xii, 152 leaves : ill. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Biochemistry, 1972

Thesis (Ph.D.) -- University of Adelaide, Dept. of Biochemistry, 1972.

No description available.

Thèse de doctorat : Chimie Informatique et Théorique : Nancy 1 : 2007. Thèse de doctorat : Chimie Informatique et Théorique : Istanbul, Boğaziçi University : 2007. / Thèse soutenue en co-tutelle. Titre provenant de l'écran-titre. Bibliogr.

That Lactobacillus arabinosus 17-5, ATCC 8014, can supply its own requirement for the amino acid, lysine, is demonstrated by the fact that the organism is capable of growth in media devoid of lysine. Since the final biosynthetic step in lysine formation in all bacteria studied to date involves the decarboxylation of meso-dlaminopimelic acid (DAP) to produce lysine, it was of interest to determine whether an enzyme catalyzing such a reaction (DAP decarboxylase) is present in L. arabinosus.

This thesis is missing page 57, no other copy of the thesis contains this page. -Digitization Centre / The experiments in this thesis were undertaken to: 1) compare the effects of cycloheximide and azaserine on asparagine synthesis in root-tip sections of corn; 2) study the effect of protein synthesis on asparagine synthesis in root-tip sections by the use of analogues of cycloheximide; and 3) study the properties of asparagine synthetase extracted from corn roots.When [2-1 4c]-acetate is fed to excised root-tip sections of corn pre-incubated in the presence of cycloheximide, protein synthesis is inhibited. The effect is almost immediate. Within the amide fraction, the levels of glutamine formed in these sections rises over the 3 hour pre-incubation period. Asparagine synthesis gradually declines over the same period. In similar experiments performed with azaserine in the pre-incubation media, protein synthesis was not markedly inhibited. Glutamine levels were immediately increased over the 3 hour period. The effect on asparagine synthesis was also rapid. In contrast to the situation with cycloheximide, the effect of azaserine on amide synthesis is constant over a 3 hour period. Two analogues of cycloheximide - cycloheximide acetate and streptovitacin A - were found to produce effects similar to that of cycloheximide. These analogues were found to inhibit both protein synthesis and asparagine synthesis after a 3 hour exposure period. Six other analogues did not show marked inhibitory effects on either protein synthesis or asparagine synthesis. Asparaqine synthetase activity was found in extracts from corn seedling tissues.. However, assays for asparagine synthetase revealed that the activity was low and 'that other aspartate utilizing enzymes were probably active in the extracts. From the results of this investigation and those of earlier published results a model has been proposed in order to explain the regulation of asparagine synthesis in corn roots. / Thesis / Master of Science (MS)

Cette thèse décrit la synthèse de l'asparagine et de la glutamine utilisés pour la biosynthèse des protéines chez Helicobacter pylori. La plupart des acides aminés (aa) sont liés à leur ARNt correspondant par les aminoacyl-ARNt synthétases (aaRS). Ces enzymes sont très spécifiques, et leur fonction est importante pour le décodage correct du code génétique. L'asparaginyl-ARNt synthétase et la glutaminyl-ARNt synthétases (AsnRS et GlnRS) sont l'une ou l'autre, ou les deux absentes de la plupart des bactéries, des archaea, et des organelles. Chez les bactéries et les organelles, des aaRS à double fonction nommées aaRS non-discriminantes (ND) participent avec une aminoacyl-ARNt amidotransférase, la GatCAB, à la formation du glutaminyl-ARNtGln et de l'asparaginyl-ARNtAsn. Les aaRS-ND, soit la glutamyl-ARNt synthétase-ND (ND-GluRS) et l'aspartyl-ARNt synthétase (ND-AspRS), forment l'aminoacyl-ARNt synonyme (Glu avec ARNtGlu) mais lient aussi l'acide aminé à l'ARNt de sa forme amidée (Glu avec ARNtGln). La GatCAB agit ensuite en transamidant le Glu-ARNtGln et l'Asp-ARNtAsn en Gln-ARNtGln et en Asn-ARNtAsn, respectivement. Chez H. pylori, la synthèse du Glu-ARNtGln est faite par une aaRS discriminante spéciale formant seulement le produit mésapparié. Cette GluGlnRS est aussi nommée GluRS2, puisque l'organisme possède une autre GluRS (GluRS1) discriminante formant seulement le Glu-ARNtGlu. La voie indirecte de la formation de l'Asn-ARNtAsn et du Gln-ARNtGln chez H. pylori et ses mécanismes de contrôle contre la mauvaise utilisation des aminoacyl-ARNt mésappariés est décrite. Tout d'abord, les premières évidences d'un channeling de l'Asp-ARNtAsn de l'AspRS-ND vers la GatCAB (Chapitre 3) mettent en scène la coopération entre ces deux enzymes permettant le contrôle de la molécule mésappariée. Une seconde publication montre la formation d'un complexe ternaire formé par la GluRS2, la GatCAB et l'ARNtGln et démontre comment ce complexe en coopération avec un rééchantillonage du substrat par la GluRS2 permettent un décodage plus fiable et plus efficace des codons Gln (Chapitre 5). Une troisième publication confirme la formation d'un complexe par l'AspRS-ND, la GatCAB et l'ARNtAsn (Chapitre 6). Ce complexe, ainsi que l'existence d'un second mode de liaison de l'ARNtAsn à l'AspRS-ND allant à l'encontre des caractéristiques connues de cette famille d'aaRS, augmentent la fidélité du décodage des codons Asn chez H. pylori. Au cours de ces travaux, en collaboration avec le groupe du Prof. Robert Chênevert (co-directeur de la thèse), des composés synthétiques ont été testés pour leur activité inhibitrice contre la GatCAB. Les premiers inhibiteurs de cette enzyme qui sont analogues à l'aa-ARNt, et le développement des méthodes de cette analyse, sont aussi présentés (Chapitres 3 et 4). / This work was focused on the formation of glutamine and asparagine used for protein biosynthesis in Helicobacter pylori. Most amino acids (aa) are linked to their cognate tRNAs by aminoacyl-tRNA synthetases (aaRS). These enzymes have a high specificity, and their function is key to the proper decoding of mRNA. One or both of the enzymes responsible for the formation of glutaminyl-tRNAGln and asparaginyl-tRNAAsn are absent from most bacteria, archaea, as well as organelles. In bacteria and organelles, dual-function aaRSs dubbed non-discriminating (ND), are used in conjunction with an aminoacyl-tRNA amidotransferase called GatCAB, to form these amidated aminoacyl-tRNAs. ND-AspRS forms the canonical Asp-tRNAAsp, but also Asp-tRNAAsn. Meanwhile, in H. pylori, the task of forming Glu-tRNAGln which is filled by an ND-GluRS in most organisms, is filled by a special, discriminating enzyme forming only the mismatched product. This GluGlnRS has been called GluRS2, the other, Glu-tRNAGlu forming enzyme being called GluRS1. Work is presented describing these two pathways in H. pylori. One publication was the first to provide data suggesting that ND-AspRS could provide Asp-tRNAAsn to GatCAB through substrate channeling (Chapter 3). The second showed formation of a ternary complex formed by GluRS2, GatCAB and tRNAGln, allowing efficient and correct decoding of Gln codons, including resampling of the substrate by GluRS2 (Chapter 5). A third manuscript confirms earlier results by describing the formation of a ternary complex formed by ND-AspRS, GatCAB and tRNAAsn (Chapter 6). This work also furthers our understanding of the kinetics of aminoacylation, by showing that ND-AspRS has two different behaviours, each one consistent with one of the two, evolutionarily unrelated families of aaRSs. Throughout my thesis, collaboration with the group of Prof. Robert Chênevert (co-director of this thesis) sought to design, synthesize and test compounds for inhibitory activity against GatCAB. The first inhibitors which are analogues of the aminoacyl-tRNA substrate for this enzyme, and the development process of the methods used to test them are described in Chapters 3 and 4).

No description available.

A importância na geração de oxaloacetato foi investigada através da determinação da atividade da piruvato carboxilase nos músculos estriados e da suplementação de seus precursores (aspartato e asparagina) na dieta de ratos. A atividade da piruvato carboxilase eleva-se durante o exercício físico e, portanto, deve fornecer mais oxaloacetato para a etapa inicial do ciclo de Krebs. A suplementação crônica (5 semanas) de aspartato e asparagina promove aumento da resistência ao esforço em ratos treinados em natação durante 1 hora diária por 5 semanas. Este efeito foi acompanhado de elevação no número e tamanho das mitocôndrias e alteração no metabolismo de glicose dos músculos esqueléticos (elevação do conteúdo de glicogênio e de sua síntese e diminuição da glicólise). Esses resultados sugerem que a geração de oxaloacetato desempenha papel fundamental na manutenção do esforço prolongado. A suplementação de aspartato e asparagina na dieta melhora a performance nessas condições, porém causa lesões na ultraestrutura muscular (mitocôndrias, linha \"Z\" e miofibrilas). / The importance of oxaloacetate formation was investigated by measuring pyruvate carboxylase activity in muscles and by given its precursors (aspartate, asparagine) in the diet of rats. The activity of pyruvate carboxylase markedly raised during physical effort and so might provide oxaloacetate for Krebs cycle functioning. The supplementation of aspartate and aspagine for a prolonged period of time (5 weeks) promotes increment in the resistance to exercise in rats trained to swimming during 1 hour daily for 5 weeks. This effect is accompanied by an increase in the size and number of mitochondria and also changes in glucose metabolism; elevation in glycogen synthesis and content and reduction in the rate of glycolysis. These results suggest that the production of oxaloacetate plays a role to maintain the moderate exercise during a prolonged period of time. Nevertheless, the aspartate and asparagine supplemented in the diet, despite improving the perfomance to moderate and prolonged exercise, provokes muscle ultraestructure lesions of mitochondria, \"Z\" line and miofibrils.

Le débourrement des bourgeons axillaires conditionne la ramification, donc l’établissement de l’architecture chez les végétaux. L’azote est impliqué dans la croissance des jeunes organes tels que les axes secondaires (axes II) issus du débourrement des bourgeons. Plusieurs études ont démontré que la concentration en acides aminés augmente dans la sève au cours de la reprise de croissance printanière, dont le débourrement des bourgeons est une étape importante. L’identité et l’origine des acides aminés impliqués dans le débourrement et les premières phases d’allongement des axes II n’ont pourtant pas encore été clairement établies. Ce travail a pour objectif de comprendre, chez Rosa hybrida, les phénomènes nutritionnels sous-jacents à l’apparition de différents phénotypes de ramification. Pour ce faire, nous avons fait varier la concentration et les périodes d’apport de nitrate dans la solution nutritive au cours de la croissance, avant et après l’initiation du débourrement par décapitation. Nous avons montré in planta que la concentration d’asparagine augmente dans la sève et dans l’ensemble des tissus pendant l’allongement des axes II et provient tout d’abord majoritairement des réserves puis, après la décapitation, en quantité de plus en plus importante de l’absorption courante. Cet acide aminé est le seul capable, en présence de sucres, d’initier une croissance efficace des axes II in vitro, notamment en contribuant à placer le statut des régulateurs de croissance dans un contexte favorable au débourrement. Une approche par RNAseq a mis en évidence 848 séquences potentiellement impliquées dans le débourrement en réponse au nitrate. Parmi elles, le couple Asparaginase / Asparagine synthétase s’exprime respectivement durant la phase de dormance ou le débourrement, ce qui renforce l’importante de l’asparagine dans ce phénomène. Ces deux échelles d’approche ont permis de compléter le modèle intégratif du débourrement en intégrant la nutrition des nouveaux organes. / Axillary bud outgrowth is an essential process of plant branching to set-up its architecture. Nitrogen is implicated in the development of young organs such as secondary axes (axes II) resulting from bud outgrowth. Several studies have previously shown that amino acid concentration increase in the xylem sap during spring regrowth whom bud outgrowth is an essential step. The exact nature of the amino acids implicated in the bud outgrowth and initial axe II elongation have not yet been determinated. The present work aims to understand in Rosa hybrida the nutrition processes implicated in the set-up of different branching phenotypes. To achieve this goal, we brought different nitrate concentrations to the plant before and after bud outgrowth initation by apex removing. We showed in planta that asparagine concentration increases in the sap and in the tissues during axes II growth, initialy originating from internal stores and, after decapitation, increasingly coming from current uptake. This amino acid is the sole able to evoke in vitro an efficient elongation of axes II in the presence of sugar throught the establishment of growth regulators metabolism status that is favorable to the outgrowth process. Transcriptome study using RNAseq features 848 sequences that are potentially implicated in bud outgrowth in response to nitrate. Among them, the expression of Asparaginase takes place during dormancy while, in contrast, Asparagine synthase gene is active during bud outgrowth, highlighting the importance of asparagine in this phenomenon. These approaches conducted at two different scales contribute to append with nitrogen nutrition the integrated model of bud outgrowth.