scholarly journals Role of Carnitine Acetyltransferases in Acetyl Coenzyme A Metabolism in Aspergillus nidulans

2011 ◽  
Vol 10 (4) ◽  
pp. 547-555 ◽  
Author(s):  
Michael J. Hynes ◽  
Sandra L. Murray ◽  
Alex Andrianopoulos ◽  
Meryl A. Davis
Keyword(s):  
Fatty Acids ◽  
Aspergillus Nidulans ◽  
Intracellular Transport ◽  
Coenzyme A ◽  
Tricarboxylic Acid Cycle ◽  
Essential Feature ◽  
Malate Synthase ◽  
Acetyl Coa ◽  
Acetyl Coenzyme A ◽  
Acetyl Coenzyme

ABSTRACTThe flow of carbon metabolites between cellular compartments is an essential feature of fungal metabolism. During growth on ethanol, acetate, or fatty acids, acetyl units must enter the mitochondrion for metabolism via the tricarboxylic acid cycle, and acetyl coenzyme A (acetyl-CoA) in the cytoplasm is essential for the biosynthetic reactions and for protein acetylation. Acetyl-CoA is produced in the cytoplasm by acetyl-CoA synthetase during growth on acetate and ethanol while β-oxidation of fatty acids generates acetyl-CoA in peroxisomes. The acetyl-carnitine shuttle in which acetyl-CoA is reversibly converted to acetyl-carnitine by carnitine acetyltransferase (CAT) enzymes is important for intracellular transport of acetyl units. In the filamentous ascomyceteAspergillus nidulans, a cytoplasmic CAT, encoded byfacC, is essential for growth on sources of cytoplasmic acetyl-CoA while a second CAT, encoded by theacuJgene, is essential for growth on fatty acids as well as acetate. We have shown that AcuJ contains an N-terminal mitochondrial targeting sequence and a C-terminal peroxisomal targeting sequence (PTS) and is localized to both peroxisomes and mitochondria, independent of the carbon source. Mislocalization of AcuJ to the cytoplasm does not result in loss of growth on acetate but prevents growth on fatty acids. Therefore, while mitochondrial AcuJ is essential for the transfer of acetyl units to mitochondria, peroxisomal localization is required only for transfer from peroxisomes to mitochondria. Peroxisomal AcuJ was not required for the import of acetyl-CoA into peroxisomes for conversion to malate by malate synthase (MLS), and export of acetyl-CoA from peroxisomes to the cytoplasm was found to be independent of FacC when MLS was mislocalized to the cytoplasm.

scholarly journals Investigation of Carbon Metabolism in “Dehalococcoides ethenogenes” Strain 195 by Use of Isotopomer and Transcriptomic Analyses

2009 ◽  
Vol 191 (16) ◽  
pp. 5224-5231 ◽  
Author(s):  
Yinjie J. Tang ◽  
Shan Yi ◽  
Wei-Qin Zhuang ◽  
Stephen H. Zinder ◽  
Jay D. Keasling ◽  
...  
Keyword(s):  
Genome Annotation ◽  
Carbon Fixation ◽  
Coenzyme A ◽  
Citrate Synthase ◽  
Tricarboxylic Acid Cycle ◽  
Acetyl Coa ◽  
Experimental Conditions ◽  
Acetyl Coenzyme A ◽  
Acetyl Coenzyme ◽  
Dehalococcoides Ethenogenes

ABSTRACT Members of the genus “Dehalococcoides” are the only known microorganisms that can completely dechlorinate tetrachloroethene and trichloroethene to the innocuous end product, ethene. This study examines the central metabolism in “Dehalococcoides ethenogenes” strain 195 via 13C-labeled tracer experiments. Supported by the genome annotation and the transcript profile, isotopomer analysis of key metabolites clarifies ambiguities in the genome annotation and identifies an unusual biosynthetic pathway in strain 195. First, the 13C-labeling studies revealed that strain 195 contains complete amino acid biosynthesis pathways, even though current genome annotation suggests that several of these pathways are incomplete. Second, the tricarboxylic acid cycle of strain 195 is confirmed to be branched, and the Wood-Ljungdahl carbon fixation pathway is shown to not be functionally active under our experimental conditions; rather, CO2 is assimilated via two reactions, conversion of acetyl-coenzyme A (acetyl coenzyme A [acetyl-CoA]) to pyruvate catalyzed by pyruvate synthase (DET0724-0727) and pyruvate conversion to oxaloacetate via pyruvate carboxylase (DET0119-0120). Third, the 13C-labeling studies also suggested that isoleucine is synthesized from acetyl-CoA and pyruvate via citramalate synthase (CimA, EC 2.3.1.182), rather than from the common pathway via threonine ammonia-lyase (EC 4.3.1.19). Finally, evidence is presented that strain 195 may contain an undocumented citrate synthase (>95% Re-type stereospecific), i.e., a novel Re-citrate synthase that is apparently different from the one recently reported in Clostridium kluyveri.

scholarly journals ς70 Is the Principal Sigma Factor Responsible for Transcription of acs, Which Encodes Acetyl Coenzyme A Synthetase in Escherichia coli

2000 ◽  
Vol 182 (2) ◽  
pp. 551-554 ◽  
Author(s):  
Suman Kumari ◽  
Erica J. Simel ◽  
Alan J. Wolfe
Keyword(s):  
Escherichia Coli ◽  
Stationary Phase ◽  
Sigma Factor ◽  
Coenzyme A ◽  
Tricarboxylic Acid Cycle ◽  
Acetyl Coa ◽  
Metabolic Switch ◽  
Acetyl Coenzyme A ◽  
Acetyl Coenzyme ◽  
Isogenic Strains

ABSTRACT Cells of Escherichia coli undergo a metabolic switch associated with the production and utilization of acetate. During exponential growth on tryptone broth, these cells excrete acetate via the phosphotransacetylase-acetate kinase (Pta-AckA) pathway. As they begin the transition to stationary phase, they instead resorb acetate, activate it to acetyl coenzyme A (acetyl-CoA) by means of the enzyme acetyl-CoA synthetase (Acs) and utilize it to generate energy and biosynthetic components via the tricarboxylic acid cycle and the glyoxylate shunt, respectively. This metabolic switch depends upon the induction of Acs. As part of our effort to dissect the mechanism(s) underlying induction and to identify the signal(s) that triggers that induction, we sought the sigma factor most responsible foracs expression. Using isogenic strains that carry a temperature sensitivity allele of the gene that encodes ς70 and either a wild-type or null allele of the gene that encodes ςS, we determined by immunoblotting, reverse transcriptase PCR, and acs::lacZtranscriptional fusion analyses that ς70 is the sigma factor primarily responsible for the acs transcription that cells induce during mid-exponential phase. In contrast, ςS partially inhibits that transcription as cells enter stationary phase.

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 Malate Synthase and β-Methylmalyl Coenzyme A Lyase Reactions in the Methylaspartate Cycle in Haloarcula hispanica

2016 ◽  
Vol 199 (4) ◽  
Author(s):  
Farshad Borjian ◽  
Jing Han ◽  
Jing Hou ◽  
Hua Xiang ◽  
Jan Zarzycki ◽  
...  
Keyword(s):  
Coenzyme A ◽  
Malate Synthase ◽  
Acetyl Coa ◽  
Acetyl Coenzyme A ◽  
Physiological Functions ◽  
Content Type ◽  
Acetate Assimilation ◽  
Acetyl Coenzyme ◽  
Haloarcula Hispanica ◽  
Anaplerotic Pathway

ABSTRACT Haloarchaea are extremely halophilic heterotrophic microorganisms belonging to the class Halobacteria (Euryarchaeota). Almost half of the haloarchaea possesses the genes coding for enzymes of the methylaspartate cycle, a recently discovered anaplerotic acetate assimilation pathway. In this cycle, the enzymes of the tricarboxylic acid cycle together with the dedicated enzymes of the methylaspartate cycle convert two acetyl coenzyme A (acetyl-CoA) molecules to malate. The methylaspartate cycle involves two reactions catalyzed by homologous enzymes belonging to the CitE-like enzyme superfamily, malyl-CoA lyase/thioesterase (haloarchaeal malate synthase [hMS]; Hah_2476 in Haloarcula hispanica) and β-methylmalyl-CoA lyase (haloarchaeal β-methylmalyl-CoA lyase [hMCL]; Hah_1341). Although both enzymes catalyze the same reactions, hMS was previously proposed to preferentially catalyze the formation of malate from acetyl-CoA and glyoxylate (malate synthase activity) and hMCL was proposed to primarily cleave β-methylmalyl-CoA to propionyl-CoA and glyoxylate. Here we studied the physiological functions of these enzymes during acetate assimilation in H. hispanica by using biochemical assays of the wild type and deletion mutants. Our results reveal that the main physiological function of hMS is malyl-CoA (not malate) formation and that hMCL catalyzes a β-methylmalyl-CoA lyase reaction in vivo. The malyl-CoA thioesterase activities of both enzymes appear to be not essential for growth on acetate. Interestingly, despite the different physiological functions of hMS and hMCL, structural comparisons predict that these two proteins have virtually identical active sites, thus highlighting the need for experimental validation of their catalytic functions. Our results provide further proof of the operation of the methylaspartate cycle and indicate the existence of a distinct, yet-to-be-discovered malyl-CoA thioesterase in haloarchaea. IMPORTANCE Acetate is one of the most important substances in natural environments. The activated form of acetate, acetyl coenzyme A (acetyl-CoA), is the high-energy intermediate at the crossroads of central metabolism: its oxidation generates energy for the cell, and about a third of all biosynthetic fluxes start directly from acetyl-CoA. Many organic compounds enter the central carbon metabolism via this key molecule. To sustain growth on acetyl-CoA-generating compounds, a dedicated assimilation (anaplerotic) pathway is required. The presence of an anaplerotic pathway is a prerequisite for growth in many environments, being important for environmentally, industrially, and clinically important microorganisms. Here we studied specific reactions of a recently discovered acetate assimilation pathway, the methylaspartate cycle, functioning in extremely halophilic archaea.

scholarly journals ATP-Citrate Lyase Is Required for Production of Cytosolic Acetyl Coenzyme A and Development in Aspergillus nidulans

2010 ◽  
Vol 9 (7) ◽  
pp. 1039-1048 ◽  
Author(s):  
Michael J. Hynes ◽  
Sandra L. Murray
Keyword(s):  
Aspergillus Nidulans ◽  
Coenzyme A ◽  
Carbon Sources ◽  
Gene Arrangement ◽  
Atp Citrate Lyase ◽  
Acetyl Coa ◽  
Acetyl Coenzyme A ◽  
Content Type ◽  
Acetyl Coenzyme ◽  
Citrate Lyase

ABSTRACT Acetyl coenzyme A (CoA) is a central metabolite in carbon and energy metabolism and in the biosynthesis of cellular molecules. A source of cytoplasmic acetyl-CoA is essential for the production of fatty acids and sterols and for protein acetylation, including histone acetylation in the nucleus. In Saccharomyces cerevisiae and Candida albicans acetyl-CoA is produced from acetate by cytoplasmic acetyl-CoA synthetase, while in plants and animals acetyl-CoA is derived from citrate via ATP-citrate lyase. In the filamentous ascomycete Aspergillus nidulans, tandem divergently transcribed genes (aclA and aclB) encode the subunits of ATP-citrate lyase, and we have deleted these genes. Growth is greatly diminished on carbon sources that do not result in cytoplasmic acetyl-CoA, such as glucose and proline, while growth is not affected on carbon sources that result in the production of cytoplasmic acetyl-CoA, such as acetate and ethanol. Addition of acetate restores growth on glucose or proline, and this is dependent on facA, which encodes cytoplasmic acetyl-CoA synthetase, but not on the regulatory gene facB. Transcription of aclA and aclB is repressed by growth on acetate or ethanol. Loss of ATP-citrate lyase results in severe developmental effects, with the production of asexual spores (conidia) being greatly reduced and a complete absence of sexual development. This is in contrast to Sordaria macrospora, in which fruiting body formation is initiated but maturation is defective in an ATP-citrate lyase mutant. Addition of acetate does not repair these defects, indicating a specific requirement for high levels of cytoplasmic acetyl-CoA during differentiation. Complementation in heterokaryons between aclA and aclB deletions for all phenotypes indicates that the tandem gene arrangement is not essential.

scholarly journals Regulation of Acetyl Coenzyme A Synthetase inEscherichia coli

2000 ◽  
Vol 182 (15) ◽  
pp. 4173-4179 ◽  
Author(s):  
Suman Kumari ◽  
Christine M. Beatty ◽  
Douglas F. Browning ◽  
Stephen J. W. Busby ◽  
Erica J. Simel ◽  
...  
Keyword(s):  
Cyclic Amp ◽  
Coenzyme A ◽  
Tricarboxylic Acid Cycle ◽  
Receptor Protein ◽  
Acetate Metabolism ◽  
Glyoxylate Shunt ◽  
Acetyl Coa ◽  
Metabolic Switch ◽  
Acetyl Coenzyme A ◽  
Acetyl Coenzyme

ABSTRACT Cells of Escherichia coli growing on sugars that result in catabolite repression or amino acids that feed into glycolysis undergo a metabolic switch associated with the production and utilization of acetate. As they divide exponentially, these cells excrete acetate via the phosphotransacetylase-acetate kinase pathway. As they begin the transition to stationary phase, they instead resorb acetate, activate it to acetyl coenzyme A (acetyl-CoA) by means of the enzyme acetyl-CoA synthetase (Acs) and utilize it to generate energy and biosynthetic components via the tricarboxylic acid cycle and the glyoxylate shunt, respectively. Here, we present evidence that this switch occurs primarily through the induction of acs and that the timing and magnitude of this induction depend, in part, on the direct action of the carbon regulator cyclic AMP receptor protein (CRP) and the oxygen regulator FNR. It also depends, probably indirectly, upon the glyoxylate shunt repressor IclR, its activator FadR, and many enzymes involved in acetate metabolism. On the basis of these results, we propose that cells induce acs, and thus their ability to assimilate acetate, in response to rising cyclic AMP levels, falling oxygen partial pressure, and the flux of carbon through acetate-associated pathways.

scholarly journals Genome Sequence of Serratia marcescens MSU97, a Plant-Associated Bacterium That Makes Multiple Antibiotics

2017 ◽  
Vol 5 (9) ◽  
Author(s):  
Miguel A. Matilla ◽  
Zulema Udaondo ◽  
Tino Krell ◽  
George P. C. Salmond
Keyword(s):  
Serratia Marcescens ◽  
Genome Sequence ◽  
Coenzyme A ◽  
Acetyl Coa Carboxylase ◽  
Acetyl Coa ◽  
Acetyl Coenzyme A ◽  
Content Type ◽  
Acetyl Coenzyme ◽  
Multiple Antibiotics

ABSTRACT Serratia marcescens MSU97 was isolated from the Guayana region of Venezuela due to its ability to suppress plant-pathogenic oomycetes. Here, we report the genome sequence of MSU97, which produces various antibiotics, including the bacterial acetyl-coenzyme A (acetyl-CoA) carboxylase inhibitor andrimid, the chlorinated macrolide oocydin A, and the red linear tripyrrole antibiotic prodigiosin.

scholarly journals The Apparent Malate Synthase Activity of Rhodobacter sphaeroides Is Due to Two Paralogous Enzymes, (3S)-Malyl-Coenzyme A (CoA)/β-Methylmalyl-CoA Lyase and (3S)- Malyl-CoA Thioesterase

2010 ◽  
Vol 192 (5) ◽  
pp. 1249-1258 ◽  
Author(s):  
Tobias J. Erb ◽  
Lena Frerichs-Revermann ◽  
Georg Fuchs ◽  
Birgit E. Alber
Keyword(s):  
Rhodobacter Sphaeroides ◽  
Coenzyme A ◽  
Glyoxylate Cycle ◽  
Condensation Reaction ◽  
Malate Synthase ◽  
Acetyl Coa ◽  
Acetyl Coenzyme A ◽  
Claisen Condensation ◽  
Enzyme Functions ◽  
The Glyoxylate Cycle

ABSTRACT Assimilation of acetyl coenzyme A (acetyl-CoA) is an essential process in many bacteria that proceeds via the glyoxylate cycle or the ethylmalonyl-CoA pathway. In both assimilation strategies, one of the final products is malate that is formed by the condensation of acetyl-CoA with glyoxylate. In the glyoxylate cycle this reaction is catalyzed by malate synthase, whereas in the ethylmalonyl-CoA pathway the reaction is separated into two proteins: malyl-CoA lyase, a well-known enzyme catalyzing the Claisen condensation of acetyl-CoA with glyoxylate and yielding malyl-CoA, and an unidentified malyl-CoA thioesterase that hydrolyzes malyl-CoA into malate and CoA. In this study the roles of Mcl1 and Mcl2, two malyl-CoA lyase homologs in Rhodobacter sphaeroides, were investigated by gene inactivation and biochemical studies. Mcl1 is a true (3S)-malyl-CoA lyase operating in the ethylmalonyl-CoA pathway. Notably, Mcl1 is a promiscuous enzyme and catalyzes not only the condensation of acetyl-CoA and glyoxylate but also the cleavage of β-methylmalyl-CoA into glyoxylate and propionyl-CoA during acetyl-CoA assimilation. In contrast, Mcl2 was shown to be the sought (3S)-malyl-CoA thioesterase in the ethylmalonyl-CoA pathway, which specifically hydrolyzes (3S)-malyl-CoA but does not use β-methylmalyl-CoA or catalyze a lyase or condensation reaction. The identification of Mcl2 as thioesterase extends the enzyme functions of malyl-CoA lyase homologs that have been known only as “Claisen condensation” enzymes so far. Mcl1 and Mcl2 are both related to malate synthase, an enzyme which catalyzes both a Claisen condensation and thioester hydrolysis reaction.

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