 / Chapter 2.4.4 --- Purification and Molecular Properties of Antiquitin --- p.49 / Chapter 2.4.5 --- Kinetic Properties of Antiquitin --- p.54 / Chapter Chapter 3 --- Discussion / Chapter 3.1 --- Tissue Distribution --- p.66 / Chapter 3.2 --- N-terminal Amino Acid Sequencing --- p.67 / Chapter 3.3 --- Purification of Seabream ALDH --- p.68 / Chapter 3.3.1 --- Separation of Two ALDH isoforms --- p.69 / Chapter 3.3.2 --- Binding Affinity of α-Cyanocinnamate Sepharose --- p.70 / Chapter 3.3.3 --- Purification --- p.72 / Chapter 3.4 --- Electrophoretic Properties --- p.73 / Chapter 3.5 --- pH and Temperature Stability --- p.74 / Chapter 3.6 --- Substrate Specificity --- p.77 / Chapter 3.7 --- Possible Functions of Antiquitin --- p.80 / Chapter 3.8 --- Future Prospects --- p.84 / Chapter Chapter 4 --- Conclusion --- p.90 / Chapter Chapter 5 --- References --- p.91

Antiquitin (ATQ) belongs to the superfamily of aldehyde dehydrogenase (ALDH). It is an evolutionarily conserved protein as shown from its high amino acid sequence identity between human and its plant counterparts. Therefore, ATQ is believed to play an important physiological role. Until now, however, studies on ATQ are limited and its cellular function is uncertain. Recently, we have first demonstrated the aldehyde oxidizing ability of ATQ purified from the liver of black seabream (Acanthopagrus schlegeli). To further investigate this protein, different attempts have been made. / Recombinant ATQ has been successfully expressed in E. coli. Kinetics studies showed that it possessed similar characteristics with its native enzyme. The recombinant protein was produced in large amount for protein crystallization. Crystal of ATQ was obtained and its X-ray structure was solved to 2.8 A in complex with NAD+. Tetrameric ATQ was a dimer of dimer. Three domains can be found in the subunit structure of ATQ, the NAD+-binding domain, catalytic domain and oligomerization domain. In each of the NAD+-binding domain, one molecule of NAD + could be found. The overall structure of ATQ was similar to other tetrameric ALDHs, but the coenzyme binding was in a single "hydride transfer" conformation and the density was well-defined which was contrast to most ALDH structures. Structural study of the substrate-binding pocket explained the failure of ATQ in oxidizing several aldehydes which is specific to certain members of ALDH. / The ATQ full-length cDNA of black seabream was obtained. It consisted of 2309 by with a 153 nucleotide long 5' UTR, and a 209 nucleotide long 3' UTR. An ORF of 1533 by which encoded a protein with 511 amino acids was found. This putative protein showed the highest of 87% sequence identity with zebrafish ATQ, and ∼60% with plant ATQs. Tissue distribution was studied by RT-PCR. A high level of mRNA expression was observed in liver and kidney. Subcellular localization study using green fluorescent protein (GFP) fusion protein showed that ATQ was expressed in cytoplasm. However, another in-frame initiation methionine (M1) was found 31 residues before this generally accepted methionine (M2). Both iPSORT analysis and experimental studies using GFP fusion protein indicated that the 31 amino acid peptide contained a mitochondrial-targeting signal. / Tang Wai Kwan. / "July 2005." / Adviser: Fong Wing Ping. / Source: Dissertation Abstracts International, Volume: 67-07, Section: B, page: 3603. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (p. 130-145). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract in English and Chinese. / School code: 1307.

Thesis (Ph. D.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains xi, 183 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references.

Alkylierte polyzyklische aromatische Kohlenwasserstoffe (alk-PAK) kommen zusammen mit rein aromatischen polyzyklischen Kohlenwasserstoffen u.a. im Zigarettenrauch, Dieselabgasen sowie einigen Lebensmitteln (z.B. Freilandgemüse, planzliche Öle und Fette) vor. Benzylische Hydroxylierung und nachfolgende Sulfokonjugation ist ein wichtiger Bioaktivierungsweg für einige alk-PAK. Oxidation der benzylischen Alkohole durch Alkoholdehydrogenasen (ADH) und Aldehyddehydrogenasen (ALDH) zur Carbonsäure könnte einen wichtigen Detoxifizierungsweg in Konkurrenz zur Aktivierung durch Sulfotransferasen (SULT) darstellen, was für 1-Hydroxymethylpyren in der Ratte bereits gezeigt wurde (Ma, L., Kuhlow, A. & Glatt, H. (2002). Polycyclic Aromat Compnds 22, 933-946). Durch Hemmung der ADH und/oder ALDH ist eine verstärkte Aktivierung zu erwarten, wie in der besagten Studie ebenfalls nachgewiesen wurde. Insbesondere Ethanol kommt in diesem Zusammenhang eine Rolle als möglicher Risikofaktor für alk-PAK induzierte Kanzerogenese zu. Menschen konsumieren häufig große Mengen Ethanol und oft besteht eine Koexposition mit alk-PAK (z.B. durch Rauchen). Ähnliches gilt für 5-(Hydroxymethyl)-2-furfural (HMF), einem Pyrolyseprodukt reduzierender Zucker, dem gegenüber Menschen in recht hohen Mengen exponiert sind. Auch bei HMF steht der ADH- und ALDH-vermittelte oxidative Metabolismus in Konkurrenz zu einer Aktivierung durch Sulfokonjugation. Um die Bedeutung humaner ADH und ALDH im Metabolismus von alk-PAK und von HMF aufzuklären, wurden alle bekannten humanen ADH sowie die humanen ALDH2 und 3A1 (aus theoretischen Überlegungen heraus die vielversprechendsten Formen) für kinetische Analysen in Bakterien exprimiert. Als Enzymquelle dienten zytosolische Präparationen und durch Anionenaustauschchromatographie partiell gereinigte Enzyme. In der vorliegenden Arbeit wurde nachgewiesen, dass primäre benzylische Alkohole von Methyl- und Dimethylpyrenen gute Substrate humaner ADH sind. Sekundäre benzylische Alkohole und benzylische Alkohole von alk-PAK mit größerem Kohlenwasserstoffgrundgerüst erwiesen sich dagegen als schlechte Substrate. Vier Formen (ADH1C, 2, 3 und 4) wurden näher analysiert. Dazu wurden sie partiell gereinigt, primär um die störende endogene Bakterien-ADH zu eliminieren. Alle untersuchten ADH waren in der Lage Pyrenylmethanole zu oxidieren. Insbesondere ADH2 katalysierte die Oxidation der Pyrenylmethanole effizient, aber auch für ADH1C und 4 waren die Pyrenylmethanole gute Substrate. ADH3 oxidierte die Pyrenylmethanole mit geringer katalytischer Effizienz. Die Reduktion der entsprechenden Pyrenaldehyde durch ADH1C, 2 und 4 wurde mit noch höherer Effizienz katalysiert als die Oxidation der Pyrenylmethanole, was die Bedeutung von ALDH für die effiziente Detoxifizierung dieser Verbindungen unterstreicht. In einer an diese Arbeit angelehnten Diplomarbeit (Rost, K. (2007). Universität Potsdam, Mathematisch-Naturwissenschaftliche Fakultät) wurde auch tatsächlich gezeigt, dass humane ALDH2 aber auch ALDH3A1 in der Lage sind, die Pyrenaldehyde zu Pyrenylcarbonsäuren zu oxidieren. Die bestimmten kinetischen Parameter legen nahe, dass insbesondere ALDH2 von Bedeutung für die Detoxifizierung von Methyl- und Dimethylpyrenen ist. Schon allein auf Grund der an der Detoxifizierung beteiligten Enzyme ist Ethanolaufnahme bei Koexposition mit Pyrenderivaten als Risiokofaktor anzusehen. Es ist wahrscheinlich, dass Ethanol und, nach dessen Oxidation, Acetaldehyd als konkurrierende Substrate die ADH- und ALDH-katalysierte Oxidation von Pyrenylmethanolen bzw. Pyrenaldehyden inhibieren und somit zu einer verstärkten SULT-vermittelten Aktivierung der Pyrenylmethanole führen. In der Tat wurde eine effiziente Inhibition der ADH2-katalysierten Oxidation von 1-Hydroxymethylpyren und von 1-(Hydroxymethyl)-8-methylpyren durch physiologisch relevante Ethanolkonzentrationen nachgewiesen. Drei humane ADH (4, 2 und 3), die HMF effizient zum 2,5-Diformylfuran oxidieren können, wurden identifiziert. Durch ALDH-katalysierte Weiteroxidation dieser Substanz entsteht schließlich 2,5-Furandicarbonsäure, die nach HMF-Exposition auch tatsächlich im menschlichen Urin gefunden wurde (Jellum, E., Børresen, H. C. & Eldjarn, L. (1973). Clin Chim Acta 47, 191-201). Weiter wurde gezeigt, dass ALDH3A1, aber auch ALDH2 HMF effizient zur 5-(Hydroxymethyl)-2-furancarbonsäure (HMFA) oxidieren können, ein weiterer nachgewiesener HMF Metabolit in vivo. Dass die ADH-katalysierte Oxidation von HMFA und nachfolgende ALDH-katalysierte Oxidation zur Bildung von 2,5-Furandicarbonsäure einen nennenswerten Anteil beträgt, kann aufgrund der kinetischen Daten für HMFA als Substrat humaner ADH ausgeschlossen werden. Die beobachteten Enzymaktivitäten lassen den Schluss zu, dass Ethanolaufnahme zu einer Reduktion des oxidativen HMF Metabolismus führt und somit eine Aktivierung von HMF durch Sulfokonjugation begünstigt. / Alkylated polycyclic aromatic hydrocabons (alk-PAH), together with purely aromatic PAH, are present e.g. in tobacco smoke, diesel exhausts and also in some foods (e.g. outdoor vegetables, vegetable oils). Benzylic hydroxylation and subsequent sulfo conjugation is an important metabolic activation pathway for some of these compounds. Nevertheless, oxidation of the benzylic alcohols by alcohol dehydrogenases (ADH) and subsequently by aldehyde dehydrogenases (ALDH) can compete with the sulfo conjugation. Therefore, this pathway is probably important in the detoxification as could be shown for the representative compound 1-hydroxymethylpyrene in the rat (Ma, L., Kuhlow, A. & Glatt, H. (2002). Polycyclic Aromat Compnds 22, 933-946). Inhibition of ADH and/or ALDH should increase bioactivation as indeed was shown for 1-hydroxymethylpyrene in this study. Particularly ethanol, a competing ADH substrate, is of high interest in this context. Humans often consume large quantities of ethanol and often they are coexposed to alk-PAH (e.g. due to tobacco smoking). Similar relationships can be considered for 5-(hydroxymethyl)-2-furfural (HMF), a common pyrolysate of reducing sugars with high exposure to humans. Oxidative metabolism of HMF by ADH and ALDH also competes with its bioactivation by sulfotransferases (SULT). To clarify the importance of human ADH and ALDH in the metabolism of alk-PAH and HMF, all known human ADH as well as human ALDH2 and 3A1 (the most promising forms according to theoretical considerations) were expressed in bacteria for kinetic anlalyses. Cytosolic preparations or enzymes partially purified by anion exchange chromatography were used as enzyme source. In the present study it was shown that primary benzylic alcohols of methyl- and dimethylpyrenes were good substrates for human ADH. However, secondary benzylic alcohols and benzylic alcohols derived from alk-PAH with a bulkier hydrocarbon skeletal were poor substrates for human ADH. The most promising forms (ADH1C, 2, 3 and 4) were partially purified and further analysed. The purification step was necessary to eliminate the bacterial ADH. Particularly ADH2 was efficient for oxidation of pyrenylmethanols, although ADH1C and 4 were relatively efficient too. ADH3 was also capable of oxidising the tested pyrenylmethanols but with low catalytic efficiency. The reduction of the corresponding pyrene aldehydes was catalysed by ADH1C, 2 and 4 even with higher efficiency than the oxidation of the pyrenylmethanols emphasising the importance of ALDH for the detoxification of these compounds. In a diploma work related to the present study (Rost, K. (2007). University of Potsdam, Mathematisch-Naturwissenschaftliche Fakultät) it was shown that human ALDH2, but also ALDH3A1, can oxidise pyrene aldehydes to pyrenylcarboxylic acids. Particularly ALDH2 efficiently catalyse these reactions and, therefore, is probably of importance for the detoxification of methyl- and dimethylpyrenes. Due to the enzymes involved ethanol consumption could be a risk factor for methyl- and dimethylpyrene induced damage in the case of coexposure to methyl- and dimethylpyrenes. It is probable that ethanol and, after its oxidation, acetaldehyde will inhibit the ADH- and ALDH-catalysed oxidation of pyrenylmethanols and pyrenealdehydes. Indeed, it was shown that ADH2 catalysed oxidation of 1-hydroxymethylpyrene and of 1-(hydroxymethyl)-8-methylpyrene was efficiently inhibited by physiologically attainable concentrations of ethanol. Three human ADHs (4, 2 and 3) that efficiently oxidise HMF to 2,5-diformylfuran were identified. Further oxidation by ALDH leads to 2,5-furandicarboxylic acid, which was found in human urine after exposure to HMF (Jellum, E., Børresen, H. C. & Eldjarn, L. (1973). Clin Chim Acta 47, 191-201). Moreover, it was shown that human ALDH3A1 and also ALDH2 efficiently oxidise HMF to 5-(hydroxymethyl)-2-furancarboxylic acid (HMFA), which was also found in human urine. That 2,5-furandicarboxylic acid can be formed in significant amounts by ADH-catalysed oxidation of HMFA and subsequent oxidation by ALDH could be ruled out due to the kinetic data with HMFA as a substrate for human ADH. Due to the enzymes involved it is probable that ethanol consumption will inhibit the oxidative metabolism of HMF and, therefore, will increase the sulfo conjugation of HMF.

Thesis (Ph. D.)--West Virginia University, 1999. / Title from document title page. Document formatted into pages; contains x, 125 p. : ill. Vita. Includes abstract. Includes bibliographical references.

Thesis (Ph. D.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains viii, 123 p. : ill. (some col.). Includes abstract. Includes bibliographical references.

Thesis (Ph. D.)--West Virginia University, 2009. / Title from document title page. Document formatted into pages; contains vii, 91 p. : ill. (some col.). Includes abstract. Includes bibliographical references.