scholarly journals Intracellular Acetyl Unit Transport in Fungal Carbon Metabolism

2010 ◽  
Vol 9 (12) ◽  
pp. 1809-1815 ◽  
Author(s):  
Karin Strijbis ◽  
Ben Distel
Keyword(s):  
Carbon Metabolism ◽  
Citrate Synthase ◽  
Current Knowledge ◽  
Glyoxylate Cycle ◽  
Carbon Sources ◽  
Fungal Species ◽  
Special Focus ◽  
Acetyl Coa ◽  
Content Type ◽  
Dependent Pathway

ABSTRACT Acetyl coenzyme A (acetyl-CoA) is a central metabolite in carbon and energy metabolism. Because of its amphiphilic nature and bulkiness, acetyl-CoA cannot readily traverse biological membranes. In fungi, two systems for acetyl unit transport have been identified: a shuttle dependent on the carrier carnitine and a (peroxisomal) citrate synthase-dependent pathway. In the carnitine-dependent pathway, carnitine acetyltransferases exchange the CoA group of acetyl-CoA for carnitine, thereby forming acetyl-carnitine, which can be transported between subcellular compartments. Citrate synthase catalyzes the condensation of oxaloacetate and acetyl-CoA to form citrate that can be transported over the membrane. Since essential metabolic pathways such as fatty acid β-oxidation, the tricarboxylic acid (TCA) cycle, and the glyoxylate cycle are physically separated into different organelles, shuttling of acetyl units is essential for growth of fungal species on various carbon sources such as fatty acids, ethanol, acetate, or citrate. In this review we summarize the current knowledge on the different systems of acetyl transport that are operational during alternative carbon metabolism, with special focus on two fungal species: Saccharomyces cerevisiae and Candida albicans.

scholarly journals Metabolic and Developmental Effects Resulting from Deletion of the citA Gene Encoding Citrate Synthase in Aspergillus nidulans

2010 ◽  
Vol 9 (4) ◽  
pp. 656-666 ◽  
Author(s):  
Sandra L. Murray ◽  
Michael J. Hynes
Keyword(s):  
Aspergillus Nidulans ◽  
Fluorescent Protein ◽  
Citrate Synthase ◽  
Glyoxylate Cycle ◽  
Single Gene ◽  
Carbon Sources ◽  
Tca Cycle ◽  
Poor Growth ◽  
Content Type ◽  
The Glyoxylate Cycle

ABSTRACT Citrate synthase is a central activity in carbon metabolism. It is required for the tricarboxylic acid (TCA) cycle, respiration, and the glyoxylate cycle. In Saccharomyces cerevisiae and Arabidopsis thaliana, there are mitochondrial and peroxisomal isoforms encoded by separate genes, while in Aspergillus nidulans, a single gene, citA, encodes a protein with predicted mitochondrial and peroxisomal targeting sequences (PTS). Deletion of citA results in poor growth on glucose but not on derepressing carbon sources, including those requiring the glyoxylate cycle. Growth on glucose is restored by a mutation in the creA carbon catabolite repressor gene. Methylcitrate synthase, required for propionyl-coenzyme A (CoA) metabolism, has previously been shown to have citrate synthase activity. We have been unable to construct the mcsAΔ citAΔ double mutant, and the expression of mcsA is subject to CreA-mediated carbon repression. Therefore, McsA can substitute for the loss of CitA activity. Deletion of citA does not affect conidiation or sexual development but results in delayed conidial germination as well as a complete loss of ascospores in fruiting bodies, which can be attributed to loss of meiosis. These defects are suppressed by the creA204 mutation, indicating that McsA activity can substitute for the loss of CitA. A mutation of the putative PTS1-encoding sequence in citA had no effect on carbon source utilization or development but did result in slower colony extension arising from single conidia or ascospores. CitA-green fluorescent protein (GFP) studies showed mitochondrial localization in conidia, ascospores, and hyphae. Peroxisomal localization was not detected. However, a very low and variable detection of punctate GFP fluorescence was sometimes observed in conidia germinated for 5 h when the mitochondrial targeting sequence was deleted.

scholarly journals Carbon Catabolite Control in Candida albicans: New Wrinkles in Metabolism

mBio ◽  
2013 ◽  
Vol 4 (1) ◽  
Author(s):  
Michael C. Lorenz
Keyword(s):  
Candida Albicans ◽  
Carbon Source ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Isocitrate Lyase ◽  
Glyoxylate Cycle ◽  
Carbon Sources ◽  
Fungal Species ◽  
Content Type ◽  
Catabolite Control

ABSTRACTMost microorganisms maintain strict control of nutrient assimilation pathways to ensure that they preferentially use compounds that generate the most energy or are most efficiently catabolized. In doing so, they avoid potentially inefficient conflicts between parallel catabolic and metabolic pathways. The regulation of carbon source utilization in a wide array of bacterial and fungal species involves both transcriptional and posttranscriptional mechanisms, and while the details can vary significantly, carbon catabolite control is widely conserved. In many fungi, the posttranslational aspect (carbon catabolite inactivation [CCI]) involves the ubiquitin-mediated degradation of catabolic enzymes for poor carbon sources when a preferred one (glucose) becomes available. A recent article presents evidence for a surprising exception to CCI in the fungal pathogenCandida albicans, an organism that makes use of gluconeogenic carbon sources during infection (D. Sandai, Z. Yin, L. Selway, D. Stead, J. Walker, M. D. Leach, I. Bohovych, I. V. Ene, S. Kastora, S. Budge, C. A. Munro, F. C. Odds, N. A. Gow, and A. J. Brown,mBio3[6]:e00495-12).In vitro, addition of glucose to cells grown in a poor carbon source rapidly represses transcripts encoding gluconeogenic and glyoxylate cycle enzymes, such as phosphoenolpyruvate carboxykinase (Pck1p) and isocitrate lyase (Icl1p), in bothC. albicansandSaccharomyces cerevisiae. Yet, uniquely, theC. albicansproteins persist, permitting parallel assimilation of multiple carbon sources, likely because they lack consensus ubiquitination sites found in the yeast homologs. Indeed, the yeast proteins are rapidly degraded when expressed inC. albicans, indicating a conservation of the machinery needed for CCI. How this surprising metabolic twist contributes to fungal commensalism or pathogenesis remains an open question.

scholarly journals Dynamic Metabolic Rewiring Enables Efficient Acetyl Coenzyme A Assimilation in Paracoccus denitrificans

mBio ◽  
2019 ◽  
Vol 10 (4) ◽  
Author(s):  
Katharina Kremer ◽  
Muriel C. F. van Teeseling ◽  
Lennart Schada von Borzyskowski ◽  
Iria Bernhardsgrütter ◽  
Rob J. M. van Spanning ◽  
...  
Keyword(s):  
Growth Rates ◽  
Carbon Metabolism ◽  
Paracoccus Denitrificans ◽  
High Growth ◽  
Central Carbon Metabolism ◽  
High Biomass ◽  
Acetyl Coa ◽  
Acetyl Coenzyme A ◽  
Content Type ◽  
Central Carbon

ABSTRACT During growth, microorganisms have to balance metabolic flux between energy and biosynthesis. One of the key intermediates in central carbon metabolism is acetyl coenzyme A (acetyl-CoA), which can be either oxidized in the citric acid cycle or assimilated into biomass through dedicated pathways. Two acetyl-CoA assimilation strategies in bacteria have been described so far, the ethylmalonyl-CoA pathway (EMCP) and the glyoxylate cycle (GC). Here, we show that Paracoccus denitrificans uses both strategies for acetyl-CoA assimilation during different growth stages, revealing an unexpected metabolic complexity in the organism’s central carbon metabolism. The EMCP is constitutively expressed on various substrates and leads to high biomass yields on substrates requiring acetyl-CoA assimilation, such as acetate, while the GC is specifically induced on these substrates, enabling high growth rates. Even though each acetyl-CoA assimilation strategy alone confers a distinct growth advantage, P. denitrificans recruits both to adapt to changing environmental conditions, such as a switch from succinate to acetate. Time-resolved single-cell experiments show that during this switch, expression of the EMCP and GC is highly coordinated, indicating fine-tuned genetic programming. The dynamic metabolic rewiring of acetyl-CoA assimilation is an evolutionary innovation by P. denitrificans that allows this organism to respond in a highly flexible manner to changes in the nature and availability of the carbon source to meet the physiological needs of the cell, representing a new phenomenon in central carbon metabolism. IMPORTANCE Central carbon metabolism provides organisms with energy and cellular building blocks during growth and is considered the invariable “operating system” of the cell. Here, we describe a new phenomenon in bacterial central carbon metabolism. In contrast to many other bacteria that employ only one pathway for the conversion of the central metabolite acetyl-CoA, Paracoccus denitrificans possesses two different acetyl-CoA assimilation pathways. These two pathways are dynamically recruited during different stages of growth, which allows P. denitrificans to achieve both high biomass yield and high growth rates under changing environmental conditions. Overall, this dynamic rewiring of central carbon metabolism in P. denitrificans represents a new strategy compared to those of other organisms employing only one acetyl-CoA assimilation pathway.

scholarly journals The Catabolite Repressor/Activator Cra Is a Bridge Connecting Carbon Metabolism and Host Colonization in the Plant Drought Resistance-Promoting Bacterium Pantoea alhagi LTYR-11Z

2018 ◽  
Vol 84 (13) ◽  
Author(s):  
Lei Zhang ◽  
Muhang Li ◽  
Qiqi Li ◽  
Chaoqiong Chen ◽  
Meng Qu ◽  
...  
Keyword(s):  
Carbon Source ◽  
Carbon Metabolism ◽  
Carbon Sources ◽  
Endophytic Bacterium ◽  
Bacterial Attachment ◽  
Gene Encoding ◽  
Wheat Roots ◽  
Host Colonization ◽  
Content Type

ABSTRACT Efficient root colonization is a prerequisite for application of plant growth-promoting (PGP) bacteria in improving health and yield of agricultural crops. We have recently identified an endophytic bacterium, Pantoea alhagi LTYR-11Z, with multiple PGP properties that effectively colonizes the root system of wheat and improves its growth and drought tolerance. To identify novel regulatory genes required for wheat colonization, we screened an LTYR-11Z transposon (Tn) insertion library and found cra to be a colonization-related gene. By using transcriptome (RNA-seq) analysis, we found that transcriptional levels of an eps operon, the ydiV gene encoding an anti-FlhD 4 C 2 factor, and the yedQ gene encoding an enzyme for synthesis of cyclic dimeric GMP (c-di-GMP) were significantly downregulated in the Δ cra mutant. Further studies demonstrated that Cra directly binds to the promoters of the eps operon, ydiV , and yedQ and activates their expression, thus inhibiting motility and promoting exopolysaccharide (EPS) production and biofilm formation. Consistent with previous findings that Cra plays a role in transcriptional regulation in response to carbon source availability, the activating effects of Cra were much more pronounced when LTYR-11Z was grown within a gluconeogenic environment than when it was grown within a glycolytic environment. We further demonstrate that the ability of LTYR-11Z to colonize wheat roots is modulated by the availability of carbon sources. Altogether, these results uncover a novel strategy utilized by LTYR-11Z to achieve host colonization in response to carbon nutrition in the environment, in which Cra bridges a connection between carbon metabolism and colonization capacity of LTYR-11Z. IMPORTANCE Rapid and appropriate response to environmental signals is crucial for bacteria to adapt to competitive environments and to establish interactions with their hosts. Efficient colonization and persistence within the host are controlled by various regulatory factors that respond to specific environmental cues. The most common is nutrient availability. In this work, we unraveled the pivotal role of Cra in regulation of colonization ability of Pantoea alhagi LTYR-11Z in response to carbon source availability. Moreover, we identified three novel members of the Cra regulon involved in EPS synthesis, regulation of flagellar biosynthesis, and synthesis of c-di-GMP and propose a working model to explain the Cra-mediated regulatory mechanism that links carbon metabolism to host colonization. This study elucidates the regulatory role of Cra in bacterial attachment and colonization of plants, which raises the possibility of extending our studies to other bacteria associated with plant and human health.

Modelling the peroxisomal carbon leak during lipid mobilization in Arabidopsis

2010 ◽  
Vol 38 (5) ◽  
pp. 1230-1233 ◽  
Author(s):  
Mark A. Hooks ◽  
Elizabeth Allen ◽  
Jonathan A.D. Wattis
Keyword(s):  
Carbon Metabolism ◽  
Glyoxylate Cycle ◽  
Seedling Development ◽  
Wild Type ◽  
Acetyl Coa ◽  
Primary Metabolite ◽  
Lipid Mobilization ◽  
Acetate Assimilation ◽  
Development Levels ◽  
The Glyoxylate Cycle

Mutation of the ACN1 (acetate non-utilizing 1) locus of Arabidopsis results in altered acetate assimilation into gluconeogenic sugars and anapleurotic amino acids and leads to an overall depression in primary metabolite levels by approx. 50% during seedling development. Levels of acetyl-CoA were higher in acn1 compared with wild-type, which is counterintuitive to the activity of ACN1 as a peroxisomal acetyl-CoA synthetase. We hypothesize that ACN1 recycles free acetate to acetyl-CoA within peroxisomes in order that carbon remains fed into the glyoxylate cycle. When ACN1 is not present, carbon in the form of acetate can leak out of peroxisomes and is reactivated to acetyl-CoA within the cytosol. Kinetic models incorporating estimates of carbon input and pathway dynamics from a variety of literature sources have proven useful in explaining how ACN1 may prevent the carbon leak and even contribute to the control of peroxisomal carbon metabolism.

scholarly journals The Functional Structure of Central Carbon Metabolism in Pseudomonas putida KT2440

2014 ◽  
Vol 80 (17) ◽  
pp. 5292-5303 ◽  
Author(s):  
Suresh Sudarsan ◽  
Sarah Dethlefsen ◽  
Lars M. Blank ◽  
Martin Siemann-Herzberg ◽  
Andreas Schmid
Keyword(s):  
Pseudomonas Putida ◽  
Carbon Metabolism ◽  
Carbon Sources ◽  
Central Carbon Metabolism ◽  
Transcriptional Level ◽  
Regulation Mechanism ◽  
Central Metabolism ◽  
Content Type ◽  
Central Carbon ◽  
Definition Of

ABSTRACTWhat defines central carbon metabolism? The classic textbook scheme of central metabolism includes the Embden-Meyerhof-Parnas (EMP) pathway of glycolysis, the pentose phosphate pathway, and the citric acid cycle. The prevalence of this definition of central metabolism is, however, equivocal without experimental validation. We address this issue using a general experimental approach that combines the monitoring of transcriptional and metabolic flux changes between steady states on alternative carbon sources. This approach is investigated by using the model bacteriumPseudomonas putidawith glucose, fructose, and benzoate as carbon sources. The catabolic reactions involved in the initial uptake and metabolism of these substrates are expected to show a correlated change in gene expressions and metabolic fluxes. However, there was no correlation for the reactions linking the 12 biomass precursor molecules, indicating a regulation mechanism other than mRNA synthesis for central metabolism. This result substantiates evidence for a (re)definition of central carbon metabolism including all reactions that are bound to tight regulation and transcriptional invariance. Contrary to expectations, the canonical Entner-Doudoroff and EMP pathwayssensu strictoare not a part of central carbon metabolism inP. putida, as they are not regulated differently from the aromatic degradation pathway. The regulatory analyses presented here provide leads on a qualitative basis to address the use of alternative carbon sources by deregulation and overexpression at the transcriptional level, while rate improvements in central carbon metabolism require careful adjustment of metabolite concentrations, as regulation resides to a large extent in posttranslational and/or metabolic regulation.

scholarly journals GntR Family Regulator DasR Controls Acetate Assimilation by Directly Repressing the acsA Gene in Saccharopolyspora erythraea

2018 ◽  
Vol 200 (13) ◽  
Author(s):  
Di You ◽  
Bai-Qing Zhang ◽  
Bang-Ce Ye
Keyword(s):  
Environmental Changes ◽  
Carbon Sources ◽  
Saccharopolyspora Erythraea ◽  
Upstream Region ◽  
Acetate Metabolism ◽  
Acetyl Coa ◽  
Content Type ◽  
Acetate Assimilation ◽  
Responsive Element ◽  
Gntr Family

ABSTRACT The GntR family regulator DasR controls the transcription of genes involved in chitin and N -acetylglucosamine (GlcNAc) metabolism in actinobacteria. GlcNAc is catabolized to ammonia, fructose-6-phosphate (Fru-6P), and acetate, which are nitrogen and carbon sources. In this work, a DasR-responsive element ( dre ) was observed in the upstream region of acsA1 in Saccharopolyspora erythraea . This gene encodes acetyl coenzyme A (acetyl-CoA) synthetase (Acs), an enzyme that catalyzes the conversion of acetate into acetyl-CoA. We found that DasR repressed the transcription of acsA1 in response to carbon availability, especially with GlcNAc. Growth inhibition was observed in a dasR -deleted mutant (Δ dasR ) in the presence of GlcNAc in minimal medium containing 10 mM acetate, a condition under which Acs activity is critical to growth. These results demonstrate that DasR controls acetate assimilation by directly repressing the transcription of the acsA1 gene and performs regulatory roles in the production of intracellular acetyl-CoA in response to GlcNAc. IMPORTANCE Our work has identified the DasR GlcNAc-sensing regulator that represses the generation of acetyl-CoA by controlling the expression of acetyl-CoA synthetase, an enzyme responsible for acetate assimilation in S. erythraea . The finding provides the first insights into the importance of DasR in the regulation of acetate metabolism, which encompasses the regulatory network between nitrogen and carbon metabolism in actinobacteria, in response to environmental changes.

scholarly journals Role of Acetyl Coenzyme A Synthesis and Breakdown in Alternative Carbon Source Utilization in Candida albicans

2008 ◽  
Vol 7 (10) ◽  
pp. 1733-1741 ◽  
Author(s):  
Aaron J. Carman ◽  
Slavena Vylkova ◽  
Michael C. Lorenz
Keyword(s):  
Fatty Acids ◽  
Candida Albicans ◽  
Coenzyme A ◽  
Glyoxylate Cycle ◽  
Functional Divergence ◽  
Carbon Sources ◽  
Growth Defect ◽  
Acetyl Coa ◽  
Acetyl Coenzyme A ◽  
Acetyl Coenzyme

ABSTRACT Acetyl coenzyme A (acetyl-CoA) is the central intermediate of the pathways required to metabolize nonfermentable carbon sources. Three such pathways, i.e., gluconeogenesis, the glyoxylate cycle, and β-oxidation, are required for full virulence in the fungal pathogen Candida albicans. These processes are compartmentalized in the cytosol, mitochondria, and peroxosomes, necessitating transport of intermediates across intracellular membranes. Acetyl-CoA is trafficked in the form of acetate by the carnitine shuttle, and we hypothesized that the enzymes that convert acetyl-CoA to/from acetate, i.e., acetyl-CoA hydrolase (ACH1) and acetyl-CoA synthetase (ACS1 and ACS2), would regulate alternative carbon utilization and virulence. We show that C. albicans strains depleted for ACS2 are unviable in the presence of most carbon sources, including glucose, acetate, and ethanol; these strains metabolize only fatty acids and glycerol, a substantially more severe phenotype than that of Saccharomyces cerevisiae acs2 mutants. In contrast, deletion of ACS1 confers no phenotype, though it is highly induced in the presence of fatty acids, perhaps explaining why acs2 mutants can utilize fatty acids. Strains lacking ACH1 have a mild growth defect on some carbon sources but are fully virulent in a mouse model of disseminated candidiasis. Both ACH1 and ACS2 complement mutations in their S. cerevisiae homolog. Together, these results show that acetyl-CoA metabolism and transport are critical for growth of C. albicans on a wide variety of nutrients. Furthermore, the phenotypic differences between mutations in these highly conserved genes in S. cerevisiae and C. albicans support recent findings that significant functional divergence exists even in fundamental metabolic pathways between these related yeasts.

scholarly journals Argentilactone Molecular Targets inParacoccidioides brasiliensisIdentified by Chemoproteomics

2018 ◽  
Vol 62 (11) ◽  
Author(s):  
Lívia do Carmo Silva ◽  
Sinji Borges Ferreira Tauhata ◽  
Lilian Cristiane Baeza ◽  
Cecília Maria Alves de Oliveira ◽  
Lucília Kato ◽  
...  
Keyword(s):  
Enzymatic Activity ◽  
Acid Metabolism ◽  
Citrate Synthase ◽  
Isocitrate Lyase ◽  
Glyoxylate Cycle ◽  
Functional Categories ◽  
Content Type ◽  
Key Enzyme ◽  
Etiological Agents ◽  
The Glyoxylate Cycle

ABSTRACTParacoccidioidomycosis (PCM) is the cause of many deaths from systemic mycoses. The etiological agents of PCM belong to theParacoccidioidesgenus, which is restricted to Latin America. The infection is acquired through the inhalation of conidia that primarily lodge in the lungs and may disseminate to other organs and tissues. The treatment for PCM is commonly performed via the administration of antifungals such as amphotericin B, co-trimoxazole, and itraconazole. The antifungal toxicity and side effects, in addition to their long treatment times, have stimulated research for new bioactive compounds. Argentilactone is a compound that was isolated from the Brazilian savanna plantHyptis ovalifolia, and it has been suggested to be a potent antifungal, inhibiting the dimorphism ofP. brasiliensisand the enzymatic activity of isocitrate lyase, a key enzyme of the glyoxylate cycle. This work was developed due to the importance of elucidating the putative mode of action of argentilactone. The chemoproteomics approach via affinity chromatography was the methodology used to explore the interactions betweenP. brasiliensisproteins and argentilactone. A total of 109 proteins were identified and classified functionally. The most representative functional categories were related to amino acid metabolism, energy, and detoxification. Argentilactone inhibited the enzymatic activity of malate dehydrogenase, citrate synthase, and pyruvate dehydrogenase. Furthermore, argentilactone induces the production of reactive oxygen species and inhibits the biosynthesis of cell wall polymers.

scholarly journals The travel of ideas: the dual structure of mobilized knowledge in the context of professional learning networks

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Livia Anna Julia Jesacher-Roessler
Keyword(s):  
Theoretical Model ◽  
Professional Learning ◽  
Exploratory Study ◽  
Current Knowledge ◽  
Organizational Level ◽  
Special Focus ◽  
Learning Networks ◽  
Content Type ◽  
Theoretical Approaches ◽  
Organizational Levels

PurposeIn the context of professional learning networks (PLNs), there are many studies which address knowledge mobilization (KMb). The majority of these focus on how research is mobilized by various actors. This paper explores the concepts of KMb both on an individual and an organizational level and discusses the role of PLN participants and PLNs as catalysts for institutional change (IC). To illustrate this, a model was developed which draws on a concept that depicts the mobilization processes at the various levels.Design/methodology/approachThe model was developed by drawing on theoretical approaches to both KMb on an individual and an organizational level of schools. The strengths and limitations of the model are then assessed as part of an exploratory study. Interviews of PLN participants (n = 7) from two schools and detailed logbooks of two participants were used to reconstruct experiences of KMb in the PLNs and the process of KMb among schools. By contrasting two schools, the study traces how mechanisms of KMb occurred. Data sources were analyzed using a structured content analysis alongside a deductive–inductive code system.FindingsThe results of the exploratory study show that, although the model is able to map the KMb practices, some refinement is still needed. While the extension of concepts describing the work of knowledge mobilizer (KM) leads to a more theoretically differentiated perspective, the data also showed that PLN participants only partially define themselves as KMs. The connection to concepts of strategies of knowledge mobilizing on an organizational level led to an increased transparency in the theoretical model. The data showed that KMb is influenced by organizational and individual beliefs.Originality/valueThe paper adds to the current knowledge base through a theoretical model that addresses the underinvestigated topic of KMb regarding the link between the individual and organizational levels. With a special focus on individual and organizational levels, a connection between KMb and IC is provided. The theoretical framework and research findings from an additional explorative study can be used to further develop relevant insights into the actions of participants from PLNs that enable IC processes among their schools.

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