Relevant bibliographies by topics / Citrate metabolism

Academic literature on the topic 'Citrate metabolism'

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Published: 20 July 2024

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Journal articles on the topic "Citrate metabolism"

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Monchi, Mehran. "Citrate pathophysiology and metabolism." Transfusion and Apheresis Science 56, no. 1 (February 2017): 28–30. http://dx.doi.org/10.1016/j.transci.2016.12.013.

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Korithoski, Bryan, Kirsten Krastel, and Dennis G. Cvitkovitch. "Transport and Metabolism of Citrate by Streptococcus mutans." Journal of Bacteriology 187, no. 13 (July 1, 2005): 4451–56. http://dx.doi.org/10.1128/jb.187.13.4451-4456.2005.

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ABSTRACT Streptococcus mutans, a normal inhabitant of dental plaque, is considered a primary etiological agent of dental caries. Two virulence determinants of S. mutans are its acidogenicity and aciduricity (the ability to produce acid and the ability to survive and grow at low pH, respectively). Citric acid is ubiquitous in nature; it is a component of fruit juices, bones, and teeth. In lactic acid bacteria citrate transport has been linked to increased survival in acidic conditions. We identified putative citrate transport and metabolism genes in S. mutans, which led us to investigate citrate transport and metabolism. Our goals in this study were to determine the mechanisms of citrate transport and metabolism in S. mutans and to examine whether citrate modulates S. mutans aciduricity. Radiolabeled citrate was used during citrate transport to identify citrate metal ion cofactors, and thin-layer chromatography was used to identify metabolic end products of citrate metabolism. S. mutans was grown in medium MM4 with different citrate concentrations and pH values, and the effects on the growth rate and cell survival were monitored. Intracellular citrate inhibited the growth of the bacteria, especially at low pH. The most effective cofactor for citrate uptake by S. mutans was Fe3+. The metabolic end product of citrate metabolism was aspartate, and a citrate transporter mutant was more citrate tolerant than the parent.
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Chen, Fangfang, Hanna Friederike Willenbockel, and Thekla Cordes. "Mapping the Metabolic Niche of Citrate Metabolism and SLC13A5." Metabolites 13, no. 3 (February 23, 2023): 331. http://dx.doi.org/10.3390/metabo13030331.

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The small molecule citrate is a key molecule that is synthesized de novo and involved in diverse biochemical pathways influencing cell metabolism and function. Citrate is highly abundant in the circulation, and cells take up extracellular citrate via the sodium-dependent plasma membrane transporter NaCT encoded by the SLC13A5 gene. Citrate is critical to maintaining metabolic homeostasis and impaired NaCT activity is implicated in metabolic disorders. Though citrate is one of the best known and most studied metabolites in humans, little is known about the consequences of altered citrate uptake and metabolism. Here, we review recent findings on SLC13A5, NaCT, and citrate metabolism and discuss the effects on metabolic homeostasis and SLC13A5-dependent phenotypes. We discuss the “multiple-hit theory” and how stress factors induce metabolic reprogramming that may synergize with impaired NaCT activity to alter cell fate and function. Furthermore, we underline how citrate metabolism and compartmentalization can be quantified by combining mass spectrometry and tracing approaches. We also discuss species-specific differences and potential therapeutic implications of SLC13A5 and NaCT. Understanding the synergistic impact of multiple stress factors on citrate metabolism may help to decipher the disease mechanisms associated with SLC13A5 citrate transport disorders.
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Mortera, Pablo, Agata Pudlik, Christian Magni, Sergio Alarcón, and Juke S. Lolkema. "Ca2+-Citrate Uptake and Metabolism in Lactobacillus casei ATCC 334." Applied and Environmental Microbiology 79, no. 15 (May 24, 2013): 4603–12. http://dx.doi.org/10.1128/aem.00925-13.

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ABSTRACTThe putative citrate metabolic pathway inLactobacillus caseiATCC 334 consists of the transporter CitH, a proton symporter of the citrate-divalent metal ion family of transporters CitMHS, citrate lyase, and the membrane-bound oxaloacetate decarboxylase complex OAD-ABDH. Resting cells ofLactobacillus caseiATCC 334 metabolized citrate in complex with Ca2+and not as free citrate or the Mg2+-citrate complex, thereby identifying Ca2+-citrate as the substrate of the transporter CitH. The pathway was induced in the presence of Ca2+and citrate during growth and repressed by the presence of glucose and of galactose, most likely by a carbon catabolite repression mechanism. The end products of Ca2+-citrate metabolism by resting cells ofLb. caseiwere pyruvate, acetate, and acetoin, demonstrating the activity of the membrane-bound oxaloacetate decarboxylase complex OAD-ABDH. Following pyruvate, the pathway splits into two branches. One branch is the classical citrate fermentation pathway producing acetoin by α-acetolactate synthase and α-acetolactate decarboxylase. The other branch yields acetate, for which the route is still obscure. Ca2+-citrate metabolism in a modified MRS medium lacking a carbohydrate did not significantly affect the growth characteristics, and generation of metabolic energy in the form of proton motive force (PMF) was not observed in resting cells. In contrast, carbohydrate/Ca2+-citrate cometabolism resulted in a higher biomass yield in batch culture. However, also with these cells, no generation of PMF was associated with Ca2+-citrate metabolism. It is concluded that citrate metabolism inLb. caseiis beneficial when it counteracts acidification by carbohydrate metabolism in later growth stages.
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Cartledge, S., D. J. Candy, and R. J. Hawker. "Citrate metabolism by human platelets." Transfusion Medicine 7, no. 3 (September 1997): 211–15. http://dx.doi.org/10.1046/j.1365-3148.1997.d01-28.x.

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Kanbe, Chiyuki, and Kinji Uchida. "Citrate Metabolism by Pediococcus halophilus." Applied and Environmental Microbiology 53, no. 6 (1987): 1257–62. http://dx.doi.org/10.1128/aem.53.6.1257-1262.1987.

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Antranikian, Garabed, and Friedrich Giffhorn. "Citrate metabolism in anaerobic bacteria." FEMS Microbiology Letters 46, no. 2 (June 1987): 175–98. http://dx.doi.org/10.1111/j.1574-6968.1987.tb02458.x.

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Sarantinopoulos, Panagiotis, George Kalantzopoulos, and Effie Tsakalidou. "Citrate Metabolism by Enterococcus faecalis FAIR-E 229." Applied and Environmental Microbiology 67, no. 12 (December 1, 2001): 5482–87. http://dx.doi.org/10.1128/aem.67.12.5482-5487.2001.

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ABSTRACT Citrate metabolism by Enterococcus faecalis FAIR-E 229 was studied in various growth media containing citrate either in the presence of glucose or lactose or as the sole carbon source. In skim milk (130 mM lactose, 8 mM citrate), cometabolism of citrate and lactose was observed from the first stages of the growth phase. Lactose was stoichiometrically converted into lactate, while citrate was converted into acetate, formate, and ethanol. When de Man-Rogosa-Sharpe (MRS) broth containing lactose (28 mM) instead of glucose was used,E. faecalis FAIR-E 229 catabolized only the carbohydrate. Lactate was the major end product, and small amounts of ethanol were also detected. Increasing concentrations of citrate (10, 40, 70, and 100 mM) added to MRS broth enhanced both the maximum growth rate ofE. faecalis FAIR-E 229 and glucose catabolism, although citrate itself was not catabolized. Glucose was converted stoichiometrically into lactate, while small amounts of ethanol were produced as well. Finally, when increasing initial concentrations of citrate (10, 40, 70, and 100 mM) were used as the sole carbon sources in MRS broth without glucose, the main end products were acetate and formate. Small amounts of lactate, ethanol, and acetoin were also detected. This work strongly supports the suggestion that enterococcal strains have the metabolic potential to metabolize citrate and therefore to actively contribute to the flavor development of fermented dairy products.
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Leandro, João G. B., Jair M. Espindola-Netto, Maria Carolina F. Vianna, Lilian S. Gomez, Thaina M. DeMaria, Monica M. Marinho-Carvalho, Patricia Zancan, Heitor A. Paula Neto, and Mauro Sola-Penna. "Exogenous citrate impairs glucose tolerance and promotes visceral adipose tissue inflammation in mice." British Journal of Nutrition 115, no. 6 (February 11, 2016): 967–73. http://dx.doi.org/10.1017/s0007114516000027.

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AbstractOverweight and obesity have become epidemic worldwide and are linked to sedentary lifestyle and the consumption of processed foods and drinks. Citrate is a metabolite that plays central roles in carbohydrate and lipid metabolism. In addition, citrate is the additive most commonly used by the food industry, and therefore is highly consumed. Extracellular citrate can freely enter the cells via the constitutively expressed plasma membrane citrate transporter. Within the cytosol, citrate is readily metabolised by ATP-citrate lyase into acetyl-CoA – the metabolic precursor of endogenously produced lipids and cholesterol. We therefore hypothesised that the citrate ingested from processed foods and drinks could contribute to increased postprandial fat production and weight gain. To test our hypothesis, we administered citrate to mice through their drinking water with or without sucrose and monitored their weight gain and other metabolic parameters. Our results showed that mice receiving citrate or citrate+sucrose did not show increased weight gain or an increase in the weight of the liver, skeletal muscles or adipose tissues (AT). Moreover, the plasma lipid profiles (TAG, total cholesterol, LDL and HDL) were similar across all groups. However, the group receiving citrate+sucrose showed augmented fasting glycaemia, glucose intolerance and the expression of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6 and IL-10) in their AT. Therefore, our results suggest that citrate consumption contributes to increased AT inflammation and altered glucose metabolism, which is indicative of initial insulin resistance. Thus, citrate consumption could be a previously unknown causative agent for the complications associated with obesity.
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Pudlik, Agata M., and Juke S. Lolkema. "Rerouting Citrate Metabolism in Lactococcus lactis to Citrate-Driven Transamination." Applied and Environmental Microbiology 78, no. 18 (July 13, 2012): 6665–73. http://dx.doi.org/10.1128/aem.01811-12.

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ABSTRACTOxaloacetate is an intermediate of the citrate fermentation pathway that accumulates in the cytoplasm ofLactococcus lactisILCitM(pFL3) at a high concentration due to the inactivation of oxaloacetate decarboxylase. An excess of toxic oxaloacetate is excreted into the medium in exchange for citrate by the citrate transporter CitP (A. M. Pudlik and J. S. Lolkema, J. Bacteriol. 193:4049–4056, 2011). In this study, transamination of amino acids with oxaloacetate as the keto donor is described as an additional mechanism to relieve toxic stress. Redirection of the citrate metabolic pathway into the transamination route in the presence of the branched-chain amino acids Ile, Leu, and Val; the aromatic amino acids Phe, Trp, and Tyr; and Met resulted in the formation of aspartate and the corresponding α-keto acids. Cells grown in the presence of citrate showed 3.5 to 7 times higher transaminase activity in the cytoplasm than cells grown in the absence of citrate. The study demonstrates that transaminases ofL. lactisaccept oxaloacetate as a keto donor. A significant fraction of 2-keto-4-methylthiobutyrate formed from methionine by citrate-driven transaminationin vivowas further metabolized, yielding the cheese aroma compounds 2-hydroxy-4-methylthiobutyrate and methyl-3-methylthiopropionate. Reducing equivalents required for the former compound were produced in the citrate fermentation pathway as NADH. Similarly, phenylpyruvate, the transamination product of phenylalanine, was reduced to phenyllactate, while the dehydrogenase activity was not observed for the branched-chain keto acids. Both α-keto acids and α-hydroxy acids are known substrates of CitP and may be excreted from the cell in exchange for citrate or oxaloacetate.
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Dissertations / Theses on the topic "Citrate metabolism"

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Levasseur, Rémi. "Aluminum citrate transport and metabolism in Pseudomonas fluorescens." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0018/MQ46489.pdf.

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Júnior, Celso Heitor de Freitas. "Avaliação metabólica de homens idosos portadores de litíase urinária." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/5/5153/tde-12012012-154818/.

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OBJETIVOS: O aumento da expectativa de vida tem gerado um envelhecimento populacional global, fazendo com que a proporção de indivíduos com mais de 60 anos de idade cresça mais rapidamente do que as demais faixas etárias. A incidência de litíase urinária em indivíduos idosos tem aumentado nos últimos anos, principalmente em nações industrializadas. Aspectos particulares do envelhecimento orgânico aumentam a morbidade associada à litíase urinária em idosos, tornando a prevenção e o tratamento clínico ainda mais relevantes nessa faixa etária. Nosso objetivo é analisar a avaliação metabólica de homens idosos portadores de cálculos renais. MATERIAIS E MÉTODOS: Realizamos um estudo clínico tipo caso-controle. Os critérios de inclusão foram: indivíduos do sexo masculino com mais de 60 anos de idade, com antecedente de cólica renal ou diagnóstico incidental de litíase urinária após os 60 anos (grupo caso); no grupo controle foram incluídos pacientes da mesma faixa etária sem antecedente de cólica renal ou diagnóstico incidental de litíase renal. Todos os participantes foram submetidos à anamnese e aqueles selecionados realizaram perfil metabólico para diagnóstico de litíase urinária: dosagem sérica de cálcio total, cálcio ionizado, ácido úrico, fósforo, glicemia, uréia, creatinina e paratormônio (PTH); coleta de urina para urocultura e pH urinário, e amostras de urina de 24 horas para quantificação do volume e dosagem de cálcio, citrato, creatinina, ácido úrico e sódio. Foram também submetidos à radiografia simples de abdome e ultrassonografia do aparelho urinário. Os indivíduos do grupo caso realizaram dois perfis metabólicos completos de urina de 24 horas, enquanto os do grupo controle somente um perfil. Os resultados foram submetidos à análise estatística. RESULTADOS: Cento e dez indivíduos foram convocados e, após aplicação dos critérios de inclusão, 70 foram selecionados. Cinquenta e um indivíduos concluíram a investigação clínica, sendo 25 no grupo caso e 26 no controle. Cinquenta e seis por cento dos pacientes do grupo caso apresentaram hipocitratúria comparados a 15,4% do grupo controle (p=0,002). A determinação de sódio em urina de 24 horas também apresentou diferença estatisticamente significativa entre casos e controles: 64% versus 30,8%, respectivamente (p=0,017). Estes resultados foram submetidos à análise de regressão logística univariada e múltipla, respectivamente, e mantiveram seus níveis de significância. CONCLUSÃO: A hipocitratúria e a hipernatriúria são os principais distúrbios metabólicos apresentados por indivíduos idosos do sexo masculino portadores de cálculo urinário
PURPOSES: Rise in life expectancy has caused a global populational ageing and people older than 60-years have increased more than any other age group. The incidence of urinary lithiasis in aging people has increased during the last years, mainly in developed nations. Some aspects concerning organic ageing increase morbidity related to urolithiasis in older individuals making prevention and medical management of urinary stones relevant in this age group. Our objective is to evaluate metabolic parameters in men older than 60 years with urinary stones. MATERIALS AND METHODS: A case-control study was performed. Inclusion criteria were: men older than 60- years old with renal pain episodes or incidental diagnosis of urinary lithiasis beginning after 60-years old (case arm). Control group was constituted by patients older than 60 years without renal colic past or diagnosis of urolithiasis. Patients were recruited from a database from the Urologic Clinic at University of São Paulo Medical School Hospital. Each individual was submitted to anamnesis and those selected underwent a metabolic evaluation for urinary stones: serum dosages of total and ionized calcium, uric acid, phosphorus, glucose, urea, creatinine and parathyroid hormone (PTH); urine culture and urinary pH. Twenty four hour urine samples were obtained for volume quantification and for calcium, citrate, creatinine, uric acid and sodium dosages. An abdominal x-ray and ultrasonography were performed in all patients. Case arm patients underwent two complete metabolic urinary investigations while control arm individuals to only one. All results were submitted to statistical analysis. RESULTS: One hundred and ten individuals were called up for initial evaluation and 70 were selected. Fifty-one individuals concluded the whole clinical investigation: 25 in the case arm and 26 in the control arm. Hypocitraturia was present in 56% of case arm patients and 15,4% of the control arm patients (p=0,002). Hypernatriuria in 24-hour urine samples was found in 64% of case arm patients and in 30,8% of control arm patients (p=0,017). These results were submitted to univariate and multiple logistic regressions and maintained their levels of significancy. CONCLUSION: Hypocitraturia and hypernatriuria are the main metabolic disorders among aging men with urolithiasis
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Jeffery, David. "Studies on citrate and malate metabolism in Lycopersicon esculentum." Thesis, University of Bath, 1985. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.353243.

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The specific activities of citrate synthase and malate dehydrogenase extracted from mature green fruit of Lycopersicon esculentum, fell 60% during the first two weeks of a twelve week experiment in which the fruit were stored in an atmosphere designed to inhibit ethylene synthesis. Throughout the remainder of the experiment, the specific activities were relatively constant. In the initial two week period, the specific activity of NADP-linked malic enzyme rose by 400%, malic acid concentration fell by 50%, while the concentration of citric acid rose by 20%. Those features of ripening such as the de novo synthesis of lycopene and polygalacturonase, which were thought to depend on ethylene for initiation of response, could not be detected until the fruit were removed to a normal atmosphere. Additionally, citrate synthase and malate dehydrogenase from mature green tomato fruit stored in the presence or absence of ethylene, showed similar trends in specific activity, and the presence of the olefin made no significant difference to the rate of loss of enzyme specific activity. The purification and partial characterisation of citrate synthase from Lycopersicon esculentum is described. The enzyme is a dimer with sub-units of similar size and a total Mr of approximately. 100,000. The characterisation revealed no obvious regulatory features that would easily account for the fall in specific activity. Sub-cellular fractionation studies demonstrated unequivocally that the site of organic acid metabolism was the mitochondrion. Citrate synthase, NAD-dependent isocitrate dehydrogenase and NAD-dependent malic enzyme were shown to be located exclusively in the mitochondrion, while malate dehydrogenase was located both in the cytosol and the mitochondrion. All these enzymes including cytosolic malate dehydrogenase exhibited the co-ordinated fall in specific activity described above. A hypothesis is proposed which includes a novel coarse control of the citric acid cycle and related enzymes, as an early indicator of senescence.
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Al-Tarrah, Mustafa. "The effect of citrate synthase on skeletal muscle metabolism." Thesis, University of Aberdeen, 2017. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=235778.

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Citrate synthase (CS) is a key mitochondrial enzyme in the tricarboxylic acid cycle (TCA). TCA provides NADH and FADH for the ETC to generate ATP through oxidative phosphorylation in muscle cells. The aim of this PhD project is to investigate the role of CS in skeletal muscle metabolism. The aim of the first study was to investigate the effects of a high fat diet (HFD, 45 % kcal fat) for 12 weeks on CS activity in the heart and gastrocnemius muscle of C57BL/6J (B6) mice and congenic (B6.A) characterised by 39% reduced CS activity. Spectrophotometric analysis of CS activity in the heart and gastrocnemius muscle revealed that HFD led to an increase in CS activity in gastrocnemius muscle but a decrease in the heart in both strains of mice. The aim of the second study was to investigate the effects of low CS activity on substrate metabolism in primary muscle cells established from B6 and B6.A mice. Primary muscle cells from both strains were incubated in radiolabelled glucose or palmitate to assess their oxidation in the mitochondria. The reduction of CS activity in B6.A muscle cells did not affect glucose and palmitate oxidation. The aim of the third study was to investigate the effects of D- and L-serine on CS activity in B6 muscle homogenates, primary muscle cells and purified CS from porcine heart. The muscle samples were incubated in D - or L-serine at 0.1 mM or 5 mM concentration and CS activity levels were assessed by spectrophotometer. D- or L-serine did not have any effect on CS activity in muscle samples. The aim of the fourth study was to investigate the effects of low CS activity on substrate metabolism in C2C12 muscle cells. Lentiviral transduction of C2C12 muscle cells with shRNA resulted in a reduction of CS activity and the metabolic pathways were assessed using XF24 Analyser, western blotting, Immunofluorescence and qRTPCR. Low CS activity was associated with a reduction in substrate oxidation by the mitochondria, an increase in glycolysis and ceramide accumulation in C2C12 muscle cells. The results highlight the significance of CS activity as a modulator of muscle metabolism.
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Dufort, Fay Josephine. "Contribution of Glucose Metabolism to the B Lymphocyte Responses." Thesis, Boston College, 2012. http://hdl.handle.net/2345/3161.

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Thesis advisor: Thomas C. Chiles
B-lymphocytes respond to environmental cues for their survival, growth, and differentiation through receptor-mediated signaling pathways. Naïve Blymphocytes must acquire and metabolize external glucose in order to support the bioenergetics associated with maintaining cell volume, ion gradients, and basal macromolecular synthesis. The up-regulation of glycolytic enzyme expression and activity via engaged B-cell receptor mediated-events was glucose-dependent. This suggests an essential role for glucose energy metabolism in the promotion of B cell growth, survival, and proliferation in response to extracellular stimuli. In addition, the activity of ATP-citrate lyase (ACL) was determined to be crucial for ex vivo splenic B cell differentiation to antibody-producing cells wherein B cells undergo endomembrane synthesis and expansion. This investigation employed knockout murine models as well as chemical inhibitors to determine the signaling components and enzymes responsible for glucose utilization and incorporation into membrane lipids. These results point to a critical role for phosphatidylinositol 3- kinase (PI3K) in orchestrating cellular glucose energy metabolism and glucosedependent de novo lipogenesis for B lymphocyte responses
Thesis (PhD) — Boston College, 2012
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Biology
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Roberts, Andrew. "Crassulacean acid metabolism and photosynthetic plasticity in the genus Clusia : an ecophysiological study." Thesis, University of Newcastle Upon Tyne, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360879.

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Saeed, Saima. "The role of mitochondrial citrate synthase in the metabolism of developing potato tubers." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621806.

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Sienkiewicz-Porzucek, Agata. "Evaluation of the role of mitochondrial citrate synthase, mitochondrial and cytosolic isoforms of isocitrate dehydrogenase in tomato leaf metabolism." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2010. http://dx.doi.org/10.18452/16074.

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Der Citratzyklus (TCA) ist einer der bedeutendsten Stoffwechselwege für alle lebenden Organismen. Trotz der zentralen Rolle dieses Prozesses im Pflanzenmetabolismus ist er nur relativ wenig untersucht worden. In dieser Arbeit berichte ich über die Produktion und die funktionale Analyse von Tomatenpflanzen (Solanum lycopersicum), die unabhängig eine leicht eingeschränkte Aktivität der mitochondrialen Citrat-Synthase (CS) und zweier Isocitrat-dehydrogenasen (mitochondriale NAD-IDH und cytosolische NADP-ICDH) zeigen. Die transgene Pflanzen wiesen mehrheitlich keine erkennbare Veränderung eines Wachstumphänotyps auf. Obwohl die photosyntetische Leistung keine Änderungen gezeigt hatte, war die mitochondriale Respiration gestiegen, begleitet von einem reduzierten Kohlenstoff-fluss durch den Citratzyklus. Darüber hinaus waren die CS Pflanzen charakterisiert durch wesentliche Änderungen im Blattmetabolismus, einschließlich eines eingeschränkten Niveaus des photosynthetischen Pigments und Zwischenprodukten des Citratzyklus zusammen mit einer Akkumulation von Nitraten, verschiedenen Aminosäuren und Stärken. Zusammengefasst deuten diese Ergebnisse auf eine Einschränkung der Nitrat-Aufnahme hin. Das mit Hilfe von TOM1 Mikroarrays und quantitativer RT-PCR durchgeführte Transcript-profiling hat gezeigt, dass die fehlende Aktivität der mitochondrialen CS teilweise von einer gestiegenen, peroxisomalen CS Isoform ausgeglichen wird. Die metabolische Verschiebung ergab eine Verstärkung der photorespiratorischen Leistung, die vermutlich eine ausgleichende Rolle in der Produktion organischer Säuren und der Wiederherstellung der Redox-Balance spielt. Interessantenweise war die metabolische Antwort von Blättern auf Stickstoffmangel in NADP-ICDH Pflanzen dramatischer als in NAD-IDH Pflanzen, was darauf hindeutet, dass die cytosolische Isoform der Hauptlieferant von 2-Oxoglutarat im Tomatenmetabolismus sein könnte.
Although the TCA cycle is a respiratory metabolic pathway of central importance for all living organisms, relatively few molecular physiological studies of plants were performed to date. Here, I report the generation and functional analysis of tomato plants (Solanum lycopersicum) independently displaying mildly limited activity of mitochondrial citrate synthase (CS) and two isocitrate dehydrogenases, namely mitochondrial NAD-IDH and cytosolic NADP-ICDH. The transgenic plants revealed minor phenotypic alterations. Although the leaf photosynthetic performance was largely unaltered, the changes in mitochondrial respiration and carbon flux through the TCA cycle were observed. Moreover, the plants were characterized by significant modifications in the leaf metabolic content and in maximal catalytic activities of several enzymes involved in primary C and N metabolism. These results hint towards limitations in nitrate assimilation pathway. The transcript profiling performed by utilizing TOM1 microarrays and quantitative RT-PCR approach revealed that the deficiency in mitochondrial CS activity was partially compensated by up-regulation of peroxisomal CS isoform. The limitations in the activities of isocitrate dehydrogenases resulted in up-regulation of the photorespiratory pathway, which presumably played a compensatory role in supporting organic acid production and re-establishing redox balance in the transgenic leaves. Interestingly, the leaf metabolic response towards nitrogen starvation conditions was far more dramatic in NADP-ICDH transgenic plants than NAD-IDH plants, hinting that the cytosolic isoform may be the major 2-oxoglutarate supplier in tomato metabolism.
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Daniels, Martin André [Verfasser]. "The mammalian citrate transporter mINDY (I’m not dead yet) and its protective role in hepatic metabolism / Martin André Daniels." Berlin : Medizinische Fakultät Charité - Universitätsmedizin Berlin, 2021. http://d-nb.info/1228860742/34.

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Alhindi, Yosra. "Effects of low citrate synthase activity on physiological responses of mice to high fat diet and palmitate induced lipotoxicity." Thesis, University of Aberdeen, 2016. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=231391.

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The main aim of this thesis was to examine the hypothesis that the A/J strain variant of H55N substitution affects citrate synthase (CS) enzyme activity and metabolic health in mice fed a high fat diet (HFD). C57BL/6J (B6) mice and congenic B6.A-(rs3676616-D10Utsw1)/KjnB6 (B6.A) mice, a strain which carries the A/J allele of Cs on the B6 strain background, were fed a HFD (45% kcal from fat) for 12 weeks. CS activity, but not that of ß-hydroxyacyl-coenzyme dehydrogenase was lower in the gastrocnemius muscle of B6.A mice compared to B6 mice (P< 0.001). During HFD feeding the glucose tolerance of mice decreased progressively and to a greater extent in B6.A females compared to B6 females, with males showing a similar trend. Interestingly, after 12 weeks of HFD feeding only B6.A males showed increases (P< 0.05) in their resting metabolic rate; moreover; core body temperature were also increased (P< 0.05) for congenic B6.A of both sexes by the end of the study. However, body weight and fat gain did not differ between B6.A and B6 mice. The second aim of the thesis was to test the hypothesis that low CS activity promotes palmitate-induced lipotoxicity in muscle cells. After 18 hours of incubation in 0.8 mM palmitate, C2C12 muscle cells with a ~50% reduction in CS activity showed low (P< 0.001) viability, increased (P< 0.001) levels of cleaved Caspase-3, high levels of AMP-activated protein kinase and acetyl-CoA carboxylase phosphorylation (P< 0.05), low levels of protein kinase B phosphorylation, high mitogen-activated protein kinases activation (P< 0.001) compared to the control shRNA cells. This was coupled with higher levels of mitochondrial proteins (P< 0.05), which are involved in oxidative phosphorylation. C2C12 cells with reduced CS activity also showed high reactive oxygen species production (P< 0.05), low intracellular ATP levels (P< 0.05), and lower basal mitochondrial respiration (P< 0.001). In summary, the A/J strain variant of H55N is associated with low CS enzyme activity and impaired metabolic health when fed HFD. Palmitate has a lipotoxic effect on Cs shRNA transfected cells and can lead to cell death.
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Books on the topic "Citrate metabolism"

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Levasseur, Rémi. Aluminum-citrate transport and metabolism in Pseudomonas fluorescens. Sudbury, Ont: Laurentian University, Chemistry and Biochemistry Department, 1999.

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Finn, Hugh Michael D. Iron (III)-citrate metabolism and iron homeostasis in Pseudomonas fluorescens. Sudbury, Ont: Laurentian University, School of Graduate Studies, 2001.

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Mackenzie, Carrie. TCA cycle enzymes and aluminum - citrate metabolism in Pseudomonas fluorescens. Sudbury, Ont: Laurentian University, 2001.

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Talbot, R. J. Biokinetics of 237Pu-citrate and nitrate in rats after the intravenous injection of only 2 pg plutonium. Oxfordshire, OX: Environmental and Medical Sciences Divison, Harwell Laboratory, 1989.

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Schlabach, Gretchen A. The effects of training and detraining on corticosterone rhythms and dietary fat selection in the Osborne-Mendel rat. 1992.

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The effects of training and detraining on corticosterone rhythms and dietary fat selection in the Osborne-Mendel rat. 1991.

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Daudon, Michel, and Paul Jungers. Uric acid stones. Edited by Mark E. De Broe. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780199592548.003.0202_update_001.

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Uric acid (UA) stones are typically red-orange and often appear as sand/ gravel though they may be large. They are totally radiolucent. They account for about 10% of all kidney stones in most countries, and up to 20% in some populations. It is twice as frequent in males, prevalence increases with age, and it is two to three times higher in patients with type 2 diabetes or with features of the metabolic syndrome. Factors that induce the formation of UA stones are a low urine volume, hyperuricosuria, and, more importantly, a permanently low urine pH (< 5). Indeed, below its pKa of 5.35 at 37°C, UA is in non-dissociated form, whose solubility is at best 100 mg/L, whereas urinary UA excretion normally exceeds 600 mg/day and may exceed 1g/day.Because UA solubility increases up to approximately 500 mg/L at urine pH > 6, urine alkalinization, with a target pH of 6.5–7, is the cornerstone of medical treatment. This most often allows dissolution of existing stones and prevention of recurrent stone formation so that urological intervention is infrequently needed. The preferred agent for alkalinization is potassium citrate (30–60 mEq/day in divided doses), because potassium urate is twice more soluble than sodium urate. However, in patients with poor gastric tolerance to potassium citrate or contraindication to potassium supplements, sodium bicarbonate is an acceptable alternative. Limitation of animal proteins, purine-rich foods (including beer), alcoholic drinks and acidified beverages (sodas) are useful measures, together with large fluid intake (> 2–2.5 L/day). Allopurinol may be indicated in cases of symptomatic hyperuricaemia. Regular observance of alkalinisation, with periodic controls of urine pH by the patient, is needed to prevent the rapid formation of UA stones. Patients affected by UANL, especially if overweight, should be evaluated for type 2 diabetes or glucose intolerance and managed accordingly.
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Book chapters on the topic "Citrate metabolism"

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Hess, Bernhard. "Urinary Citrate and Citrate Metabolism." In Urinary Tract Stone Disease, 181–84. London: Springer London, 2010. http://dx.doi.org/10.1007/978-1-84800-362-0_14.

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Franklin, Renty B., and Leslie C. Costello. "Citrate Metabolism in Prostate and Other Cancers." In Mitochondria and Cancer, 61–78. New York, NY: Springer New York, 2008. http://dx.doi.org/10.1007/978-0-387-84835-8_4.

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Armstrong, W. D., and Leon Singer. "In vitro Uptake and Exchange of Bone Citrate." In Ciba Foundation Symposium - Bone Structure and Metabolism, 103–16. Chichester, UK: John Wiley & Sons, Ltd., 2008. http://dx.doi.org/10.1002/9780470715222.ch9.

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Adler, S. "Urinary Excretion of Citrate — Influence Of Metabolism and Acid-Base Conditions." In Urolithiasis and Related Clinical Research, 173–80. Boston, MA: Springer US, 1985. http://dx.doi.org/10.1007/978-1-4684-7272-1_33.

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Kollmeier, M., and W. J. Horst. "Aluminium-induced exudation of citrate from the root tip of Zea mays (L.): Are differential impacts of Al on citrate metabolism involved in genotypical differences?" In Plant Nutrition, 492–93. Dordrecht: Springer Netherlands, 2001. http://dx.doi.org/10.1007/0-306-47624-x_238.

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Jenkins, A. D., T. P. Dousa, and L. H. Smith. "Effects of Metabolic Acidosis and Alkalosis on the Renal Brush Border Membrane Transport of Citrate." In Urolithiasis and Related Clinical Research, 189–91. Boston, MA: Springer US, 1985. http://dx.doi.org/10.1007/978-1-4684-7272-1_35.

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GLUSKER, JENNY P. "Structural Aspects of Citrate Biochemistry." In From Metabolite, to Metabolism, to Metabolon, 169–84. Elsevier, 1992. http://dx.doi.org/10.1016/b978-0-12-152833-1.50015-0.

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SRERE, PAUL A. "The Molecular Physiology of Citrate." In From Metabolite, to Metabolism, to Metabolon, 261–75. Elsevier, 1992. http://dx.doi.org/10.1016/b978-0-12-152833-1.50020-4.

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REMINGTON, S. JAMES. "Structure and Mechanism of Citrate Synthase." In From Metabolite, to Metabolism, to Metabolon, 209–29. Elsevier, 1992. http://dx.doi.org/10.1016/b978-0-12-152833-1.50017-4.

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KWACK, HEEMUN, and RICHARD L. VEECH. "Citrate: Its Relation to Free Magnesium Ion Concentration and Cellular Energy." In From Metabolite, to Metabolism, to Metabolon, 185–207. Elsevier, 1992. http://dx.doi.org/10.1016/b978-0-12-152833-1.50016-2.

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Conference papers on the topic "Citrate metabolism"

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Greenwood, Dalton L., and Jeffrey C. Rathmell. "Abstract PR07: Connecting acetate and citrate metabolism with epigenetic regulation of hematopoiesis." In Abstracts: AACR Special Virtual Conference on Epigenetics and Metabolism; October 15-16, 2020. American Association for Cancer Research, 2020. http://dx.doi.org/10.1158/1538-7445.epimetab20-pr07.

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Scharf, R. E., A. Wehmeier, and W. Schneider. "REDUCED PLATELET THROMBOXANE FORMATION IN ACUTE THROMBOTIC THROMBOCYTOPENIC PURPURA (TP): EVIDENCE FOR AN ABNORMAL PLATELET POPULATION WITH A TRANSIENT CYCLOOXYGENASE DEFECT." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644588.

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We have recently shown that alpha-granule-depleted platelets circulate in acute TTP. These platelets are hemostatically defective due to partial loss of granular constituents and/or metabolic abnormalities. To further evaluate morphometric and metabolic changes of "exhausted" platelets, we studied their volume distribution and thromboxane A2 (TXA2) formation in a 35-year-old patient with primary TTP. Platelet volume distribution in whole blood was determined by the impedance method using citrate (0.38%)/glutaraldehyde (0.125%) as anticoagulant. TXB2 production was measured radioimmunologically after incubation of platelet-rich plasma (PRP) with thrombin (10 U/ml) or arachido-nic acid (AA, 450 μM) for 5 min. During the acute phase of TTP, the thrombin-induced platelet TXB2 formation was significantly reduced (n=6, 0.32±0.08, ±SD, nmoles/109 platelets) as compared to controls (n=12, 2.7±0.9 nmoles/109 platelets, p < 0.001). Incubation of PRP with exogenous AA failed to restore normal TXB2 production in acute TTP. In addition, volume analysis showed an abnormally small-sized platelet population (modal volume < 1.5 fl) during the acute phase of TTP. Clinical remission was achieved by repeated plasmapheresis with substitution of fresh frozen plasma. Following normalization of the platelet count, platelet volume gradually increased (modal volume 3.3 fl), and the platelets recovered a normal in vitro thrombin- and AA-inducible TXA2 synthesis capacity. We conclude that (1) an abnormal (small-sized) platelet population and (2) a disorder of platelet arachidonic acid metabolism exist in acute TTP, leading to reduced TXA2 production. These changes may reflect the previous activation and consumption of platelets in vivo. The reduced platelet thromboxane synthesis is consistent with a transient cyclooxygenase defect which disappears following remission of TTP.
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Lanza, M., A. Beretz, A. Stierlé, D. Hanau, M. Kubina, and J. P. Cazenave. "ADRENALINE ACTIVATES HUMAN PLATELETS BUT IS NOT PER SE AN AGGREGATING AGENT. EFFECTS ON PLATELET MORPHOLOGY, MEMBRANEFLUIDITY, FIBRINOGEN BINDING, CYTOPLASMIC FREE CALCIUM AND PROTEIN PHOSPHORYLATION." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643762.

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Adrenaline (Adr) is generally considered as a full agonist able to induce in vitro the aggregation of human platelets and could play an important role in vivo in the appearance of thrombotic disorders when catecholamine levels are increased. Adr 2.5 M) induces the aggregation and secretion of 41 % of preloaded 3H-serotonin in human platelets in citrated plasma. This effect is not seen in plasma collected on 50 ATU/ml hirudin, and is due to the generation of traces of thrombin during blood collection and not to a direct effect of citrate itself, such asthe lowering of plasma free calcium. With washed human platelets suspended in Tyrode's buffer containing 2 mM Ca2+, 0.35 %albumin and apyrase, Adr (0.1 -100 M) doesnot cause shape change, aggregation or secretion of serotonin and does not modify platelet ultrastructure as judged by electron microscopy. Adr (1-100 M) does not change platelet membrane fluidity, as studied with the lipophilic fluorescent probe TMA-DPH. Adr has no direct effect on fibrinogen binding to intact platelets, intracellular Ca2+levels measured with quin2, or phosphorylation of 20 KDa or 47 KDapolypeptides, whereas all these parameters are modified after stimulation with ADP orthrombin. Adr potentiates the action of all types of aggregating agents on aggregation, secretion, intracellular Ca2+ levels,membrane fluidity, fibrinogen binding or protein phosphorylation. This effect is also seen with alpha2-adrenergic agonists (noradrenaline, alpha-methyl noradrenaline, clonidine) and is inhibited by alpha2-adrenergicantagonists such as yohimbine. The potentiation of platelet aggregation by Adr is not modified by prior incubation of the platelets with1mM aspirin for 15 min. This study shows that Adr alone does not induce modifications ofmorphology, metabolism or function of intactand functional washed human plateletsand that Adr cannot be considered per se as an aggregating agent. However, Adr interactswith alpha2-adrenergic receptors on human plateletsand potentiates biochemical and aggregatory responses induced by other platelet agonists.
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Smith, S. R., A. Kurundkar, N. J. Logsdon, M. L. Locy, and V. J. Thannickal. "Metabolic Regulation of Fibroblast Phenotype During Lung Fibrosis by ATP Citrate Lyase." In American Thoracic Society 2019 International Conference, May 17-22, 2019 - Dallas, TX. American Thoracic Society, 2019. http://dx.doi.org/10.1164/ajrccm-conference.2019.199.1_meetingabstracts.a5343.

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Romanet, C., A. Bourgeois, Y. Grobs, T. Shimauchi, T. Yokokawa, K. Habbout, S. E. Lemay, et al. "ATP Citrate Lyase Orchestrates Metabolic and Epigenetic Modifications in Pulmonary Arterial Hypertension." In American Thoracic Society 2022 International Conference, May 13-18, 2022 - San Francisco, CA. American Thoracic Society, 2022. http://dx.doi.org/10.1164/ajrccm-conference.2022.205.1_meetingabstracts.a4806.

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Peixoto Rodrigues, Vinícius, Maycon Emílio-Silva, Rie Ohara, Gabriela Bueno, Priscila Romano Raimundo, Victoria Gomes, Lúcia Machado da Rocha, and Clélia Akiko Hiruma-Lima. "Citral, a valuable aid against metabolic inflammation?" In MOL2NET'21, Conference on Molecular, Biomedical & Computational Sciences and Engineering, 7th ed. Basel, Switzerland: MDPI, 2021. http://dx.doi.org/10.3390/mol2net-07-11805.

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Sultana, Sharmin, Md Sad Salabi Sawrav, Snygdha Rani Das, Mehfuz Alam, Md Abdul Aziz, Md Al-Amin Hossain, and Md Azizul Haque. "Isolation and Biochemical Characterization of Cellulase Producing Goat Rumen Bacteria." In International Conference on Emerging Trends in Engineering and Advanced Science. AIJR Publisher, 2022. http://dx.doi.org/10.21467/proceedings.123.12.

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Cellulose is the most prevalent polymer on the planet and has long been utilized for a variety of industrial applications. The study's goal was to screen and isolate cellulase-producing bacteria from the rumen of a goat collected from different location of Dinajpur district. To do so, rumen content samples from two distinct goats were collected. In this investigation, rumen cellulase-producing bacteria were isolated and characterized after serial dilution of five isolates up to six fold and inoculation into Nutrient agar. Following that, all of the isolates were underwent Methyl Red (MR) test & Voges-Proskauer (VP) test to identify organism’s metabolic pathway, Triple Sugar Iron Agar (TSI) Test to determine bacterial ability to utilize sugar, Motility Indole and Urease activity test (MIU) to determine motility, Urease utilization and can produce Indole or not, Citrate utilization test to utilize citrate as carbon and energy source, Oxidase test, Catalase test to check the presence of catalytic enzyme. The result revealed the colonial characterization of bacteria and also where proven all five isolates are promising enough and superior in quality to produce cellulose.
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Sultana, Sharmin, Md Sad Salabi Sawrav, Md Bokhtiar Rahma, Md Shohorab Hossain, and Md Azizul Haque. "Isolation and Biochemical Characterization of Xylanase Enzyme Producing Bacteria from Goat Rumen." In International Conference on Emerging Trends in Engineering and Advanced Science. AIJR Publisher, 2022. http://dx.doi.org/10.21467/proceedings.123.1.

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The rumen microbial communities of ruminants are thought to be the most promising biochemical source of inordinately diversified and multi-functional cellulolytic enzymes with unique functional adaptations to improve biotechnological processes. The exploitation of rumen microbial genetic variety has been limited due to a lack of effective screening culture techniques and a lack of understanding of the rumen microbial genetic diversity. This study is conducted to isolate and characterize rumen bacteria from goat rumen that have capability to produce xylanase enzyme. Serial dilutions technique is applied to isolate bacteria from goat rumen and repeated tubing of the selectively enriched microbial cultures by using the specific media for rumen bacteria. Following that, all of the isolates were underwent Methyl Red (MR) test & Voges-Proskauer (VP) test to identify organisms metabolic pathway, Triple Sugar Iron Agar (TSI) Test to determine bacterial ability to utilize sugar, Motility Indole and Urease activity test (MIU) to determine motility, Urease utilization and can produce Indole or not, Citrate utilization test to utilize citrate as carbon and energy source, Oxidase test, Catalase test to check the presence of catalytic enzyme where all isolates found promising which indicates that all five isolates are superior and capable to produce xylanase.
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Cheung, Justin Chak-Ting, Simon Siu-Man Ng, Nathalie Wong, and Yujuan Dong. "IDDF2023-ABS-0187 Novel exon-skipping citrate synthase isoform identified in hybrid sequencing contributes to metastatic phenotype in colorectal cancer through metabolic alterations." In Abstracts of the International Digestive Disease Forum (IDDF), Hong Kong, 10–11 June 2023. BMJ Publishing Group Ltd and British Society of Gastroenterology, 2023. http://dx.doi.org/10.1136/gutjnl-2023-iddf.88.

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Reports on the topic "Citrate metabolism"

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Blumwald, Eduardo, and Avi Sadka. Citric acid metabolism and mobilization in citrus fruit. United States Department of Agriculture, October 2007. http://dx.doi.org/10.32747/2007.7587732.bard.

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Accumulation of citric acid is a major determinant of maturity and fruit quality in citrus. Many citrus varieties accumulate citric acid in concentrations that exceed market desires, reducing grower income and consumer satisfaction. Citrate is accumulated in the vacuole of the juice sac cell, a process that requires both metabolic changes and transport across cellular membranes, in particular, the mitochondrial and the vacuolar (tonoplast) membranes. Although the accumulation of citrate in the vacuoles of juice cells has been clearly demonstrated, the mechanisms for vacuolar citrate homeostasis and the components controlling citrate metabolism and transport are still unknown. Previous results in the PIs’ laboratories have indicated that the expression of a large number of a large number of proteins is enhanced during fruit development, and that the regulation of sugar and acid content in fruits is correlated with the differential expression of a large number of proteins that could play significant roles in fruit acid accumulation and/or regulation of acid content. The objectives of this proposal are: i) the characterization of transporters that mediate the transport of citrate and determine their role in uptake/retrieval in juice sac cells; ii) the study of citric acid metabolism, in particular the effect of arsenical compounds affecting citric acid levels and mobilization; and iii) the development of a citrus fruit proteomics platform to identify and characterize key processes associated with fruit development in general and sugar and acid accumulation in particular. The understanding of the cellular processes that determine the citrate content in citrus fruits will contribute to the development of tools aimed at the enhancement of citrus fruit quality. Our efforts resulted in the identification, cloning and characterization of CsCit1 (Citrus sinensis citrate transporter 1) from Navel oranges (Citrus sinesins cv Washington). Higher levels of CsCit1 transcripts were detected at later stages of fruit development that coincided with the decrease in the juice cell citrate concentrations (Shimada et al., 2006). Our functional analysis revealed that CsCit1 mediates the vacuolar efflux of citrate and that the CsCit1 operates as an electroneutral 1CitrateH2-/2H+ symporter. Our results supported the notion that it is the low permeable citrateH2 - the anion that establishes the buffer capacity of the fruit and determines its overall acidity. On the other hand, it is the more permeable form, CitrateH2-, which is being exported into the cytosol during maturation and controls the citrate catabolism in the juice cells. Our Mass-Spectrometry-based proteomics efforts (using MALDI-TOF-TOF and LC2- MS-MS) identified a large number of fruit juice sac cell proteins and established comparisons of protein synthesis patterns during fruit development. So far, we have identified over 1,500 fruit specific proteins that play roles in sugar metabolism, citric acid cycle, signaling, transport, processing, etc., and organized these proteins into 84 known biosynthetic pathways (Katz et al. 2007). This data is now being integrated in a public database and will serve as a valuable tool for the scientific community in general and fruit scientists in particular. Using molecular, biochemical and physiological approaches we have identified factors affecting the activity of aconitase, which catalyze the first step of citrate catabolism (Shlizerman et al., 2007). Iron limitation specifically reduced the activity of the cytosolic, but not the mitochondrial, aconitase, increasing the acid level in the fruit. Citramalate (a natural compound in the juice) also inhibits the activity of aconitase, and it plays a major role in acid accumulation during the first half of fruit development. On the other hand, arsenite induced increased levels of aconitase, decreasing fruit acidity. We have initiated studies aimed at the identification of the citramalate biosynthetic pathway and the role(s) of isopropylmalate synthase in this pathway. These studies, especially those involved aconitase inhibition by citramalate, are aimed at the development of tools to control fruit acidity, particularly in those cases where acid level declines below the desired threshold. Our work has significant implications both scientifically and practically and is directly aimed at the improvement of fruit quality through the improvement of existing pre- and post-harvest fruit treatments.
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Blumwald, Eduardo, and Avi Sadka. Sugar and Acid Homeostasis in Citrus Fruit. United States Department of Agriculture, January 2012. http://dx.doi.org/10.32747/2012.7697109.bard.

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Citrus fruit quality standards have been determined empirically, depending on species and on the particular growing regions. In general, the TSS (total soluble solids) to total acidity (TA) ratio determines whether citrus fruit can be marketed. Soluble sugars account for most of the TSS during harvest while TA is determined almost solely by the citric acid content, which reaches levels of 1-5% by weight in many cultivated varieties. Acid and sugar homeostasis in the fruit is critical for the management of existing cultivars, the development of new cultivars, the improvement of pre- and post-harvest strategies and the control of fruit quality and disorders. The current proposal (a continuation of a previous proposal) aimed at: (1) completing the citrus fruit proteome and metabolome, and establish a citrus fruit functional database, (2) further characterization of the control of fruit acidity by studying the regulation of key steps affecting citrate metabolism, and determine the fate of citrate during acid decline stage, and (3) Studying acid and sugar homeostasis in citrus fruits by characterizing transport mechanisms across membranes. These aims were completed as the following: (1) Our initial efforts were aimed at the characterization and identification of citric acid transporters in citrus juice cells. The identification of citrate transporters at the vacuole of the citrus juice cell indicated that the steady-state citrate cytosolic concentration and the action of the cytosolic aconitase were key elements in establishing the pH homeostat in the cell that regulates the metabolic shift towards carbon usage in the fruit during the later stages of fruit development. We focused on the action of aconitase, the enzyme mediating the metabolic use of citric acid in the cells, and identified processes that control carbon fluxes in developing citrus fruits that control the fruit acid load; (2) The regulation of aconitase, catalyzing a key step in citrate metabolism, was further characterized by using two inhibitors, citramalte and oxalomalte. These compounds significantly increased citrate content and reduced the enzyme’s activity. Metabolite profiling and changes of amino-acid metabolizing enzymes in oxalomalate- treated cells suggested that the increase in citrate, caused by aconitase inhibition, induces amino acid synthesis and the GABA shunt, in accordance with the suggested fate of citrate during the acid decline stage in citrus fruit. (3) We have placed a considerable amount of time on the development of a citrus fruit proteome that will serve to identify all of the proteins in the juice cells and will also serve as an aid to the genomics efforts of the citrus research community (validating the annotation of the fruit genes and the different ESTs). Initially, we identified more than 2,500 specific fruit proteins and were able to assign a function to more than 2,100 proteins (Katz et al., 2007). We have now developed a novel Differential Quantitative LC-MS/MS Proteomics Methodology for the identification and quantitation of key biochemical pathways in fruits (Katz et al., 2010) and applied this methodology to identify determinants of key traits for fruit quality (Katz et al., 2011). We built “biosynthesis maps” that will aid in defining key pathways associated with the development of key fruit quality traits. In addition, we constructed iCitrus (http://wiki.bioinformatics.ucdavis.edu/index.php/ICitrus), a “functional database” that is essentially a web interface to a look-up table that allows users to use functional annotations in the web to identify poorly annotated citrus proteins. This resource will serve as a tool for growers and field extension specialists.
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Sadka, Avi, Mikeal L. Roose, and Yair Erner. Molecular Genetic Analysis of Citric Acid Accumulation in Citrus Fruit. United States Department of Agriculture, March 2001. http://dx.doi.org/10.32747/2001.7573071.bard.

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The acid content of the juice sac cells is a major determinant of maturity and fruit quality in citrus. Many citrus varieties accumulate acid in concentrations that exceed market desires, reducing grower income and consumer satisfaction. Pulp acidity is thought to be dependent on two mechanisms: the accumulation of citric acid in the vacuoles of the juice sac cells, and acidification of the vacuole. The major aim of the project was to direct effort toward understanding the mechanism of citric acid accumulation in the fruit. The following objectives were suggested: Measure the activity of enzymes likely to be involved in acid accumulation and follow their pattern of expression in developing fruit (Sadka, Erner). Identify and clone genes which are associated with high and low acid phenotypes and with elevated acid level (Roose, Sadka, Erner). Convert RAPD markers that map near a gene that causes low acid phenotype to specific co dominant markers (Roose). Use genetic co segregation to test whether specific gene products are responsible for low acid phenotype (Roose and Sadka). Objective 1 was fully achieved. Most of the enzymes of organic acid metabolism were cloned from lemon pulp. Their expression was studied during fruit development in low and high acid varieties. The activity and expression of citrate synthase, aconitase and NADP-isocitrate dehydrogenase (IDH) were studied in detail. The role that each enzyme plays in acid accumulation and decline was evaluated. As a result, a better understanding of the metabolic changes that contribute to acid accumulation was achieved. It was found that the activity of the mitochondrial aconitase is greatly reduced early in high-acid fruits, but not in acidless ones, suggesting that this enzyme plays an important role in acid accumulation. In addition, it was demonstrated that increases in the cytosolic forms of aconitase and NADP-IDH towards fruit maturation play probably a major role in acid decline. Our studies also demonstrated that the two mechanisms that contribute to fruit acidity, vacuolar acidification and citric acid accumulation, are independent, although they are tightly co-regulated. Additional, we demonstrated that sodium arsenite, which reduce fruit acidity, causes a transient inhibition in the activity of citrate synthase, but an induction in the gene expression. This part of the work has resulted in 4 papers. Objective 3 was also fully achieved. Using bulked segregant analysis, three random amplified polymorphic DNA (RAPD) markers were identified as linked to acitric, a gene controlling the acidless phenotype of pummelo 2240. One of them, which mapped 1.2 cM from acitric was converted into sequence characterized amplified region (SCAR marker, and into co dominant restriction length polymorphism (RFLP) marker. These markers were highly polymorphic among 59 citrus accessions, and therefore, they should be useful for selecting seedling progeny heterozygous for acitric in nearly all crosses between pummelo 2240 and other citrus genotypes. This part of the project resulted in one paper. Objective 4 was also fully achieved. Clones isolated by the Israeli group were sent to the American laboratory for co segregation analysis. However, none of them seemed to co segregate with the low acid phenotype. Both laboratories invested much effort in achieving the goals of Objective 2, namely the isolation of genes that are elevated in expression in low and high acid phenotypes, and in tissue cultures treated with arsenite (a treatment which reduces fruit acidity). However, conventional differential display and restriction fragment differential display analyses could not identify any differentially expressed genes. The isolation of such genes was the major aim of a continuation project, which was recently submitted.
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