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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
141

Functional Characterization of Serine Hydrolases Mediating Lipid Metabolism and Protein Depalmitoylation in Asexual Stage Plasmodium Falciparum

Liu, Jiapeng 05 June 2023 (has links)
Malaria is an infectious disease caused by Plasmodium parasites and transferred by Anopheles mosquitos. Due to Artemisinin resistance, new druggable targets identification and new drug development are urgently needed. Serine hydrolases (SHs) are one of the largest classes of enzymes having important roles in life processes. The deadliest malaria parasite, P. falciparum, encodes more than 50 SHs including proteases, lipases, esterase and others, while only several of them have been characterized. The study of uncharacterized SHs will shed light on future drug development to treat malaria. In this study, we applied chemical biology and genetic approaches to identify SHs important for the pathogenic asexual stage growth of P. falciparum parasites. We mainly focused on a depalmitoylase essential for merozoite invasion and lysophospholipases (LPLs) essential for acquiring fatty acids (FAs) from the host. Identifying essential metabolic enzymes will benefit the treatment to malaria. We focused on metabolic SHs and identified two SHs were refractory to knock out. We studied a likely essential SH named PfABHD17A, which is a human depalmitoylase homolog. PfABHD17A is localized on the rhoptry, an organelle essential for invasion. We expressed the recombinant PfABHD17A, conducted inhibitor screen and discovered that human depalmitoylase inhibitor ML211 inhibits PfABHD17A in vitro. ML211 inhibits merozoite invasion but not egress, which together with the localization of PfABHD17A on the rhoptries, suggested that PfABHD17A is essential in merozoite invasion. We also purified PfABHD17A and verified that PfABHD17A may exhibit depalmitoylase activity in vitro. LPLs are important for asexual stage parasites acquiring FAs from the host. The P. falciparum genome includes 17 putative LPLs while LPLs responsible for hydrolyzing FA from lysophosphatidylcholine (LPC) in the asexual stage are currently unknown. Using a chemical biology approach, we identified serine hydrolase inhibitor AKU-010 inhibits LPC hydrolysis effectively. Using activity-based protein profiling (ABPP) and genetic approaches, we identified that AKU-010 inhibits a series of SHs including Exported Lipases (XLs), Exported Lipases Homolog (XLH) and Plasmodium falciparum prodrug activation and resistance esterase (PfPARE). We generated a series of knockout parasite lines on the AKU-010 targets and identified that red blood cell (RBC)-localized XL2 and cytosolic XLH4 contribute to most LPC hydrolysis activity in the asexual stage. XLs and XLHs are important for parasites using LPC for growth and contribute to detoxification from accumulated LPC. XL2 and XL4 together are essential for parasite growth under high LPC concentration medium, such as human serum. XL/XLH-deficient parasites could still acquire FA from LPC, which is mainly contributed by parasite membrane- localized PfPARE. PfPARE has little impact on parasite growth and LPC metabolism with the existence of XLs and XLHs but is important after the loss of XLs and XLHs. Parasites deficient in PfPARE, XLs and XLHs have little ability to release FA from LPC and cannot use LPC as FAs source for growth. In summary, we identified metabolic SHs mediating protein depalmitoylation and lipid metabolism and in asexual stage Plasmodium falciparum, which may benefit future drug development to treat malaria. / Doctor of Philosophy / Malaria is an infectious disease caused by Plasmodium parasites and transferred by mosquitos. New druggable target identification and drug development are urgently needed to deal with the malaria issue. We focused on an understudied enzyme superfamily termed serine hydrolase (SHs), which includes more than 50 members in the deadliest malaria parasite, P. falciparum. We identified that several druggable enzymes, which can mediate protein depalmitoylation and lipid metabolism, are important for parasite growth in the pathogenic stage. Identifying essential metabolic enzymes will benefit the treatment to malaria. We screened eleven SHs and discovered that two of them are likely essential in the pathogenic stage. We focused on one human depalmitoylase homolog termed PfABHD17A. We screened the inhibitors on PfABHD17A and used the inhibitor to suggest that PfABHD17A is essential for the growth of pathogenic stage parasites. We also identified lipases important for acquiring fatty acids (FAs) from the host. Using chemical biology and genetic approaches, we discovered that three lipases are important for acquiring FAs form the host in the pathogenic stage. Inhibiting these enzymes may kill the parasite in the host.
142

Un niveau minimal d'un homologue potentiel de la phosphoinositide-phosphatase SAC1 chez "Plasmodium falciparum" semble requis pour assurer la survie durant le stade érythrocytaire asexué

Thériault, Catherine. 24 April 2018 (has links)
La malaria, endémique dans 91 pays tropicaux et sub-tropicaux, est l’une des maladies infectieuses les plus mortelles chez l’humain. Le fardeau de cette maladie porte principalement sur l’Afrique, qui compte plus de 90% des cas d’infections ainsi que des morts enregistrés, la majorité étant des enfants en bas âge. Des cinq espèces de parasites du genre Plasmodium qui peuvent causer la maladie chez l’humain, Plasmodium falciparum est de loin la plus mortelle et la plus étudiée. La résistance aux médicaments actuels et l’absence d’un vaccin préventif procurant une immunité de longue durée démontrent l’urgent besoin de trouver de nouvelles cibles thérapeutiques. Chez les cellules eucaryotes, l’identité des organites cellulaires est définie par les phosphoinositides, des composants mineurs des membranes cellulaires, et maintenue grâce aux kinases et aux phosphatases impliquées dans leur métabolisme. Les rôles de certaines phospholipides-kinases dans plusieurs étapes critiques du cycle de vie de Plasmodium ont récemment été découverts, toutefois, rien n’est connu quant aux fonctions des phosphoinositides phosphatases de cet organisme. Les travaux décrits ci-dessous présentent une première caractérisation d’une protéine homologue à la famille des phosphoinositides phosphatases SAC1. Les résultats montrent que cette protéine est exprimée durant tout le cycle érythrocytaire asexué et qu’elle se localise au réticulum endoplasmique ainsi que potentiellement à l’appareil de Golgi. L’étude de lignées conditionnelles et knockout suggèrent qu’un niveau minimal de la protéine est nécessaire pour la survie du parasite durant le cycle érythrocytaire. En somme, la combinaison des résultats obtenus laisse penser que cette protéine pourrait avoir une fonction dans le système de sécrétion du parasite P. falciparum et qu’elle pourrait donc constituer une cible thérapeutique intéressante pour le développement de nouveaux antimalariaux. / Malaria is endemic in 91 tropical and sub-tropical countries and is one of the deadliest infectious human diseases. Africa has the highest burden with more than 90% of cases and malaria deaths registered yearly, mostly in children under 5 years-old. Despite the fact that infection in human can be caused by five Plamsodium species, infection by Plasmodium falciparum is the most severe and therefore the most studied. Resistance to antimalarials and the absence of a preventive vaccine show the urgent need of new therapeutic targets. In eukaryotic cells, organelles identity is defined by phosphoinositides, minor membranes components, and maintained by the kinases and phosphatases involved in their metabolism. The fact that certain kinases have roles in critical steps of Plasmodium life cycle has recently been acknowledged. However, the roles of the phosphatases are still unknown. My work presents a first characterization of a putative phosphoinositide phosphatase of the SAC1 family. Results provided show that the protein is expressed throughout the asexual blood stages and that it localizes to endoplasmic reticulum and potentially to the Golgi apparatus. Studies on knockdown and knockout strains suggest that a minimal amount of the protein is required during the asexual blood stages. In summary, the combination of the results presented suggests that the protein has an important function in the parasite P. falciparum secretion system and therefore, may represent an interesting potential target for drug development.
143

Repurposing of Human Protein Kinase Inhibitors Identifies Dual Stage Active Antimalarials

Bohmer, Monica J 01 January 2023 (has links) (PDF)
Malaria, a disease caused by members of the Plasmodium genus, remains a threat to global health. Despite the availability of therapeutics, Plasmodium's propensity for generating resistance-conferring mutations threatens the efficacy of these drugs. Therefore, it is essential to develop novel therapeutics, and one approach to discover such compounds is to repurpose current drugs as antimalarials. Human kinase inhibitors, most of which are developed as antineoplastics, are a valuable source of such novel compounds. Human kinase inhibitor research spans over twenty years, generating a wellspring of knowledge regarding compound design, mechanism, and tolerability that can be leveraged in the quest to develop new antiplasmodial drugs. Furthermore, the plasmodial kinome differs substantially from the human kinome, providing opportunities for selectivity and minimization of off-target effects in the host. To this end, we sought to identify and characterize compounds within human kinase inhibitor collections that have antiplasmodial effects. One library yielded a potent polo-like kinase 1 (PLK1) kinase inhibitor, BI-2536, which possessed potent antiplasmodial activity in both the asexual blood stage and liver stage and likely acts through involvement of amino acid starvation. Another library comprised exclusively of type II kinase inhibitors, designed to target kinases in the inactive conformation, produced several interesting lead compounds – TL5-135, YLIU-06-026-1, and the analog pair XMD13-99 and WZ9-034-2. These compounds were highly active against asexual blood stage parasites, killing rapidly while also possessing favorable selectivity and liver stage activity. In vivo, TL5-135 and YLIU-06-026-1 acted prophylactically by preventing infection, and therapeutically by resolving an established infection. Currently, investigations are underway to determine the mechanism of action of the lead compounds and to improve their druglike properties. In whole, this effort has not only yielded promising antiplasmodial compounds, but it also underscores the value of the repurposing approach in the quest for novel antimalarial drugs.
144

Analysis of Plasmodium falciparum pre-replication complex and search for new antimalarials

Moe, David Jason 01 July 2002 (has links)
No description available.
145

Une protéine à domaine PHOX de liaison aux phosphoinositides impliquée dans le transport de l'hémoglobine chez le parasite de la malaria Plasmodium falciparum

Crochetière, Marie-Ève 06 September 2019 (has links)
La malaria est un des fléaux les plus dévastateurs dans les pays en voie de développement. L’absence d’un vaccin et la résistance aux agents antimalariaux disponibles démontrent le besoin urgent d’identifier de nouvelles cibles thérapeutiques. Les phosphoinositides (PIP) sont des composants essentiels des membranes cellulaires chez les eucaryotes jouant un rôle important dans la signalisation intracellulaire, la synthèse d’ADN et le trafic protéique, par exemple. Malgré leur importance chez les eucaryotes, on en connaît peu sur leurs fonctions chez le parasite de la malaria Plasmodium falciparum. Dans notre laboratoire, nous avons réalisé un criblage par inactivation génique de 36 effecteurs potentiels de la voie métabolique PIP pour identifier les gènes qui sont essentiels à la prolifération chez P. falciparum. Notre étude a montré que 72% des gènes potentiellement impliqués dans la voie métabolique des PIP ne pouvaient être inactivés et sont donc potentiellement essentiels pour la survie du parasite. L’analyse d’une souche knock-out pour la protéine PfPX, ayant un domaine de liaison aux PIP de type Phox, a démontré un ralentissement sévère de la croissance du parasite. La caractérisation de la protéine PfPX a révélé qu’elle se localisait à la membrane de la vacuole digestive, le site où le parasite digère l'hémoglobine (Hb) de l'hôte afin de subvenir à ses besoins en acides aminés. Nous avons montré que les parasites dépourvus de la protéine Phox accumulaient plus d'Hb et que celle-ci était piégée dans des vésicules à proximité de la vacuole digestive, suggérant un rôle pour cette protéine dans la fusion des vésicules d’Hb avec la membrane de la vacuole digestive. Globalement, nos résultats ont révélé que les PIP ont un rôle important dans le transport de l'Hb chez P. falciparum / Malaria is one of the most devastating curses in developing countries. The absence of a vaccine and resistance to available antimalarial agents demonstrate the urgent need to identify new therapeutic targets. Phosphoinositides (PIPs) are essential components of cell membranes in eukaryotes, playing an important role in intracellular signaling, DNA synthesis and protein trafficking, for example. Despite their importance in eukaryotes, little is known about their functions in the malaria parasite Plasmodium falciparum. In our laboratory, we screened 36 putative effectors of the PIP pathway by gene inactivation to identify the genes that are essential for proliferation in P. falciparum. Our studies showed that 72% of genes possibly involved in the PIP pathway could not be inactivated and are therefore potentially essential for parasite survival. Analysis of a knockout strain for PfPX protein, having a Phox-like PIP binding domain, demonstrated a severe slowdown in parasite growth. Characterization of the PfPX protein revealed that it was localized to the food vacuole membrane, the site where the parasite digests the hemoglobin (Hb) of the host in order to meet his needs in amino acids, and in vesicular type structures. We have shown that parasites lacking the Phox protein accumulate more Hb and that it is trapped in vesicles near the digestive vacuole, suggesting a role for this protein in the fusion of Hb vesicles with the membrane of the digestive vacuole. Overall, our results revealed that PIPs play an important role in the transport of P. falciparum Hb
146

Planejamento, síntese e avaliação biológica de inibidores de falcipaína 2 como candidatos a antimaláricos / Design, synthesis and biological evaluation of falcipain 2 inhibitors as candidates for antimalarials

Oliveira, Thuane Duarte 23 May 2019 (has links)
A malária, doença causada pelo protozoário do gênero Plasmodium, está entre as doenças que mais causam mortes os países subdesenvolvidosn. O hospedeiro é infectado por meio da picada do mosquito do gênero Anopheles, que introduz o parasita durante a hematofagia. As formas mais graves são causadas pelo Plasmodium vivax e o Plasmodium falciparum. As regiões mais afetadas por estas formas são África Subsaariana, Ásia, América Central e Sul. Desde o começo do século XXI, a Organização Mundial de Saúde (OMS) busca erradicar a doença, porém o P.falciparum se mostrou resistente aos fármacos antimaláricos existentes, dificultando a eficácia do tratamento. Isto, entre outros fatores, como mortalidade e alto índice de infecção, tornam necessárias novas pesquisas para a descoberta de novos fármacos mais seguros e eficazes contra a malária. Estudos têm mostrado como um alvo promissor para a criação de novos antimaláricos, a cisteína protease falcipaína, a qual se apresenta em três isoformas no parasita, sendo elas, falcipaína 1, 2 e 3. A falcipaína 2 está ligada com a hidrólise da hemoglobina, e seus inibidores vem sendo estudados como alternativas na busca de agentes antimaláricos. Derivados de semicarbazona, tais como o nitrofural e o hidroximetilnitrofural demonstraram atividade inibitória de cisteíno proteases parasitárias. Utilizando estratégias modernas de planejamento de fármacos e por meio da integração entre técnicas computacionais e experimentais, realizou-se o planejamento, síntese e avaliação biológica de compostos derivados dos ditiocarbazatos e tiossemicarbazonas, bioisosteros de semicarbazona, como inibidores da cisteíno protease falcipaína 2, no intuito de obter novos antimaláricos. Aplicaram-se técnicas de modelagem molecular em três séries de compostos (A, B e C), sendo a A e B derivados dos ditiocarbazatos e a C das tiossemicarbazonas. Estes estudos sugerem, três compostos da série A, quatro na série B e três na C com maior potencial para inibição da falcipaína 2. Isso devido aos resultados teóricos indicarem condições favoráveis ao ataque nucleofílico da cisteína 42 catalítica da falcipaína 2 às tiocarbonilass presentes nos compostos planejados. Estes derivados foram sintetizados, analisados por espectroscopia de ressonância magnética de 1H e 13C, espectroscopia de IV, ponto de fusão e pureza caracterizando sua formação. Após a obtenção, os compostos foram enviados para ensaios biológicos frente ao parasita P. falciparum. Os compostos testados não apresentaram inibição, porém é sabido que muitos inibidores enzimáticos não são ativos contra o parasita mesmo tendo alta potência contra a enzima, isto devido às barreiras a serem ultrapassadas até chegar ao alvo bioquímico, deste modo faz-se necessário ensaios contra a enzima para validar nossa hipótese. / Malaria, a disease caused by the protozoan of the genus Plasmodium, is among the most deadly diseases in poor countries. The host is infected through the bite of the mosquito of the genus ,i>Anopheles, which introduces the parasite during hematophagy. The most severe forms are caused by Plasmodium vivax and Plasmodium falciparum. The regions most affected by these forms are Sub-Saharan Africa, Asia, Central and South America. Since the beginning of the 21st century, the World Health Organization (WHO) has sought to eradicate the disease, but P. falciparum has been resistant to antimalarial drugs treatment. Among other factors, such as mortality and high infection rates, new research is needed to find new, safer and more effective drugs against malaria. Studies have shown as a promising target for the creation of new antimalarial drugs, the cysteine protease falcipain, which is present in three isoforms in the parasite: falcipain 1, 2 and 3. Falcipain 2 is linked to the hydrolysis of hemoglobin, and its inhibitors have been studied as alternatives in the search for antimalarial agents. Derivatives of semicarbazone such as nitrofural and hydroxymethylnitrofural demonstrated inhibitory activity of parasitic cysteine proteases. Using modern strategies for drug design and the integration of computational and experimental techniques, the design, synthesis and biological evaluation of compounds derived from dithiocarbazates and thiossemicarbazones, semicarbazone biosynthesis as inhibitors of cysteine protease falcipain 2 were carried out in order to new antimalarials. Molecular modeling studies were performed in three series of compounds (A, B and C), with A and B being derived from dithiocarbazates and C from thiossemicarbazones. These studies suggest three compounds in the A series, four in the B series, and three in the C group with the greatest potential for inhibition of falcipain 2. This is due to the theoretical results indicating favorable conditions for the nucleophilic attack of the catalytic cysteine of falcipain 2 on thionyls present in the compounds planned. These derivatives were synthesized, analyzed by 1H and 13C magnetic resonance spectroscopy, IR spectroscopy and melting point, characterizing their formation. After being obtained, the compounds were sent for biological assays against the P. falciparum parasite. The compounds tested did not show inhibition, but it is known that many enzyme inhibitors are not active against the parasite even though they have high potency against the enzyme, this is due to the barriers to be overcome until reaching the biochemical target, thus enzyme to validate our hypothesis.
147

Investigação de PfSR25, putativo receptor serpentino de Plasmodium falciparum. / Investigation of PfSR25, putative serpentine receptor of Plasmodium falciparum.

Chaves, Gepoliano dos Santos 07 August 2014 (has links)
Este trabalho teve por objetivo dissecar o papel potencial de fosforilação/desfosforilação como efeitos da ativação de PfSR25, um candidato a receptor serpentina de P. falciparum. Como a sinalização é um evento celular complexo, não excluímos a possibilidade de que outros mecanismos moleculares ocorram além dos aqui descritos. Nossas conclusões são que potássio modula PfSR25, ativando quinases/fosfatases, levando à ativação de moléculas efetoras. Encontramos MSP1, proteína já caracterizada e Pf4-4-13 e o fator básico de transcrição 3B (PfBTF3B), que ainda não foram caracterizados em P. falciparum, como efetores. Estes dados sugerem que pelo menos em parte, o mecanismo pelo qual PfSR25 exerce seu papel no desenvolvimento de P. falciparum seja através da ativação de quinases/fosfatases. Isto não é surpreendente, pois a sinalização de PfSR25 ocorre através de K+/cálcio e o segundo mensageiro é um modulador destas classes de proteínas. No entanto, deve ser investigado se cálcio tem algum efeito direto sobre o processamento/ativação dos efetores aqui identificados. / This work aimed at dissecting the potential role of phosphorylation/dephosphorylation as downstream effect of PfSR25 activation. PfSR25 is a serpentine receptor candidate from P. falciparum. As signaling is a quite complex cellular event, we do not exclude the possibility that other molecular mechanisms, take place additionally to those here described. Our conclusions are that potassium modulates PfSR25 by activation of kinases/phosphatases, leading to activation of effector molecules. We found MSP1 already characterized protein and Pf4.4.13 and the basic transcription factor 3B (PfBTF3B), which have not yet been characterized in P. falciparum as effectors. These data suggest that, at least in part, the mechanism by which PfSR25 exerts its role in the P. falciparum development is through the activation of kinase/phosphatase. This is not surprising, since PfSR25 signaling occurs through K+/Calcium and the second messenger is a modulator of these classes of proteins. However, remains to be investigated rather calcium has a direct effect on processing/activation the effectors here identified.
148

Caracterização da apirase do parasita P. falciparum e análise do papel do Ca2+ no egresso de T. gondii. / Characterization of P. falciparum apyrase and analysis of the role of Ca2+ in T. gondii egress.

Pereira, Lucas Borges 18 February 2016 (has links)
Plasmodium falciparum e Toxoplasma gondii são protozoários parasitas pertencentes ao filo Apicomplexa. Apirases são enzimas metabolizadoras de nucleotídeos extracelulares. Nesta tese mostramos pela primeira vez a presença de um membro desta família de enzimas em P. falciparum, o qual foi capaz de degradar ATP extracelular. Análises por RT-qPCR revelaram a expressão da apirase durante todo o ciclo intraeritrocítico. A adição de inibidores desta classe de enzimas foi capaz de prejudicar o desenvolvimento dos parasitas e a invasão de novas hemácias pelos merozoitos, sugerindo assim um papel da apirase nestes processos. A via de sinalização por Ca2+ é universal e vital para todas as células. Para melhor entender a fisiologia celular de P. falciparum construímos uma nova linhagem de parasitas transgênicos, PfGCaMP3, que nos tornam capazes de monitorar a dinâmica de Ca2+ sem o uso de protocolos invasivos de marcação. De modo semelhante utilizamos uma nova linhagem de T. gondii expressando de forma estável o indicador de Ca2+ GCaMP3 para estudar o papel deste íon na saída da célula. T. gondii possui o Ca2+ necessário para promover este processo, entretanto Ca2+ extracelular age como um fator intensificador neste passo essencial do ciclo lítico. / Plasmodium falciparum and Toxoplasma gondii are protozoan parasites that belong to phylum Apicomplexa. Apirases are metabolizing enzymes of extracellular nucleotides. In this work we show for the first time the presence of an apyrase in P. falciparum, which was able to degrade extracellular ATP. RTqPCR analysis revealed the expression of apyrase throughout the intraerythrocytic cycle. Addition of apyrase inhibitors was able to impair the development of the parasites and the invasion of new erythrocytes by merozoites, thus suggesting a role of apyrase in these processes. Calcium signaling is universal and vital to all cells. To better understand the cellular physiology of P. falciparum we construct a new strain of transgenic parasites, PfGCaMP3, which enable us to monitor the Ca2+ dynamics without using invasive protocols. Similarly we use a new strain of T. gondii that stably express the Ca2+ indicator GCaMP3 to study the role Ca2+ in parasite egress. T. gondii has the Ca2+ required to promote this process, however extracellular Ca2+ acts as an enhancer factor in this crucial step of the lytic cycle.
149

Investigação bioquímica da ocorrência da biossíntese de vitamina K e retinóides no ciclo intraeritrocitário do Plasmodium falciparum. / Biochemical investigation of occurence of retinoids and vitamin K biosynthesis in intraerythrocytic stages of Plasmodium falciparum.

Matsumura, Miriam Yukiko 14 November 2008 (has links)
A malária é uma das principais doenças parasitárias no mundo, e o aumento da resistência aos antimaláricos atualmente utilizados dificulta o controle dessa parasitose. Assim, é de interesse a descoberta de novas vias metabólicas que sirvam de alvos para o desenvolvimento de drogas para combater essa doença. Nosso laboratório, nos últimos anos, tem investido na caracterização de intermediários e produtos finais da via de isoprenóides. Baseando-se na presença das vias 2-C-metil-D-eritritol 4-fosfato e do chiquimato, decidimos verificar se ocorriam as biossínteses de retinóides e vitamina K no ciclo intraeritrocitário do P. falciparum, através da análise de produtos metabolicamente marcados com [1(n)-3H]-pirofosfato de geranilgranila por análises cromatográficas (HPLC e TLC), além da espectrometria de massas. Não identificamos a presença de retinal, retinol e ácido retinóico no ciclo intraeritrocitário do P. falciparum. Já a biossíntese de vitamina K precisa ser estudada com mais profundidade, pois há indícios de biossíntese, em especial da menaquinona-4. / Malaria is one of the most important parasitic diseases in the world. The spread of resistance to the antimalarials impairs the parasite\'s control. Therefore, is necessary the discovery of new metabolic routes to allow new antimalarials development. Our group has been studying the isoprenoid pathway, characterizing the intermediate and secondary products of this pathway. Based on the presence of 2-C-methyl-D-erythritol 4-phosphate and shikimate pathways, we decided to investigate the occurrence of retinoids and vitamin K biosynthesis in P. falciparum, through the chromatography of [1(n)-3H]Geranylgeranylpyrophosphate labeled products of intraerythrocytic stages of P. falciparum, and mass espectometry analysis. The retinal, retinol and retinoic acid were not identified in P. falciparum. The results indicate the menaquinone-4 biosynthesis, although deeper investigation is necessary.
150

Estudo da via de heme farnesilado e dos inibidores desta via em estágios intraeritrocitários de P. falciparum. / Study of the farnesylated heme synthesis pathway in intra-erythrocyte stages of P. falciparum and inhibitors of this pathway.

Gurge, Raquel Maria Simão 04 July 2017 (has links)
O desenvolvimento de antimaláricos é necessario pois, há linhagens de Plasmodium resistentes às drogas em uso e um alvo importante é a via de isoprenoides. Importantes alvos derivados desta via são: heme O já que, há antimaláricos relacionados ao heme; e a giberilina pois, há inibidores desta que não são prejudiciais ao homem. Inabenfide (INA) e uniconazol-P (UNP) inibem a biossíntese de giberilina em plantas e o crescimento de P. falciparum. Inicialmente, identificamos no parasita genes homólogos para a síntese de heme O e A, cox10 e 15, que codificam as enzimas HOS e HAS. Parasitas transgênicos com HOS e HAS marcados com GFP permitiram identificar a localização de cox10 no núcleo e de cox15 na mitocôndria. Identificamos heme O por marcações metabólicas e espectrometria de massa. Entretanto, não identificamos heme A e giberelina. INA e UNP diminuem a biossíntese de heme O e a parasitemia, observado por oxido-redução e marcação metabólica, o que torna a sintese de heme O um interessante alvo para antimaláricos. / The development of antimalarials is necessary because there are Plasmodium strains resistant to the drugs in use and an important target is the isoprenoid pathway. Targets derived from the isoprenoid pathway are: heme O as there are antimalarial drugs related to heme; And gibberillin, because there are inhibitors which are not harmful to man. Inabenfide (INA) and uniconazole-P (UNP) inhibit biosynthesis of gibberillin in plants and of growth the P. falciparum. Initially, we identified in P. falciparum genes homologous to cox10 and 15 encoding the enzymes (HOS and HAS) for synthesis of heme O and A. We created transgenic parasite lines which had HOS and HAS tagged to GFP. These revealed that the subcellular location of cox10 is in the nucleus and of cox15 in mitochondria. We identified heme O by metabolic labeling and mass spectrometry. However, no heme A or gibberellin was detected. INA and UNP decreased heme O biosynthesis and parasitemia as observed by oxido-reduction and metabolic labeling. Our data point to heme O as an important target for antimalarials.

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