β-N-acetylhexosaminidases (EC 3.2.1.52, GH 20) are retaining exo-glycosidases that in vivo cleavage both β-N-acetylglucosamine (GlcNAc) or β-N-acetylgalactosamine (GalNAc) residues fom glycostructures. Under suitable reaction conditions, these enzymes are able to synthesize the glycosidic bond in good yields. Substitution of selected amino acid(s) in the emzyme active site by site-directed mutagenesis may change the enzyme's substrate specificity or suppress the hydrolytic activity of the enzyme in favor of synthesis. The present thesis deals with three mutant β-N-acetylhexosaminidases from Talaromyces flavus, in which the amino acid residues responsible for binding to C-4 hydroxyl of the substrate (Arg218, Glu546) were exchanged for amino acids proposed on the basis of molecular modeling. The effect of introduced single point mutations on substrate specificity of prepared enzymes was studied. Mutant β-N-acetylhexosaminidases were heterologously expressed in Pichia pastoris and characterized. Furthermore, transglycosylation reactions with these enzymes were performed. The prepared carbohydrate products were characterized by NMR.

L’aquaporine-2 (AQP2) est le canal responsable de la réabsorption finale d’eau au niveau du tubule collecteur du rein. À la base, contenue dans des vésicules internes, l’AQP2 est acheminée à la membrane apicale des cellules principales du tubule collecteur suite à une stimulation par l’hormone antidiurétique (ADH). L’incapacité à accomplir cette fonction entraîne le diabète insipide néphrogénique (DIN), une maladie caractérisée par l’inhabileté du rein à concentrer l’urine, entraînant une production de volumes urinaires élevés. Alors que les mutations récessives génèrent des protéines mal structurées et incapables de former des tétramères, les mutations dominantes sont capables de s’associer à leurs homologues sauvages, engendrant ainsi un DIN même chez les patients hétérozygotes. Ce mémoire présente l’analyse biochimique et fonctionnelle d’une nouvelle mutation naturelle de l’AQP2, la mutation T179N, aussi responsable du DIN. Cette dernière est particulièrement intéressante de par son génotype qui implique un caractère dominant, et sa position extracellulaire habituellement réservée aux mutations récessives. Les études comparatives de T179N à deux modèles de mutation récessive et dominante démontrent, tant en ovocytes de Xenopus laevis qu’en lignée cellulaire mpkCCDc14, le caractère récessif de cette nouvelle mutation. Les tests d’immunobuvardage de lysats d’ovocytes en membranes totales et membranes plasmiques purifiées ont révélé que seule la forme sauvage atteint la membrane plasmique alors que le mutant T179N est séquestré dans la cellule. En accord avec ce résultat, les analyses de perméabilité fonctionnelle démontrent aussi une absence d’activité pour T179N. En cellule mpkCCDc14, le mutant T179N exprimé seul n’atteint pas la membrane plasmique suite à l’action de la forskoline, contrairement à la forme sauvage. Cependant, ce mutant peut s’associer à son homologue sauvage en coexpression tant dans les ovocytes qu’en lignée mpkCCDc14 sans toutefois engendrer l’effet typique de dominance négative. En fait, dans ce contexte de coexpression, on remarque une augmentation de la Pf de 83±7 % et une récupération d’adressage à la membrane plasmique en cellule (immunofluorescence). En conclusion, T179N serait un mutant récessif fonctionnellement récupérable lorsqu’en présence de l’AQP2 sauvage. / Aquaporin-2 (AQP2) is the channel responsible for the final reabsorption of water in the collecting duct of the kidney. Basically, contained in internal vesicles, the AQP2 is delivered to the apical membrane of the principal cells of the collecting tubule after stimulation by the antidiuretic hormone (ADH). The failure to perform this function causes nephrogenic diabetes insipidus (NDI); a disease characterized by the inability of the kidney to concentrate urine and induces the production of high urinary volumes. While recessive mutations generate poorly structured proteins unable to form tetramers, dominant mutations are capable of associating with their wild counterparts, thus generating a NDI even in heterozygous patients. This paper presents the biochemical and functional analysis of T179N, a new NDI-causing mutation of the human AQP2. The mutant is particularly interesting because of its dominant genotype, despite its extracellular position usually restricted to recessive mutations. Here, we compare T179N against archetypal recessive and dominant mutations using both Xenopus laevis oocytes and in mpkCCDc14 cell model, and show the recessive nature of the mutation. The immunoblot tests on oocytes lysates in purified total and plasma membranes revealed that only the wild type protein reaches the plasma membrane while the T179N mutant is sequestered within cellular stores. Accordingly, functional analyzes indicate that T179N is inactive. In mpkCCDc14 cells, T179N expressed alone does not reach the plasma membrane in response to forskolin stimulation, unlike the wild-type. However, T179N does show the capacity to associate with its wild-type counterpart in both oocytes and in mpkCCDc14 cells, although without displaying the typical dominant negative effect. In fact, when coexpressed along wild-type, T179N gains back the functionality, with a Pf increase of 83±7 % and adequate plasma membrane targeting in cells (immunofluorescence). In conclusion, the mutant T179N is a mild recessive mutation that is susceptible to functional recovery when in presence of wild type AQP2.

La production biologique d'hydrogène (H2) représente une technologie possible pour la production à grande échelle durable de H2 nécessaire pour l'économie future de l'hydrogène. Cependant, l'obstacle majeur à l'élaboration d'un processus pratique a été la faiblesse des rendements qui sont obtenus, généralement autour de 25%, bien en sous des rendements pouvant être atteints pour la production de biocarburants à partir d'autres processus. L'objectif de cette thèse était de tenter d'améliorer la production d'H2 par la manipulation physiologique et le génie métabolique. Une hypothèse qui a été étudiée était que la production d'H2 pourrait être améliorée et rendue plus économique en utilisant un procédé de fermentation microaérobie sombre car cela pourrait fournir la puissance supplémentaire nécessaire pour une conversion plus complète du substrat et donc une production plus grande d'H2 sans l'aide de l'énergie lumineuse. Les concentrations optimales d’O2 pour la production de H2 microaérobie ont été examinées ainsi que l'impact des sources de carbone et d'azote sur le processus. La recherche présentée ici a démontré la capacité de Rhodobacter capsulatus JP91 hup- (un mutant déficient d’absorption-hydrogénase) de produire de l'H2 sous condition microaérobie sombre avec une limitation dans des quantités d’O2 et d'azote fixé. D'autres travaux devraient être entrepris pour augmenter les rendements d'H2 en utilisant cette technologie. De plus, un processus de photofermentation a été créé pour améliorer le rendement d’H2 à partir du glucose à l'aide de R. capsulatus JP91 hup- soit en mode non renouvelé (batch) et / ou en conditions de culture en continu. Certains défis techniques ont été surmontés en mettant en place des conditions adéquates de fonctionnement pour un rendement accru d'H2. Un rendement maximal de 3,3 mols de H2/ mol de glucose a été trouvé pour les cultures en batch tandis que pour les cultures en continu, il était de 10,3 mols H2/ mol de glucose, beaucoup plus élevé que celui rapporté antérieurement et proche de la valeur maximale théorique de 12 mols H2/ mol de glucose. Dans les cultures en batch l'efficacité maximale de conversion d’énergie lumineuse était de 0,7% alors qu'elle était de 1,34% dans les cultures en continu avec un rendement de conversion maximum de la valeur de chauffage du glucose de 91,14%. Diverses autres approches pour l'augmentation des rendements des processus de photofermentation sont proposées. Les résultats globaux indiquent qu'un processus photofermentatif efficace de production d'H2 à partir du glucose en une seule étape avec des cultures en continu dans des photobioréacteurs pourrait être développé ce qui serait un processus beaucoup plus prometteur que les processus en deux étapes ou avec les co-cultures étudiés antérieurément. En outre, l'expression hétérologue d’hydrogenase a été utilisée comme une stratégie d'ingénierie métabolique afin d'améliorer la production d'H2 par fermentation. La capacité d'exprimer une hydrogénase d'une espèce avec des gènes de maturation d'une autre espèce a été examinée. Une stratégie a démontré que la protéine HydA orpheline de R. rubrum est fonctionnelle et active lorsque co-exprimée chez Escherichia coli avec HydE, HydF et HydG provenant d'organisme différent. La co-expression des gènes [FeFe]-hydrogénase structurels et de maturation dans des micro-organismes qui n'ont pas une [FeFe]-hydrogénase indigène peut entraîner le succès dans l'assemblage et la biosynthèse d'hydrogénase active. Toutefois, d'autres facteurs peuvent être nécessaires pour obtenir des rendements considérablement augmentés en protéines ainsi que l'activité spécifique des hydrogénases recombinantes. Une autre stratégie a consisté à surexprimer une [FeFe]-hydrogénase très active dans une souche hôte de E. coli. L'expression d'une hydrogénase qui peut interagir directement avec le NADPH est souhaitable car cela, plutôt que de la ferrédoxine réduite, est naturellement produit par le métabolisme. Toutefois, la maturation de ce type d'hydrogénase chez E. coli n'a pas été rapportée auparavant. L'opéron hnd (hndA, B, C, D) de Desulfovibrio fructosovorans code pour une [FeFe]-hydrogénase NADP-dépendante, a été exprimé dans différentes souches d’E. coli avec les gènes de maturation hydE, hydF et hydG de Clostridium acetobutylicum. L'activité de l'hydrogénase a été détectée in vitro, donc une NADP-dépendante [FeFe]-hydrogénase multimérique active a été exprimée avec succès chez E. coli pour la première fois. Les recherches futures pourraient conduire à l'expression de cette enzyme chez les souches de E. coli qui produisent plus de NADPH, ouvrant la voie à une augmentation des rendements d'hydrogène via la voie des pentoses phosphates. / Biological hydrogen (H2) production represents a possible technology for the large scale sustainable production of H2 needed for a future hydrogen economy. However, the major obstacle to developing a practical process has been the low yields that are obtained, typically around 25%, well below those achievable for the production of other biofuels from the same feedstock. The goal of this thesis was to improve H2 production through physiological manipulation and metabolic engineering. One investigated hypothesis was that H2 production could be improved and made more economical by using a microaerobic dark fermentation process since this could provide the extra reducing power required for driving substrate conversion to completion and hence more H2 production might be obtained without using light energy. The optimal O2 concentrations for microaerobic H2 production were examined as well as the impact of carbon and nitrogen sources on the process. The research reported here proved the capability of Rhodobacter capsulatus JP91 hup- (an uptake-hydrogenase deficient mutant) to produce H2 under microaerobic dark conditions with limiting amounts of O2 and fixed nitrogen. Further work should be undertaken to increase H2 yields using this technology. In addition, a photofermentation process was established to improve H2 yield from glucose using R. capsulatus JP91 hup- strain either in batch and/or continuous culture conditions. Some technical challenges in establishing the proper operational conditions for increased H2 yield were overcome. A maximum yield of 3.3 mols of H2/ mol of glucose was found for batch cultures whereas in continous cultures it was 10.3 mols H2/ mol glucose, much higher than previously reported and close to the theoretical maximum value of 12 mols H2/ mol glucose. In batch cultures the maximum light conversion efficiency was 0.7% whereas it was 1.34% in continuous cultures with a maximum conversion efficiency of the heating value of glucose of 91.14%. Various approaches to further increasing yields in photofermentation processes are proposed. The overall results suggest that an efficient single stage photofermentative H2 production process from glucose using continuous cultures in photobioreactors could be developed which would be a much more promising alternative process to the previously studied two stage photofermentation or co-culture approaches. Furthermore, the heterologous expression of hydrogenases was used as a metabolic engineering strategy to improve fermentative H2 production. The capability of expressing a hydrogenase from one species with the maturation genes from another was examined. One strategy demonstrated that the orphan hydA of R. rubrum is functional and active when co-expressed in E. coli with hydE, hydF and hydG from different organisms. Co-expression of the [FeFe]-hydrogenase structural and maturation genes in microorganisms that lack a native [FeFe]-hydrogenase can successfully result in the assembly and biosynthesis of active hydrogenases. However, other factors may be required for significantly increased protein yields and hence the specific activity of the recombinant hydrogenases. Another strategy was to overexpress one of the highly active [FeFe]-hydrogenases in a suitable E. coli host strain. Expression of a hydrogenase that can directly interact with NADPH is desirable as this, rather than reduced ferredoxin, is naturally produced by its metabolism. However, the successful maturation of this type of hydrogenase in E. coli had not been previously reported. The Desulfovibrio fructosovorans hnd operon (hndA, B, C, and D genes), encoding a NADP-dependent [FeFe]-hydrogenase, was expressed in various E. coli strains with the maturation genes hydE, hydF and hydG of Clostridium acetobutylicum. Hydrogenase activities were detected in vitro, thus a multi-subunit NADP-dependent [FeFe]-active hydrogenase was successfully expressed and matured in E. coli for the first time. Future research could lead to the expression of this hydrogenase in E. coli host strains that overproduce NADPH, setting the stage for increased hydrogen yields via the pentose phosphate pathway.

Les furocoumarines constituent l'une des classes de métabolites secondaires dérivant de la voie de biosynthèse des phénylpropanoïdes. Elles ont été décrites comme étant des phytoaléxines mais sont également très largement utilisées par l'Homme pour leurs propriétés thérapeutiques. Un certain nombre d'études biochimiques ont été réalisées afin d'en comprendre la biosynthèse mais peu de choses sont connues concernant leur déterminisme moléculaire. Dans cette étude, nous nous sommes concentrés sur la caractérisation fonctionnelle de gènes appartenant aux prényltransférases aromatiques potentiellement impliquées dans cette voie de biosynthèse. Les prényltransférases catalysent la première étape de la voie de biosynthèse des furocoumarines linéaires ou angulaires. Elles permettent l'addition d'un groupement dimethylally pyrophosphate (DMAPP) sur l'umbelliférone. En utilisant SfN8DT-1, une prényltransférase aromatique récemment caractérisée, comme sonde, nous avons identifié 7 gènes candidats chez deux familles de plantes (Rutaceae et Apiaceae). Dans la mesure où il a été décrit que ces enzymes étaient des protéines membranaires, nous avons adapté un système d'expression hétérologue basé sur l'utilisation de N. benthamiana. Ce système a été validé par l'expression de deux protéines membranaires : un cytochrome P450 CYP98A22 et une prényltransférase déjà caractérisée SfN8DT-1. Nous avons ensuite utilisé ce système d'expression pour réaliser l'étude des 7 gènes nouvellement isolés. Ces travaux nous ont permis de caractériser la première umbelliferone prenyltransferase de Petroselinum crispum capable de catalyser in vitro et in vivo la prénylation du carbone 6 ou 8 de l'umbelliférone en présence de DMAPP permettant ainsi la synthèse respectivement de demethylsuberosin et d'osthenol. Par ailleurs, une étude réalisée in planta chez le persil a permis de mettre en évidence une relation positive entre le niveau d'expression du gène et la teneur en umbelliférone prénylée. L'étude de la surexpression du gène chez Ruta graveolens a permis de mettre en évidence un lien entre l'expression du gène et la disparition de l'umbelliférone. Enfin nous avons identifié la même activité pour une prényltransférase de Pastinaca sativa, ce qui nous amène à émettre l'hypothèse que l'étape de prénylation n'est pas une étape limitante dans la biosynthèse des furocoumarines angulaires, étant donné que le persil ne produit que des furocoumarines linéaires, tandis que le panais produit des furocoumarines linéaires et angulaires. L'utilisation de ces mêmes systèmes d'expression hétérologue de N. benthamiana et R. graveolens nous a également permis d'identifier une seconde prényltransférase aromatique capable de catalyser l'addition de géranylpyrophosphate (GPP) sur l'umbelliférone et sur l'esculétine / Furanocoumarins constitute one of the classes of secondary metabolites deriving from the phenylpropanoid biosynthetic pathway. These molecules are described as phytoalexins in plants but are also used by humans for their pharmaceutical properties. A large number of biochemical studies were carried out to understand their biosynthetic pathway but little information was available concerning the genes involved in the pathway. In this study, we focused on the characterization of genes encoding for aromatic prenyltransferases which were described to be involved in this pathway. Prenlyltransferases catalyze the entry step to the linear or angular furanocoumarin pathway. Hence they catalyze the addition of a dimethylallyl pyrophosphate (DMAPP) prenyl moiety to umbelliferone. Using a recently characterized aromatic prenyltransferase (SfN8DT-1) as a probe, we isolated 7 different candidate genes from two plant families (Rutaceae and Apiaceae). As these enzymes were described as membrane bound proteins, we adapted a heterologous expression system made up of Nicotiana benthamian aand we validated its efficiency by using two membrane-associated enzymes: a cytochrome P450 (CYP98A22) and the already described prenyltransferase SfN8DT-1. Subsequently, this system was used to perform the functional characterization of the 7 newly identified proteins. This way we succeeded to characterize the first umbelliferone prenyltransferase of Petroselinum crispum that was able to catalyze both the 6-C and 8-C prenylation of umbelliferone with DMAPP producing demethylsuberosin and osthenol respectively. We made evidence that these reactions occurred both in vitro and in vivo. In addition, in planta studies performed in P.crispum showed a positive relationship between the gene expression level and the content of prenylated umbelliferone. The overexpression of this gene was investigated in Ruta graveolens and we could provide evidences of a link between the enzymatic activity and the disappearance of umbelliferone. We also reported a similar activity for a prenyltransferase isolated from Pastinaca sativa, which makes us assume that the prenylation step is not a rate limiting step in the biosynthetic pathway of angular furanocoumarins since parsley is producing only linear furanocoumarins whereas parsnip is producing both linear and angular furanocoumarins. In addition, using the same N. benthamiana and R. graveolens heterologous expression systems, we identified a second aromatic prenyltransferase able to catalyze the addition of geranyl pyrophosphate (GPP) both to umbelliferone and esculetin

4 ABSTRACT Interleukin-1α (IL-1α) is a pleiotropic cytokine and a key mediator of host immune response. It is synthesised as a 31-kDa precursor, that is cleaved by the cysteine protease calpain into the 17-kDa mature IL-1α and the 16-kDa N- terminal peptide of IL-1α (IL-1αNTP). Although IL-1α can be secreted, act on target cells through the surface receptor IL-1RI and trigger the signal transduction pathway, increasing evidence points toward the involvement of IL-1α in certain nuclear processes. IL-1αNTP is highly conserved among higher eukaryotes and contains a nuclear localisation sequence; indeed, both the precursor and IL-1αNTP are found in the cell nucleus. Previously, a genetic interaction of IL-1α with nuclear histone acetyltransferase (HAT) complexes has been reported from mammalian cells and, interestingly, also from the heterologous yeast model. This thesis extends the research of the nuclear function of IL-1α and demonstrates that IL-1α physically associates with the HAT/Core module of yeast SAGA and ADA HAT complexes. Results of the HAT subunit gene knock-out experiments followed by a set of co-immunoprecipitations also suggest a novel model of the yeast SAGA complex assembly, in which ADA appears to represent only a partly functional HAT complex. In its natural milieu of mammalian cells, IL-1α...

Parmi les activités catalytiques les plus intéressantes présentes dans le latex de Carica papaya on trouve l'activité lipolytique (EC 3.1.1.X). En effet les enzymes lipolytiques peuvent catalyser des réactions d’hydrolyse sur divers substrats mais également, dans des conditions thermodynamiques favorables, des réactions de synthèse. De plus, elles sont actives en présence de solvants organiques, ce qui fait de ce type d’enzymes des biocatalyseurs spécialement attractifs pour des applications industrielles. Enfin, cette activité lipolytique est associée à la matrice insoluble du latex, et constitue donc une activité immobilisée. Cependant et pour cette même raison, il n'a pas été possible jusqu'à présent d'élucider la ou les séquences protéiques dans le latex responsables de cette activité lipolytique. En conséquence, cette thèse est dédiée à l'étude de l'activité lipolytique du latex de C. papaya. Pour cela, la purification partielle du latex de C. papaya a été réalisée. Ainsi, les propriétés catalytiques des fractions partiellement purifiées ont pu être déterminées pour l'hydrolyse de triglycérides, la résolution de mélanges racémique d'octyl ester de l'acide 2-bromo-phenylacétique, la synthèse de biopolymères et des lipides structurés. Parallèlement à cela, une recherche dans le génome de C. papaya des séquences codant les motifs conservés dans les protéines lipolytiques, ainsi que des essais d'expression in vivo dans les feuilles de la plante en conditions de stress a été effectuée, ce qui a permis d’isoler pour la première fois une lipase, CpLip2, exprimée in vivo chez C. papaya. Cette protéine, ainsi que 2 autres protéines déjà identifiées dans le latex de C. papaya, CpEst et CpLip1, ont été produites sous forme fonctionnelle en employant respectivement Nicothiana sp., Yarrowia lipolytica et Pichia pastoris comme systèmes d'expression. Finalement, certaines des propriétés biochimiques et catalytiques de ces protéines recombinantes ont pu être déterminées / Lipolytic activity (EC 3.1.1.X) is one of the most interesting catalytic activities from Carica papaya latex. Indeed lipolytic enzymes can catalyze not only hydrolysis but also various synthesis reactions due to their activity in organic solvents, which make them especially attractive for industrial applications. Nevertheless, most of the lipolytic activity present in latex is tightly associated to the insoluble fraction of the latex and up to now it has not been possible to determine which enzymes are responsible for the lipolytic activity of C. papaya latex. This PhD work is dedicated to the study of the lipolytic activity present in Carica papaya. Partial purification of lipolytic activity from C. papaya latex was carried out to evaluate the catalytic properties of the partially purified fractions in the hydrolysis of triglycerides, the resolution of racemic mixtures of 2-bromo-phenylacetic octyl ester, biopolymers and structured lipids synthesis. Bioinformatic analysis was also realized on C. papaya genome by searching conserved motifs for lipolytic proteins. Finally, assays of in vivo transcriptomic in the leaves of stressed C. papaya allowed the isolation of a new lipase produced in vivo (CpLip2, gene 1973.2). This protein, as well as two previously identified lipolytic enzymes from C. papaya, CpEst (gen 25.180) and CpLip1 (gen 55.143) were functionally expressed using Nicotiana sp.,Yarrowia lipolytica and Pichia pastoris as expression hosts, respectively. Finally, some of the biochemical and catalytic properties of these produced recombinant proteins were evaluated / Una de las actividades catalíticas más interesantes presentes en el látex de Carica papaya es la actividad lipolítica (3.1.1.X).Las enzimas lipolíticas pueden catalizar reacciones de hidrólisis sobre varios sustratos e igualmente, en condiciones termodinámicas favorables, pueden catalizar reacciones de síntesis. Adicionalmente, son activas en presencia de solventes orgánicos, por lo que son biocatalizadores atractivos para aplicaciones industriales. Sin embargo, la mayor parte de la actividad lipolítica del látex se encuentra asociada a la matriz insoluble del látex, formando un biocatalizador auto-inmovilizado.Por esta razón, hasta la fecha no ha sido posible elucidar qué enzima o enzimas son responsables de la actividad lipolítica observada en el látex de C. papaya. En consecuencia, la presente investigación está dedicada al estudio de la actividad lipolítica en Carica papaya. Para ello, se realizaron estudios de purificación parcial del látex de Carica papaya, así como la evaluación de las propiedades catalíticas de las fracciones parcialmente purificadas en la hidrólisis de triglicéridos, resolución de mezclas racémicas de octil éster del ácido 2-bromo-fenilacético y síntesis de biopolímeros y lípidos estructurados. Paralelamente, se realizó un análisis genómico mediante la búsqueda con motivos conservados que codifican para diversas proteínas lipolíticas, así como ensayos de transcriptómica para buscar la expresión in vivo de secuencias seleccionadas en las hojas de la planta, que permitieron encontrar por primera vez una expresión in vivo de una lipasa en C. papaya (CpLip2). Esta proteína y otras dos previamente identificadas en el látex de papaya (CpEst y CpLip1), fueron expresadas de forma funcional empleando respectivamente Nicotiana sp., Yarrowia lipolytica y Pichia pastoris como sistemas de expresión. Finalmente algunas de las propiedades bioquímicas y catalíticas de las proteínas expresadas fueron determinadas

Nitrilases are enzymes which catalyze the hydrolysis of a nitrile into the corresponding carboxylic acid and ammonia. These enzymes are potentially applicable in biocatalysis and bioremediation because of their advantages over the conventional (chemical) methods of nitrile hydrolysis (lower demand for energy, safety, simplicity, high yields, selectivity). In this work, genome mining was used to search for the sequences of hypothetical nitrilases from filamentous fungi. The amino acid sequences of previously characterized fungal nitrilases were used as the templates. Then the new synthetic genes together with other genes from our nitrilase library were expressed in E. coli and the substrate specificities of the enzymes thus produced were compared. Significant attention was focused on the relationships between the sequence of the enzyme and its substrate specificity. The arylacetonitrilases from Arthroderma benhamiae (NitAb) and Nectria haematococca (NitNh) were purified and characterized. Their substrate specificities, kinetic parameters, pH and temperature profiles and subunit and holoenzyme size were assessed. NitAb and NitNh together with other recombinant fungal nitrilases were employed in the hydrolysis of high concentrations of (R,S)-mandelonitrile in a batch or fed-batch mode. Nitrilase from...

6 Abstract Ellipticine (5,11-dimethyl-6H-pyrido[4,3-b]carbazole), an alkaloid isolated from Apocynaceae plants, exhibits significant antitumor and HIV activity. This antitumor agent binds to DNA and forms covalent DNA adducts. Enzymes, which are involved in its enzymatic activation, are cytochromes P450 (CYP) and peroxidases. To elucidate the effect of ellipticine on the expression and enzymatic activity of the individual components of the microsomal mixed function oxidase system in different tissues, we used rat model. Simultaneously, the effect of ellipticine and its cytotoxicity on different tumor cell lines was also investigated. Another part of the presented work was targeted on preparation of anti-peptide antibody against orphan cytochrome P450 2S1, which is highly expressed in many human tumours of the epithelial origin, for its detection in these tissues. For better understanding how CYP2S1 can contribute to the metabolism of xenobiotics, the protein was prepared by heterologous expression in E. coli. Furher, its role in metabolism of an antitumor drug ellipticine, a carcinogenic environmental pollutant benzo[a]pyrene (BaP) and its derivate BaP-7,8-dihydrodiol was examined. Utilizing a mouse model, the impact of pulmonary inflammation on the metabolism of an environmental carcinogen was...

A biologia da reprodução sexual de plantas é um campo de pesquisa de grande importância, já que a maioria dos alimentos consumidos pelo homem é composta de partes reprodutivas das plantas (frutos e sementes), oriundas do desenvolvimento de partes do pistilo fertilizado. Em Nicotiana tabacum, identificou-se um gene específico de estigma/estilete, SCI1 (Stigma/style Cell-cycle Inhibitor 1), que atua na inibição da proliferação celular (DePaoli et al., 2011). Através de ensaios de pull-down, verificou-se a interação da proteína SCI1 com uma proteína quinase dependente de ciclina (CDK) (Strini, dados não publicados). Este trabalho visou à caracterização dessa nova CDK, ortóloga da CDKG;2 de Arabidopsis. A sequência correspondente de N. tabacum (NtCDKG;2) foi amplificada por PCR, a partir de cDNAs de estigmas/estiletes, clonada e sequenciada, o que permitiu a confirmação de sua identidade. A expressão de NtCDKG;2 foi analisada nos diferentes órgãos vegetativos e reprodutivos, por qRT-PCR, o que evidenciou um perfil de expressão ubíqua. Ao estudar o perfil de expressão desse gene nos estigmas/estiletes dos doze estádios de desenvolvimento floral de N. tabacum, observa-se que NtCDKG;2 é mais expresso nos estádios tardios do desenvolvimento em direção à antese, indicando uma função importante de sua proteína ao final do desenvolvimento do pistilo. Análises de expressão de NtCDKG;2 em estigmas/estiletes, de plantas de N. tabacum com produção aumentada do hormônio auxina no pistilo, sugerem que NtCDKG;2 é regulado transcricionalmente por esse hormônio. A expressão transiente da proteína de fusão NtCDKG;2-GFP, em folhas de N. tabacum, evidenciou a localização nuclear da proteína em estudo. Também foram geradas plantas transgênicas estáveis com superexpressão e com silenciamento por RNAi de NtCDKG;2. Apesar dos altos níveis de transcritos de NtCDKG;2 nas plantas de superexpressão e dos baixos níveis nas plantas silenciadas, não foram observadas alterações fenotípicas macroscópicas nessas plantas. Adicionalmente, obteve-se a expressão da proteína NtCDKG;2, fusionada a uma tag de histidina em sua porção N-terminal, em células de Escherichia coliBL21(DE3)CodonPlusRP. Através dos estudos realizados neste trabalho e análises conjuntas da literatura, é possível propor que NtCDKG;2 codifique uma proteína que está envolvida no controle do ciclo celular nos estigmas/estiletes de N. tabacum. / The biology of plant sexual reproduction is a research field of great importance, since most of the food consumed by humans is composed of plant reproductive parts (fruits and seeds), originated by the development of fertilized pistil parts. In Nicotiana tabacum, it was identified a stigma/style-specific gene, SCI1 (Stigma/style Cell-cycle Inhibitor 1), which acts in the inhibition of cell proliferation (DePaoli et al., 2011). Through pull down assays, the interaction of the SCI1 protein with a cyclin-dependent protein kinase (CDK) was verified (Strini, unpublished). This work aimed the characterization of this new CDK, orthologous to the Arabidopsis CDKG;2. The N. tabacum corresponding sequence (NtCDKG;2) was PCR amplified, from stigmas/styles cDNAs, cloned and sequenced, which allowed the confirmation of its identity. The NtCDKG;2 expression was analyzed in the different vegetative and reproductive organs, by qRT-PCR, evidentiating an ubiquitous expression pattern. Studying the expression pattern of this gene in stigmas/styles of the twelve stages of N. tabacum flower development, it was observed that NtCDKG;2 is more expressed at the later developmental stages towards anthesis, indicating an important function of its protein in the end of pistil development. NtCDKG;2 expression analyses in stigmas/styles of N. tabacum plants with an enhanced auxin production in the pistil suggest that NtCDKG;2 is transcriptionally regulated by this hormone. The transient expression of the fusion protein NtCDKG;2-GFP, in N. tabacum leaves, evidentiated the nuclear localization of the studied protein. Stable transgenic plants overexpressing and silencing NtCDKG;2 by RNAi were also generated. Despite the high transcript levels in the plants overexpressing NtCDKG;2 and the low transcript levels in the silencing plants, macroscopic phenotypic alterations were not observed on these plants. Additionally, the expression of the NtCDKG;2 protein, with a histidine tag fused in its N-terminal, was obtained in Escherichia coli BL21(DE3)CodonPlusRP cells. Through studies performed on this work and literature analyses, it is possible to propose that NtCDKG;2 encodes a protein that is involved in the control of cell cycle at the N. tabacum stigmas/styles.

A biomassa vegetal pode ser uma importante fonte de obtenção de diversos produtos a partir da desestruturação de suas frações por um vasto grupo de enzimas. No entanto, a geração de compostos de alto valor agregado a partir da biomassa lignocelulósica requer o desenvolvimento de novos sistemas enzimáticos. Pensando nisso, a prospecção e a caracterização de novas enzimas que estão presentes no secretoma de fungos degradadores da biomassa lignocelulósica tem sido fonte de pesquisa por pesquisadores do mundo todo. O objetivo deste trabalho foi prospectar, clonar e expressar de maneira heteróloga o gene codificante de uma enzima putativa do fungo termofílico T. terrestris em cepas do fungo filamentoso A. nidulans A773 e promover sua caracterização bioquímica e biofísica. O gene da enzima foi amplificado, clonado e inserido no vetor pEXPYR antes de ser inserido no sistema de expressão do A. nidulans. Os transformantes obtidos foram induzidos em meio mínimo de cultivo contendo 3% (m/v) de maltose e 1% (m/v) de glicose em meio estacionário para a produção, seguido da purificação da enzima. Estudos bioquímicos foram realizados para determinar o pH e a temperatura ótima de reação, bem como, a especificidade aos substratos e a determinação dos parâmetros cinéticos. A termoestabilidade da enzima também foi avaliada por estudo de dicroísmo circular (DC). Além disso, foi avaliado o efeito colaborativo entre uma xilanase GH10 e a enzima em estudo na hidrólise do bagaço de cana-de-açúcar pré-tratado. A enzima obtida por expressão heteróloga foi caracterizada como uma xilo-oligossacarídeo oxidase (XylO). Por meio da análise filogenética das sequências de aminoácidos entre a enzima expressa e outras enzimas oxidativas, a XylO foi classificada como pertencente a família das flavoproteínas e subfamília das BBE. A enzima TtXylO demonstrou ter especificidade em oligossacarídeos de C5 apresentando boa atividade enzimática em substratos complexos de xilana. A enzima possui pH ótimo de 5,5 e temperatura ótima de 25 ºC. As análises de DC indicaram temperatura de desnaturação de 62,7 ºC, caracterizando esta enzima como termofílica. Contudo, novos estudos ainda são necessários para avaliar os produtos gerados a partir da oxidação dos diferentes xilo-oligossacarídeos pela XylO e seu potencial uso na indústria. / Plant biomass is an important source for generation of several products obtained from enzymatic cleavage of its fractions by a large group of enzymes. However, the generation of high value compounds from lignocellulosic biomass requires the development of new enzymatic systems. Considering that, prospection and characterization of enzymes present in the biomass-degrading fungi secretome has been a source of study by researchers around the world. The aim of this work was to prospect, clone and heterologously express a putative enzyme encoding gene from the thermophilic fungus T. terrestris in A. nidulans A773 strains and to promote its biochemical and biophysical characterization. The gene was amplified, cloned and inserted into the pEXPYR vector before being inserted into A. nidulans expression system. The transformants were induced by culture in minimal médium containing 3% (w/v) maltose and 1% (w/v) glucose by stationary culture for the production, followed by enzyme purification. Biochemical analyses were performed to determine optimum pH and temperature as well as the substrate specificities and kinetic parameters. The enzyme thermostability was also evaluated by circular dichroism (CD). In addition, the collaborative effect between the enzyme and a GH10 on hydrolys of pre-treated sugarcane bagasse was evaluated. The enzyme obtained by heterologous expression was characterized as a xylooligosaccharide oxidase (XylO). Phylogenetic analysis between amino acid sequences of expressed enzyme and other oxidative enzymes classified XylO as belonging to flavoproteins family and subfamily of BBE. TtXylO has been shown to have specificity on C5 oligosaccharides exhibiting good enzymatic activity on complex xylan substrates. The enzyme has an optimum pH of 5.5 and optimum temperature of 25 ºC. DC analyses showed melting temperature of 62.7 ºC, characterizing this enzyme as thermophilic. In general, further studies are still needed to evaluate the products generated from oxidation of xylooligosaccharides by XylO and their potential use in the industry.