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 Evidence that ACN1 (acetate non-utilizing 1) prevents carbon leakage from peroxisomes during lipid mobilization in Arabidopsis seedlings

2011 ◽  
Vol 437 (3) ◽  
pp. 505-513 ◽  
Author(s):  
Elizabeth Allen ◽  
Annick Moing ◽  
Jonathan A. D. Wattis ◽  
Tony Larson ◽  
Mickaël Maucourt ◽  
...  
Keyword(s):  
Carbon Sink ◽  
Glyoxylate Cycle ◽  
Eicosenoic Acid ◽  
Primary Metabolism ◽  
Acetyl Coa ◽  
Primary Metabolite ◽  
Lipid Mobilization ◽  
Transcript Levels ◽  
Chain Acyl ◽  
Acetate Accumulation

ACN1 (acetate non-utilizing 1) is a short-chain acyl-CoA synthetase which recycles free acetate to acetyl-CoA in peroxisomes of Arabidopsis. Pulse-chase [2-13C]acetate feeding of the mutant acn1–2 revealed that acetate accumulation and assimilation were no different to that of wild-type, Col-7. However, the lack of acn1–2 led to a decrease of nearly 50% in 13C-labelling of glutamine, a major carbon sink in seedlings, and large decreases in primary metabolite levels. In contrast, acetyl-CoA levels were higher in acn1–2 compared with Col-7. The disappearance of eicosenoic acid was slightly delayed in acn1–2 indicating only a small effect on the rate of lipid breakdown. A comparison of transcript levels in acn1–2 and Col-7 showed that induced genes included a number of metabolic genes and also a large number of signalling-related genes. Genes repressed in the mutant were represented primarily by embryogenesis-related genes. Transcript levels of glyoxylate cycle genes also were lower in acn1–2 than in Col-7. We conclude that deficiency in peroxisomal acetate assimilation comprises only a small proportion of total acetate use, but this affects both primary metabolism and gene expression. We discuss the possibility that ACN1 safeguards against the loss of carbon as acetate from peroxisomes during lipid mobilization.

Acetate metabolism in Escherichia coli

1978 ◽  
Vol 24 (2) ◽  
pp. 149-153 ◽  
Author(s):  
T. M. Lakshmi ◽  
Robert B. Helling
Keyword(s):  
Isocitrate Dehydrogenase ◽  
Citrate Synthase ◽  
Isocitrate Lyase ◽  
Glyoxylate Cycle ◽  
Acetate Metabolism ◽  
Wild Type ◽  
Intermediary Metabolites ◽  
Lyase Activity ◽  
Acetate Medium ◽  
The Glyoxylate Cycle

Levels of several intermediary metabolites were measured in cells grown in acetate medium in order to test the hypothesis that the glyoxylate cycle is repressed by phosphoenolpyruvate (PEP). Wild-type cells had less PEP than either isocitrate dehydrogenase – deficient cells (which had greater isocitrate lyase activity than the wild type) or isocitrate dehydrogenase – deficient, citrate synthase – deficient cells (which are poorly inducible). Thus induction of the glyoxylate cycle is more complicated than a simple function of PEP concentration. No correlation between enzyme activity and the level of oxaloacetate, pyruvate, or citrate was found either. Citrate was synthesized in citrate synthase – deficient mutants, possibly via citrate lyase.

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.

scholarly journals Peroxysomal Carnitine Acetyl Transferase Influences Host Colonization Capacity in Sclerotinia sclerotiorum

2013 ◽  
Vol 26 (7) ◽  
pp. 768-780 ◽  
Author(s):  
D. Liberti ◽  
J. A. Rollins ◽  
K. F. Dobinson
Keyword(s):  
Fatty Acids ◽  
Oxalic Acid ◽  
Sclerotinia Sclerotiorum ◽  
Magnaporthe Grisea ◽  
Glyoxylate Cycle ◽  
Wild Type ◽  
Transcript Accumulation ◽  
Acetyl Coa ◽  
Host Colonization ◽  
Carnitine Acetyl Transferase

In lower eukaryotes, the glyoxylate cycle allows cells to utilize two-carbon compounds when simple sugars are not available. In filamentous fungi, glyoxylate metabolism is coupled with β-oxidation of fatty acids, and both are localized to ubiquitous eukaryotic organelles called peroxisomes. Acetyl coenzyme A (acetyl-CoA) produced during β-oxidation is transported via the cytosol into mitochondria for further metabolism. A peroxisomal-specific pathway for acetyl-CoA transport requiring peroxisomal carnitine acetyl transferase (CAT) activity has been identified in Magnaporthe grisea peroxisomes. Here, we report that a Sclerotinia sclerotiorum ortholog of the M. grisea peroxisomal CAT-encoding gene Pth2 (herein designated Ss-pth2) is required for virulence-associated host colonization. Null (ss-pth2) mutants, obtained by in vitro transposon mutagenesis, failed to utilize fatty acids, acetate, or glycerol as sole carbon sources for growth. Gene expression analysis of these mutants showed altered levels of transcript accumulation for glyoxylate cycle enzymes. Ss-pth2 disruption also affected sclerotial, apothecial, and appressorial development and morphology, as well as oxalic acid accumulation when cultured with acetate or oleic acid as sole carbon nutrient sources. Although mutants were able to penetrate and initially colonize host tissue, subsequent colonization was impaired. Genetic complementation with the wild-type Ss-pth2 restored wild-type virulence phenotypes. These findings suggest an essential role in S. sclerotiorum for the peroxisomal metabolic pathways for oxalic acid synthesis and host colonization.

Arabidopsis thaliana mutants disrupted in lipid mobilization

2000 ◽  
Vol 28 (6) ◽  
pp. 762-765 ◽  
Author(s):  
P. R. Lange ◽  
I. Graham
Keyword(s):  
Arabidopsis Thaliana ◽  
Glyoxylate Cycle ◽  
Lipid Mobilization ◽  
Storage Lipid ◽  
Resistant Mutants ◽  
The Glyoxylate Cycle ◽  
Exogenous Sugar

To isolate mutants in the process of lipid mobilization during post-germinative growth we employed a screen using the pro-herbicide 2,4-dichlorophenoxybutyric acid (2,4-DB). The phenotypes of a number of 2,4-DB-resistant mutants are compared with previously characterized mutants disrupted in β-oxidation or the glyoxylate cycle. We conclude that the strength of 2,4-DB resistance and the ability of the seedlings to grow in the absence of exogenous sugar are inversely correlated. Sugar dependence of 2,4-DB-resistant seedlings is a consequence of impaired storage-lipid mobilization.

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 Inhibitory Effects of Diketopiperazines from Marine-Derived Streptomyces puniceus on the Isocitrate Lyase of Candida albicans

Molecules ◽  
2019 ◽  
Vol 24 (11) ◽  
pp. 2111 ◽  
Author(s):  
Heegyu Kim ◽  
Ji-Yeon Hwang ◽  
Jongheon Shin ◽  
Ki-Bong Oh
Keyword(s):  
Candida Albicans ◽  
Cyclic Peptides ◽  
Inhibitory Concentration ◽  
Isocitrate Lyase ◽  
Glyoxylate Cycle ◽  
Malate Synthase ◽  
Wild Type ◽  
Inhibitory Effects ◽  
Reported Data ◽  
The Glyoxylate Cycle

The glyoxylate cycle is a sequence of anaplerotic reactions catalyzed by the key enzymes isocitrate lyase (ICL) and malate synthase, and plays an important role in the pathogenesis of microorganisms during infection. An icl-deletion mutant of Candida albicans exhibited reduced virulence in mice compared with the wild type. Five diketopiperazines, which are small and stable cyclic peptides, isolated from the marine-derived Streptomyces puniceus Act1085, were evaluated for their inhibitory effects on C. albicans ICL. The structures of these compounds were elucidated based on spectroscopic data and comparisons with previously reported data. Cyclo(L-Phe-L-Val) was identified as a potent ICL inhibitor, with a half maximal inhibitory concentration of 27 μg/mL. Based on the growth phenotype of the icl-deletion mutants and icl expression analyses, we demonstrated that cyclo(L-Phe-L-Val) inhibits the gene transcription of ICL in C. albicans under C2-carbon-utilizing conditions.

scholarly journals Transcriptomic and proteomic profiling revealed reprogramming of carbon metabolism in acetate-grown human pathogen Candida glabrata

2021 ◽  
Vol 28 (1) ◽  
Author(s):  
Shu Yih Chew ◽  
Alistair J. P. Brown ◽  
Benjamin Yii Chung Lau ◽  
Yoke Kqueen Cheah ◽  
Kok Lian Ho ◽  
...  
Keyword(s):  
Carbon Source ◽  
Carbon Metabolism ◽  
Candida Glabrata ◽  
Glyoxylate Cycle ◽  
Glucose Deprivation ◽  
Malate Synthase ◽  
Metabolic Responses ◽  
Metabolic Adaptation ◽  
High Morbidity ◽  
The Glyoxylate Cycle

Abstract Background Emergence of Candida glabrata, which causes potential life-threatening invasive candidiasis, has been widely associated with high morbidity and mortality. In order to cause disease in vivo, a robust and highly efficient metabolic adaptation is crucial for the survival of this fungal pathogen in human host. In fact, reprogramming of the carbon metabolism is believed to be indispensable for phagocytosed C. glabrata within glucose deprivation condition during infection. Methods In this study, the metabolic responses of C. glabrata under acetate growth condition was explored using high-throughput transcriptomic and proteomic approaches. Results Collectively, a total of 1482 transcripts (26.96%) and 242 proteins (24.69%) were significantly up- or down-regulated. Both transcriptome and proteome data revealed that the regulation of alternative carbon metabolism in C. glabrata resembled other fungal pathogens such as Candida albicans and Cryptococcus neoformans, with up-regulation of many proteins and transcripts from the glyoxylate cycle and gluconeogenesis, namely isocitrate lyase (ICL1), malate synthase (MLS1), phosphoenolpyruvate carboxykinase (PCK1) and fructose 1,6-biphosphatase (FBP1). In the absence of glucose, C. glabrata shifted its metabolism from glucose catabolism to anabolism of glucose intermediates from the available carbon source. This observation essentially suggests that the glyoxylate cycle and gluconeogenesis are potentially critical for the survival of phagocytosed C. glabrata within the glucose-deficient macrophages. Conclusion Here, we presented the first global metabolic responses of C. glabrata to alternative carbon source using transcriptomic and proteomic approaches. These findings implicated that reprogramming of the alternative carbon metabolism during glucose deprivation could enhance the survival and persistence of C. glabrata within the host.

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