scholarly journals Metabolic fitness of Candida albicans is indispensable for functional drug efflux, ergosterol, and chitin biosynthesis

2020 ◽  
Author(s):  
Sandeep Hans ◽  
Zeeshan Fatima ◽  
Saif Hameed
Keyword(s):  
Drug Targets ◽  
Efflux Pump ◽  
Fungal Infections ◽  
Isocitrate Lyase ◽  
Glyoxylate Cycle ◽  
Pathogenic Fungus ◽  
Nile Red ◽  
Malate Synthase ◽  
Drug Efflux ◽  
Metabolic Fitness

Background and Purpose: The increment in fungal infections, particularly due to Candida species, is alarming due to the emergence of multidrug resistance (MDR). Hence, the identification of novel drug targets to circumvent the problem of MDR requires immediate attention. The metabolic pathway, such as glyoxylate cycle (GC), which utilizes key enzymes (isocitrate lyase [ICL] and malate synthase [MLS]), enables C. albicans to adapt under glucose-deficient conditions. This study uncovers the effect of GC disruption on the major MDR mechanisms of C. albicans as a human pathogenic fungus. Materials and Methods: For the purpose of the study, efflux pump activity was assessed by phenotypic susceptibilities in the presence of substrates rhodamine 6G (R6G) and Nile red, along with R6G extracellular concentration (527 nm). In addition, ergosterol content was estimated by the alcoholic potassium hydroxide hydrolysis method. The estimation of chitin was also accomplished by the absorbance (520 nm) of glucosamine released by acid hydrolysis. Results: The results revealed that the disruption of ICL enzyme gene (Δicl1) led to the impairment of the efflux activity of multidrug transporters belonging to the ATP-binding cassette superfamily. It was further shown that Δicl1 mutant exhibited diminished ergosterol and chitin contents. In addition, all abrogated phenotypes could be rescued in the reverting strain of Δicl1 mutant. Conclusion: Based on the findings, the disruption of GC affected efflux activity and the synthesis of ergosterol and chitin. The present study for the first time revealed that metabolic fitness was associated with functional drug efflux, ergosterol and chitin biosynthesis and validated GC as an antifungal target. However, further studies are needed to comprehend and exploit this therapeutic opportunity.

Co-ordinate regulation of genes involved in storage lipid mobilization in Arabidopsis thaliana

2001 ◽  
Vol 29 (2) ◽  
pp. 283-286 ◽  
Author(s):  
E. L. Rylott ◽  
M. A. Hooks ◽  
I. A. Graham
Keyword(s):  
Arabidopsis Thaliana ◽  
Enzyme Activities ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Isocitrate Lyase ◽  
Glyoxylate Cycle ◽  
Molecular Genetic ◽  
Regulation Of Gene Expression ◽  
Growth Period ◽  
Malate Synthase ◽  
The Glyoxylate Cycle

Molecular genetic approaches in the model plant Arabidopsis thaliana (ColO) are shedding new light on the role and control of the pathways associated with the mobilization of lipid reserves during oilseed germination and post-germinative growth. Numerous independent studies have reported on the expression of individual genes encoding enzymes from the three major pathways: β-oxidation, the glyoxylate cycle and gluconeogenesis. However, a single comprehensive study of representative genes and enzymes from the different pathways in a single plant species has not been done. Here we present results from Arabidopsis that demonstrate the co-ordinate regulation of gene expression and enzyme activities for the acyl-CoA oxidase- and 3-ketoacyl-CoA thiolasemediated steps of β-oxidation, the isocitrate lyase and malate synthase steps of the glyoxylate cycle and the phosphoenolpyruvate carboxykinase step of gluconeogenesis. The mRNA abundance and enzyme activities increase to a peak at stage 2, 48 h after the onset of seed germination, and decline thereafter either to undetectable levels (for malate synthase and isocitrate lyase) or low basal levels (for the genes of β-oxidation and gluconeogenesis). The co-ordinate induction of all these genes at the onset of germination raises the possibility that a global regulatory mechanism operates to induce the expression of genes associated with the mobilization of storage reserves during the heterotrophic growth period.

scholarly journals Identification of RamA, a Novel LuxR-Type Transcriptional Regulator of Genes Involved in Acetate Metabolism of Corynebacterium glutamicum

2006 ◽  
Vol 188 (7) ◽  
pp. 2554-2567 ◽  
Author(s):  
Annette Cramer ◽  
Robert Gerstmeir ◽  
Steffen Schaffer ◽  
Michael Bott ◽  
Bernhard J. Eikmanns
Keyword(s):  
Corynebacterium Glutamicum ◽  
Isocitrate Lyase ◽  
Glyoxylate Cycle ◽  
Transcriptional Regulator ◽  
Malate Synthase ◽  
Acetate Kinase ◽  
Acetate Metabolism ◽  
Promoter Regions ◽  
Cell Extracts ◽  
Peptide Mass

ABSTRACT In Corynebacterium glutamicum, the acetate-activating enzymes phosphotransacetylase and acetate kinase and the glyoxylate cycle enzymes isocitrate lyase and malate synthase are coordinately up-regulated in the presence of acetate in the growth medium. This regulation is due to transcriptional control of the respective pta-ack operon and the aceA and aceB genes, brought about at least partly by the action of the negative transcriptional regulator RamB. Using cell extracts of C. glutamicum and employing DNA affinity chromatography, mass spectrometry, and peptide mass fingerprinting, we identified a LuxR-type transcriptional regulator, designated RamA, which binds to the pta-ack and aceA/aceB promoter regions. Inactivation of the ramA gene in the genome of C. glutamicum resulted in mutant RG2. This mutant was unable to grow on acetate as the sole carbon and energy source and, in comparison to the wild type of C. glutamicum, showed very low specific activities of phosphotransacetylase, acetate kinase, isocitrate lyase, and malate synthase, irrespective of the presence of acetate in the medium. Comparative transcriptional cat fusion experiments revealed that this deregulation takes place at the level of transcription. By electrophoretic mobility shift analysis, purified His-tagged RamA protein was shown to bind specifically to the pta-ack and the aceA/aceB promoter regions, and deletion and mutation studies revealed in both regions two binding motifs each consisting of tandem A/C/TG4-6T/C or AC4-5A/G/T stretches separated by four or five arbitrary nucleotides. Our data indicate that RamA represents a novel LuxR-type transcriptional activator of genes involved in acetate metabolism of C. glutamicum.

scholarly journals Physiological Ecology of Stenoxybacter acetivorans, an Obligate Microaerophile in Termite Guts

2007 ◽  
Vol 73 (21) ◽  
pp. 6829-6841 ◽  
Author(s):  
John T. Wertz ◽  
John A. Breznak
Keyword(s):  
Isocitrate Lyase ◽  
Tricarboxylic Acid Cycle ◽  
Glyoxylate Cycle ◽  
Reticulitermes Flavipes ◽  
Peripheral Region ◽  
Malate Synthase ◽  
Rrna Gene ◽  
Potential Contribution ◽  
Cell Extracts

ABSTRACT Stenoxybacter acetivorans is a newly described, obligately microaerophilic β-proteobacterium that is abundant in the acetate-rich hindgut of Reticulitermes. Here we tested the hypotheses that cells are located in the hypoxic, peripheral region of Reticulitermes flavipes hindguts and use acetate to fuel their O2-consuming respiratory activity in situ. Physical fractionation of R. flavipes guts, followed by limited-cycle PCR with S. acetivorans-specific 16S rRNA gene primers, indicated that cells of this organism were indeed located primarily among the microbiota colonizing the hindgut wall. Likewise, reverse transcriptase PCR of hindgut RNA revealed S. acetivorans-specific transcripts for acetate-activating enzymes that were also found in cell extracts (acetate kinase and phosphotransacetylase), as well as transcripts of ccoN, which encodes the O2-reducing subunit of high-affinity cbb 3-type cytochrome oxidases. However, S. acetivorans strains did not possess typical enzymes of the glyoxylate cycle (isocitrate lyase and malate synthase A), suggesting that they may use an alternate pathway to replenish tricarboxylic acid cycle intermediates or they obtain such compounds (or their precursors) in situ. Respirometric measurements indicated that much of the O2 consumption by R. flavipes worker larvae was attributable to their guts, and the potential contribution of S. acetivorans to O2 consumption by extracted guts was about 0.2%, a value similar to that obtained for other hindgut bacteria examined. Similar measurements obtained with guts of larvae prefed diets to disrupt major members of the hindgut microbiota implied that most of the O2 consumption observed with extracted guts was attributable to protozoans, a group of microbes long thought to be “strict anaerobes.”

scholarly journals Isocitrate Lyase Is Essential for Pathogenicity of the Fungus Leptosphaeria maculans to Canola (Brassica napus)

2002 ◽  
Vol 1 (5) ◽  
pp. 719-724 ◽  
Author(s):  
Alexander Idnurm ◽  
Barbara J. Howlett
Keyword(s):  
Brassica Napus ◽  
Reverse Genetics ◽  
Isocitrate Lyase ◽  
Glyoxylate Cycle ◽  
Pathogenic Fungus ◽  
Leptosphaeria Maculans ◽  
Bacterial Pathogen ◽  
Hygromycin Resistance ◽  
Wild Type ◽  
Glyoxylate Pathway

ABSTRACT A pathogenicity gene has been identified in Leptosphaeria maculans, the ascomycetous fungus that causes blackleg disease of canola (Brassica napus). This gene encodes isocitrate lyase, a component of the glyoxylate cycle, and is essential for the successful colonization of B. napus. It was identified by a reverse genetics approach whereby a plasmid conferring hygromycin resistance was inserted randomly into the L. maculans genome. Twelve of 516 transformants tested had reduced pathogenicity on cotyledons of B. juncea and B. napus, and 1 of these 12 had a deletion of the isocitrate lyase gene, as well as an insertion of the hygromycin resistance gene. This mutant was unable to grow on fatty acids, including monolaurate, and the isocitrate lyase transcript was not detected. When the wild-type gene was reintroduced into the mutant, growth on monolaurate was restored and pathogenicity was partially restored. L. maculans isocitrate lyase is produced during infection of B. napus cotyledons, while the plant homologue is not. When 2.5% glucose was added to the inoculum of the isocitrate lyase mutant, lesions of sizes similar to those caused by wild-type isolate M1 developed on B. napus cotyledons. These findings suggest that the glyoxylate pathway is essential for disease development by this plant-pathogenic fungus, as has been shown recently for a fungal and bacterial pathogen of animals and a bacterial pathogen of plants. Involvement of the glyoxylate pathway in pathogenesis in animals and plants presents potential drug targets for control of diseases.

STUDIES ON RUMEN COLIFORM ORGANISMS: II. UTILIZATION OF ACETATE BY ESCHERICHIA COLI 64 ISOLATED FROM THE RUMEN FLUID OF A COW FED ALFALFA HAY

1967 ◽  
Vol 47 (3) ◽  
pp. 199-209 ◽  
Author(s):  
C. R. Krishnamurti ◽  
L. W. McElroy
Keyword(s):  
Sodium Acetate ◽  
Isocitrate Lyase ◽  
Protein Hydrolysate ◽  
Rumen Fluid ◽  
Glyoxylate Cycle ◽  
Malate Synthase ◽  
E Coli ◽  
Spectrophotometric Methods ◽  
Acetate Medium ◽  
The Glyoxylate Cycle

When cells of E. coli 64 were harvested in their exponential phase of growth in an acetate medium and incubated aerobically with sodium acetate-2-C14, about 33% of the label appeared in CO2 after 1 hr. Of the radioactivity in the cells, 72% was recovered in the protein hydrolysate, 8% in the nucleic acid, 6% in the lipid and 14% in the ethanol-soluble fractions. The radioactivity in the protein hydrolysate of cells incubated with sodium acetate-2-C14 was approximately 20 times that in the hydrolysate of cells incubated with C14O2 as the carbon source. By spectrophotometric methods, it was demonstrated that cell-free extracts of cells grown on acetate contained acetate kinase and phosphate acetyltransferase, plus, as demonstrated by spectrophotometric and isotopic methods, isocitrate lyase and malate synthase which are characteristic of the glyoxylate cycle. The enzymes of the glyoxylate cycle could not be demonstrated in cell-free extracts of E. coli 64 grown on glucose under either aerobic or anaerobic conditions. Possible functions that E. coli 64 may have in the maintenance of anaerobiosis in the rumen and utilization of acetate through the glyoxylate pathway are discussed.

Re-Activation of the Expression of Glyoxysomal Genes in Green Plant Tissue

1990 ◽  
Vol 45 (1-2) ◽  
pp. 107-111 ◽  
Author(s):  
Ralf Birkhan ◽  
Helmut Kindl
Keyword(s):  
Gene Expression ◽  
Isocitrate Lyase ◽  
Glyoxylate Cycle ◽  
Green Plant ◽  
Malate Synthase ◽  
Dna Library ◽  
Glycollate Oxidase ◽  
Differential Gene ◽  
Cucumber Cotyledons ◽  
Leaf Peroxisome

Abstract Biochemie, Fachbereich Chemie, Universität Marburg, Hans-Meerwein-Straße, D-3550 Marburg, Bundesrepublik Deutschland Z. Naturforsch. 45c, Isocitrate Lyase c DNA, Malate Synthase c DNA, Glyoxysome, Leaf Peroxisome, Transition of Organelles Glyoxysomes are being replaced by leaf-type peroxisom es during the greening of dark-grown cucumber cotyledons. Light functions in this process as negative modulator of the gene expression of glyoxylate cycle enzymes but as positive regulator for the activation of glycollate oxidase formation. The differential gene expression was investigated at the level of m RNA amounts using c DNA probes hybridizing with malate synthase m RNA, isocitrate lyase m RNA, and glycollate oxidase m RNA. Hybrid ization probes were obtained from a c DNA library complementary to the germinationspecific m RNA s of cucumber cotyledons. The process of replacem ent of glyoxysomal proteins by leaf peroxisom al proteins was reversed to a certain extend when greened cotyledons were brought back in the dark. Hybridization on Northern b lots provided evidences that in greened cotyledons the amount of malate synthase m RNA and isocitratelyase m RNA starts to increase up on dark treatment.

Characterization of a Bifunctional Glyoxylate Cycle Enzyme, Malate Synthase/Isocitrate Lyase, of Euglena gracilis

2011 ◽  
Vol 58 (2) ◽  
pp. 128-133 ◽  
Author(s):  
MASAMI NAKAZAWA ◽  
MASAAKI NISHIMURA ◽  
KENGO INOUE ◽  
MITSUHIRO UEDA ◽  
HIROSHI INUI ◽  
...  
Keyword(s):  
Euglena Gracilis ◽  
Isocitrate Lyase ◽  
Glyoxylate Cycle ◽  
Malate Synthase ◽  
Cycle Enzyme

scholarly journals Induction of Glyoxylate Cycle–Key Enzymes, Malate Synthase, and Isocitrate Lyase in Ethanol-grownEuglena gracilis

1994 ◽  
Vol 58 (3) ◽  
pp. 582-583 ◽  
Author(s):  
Kouki Ono ◽  
Kazutaka Miyatake ◽  
Hiroshi Inui ◽  
Shozaburo Kitaoka ◽  
Yoshihisa Nakano
Keyword(s):  
Isocitrate Lyase ◽  
Glyoxylate Cycle ◽  
Malate Synthase ◽  
Key Enzymes

Changes in metabolic reserves and enzyme activities during zoospore motility and cyst germination in Phytophthora palmivora

1975 ◽  
Vol 53 (14) ◽  
pp. 1411-1416 ◽  
Author(s):  
Christina E. Bimpong
Keyword(s):  
Specific Activity ◽  
Isocitrate Lyase ◽  
Glyoxylate Cycle ◽  
Krebs Cycle ◽  
Malate Synthase ◽  
Phytophthora Palmivora ◽  
Germination Period ◽  
Major Energy Source ◽  
The Glyoxylate Cycle ◽  
Cyst Germination

Lipids measured as acyl glycerides and free fatty acids provided the major energy source during a 6-h motile and a 2-h germination period in zoospores and cysts, respectively, of Phytophthora palmivora. Carbohydrates and proteins decreased slightly during the 6-h motile period but increased significantly during germination. Specific activity of isocitrate lyase decreased both during zoospore motility and cyst germination. Only trace amounts of malate synthase activity were detected in zoospores and cysts. The activities of both NAD-isocitrate and malate dehydrogenases increased slightly, while those of NADP-isocitrate and succinate dehydrogenases decreased during the 6-h motile period. During the 2-h germination period the specific activities of NAD- and NADP-isocitrate, malate, and succinate dehydrogenases increased. It appears that during the motile stage the glyoxylate cycle provided more metabolites for the Krebs cycle than it did during germination.

scholarly journals Delicate Metabolic Control and Coordinated Stress Response Critically Determine Antifungal Tolerance of Candida albicans Biofilm Persisters

2015 ◽  
Vol 59 (10) ◽  
pp. 6101-6112 ◽  
Author(s):  
Peng Li ◽  
Chaminda J. Seneviratne ◽  
Emanuele Alpi ◽  
Juan A. Vizcaino ◽  
Lijian Jin
Keyword(s):  
Candida Albicans ◽  
Stress Response ◽  
Metabolic Control ◽  
Isocitrate Lyase ◽  
Tricarboxylic Acid Cycle ◽  
Glyoxylate Cycle ◽  
Malate Synthase ◽  
Content Type ◽  
Liquid Chromatography Tandem Mass ◽  
Metabolic Activities

ABSTRACTCandidainfection has emerged as a critical health care burden worldwide, owing to the formation of robust biofilms against common antifungals. Recent evidence shows that multidrug-tolerant persisters critically account for biofilm recalcitrance, but their underlying biological mechanisms are poorly understood. Here, we first investigated the phenotypic characteristics ofCandidabiofilm persisters under consecutive harsh treatments of amphotericin B. The prolonged treatments effectively killed the majority of the cells of biofilms derived from representative strains ofCandida albicans,Candida glabrata, andCandida tropicalisbut failed to eradicate a small fraction of persisters. Next, we explored the tolerance mechanisms of the persisters through an investigation of the proteomic profiles ofC. albicansbiofilm persister fractions by liquid chromatography-tandem mass spectrometry. TheC. albicansbiofilm persisters displayed a specific proteomic signature, with an array of 205 differentially expressed proteins. The crucial enzymes involved in glycolysis, the tricarboxylic acid cycle, and protein synthesis were markedly downregulated, indicating that major metabolic activities are subdued in the persisters. It is noteworthy that certain metabolic pathways, such as the glyoxylate cycle, were able to be activated with significantly increased levels of isocitrate lyase and malate synthase. Moreover, a number of important proteins responsible forCandidagrowth, virulence, and the stress response were greatly upregulated. Interestingly, the persisters were tolerant to oxidative stress, despite highly induced intracellular superoxide. The current findings suggest that delicate metabolic control and a coordinated stress response may play a crucial role in mediating the survival and antifungal tolerance ofCandidabiofilm persisters.

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