Transgenic tobacco plants were developed containing a partial PLD clone in antisense orientation. The PLD isoform targeted by the insertion was identified. A PLD clone was isolated from a cDNA library using the partial PLD as a probe: Nt10B1 shares 92% identity with PLDβ1 from tomato but lacks the C2 domain. PCR analysis confirmed insertion of the antisense fragment into the plants: three introns distinguished the endogenous gene from the transgene. PLD activity was assayed in leaf homogenates in PLDβ/g conditions. When phosphatidylcholine was utilized as a substrate, no significant difference in transphosphatidylation activity was observed. However, there was a reduction in NAPE hydrolysis in extracts of two transgenic plants. In one of these, a reduction in elicitor- induced PAL expression was also observed.

Les phospholipases et en particulier les phospholipases C sont d'importants facteurs de virulence chez de nombreuses bactéries pathogènes (C. perfringens, B. Cereus et P. aeruginosa). Cependant, peu de choses sont connues sur l'implication de ces enzymes dans le processus de virulence des mycobactéries. Bien que l'étude des mutants des phospholipases C de M. tuberculosis dans un modèle d'infection chez la souris ait permis de proposer une implication de ces protéines dans la virulence de ce bacille, leurs propriétés biochimiques, leur mode d'action et leur rôle physiologique exact restent à élucider. Ce manque de données biochimiques sur les phospholipases mycobactériennes peuvent être attribuée à la difficulté à produire et à purifier des quantités importantes de ces enzymes. Dans le but de mieux caractériser le rôle physiologique des phospholipase mycobactériennes, l'objectif de ma thèse a été de mettre au point des conditions d'expression hétérologue permettant la production des phospholipases C mycobactériennes recombinantes (rPLC) dans différents systèmes d'expression (E. coli, Pichia pastoris et baculovirus/cellules d'insectes). Ces systèmes d'expression n'ayant pas donné des résultats satisfaisants, nous avons développé une méthode efficace d'expression de ces protéines en utilisant M. smegmatis.Ce système d'expression nous a permis de produire et de purifier les quate PLC (PLC-A, PLC-B, PLC-C et PLC-D) de M. tuberculosis et la PLC de M. Abscessus sous forme soluble et active. Nous avons pour la première fois montré que ces protéines purifiées avaient un effet cytotoxique sur les macrophages de souris en culture mais ne présentaient aucune activité hémolytique. en utilisant des marquages radioactifs, nous avons confirmé que l'effet cytotoxique observé était lité à l'hydrolyse des phospholipides des membranaires des cellules hôtes. Pour la première fois, nous avons pu confirmer que ces PLC sont directement impliquées dans le processus d'infection et de virulence.Un autre aspect de mon travail de thèse a concerné l'étude de deux autres protéines sécrétées par M. tuberculosis appartenant à la famille des cutinases : la Rv1984c et la Rv3452. Après les avoir produites et purifiées chez E. Coli, nouq avons montré que malgré ces deux protéines présentent 50% d'identité de séquence en acides aminés, elles ont des spécificités de substrat différentes et probablement un rôle physiologique différent. La Rv1984c est une lipase capacle d'hydrolyser des lipides à chaines moyennes, alors que la Rv3452 est une phospholipase de type A2 et est capable d'induire la lyse de macrophage de souris en culture. / Phospholipases, particularly phospholipases C, are important virulence factors in several pathogenic bacteria (C. perfringens, B. cereus, L. monocytogenese and P. aeruginosa). However, little is know on the involvement of thses enzymes in mycobacteria pathogenesis. Although study on M. tuberculosis phospholipases C mutants in a mouse aerosol model of infection gave rise to the contribution of these proteins in virulence process, but their exact biochemical properties, mechanism of action and physiological role remain to be elucidated. This lack of data on mycobacterial phospholipases is mainly due to the difficulty to produce and purify these enzymes in large scale.With the aim to better characterise the physiological role of mycobacterial phospholipases, the main challenge of my thesis was to develop an efficient method for expression and purification of recombinant mycobacterial phospholipases C. Since no satisfactory results have been obtained with standard expression systems (E. coli, Pichia pastoris and baculovirus / insect cells), we develop a robust expression technique for these proteins using M. smegmatis as expression system.This allowed us to produce and purify all four PLC (PLC-A, PLC-B, PLC-C and PLC-D) of M. tuberculosis and the PLC of M. abscessus in soluble and active form. For the first time, we have show, that purified proteins have cytotoxic effect on mouse macrophages but have not haemolytic activity. Using radiolabelled lipids, we have confirmed that this first direct evidence that PLC are involved in infection and virulence processes. Another aspect of my thesis work concerned the study of two other secreted proteins of M. tuberculosis belonging to the cutinase family : the Rv 1984c ant the Rv3452. Recombinant proteins obtains in E. coli were found to have distinct substrate specificities and most likely distict physiological role, despite showing 50% amino acids sequence identity. Rv1984c is a lipase and is able to hydrolyse lipids with medium chains lengthn whereas Rv3452 is type A2, phospholipase and i able to induce macrophage lysis.

Pseudomonas aeruginosa est une bactérie à Gram négatif ubiquitaire, pathogène opportuniste. Elle est la 3ème cause d’infections nosocomiales, notamment chez les immunodéprimés et les grands brûlés. Elle est aussi responsable de la mort de nombreux patients atteints de la mucoviscidose. Sa virulence est largement due à son aptitude à sécréter de nombreuses enzymes dégradatives et toxines, parmi lesquelles la protéine ExoU, sécrétée par le Système de Sécrétion de Type III. ExoU est une phospholipase, de la famille des « patatin-like proteins », dont l’activité est portée par une dyade catalytique Ser-Asp.Mon travail de thèse a permis d’identifier 4 homologues d’ExoU (PlpA, PlpB, PlpC et PlpD) dans le protéome de la souche PAO1 de P. aeruginosa (qui est dépourvu de cette protéine). En étudiant le mode de sécrétion de PlpD, nous avons découvert une nouvelle branche du Système de Sécrétion de Type V (SST5), le SST5d. La protéine représentant ce nouveau système possède un domaine C-terminal transporteur de type TpsB (SST5b), fusionné à un domaine N-terminal patatine sécrété dans le milieu extracellulaire (à l’image d’un autotransporteur, ou SST5a). Ce mode de sécrétion serait un mode dédié à la sécrétion de « patatin-like proteins », comme le suggèrent nos analyses phylogénétiques, à Nous avons en outre démontré que PlpD possède une activité lipase.L’autre protéine étudiée, PlpA, est également sécrétée, bien que nous n’ayons pu établir avec certitude sa voie de transport. Nous avons évalué le rôle de cette protéine lors de l’interaction de P. aeruginosa avec des cellules hôtes de type macrophages et cellules épithéliales. Nous avons observé que cette protéine confère une protection temporaire aux cellules infectées par P. aeruginosa. Ce retard semble être directement imputable à l’activité de la protéine, puisqu’il est dépendant de l’intégrité de la dyade catalytique putative de PlpA / Pseudomonas aeruginosa is an ubiquitous Gram negative bacteria, and efficient opportunistic pathogen. It is the third most common cause of nosocomial infections, most particularly within immunocompromized or burn patients. This pathogen is responsible for the death of numerous cystic fibrosis patients. Its virulence is due mainly to its capacity to secrete numerous degradative enzymes and toxins, among them, ExoU which is secreted via the Type III Secretion System. ExoU is a phospholipase of the patatin-like protein family, and its activity is based on a Ser-Asp catalytic dyad.During my thesis, we identify 4 ExoU homologs (PlpA, PlpB, PlpC, and PlpD) in the proteome of the P. aeruginosa PAO1 strain (this strain does not possess ExoU). Results obtained studying PlpD secretion led us to discover a new branch of the Type V Secretion System (T5SS), the T5dSS. PlpD is composed of a C-terminal TpsB-like transporter domain (like T5bSS), fused to a N-terminal patatin domain which is secreted into the extracellular medium (like autotransporters, or T5aSS). Our phylogenetic analysis suggests that this secretion pathway may be dedicated to the secretion of PLPs, like T5cSS, which secretes only adhesins. Moreover, we demonstrated that PlpD is a lipase.The other studied protein, PlpA, is also a secreted protein, but we still do not know which secretion system is involved in its secretion. We tested the role of PlpA during interaction of P. aeruginosa with host cells by carrying out infections of murin macrophages and epithelial cells. We observed a transitory protection of cells infected with P. aeruginosa. This protection seems to require an active PlpA protein as it is dependent on a intact catalytic dyad in this protein

Sterol regulatory element-binding proteins (SREBP) are transcription factors that regulate genes involved in lipid metabolism especially in the liver. Therefore, hepatic SREBP is significant regulator of systemic lipid metabolism. Evidence demonstrates that insulin and dietary unsaturated fatty acid (UFA) regulate SREBP1 expression and subsequent SREBP1-mediated gene transcription, events that in many instances result in modulation of systemic fatty acid and triglyceride (TG) homeostasis. A series of investigations was designed to uncover novel regulators of SREBP1. Dietary and exogenous addition of UFA has been shown to regulate SREBP function yet, an endogenous source of UFA capable of modulating SREBP remains elusive. Group VIA calcium-independent phospholipase A2 (iPLA2) releases UFA from the sn-2 position of glycerophospholipids. We hypothesized that iPLA2 provides UFA to suppress SREBP. iPLA2 overexpression and inhibition studies were implemented. iPLA2 inhibition increased SREBP1 expression, SREBP-mediated transcription and the expression of SREBP1 gene targets in vitro. In vivo overexpression of iPLA2 resulted in decreased expression of SREBP1 protein and plasma triglyceride. In contrast, iPLA2 overexpression attenuated SREBP1 expression, SREBP-mediated transcription and expression of SREBP1 targets genes. These data support the hypothesis that iPLA2 generates endogenous UFA that limit SREBP function. Use of a replication-deficient adenovirus 5 (Ad-5) expression vector in the iPLA2 study led to the unexpected observation of hepatic SREBP1 activation following Ad-5 infection. Because of this observation, we tested the hypothesis that replication-deficient Ad-5 might augment lipid synthesis in liver. We demonstrate that first generation Ad-5, a ubiquitous transgene expression vector, induces expression of SREBP1 and its target genes and leads to increases in fatty acid synthesis in vivo and in vitro. The phosphatidylinositol 3-kinase (PI3K) inhibitor, PX-866, suppressed Ad-5-induced SRBEP1 expression and hypertriglyceridemia implicating the PI3K/Akt pathway in Ad-5 activation of SREBP1. Use of PX-866 led to the discovery of a third mechanism of SREBP1 regulation. In vivo studies demonstrate that PX-866 modulates basal lipid metabolism in part through decreasing plasma TG, an increased trend toward decreased SREBP1 expression and a significant increase in plasma cholesterol. These studies characterize three distinct novel regulatory mechanisms of SREBP1.

As Fosfolipases A2 (PLA2) são enzimas que atuam desconstruindo membranas celulares, resultando em ácidos graxos e lisofosfolipidios, causando inflamação tecidual. Evidências indicam que serpentes possuem uma resistência natural devido a propriedades presentes no sangue, que inibem ações de proteínas presentes no veneno. Portanto, no presente trabalho foi isolado e caracterizado bioquimicamente e biologicamente o primeiro inibidor de PLA2 do tipo gama (γPLI) do soro da serpente B. jararaca, denominado PLI_BJ. O inibidor de PLA2 foi isolado utilizando dois passos cromatográficos. O PLI_BJ mostrou, por SDS-PAGE, uma massa molecular aparente de 25 000 e 20 000 em condições redutoras e não redutoras, respectivamente. A sequência de aminoácidos parcial de PLI_BJ foi determinada por espectrometria de massa e corresponde a 72% e 68% de cobertura da sequência de aminoácidos de duas proteínas já descritas como PLI. O PLI_BJ mostrou também atividade inibitória satisfatória nos três testes realizados sugerindo um papel deste inibidor nos efeitos de envenenamento da serpente. / Phospholipases A2 (PLA2) are enzymes that act on cell membrane phospholipids resulting in fatty acids and lysophospholipids, deconstructing the cell wall causing tissue inflammation. Evidence indicates that snakes have natural resistance due to protective properties of blood that inhibits the action of proteins present in the venom. This study aimed to purify and characterize PLA2 inhibitors (PLI) from serum of the Bothrops jararaca snakes. PLA2 inhibitor was isolated using two chromatographic steps, and was named PLI_BJ. The purity of the PLI_BJ was confirmed by HPLC and SEC. The PLI_BJ showed, by SDS-PAGE, an molecular mass of 25,000 and 20,000 under reducing and non-reducing conditions, respectively. The partial amino acid sequence of PLI_BJ was determined by mass spectrometry and it corresponds to 72% and 68% of coverage of the amino acid sequence of two proteins already described as PLI. The PLI_BJ also showed satisfactory inhibitory activity in the three tests performed suggesting a role of this inhibitor in snake envenomation effects.

Glioblastoma (GBM) é caracterizado por sua agressividade e invasão infiltrativa do tecido cerebral. Mecanismos inflamatórios demonstram associação direta com processos carcinogênicos, especialmente aqueles relacionados à produção de eicosanoides através da ativação da fosfolipase A2 (PLA2). Compostos metálicos como o rutênio associado a drogas anti-inflamatórias não esteroides (AINEs) surgem como tratamentos antitumorais promissores. O objetivo foi avaliar in vitro a ação desses complexos de rutênio em linhagens celulares de GBM. Pudemos observar que todos os complexos de Rutênio utilizados apresentaram diminuição na contagem celular, aumento de apoptose e diminuição da mitose, destaque para a linhagem U87MG para o tratamento RuIBpOTf com diminuição de 65,4% e na linhagem A172 para aumento de apoptose em todos os tratamentos, especialmente RuIBpCl com 106,8% . Em ambas as linhagens celulares verificamos que houve a captação dos complexos, inclusive em suas frações celulares como o núcleo. Alterações nas enzimas PLA2 e COX 1 e 2 também foram detectadas nos ensaios realizados ELISA e RT-PCR. Através destes resultados, concluímos que os complexos de rutênio foram eficazes na diminuição do número de células de GBM em concentrações e tempos pré-determinados, aumento da apoptose e diminuição das mitoses, características que são fortemente recomendadas para novos fármacos. / Glioblastoma (GBM) is characterized by its aggressiveness and infiltrative invasion of brain tissue. Inflammatory mechanisms demonstrate direct association with carcinogenic processes, especially those related to the production of eicosanoids through the activation of phospholipase A2 (PLA2). Metal compounds such as ruthenium associated with non-steroidal anti-inflammatory drugs (NSAIDs) appear as promising antitumor treatments. The objective was to evaluate in vitro the action of these ruthenium complexes in GBM cell lines. It was observed that all the Ruthenium complexes showed decrease in the cell count, increase of apoptosis and decrease of mitosis, highlight to the U87MG cell line for the treatment RuIBpOTf with reduction of 65.4% and in cell line A172 to increase apoptosis in all the treatments, especially RuIBpCl with 106.8%. In both cell lines we verified that there was the uptake of the complexes, including in their cellular fractions as the nucleus. Changes in PLA2 and COX 1 and 2 enzymes were also detected in ELISA and RT-PCR assays. Through these results, we conclude that ruthenium complexes were effective in decreasing the number of GBM cells at predetermined concentrations and times, increased apoptosis and decreased mitoses, characteristics that are strongly recommended for new drugs.

Os insetos são os mais numerosos animais encontrados no mundo, com mais de 675 mil espécies conhecidas. Pertencentes à ordem Hymenoptera, da superfamília Apoidea, as abelhas são encontradas distribuídas em aproximadamente 20 mil espécies. No Brasil estima-se que existam 1.700 espécies. Uma das principais espécies é a Apis mellifera, com ocorrência cosmopolita. A Apis mellifera, popularmente conhecida como abelha africanizada, é agressiva, enxameia várias vezes ao ano e utiliza uma grande variedade de locais para nidificar. Esse comportamento aumenta o contato direto entre o inseto e a população, aumentando o número de acidentes. Os acidentes com abelhas representam um problema de saúde pública em diversos países do mundo pela freqüência com que ocorrem e pela mortalidade que ocasionam. O presente estudo propõe a busca por inibidores naturais contra o veneno de abelhas. Um sistema e uma base de dados foram desenvolvidos para a integração entre dados de plantas medicinais antivenenos e os venenos de abelhas. As atividades anti-hemorrágica, anti-proteolítica, anti-miotóxica, antifosfolipase e anti-edema de plantas medicinais antiveneno foram analisadas por meio de ensaios farmacológicos. As possíveis interações entre as toxinas Melitina e Fosfolipase A2 com inibidores foram avaliadas, através do docking virtual. O banco de dados, denominado Bee Venom, foi implementado e os dados de bancos de dados públicos foram inseridos no sistema. O sistema foi liberado para acesso público no endereço eletrônico http://gbi.fmrp.usp.br/beevenom/. Durante a análise da proteína Melitina foram encontradas as regiões da proteína em que os possíveis inibidores devem interagir e identificadas as propriedades químicas que os inibidores devem possuir para interagir corretamente com a Melitina. Nas análises in silico foi possível identificar 10 possíveis inibidores que interagiram corretamente com o sítio ativo da Fosfolipase A2. Algumas espécies do Banco de Germoplasma da FMRP/USP foram obtidas e utilizadas nos experimentos de atividade fosfolipásica indireta e de Edema, sendo possível observar inibição do veneno total e da proteína Fosfolipase A2. Os compostos sintéticos e inibidores avaliados não causaram inibição em todos os experimentos avaliados. Já as plantas obtidas no laboratório de Toxinas Animais e Inibidores Naturais e Sintéticos causaram inibição do veneno total e da proteína Fosfolipase A2. / Insects are the most numerous animals worldwide, with more than 675 thousand known species. Belonging to Hymenoptera order, Apoidea, superfamily, bees are found distributed in approximately 20 thousand species. In Brazil there are about 1,700 species. One of the major species is Apis mellifera, with cosmopolitan occurrence. Apis mellifera, popularly known as Africanized bee, is aggressive, swarm several times per year and uses a great variety of locals to nidificate. This behavior raises the contact between the insect and the population, increasing the accidents numbers. Bee accidents represent a public health problem in many countries because of their frequency and mortality. The present study proposes to search for natural inhibitors of bee venom. A system and a data base have been developed to integrate anti-venom medicinal plants data and bee venoms. Plants activities against venom have been evaluated by farmacological assays, such as anti-hemorraghic, anti-proteolitic, anti-myotoxicity, anti-Phospholipase and anti-edema. The possible interactions between Melittin and Phospholipase A2 toxins with inhibitors have been evaluated by virtual docking. The data base, denominated Bee Venom, was implemented and the data from public data bases have been inserted in the system. The system was released to public access in the following address http://gbi.fmrp.usp.br/beevenom/. In Melittin analysis the protein regions which the inhibitors may act have been found and also the chemical properties that the inhibitors must have to interact with Melitina have been identified. During in silico analysis it was possible to identify 10 possible inhibitors that interacted well with Phospholipase A2 active site. Some plants species from FMRP/USP Germoplam Bank have been obtained and used in the indirect Phospholipase activity and edema, being possible to observe inhibitions of total venom and Phospholipase A2 protein. The synthetic compounds and inhibitors evaluated did not cause inhibition in any experiments. However, the plants obtained on Animals Toxins and Natural and synthetic Inhibitors laboratory have caused inhibition of total venom and Phospholipase A2 protein.

A quantificação dos componentes bioquímicos como frutose, ácido cítrico e proteína total existentes no plasma seminal de caprinos e ovinos localizados na região Centro-Oeste do Brasil é uma forma de avaliar a atividade fisiológica e bioquímica espermáticas. Estes dados servem como indicadores de prováveis problemas com os testículos e glândulas acessórias desses animais e de sua respectiva fertilidade. A frutose e o ácido cítrico são importantes para o sêmen como fonte de energia metabólica e como componente de sistema tampão, respectivamente. A frutose é um marcador da função secretora das vesículas seminais, e é um componente importante para a sobrevivência dos espermatozóides em condições anaeróbicas e está estreitamente relacionada com a motilidade inicial das células espermáticas. Sendo assim, os objetivos do presente projeto foram analisar quantitativamente esses componentes do plasma seminal de bodes e carneiros sob latitude 20°31\'S em quatro épocas do ano e purificar, através de técnicas cromatográficas, a enzima fosfolipase A2, importante proteína presente no plasma seminal. As análises bioquímicas foram feitas usando-se um espectrofotômetro UV/Vis para obtenção da curva padrão e para a determinação das concentraçõoes mensais e da concentração anual média dos constituintes analisados. A purificação da PLA2 foi feita por cromatografia líquida preparativa usando-se como fase estacionária a coluna Superdex 75-16/60 (GE HealthCare) de exclusão por tamanho e membranas semipermeáveis de 10 e 30 kDa. Como resultado das análises bioquímicas, obteve-se a concentração anual média de proteínas totais de 3,27 ± 0,60 g/dL para ovinos e de 5,02 ± 0,43 para caprinos, ácido cítrico de 1015,33 ± 66,50 µg/mL para ovinos e de 1584,35 ± 143,90 µg/mL para caprinos e frutose de 23,40 ± 4,80 mg/dL para ovinos e 72,73 ± 18,50 mg/dL para caprinos. Os resultados mostraram que a PLA2 extraída do plasma seminal de ovinos tem massa molecular próxima de 13,8 kDa e a PLA2 do plasma seminal de caprinos tem massa molecular próxima a 12,8 kDa. / Quantification of biochemical components in seminal plasma including fructose, citric acid and total protein of goat and sheep of the Midwest region of Brazil is one way of evaluating the biochemical and physiological activity of the sperm. These data serve as indicators of potential problems with the testicles and accessory glands of these animals and their relative fertility. The fructose and citric acid are important for the semen as a source of metabolic energy and as a component of a buffer, respectively. Fructose is a marker of secretory function of seminal vesicles, important for the survival of spermatozoa under anaerobic conditions, and is closely related to the initial motility of sperm cells. Therefore, the objectives of this project were to quantitatively analyze these components in the seminal plasma of goats and sheep in latitude 20°31\'S 3 1\'S in four seasons and purify by chromatographic techniques the enzyme phospholipase A2, an important protein in the seminal plasma. Biochemical analysis were done using a spectrophotometer UV / Vis to obtaining the standard curve and to determine the monthly and annual average concentration of the constituents analyzed. The purification of PLA2 was performed by preparative liquid chromatography using the column as stationary phase Superdex 75-16/60 (GE HealthCare) by size exclusion and semipermeable membranes 10 and 30 kDa. As a result of biochemical analysis, we obtained the annual average concentration of total protein of 3,27 ± 0,60 g / dL for sheep and 5,02 ± 0,43 g/dL for goats, citric acid of 1015,33 ± 66, 50 g / mL for sheep and 1584,35 ± 143,90 g / mL for goats and fructose 23,40 ± 4,80 mg / dL for sheep and 72,73 ± 18,50 mg / dL for goats. The results showed that the PLA2 extracted from seminal plasma of sheep has a molecular mass of 13,8 kDa and the next PLA2 from goat seminal plasma has a molecular mass close to 12,8 kDa.

Thesis advisor: Mary F. Roberts / Thesis advisor: Eranthie Weerapana / Peripheral proteins from mammals often exhibit multi-domain structures and require metal ions such as calcium as co-factors. This dissertation investigates two types of such proteins -- pulmonary collectins (surfactant proteins A and D) and phosphatidylinositol-specific phospholipase C (PLC) delta1 -- and their interactions with model membranes. One approach to work around the complexity brought upon by such multi-domain protein structure is to use a truncated construct or an isolated single domain. For pulmonary collectins, homotrimers consisting of the neck domain and the carbohydrate recognition domain were used in a novel NMR assay for better understanding of their lipid-specific interactions with the membranes. For PLC delta1, we were particularly interested in the role of the EF-hand domain. The isolated EF-hand domain of PLC delta1 was first used to characterize its interactions with membranes and identify key residues responsible for such interactions. These key residues in the N terminal lobe of the EF-hand domain, either cationic or hydrophobic, were then found to affect the hydrolysis activity of the full-length enzyme. A common role for this region of the PLC in facilitating proper membrane association was thus proposed. / Thesis (PhD) — Boston College, 2013. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Thesis advisor: Mary F. Roberts / Secreted phosphatidylinositol-specific phospholipase Cs (PI-PLCs) are often virulence factors in pathogenic bacteria. Understanding how these enzymes interact with target membranes may provide novel methods to control bacterial infections. In this work, two typical PI-PLC enzymes, from Bacillus thuringiensis (Bt) and Staphylococcus aureus (Sa), were studied and their membrane binding properties were examined and correlated with enzymatic activity. BtPI-PLC is kinetically activated by allosteric binding of a phosphatidylcholine (PC) molecule. MD simulations of the protein in solution suggested correlated loop and helix motions around the active site could regulate BtPI-PLC activity. Vesicle binding and enzymatic studies of variants of two proline residues, Pro245 and Pro254, that were associated with these motions showed that loss of the correlated motions between the two halves of PI-PLC were more critical for enzymatic activity than for vesicle binding. Furthermore, loss of enzyme activity could be rescued to a large extent with PC present in a vesicle. This suggests that binding to PC changes the enzyme conformation to keep the active site accessible. SaPI-PLC shows 41.3% sequence similarity with BtPI-PLC but has very different ways its activity is regulated. While it is kinetically activated by PC it does not in fact bind to that phospholipid. Enzymatic and membrane interaction assays showed that SaPI-PLC has evolved a complex, apparently unique way to control its access to PI or GPI-anchored substrate. (i) An intramolecular cation-pi latch facilitates soluble product release under acidic conditions without dissociation from the membrane. (ii) There is a cationic pocket on the surface of enzyme that likely modulates the location of the protein. (iii) Dimerization of protein is enhanced in membranes containing phosphatidylcholine (PC), which acts not by specifically binding to the protein, but by reducing anionic lipid interactions with the cationic pocket that stabilizes monomeric protein. SaPI-PLC activity is modulated by competition between binding of soluble anions or anionic lipids to the cationic sensor and transient dimerization on the membrane depleted in anionic phospholipids. This protein also served as a way to test the hypothesis that a cation-pi box provides for PC recognition site. This structural motif was engineered into SaPI-PLC by forming N254Y/H258Y. This variant selectively binds PC-enriched vesicles and the enzyme binding behavior mimics that of BtPI-PLC. Itaconic acid (ITA) is a metabolite synthesized in macrophages and related cell lines by a cis-aconitate decarboxylase (cADC). cADC activity is dramatically increased upon macrophage stimulation. In this work, the cell line RAW264.7 was used to show that cADC activity upon stimulation requires de novo protein synthesis. MS analyses of partially purified RAW264.7 protein extracts from stimulated cells show a large increase for immunoresponsive gene 1 protein (IRG1) and siRNA knockdown of the IRG1 reduces cADC activity upon stimulation. Suspected active site residues of IRG1 were identified by mutagenesis studies of the recombinant protein based on a homology structure model of fungal cADC. The cloning and overexpression of this enzyme should help clarify the cofactor-independent decarboxylation mechanism of this mammalian enzyme as well as open up future studies into the specific role of ITA in the mammalian immune system and cancers. / Thesis (PhD) — Boston College, 2013. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.