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Laussel C, Léon S. Cellular toxicity of the metabolic inhibitor 2-deoxyglucose and associated resistance mechanisms. Biochem Pharmacol 2020; 182:114213. [PMID: 32890467 DOI: 10.1016/j.bcp.2020.114213] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Revised: 08/28/2020] [Accepted: 08/31/2020] [Indexed: 12/31/2022]
Abstract
Most malignant cells display increased glucose absorption and metabolism compared to surrounding tissues. This well-described phenomenon results from a metabolic reprogramming occurring during transformation, that provides the building blocks and supports the high energetic cost of proliferation by increasing glycolysis. These features led to the idea that drugs targeting glycolysis might prove efficient in the context of cancer treatment. One of these drugs, 2-deoxyglucose (2-DG), is a synthetic glucose analog that can be imported into cells and interfere with glycolysis and ATP generation. Its preferential targeting to sites of cell proliferation is supported by the observation that a derived molecule, 2-fluoro-2-deoxyglucose (FDG) accumulates in tumors and is used for cancer imaging. Here, we review the toxicity mechanisms of this drug, from the early-described effects on glycolysis to its other cellular consequences, including inhibition of protein glycosylation and endoplasmic reticulum stress, and its interference with signaling pathways. Then, we summarize the current data on the use of 2-DG as an anti-cancer agent, especially in the context of combination therapies, as novel 2-DG-derived drugs are being developed. We also show how the use of 2-DG helped to decipher glucose-signaling pathways in yeast and favored their engineering for biotechnologies. Finally, we discuss the resistance strategies to this inhibitor that have been identified in the course of these studies and which may have important implications regarding a medical use of this drug.
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Affiliation(s)
- Clotilde Laussel
- Université de Paris, CNRS, Institut Jacques Monod, F-75006 Paris, France
| | - Sébastien Léon
- Université de Paris, CNRS, Institut Jacques Monod, F-75006 Paris, France.
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2
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Xylose transport in yeast for lignocellulosic ethanol production: Current status. J Biosci Bioeng 2017; 125:259-267. [PMID: 29196106 DOI: 10.1016/j.jbiosc.2017.10.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Revised: 09/07/2017] [Accepted: 10/10/2017] [Indexed: 01/07/2023]
Abstract
Lignocellulosic ethanol has been considered as an alternative transportation fuel. Utilization of hemicellulosic fraction in lignocelluloses is crucial in economical production of lignocellulosic ethanol. However, this fraction has not efficiently been utilized by traditional yeast Saccharomyces cerevisiae. Genetically modified S. cerevisiae, which can utilize xylose, has several limitations including low ethanol yield, redox imbalance, and undesired metabolite formation similar to native xylose utilizing yeasts. Besides, xylose uptake is a major issue, where sugar transport system plays an important role. These genetically modified and wild-type yeast strains have further been engineered for improved xylose uptake. Various techniques have been employed to facilitate the xylose transportation in these strains. The present review is focused on the sugar transport machineries, mechanisms of xylose transport, limitations and how to deal with xylose transport for xylose assimilation in yeast cells. The recent advances in different techniques to facilitate the xylose transportation have also been discussed.
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Vishwanatha A, D'Souza CJM. Multifaceted effects of antimetabolite and anticancer drug, 2-deoxyglucose on eukaryotic cancer models budding and fission yeast. IUBMB Life 2017; 69:137-147. [DOI: 10.1002/iub.1599] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Accepted: 12/20/2016] [Indexed: 01/14/2023]
Affiliation(s)
- Akshay Vishwanatha
- Department of Studies in Biochemistry; University of Mysore; Manasagangotri Mysore Karnataka India
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4
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Vishwanatha A, Rallis C, Bevkal Subramanyaswamy S, D'Souza CJM, Bähler J, Schweingruber ME. Identification of nuclear genes affecting 2-Deoxyglucose resistance in Schizosaccharomyces pombe. FEMS Yeast Res 2016; 16:fow061. [PMID: 27481777 PMCID: PMC5452730 DOI: 10.1093/femsyr/fow061] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/25/2016] [Indexed: 01/16/2023] Open
Abstract
2-Deoxyglucose (2-DG) is a toxic glucose analog. To identify genes involved in 2-DG toxicity in Schizosaccharomyces pombe, we screened a wild-type overexpression library for genes which render cells 2-DG resistant. A gene we termed odr1, encoding an uncharacterized hydrolase, led to strong resistance and altered invertase expression when overexpressed. We speculate that Odr1 neutralizes the toxic form of 2-DG, similar to the Saccharomyces cerevisiae Dog1 and Dog2 phosphatases which dephosphorylate 2-DG-6-phosphate synthesized by hexokinase. In a complementary approach, we screened a haploid deletion library to identify 2-DG-resistant mutants. This screen identified the genes snf5, ypa1, pas1 and pho7. In liquid medium, deletions of these genes conferred 2-DG resistance preferentially under glucose-repressed conditions. The deletion mutants expressed invertase activity more constitutively than the control strain, indicating defects in the control of glucose repression. No S. cerevisiae orthologs of the pho7 gene is known, and no 2-DG resistance has been reported for any of the deletion mutants of the other genes identified here. Moreover, 2-DG leads to derepressed invertase activity in S. pombe, while in S. cerevisiae it becomes repressed. Taken together, these findings suggest that mechanisms involved in 2-DG resistance differ between budding and fission yeasts.
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Affiliation(s)
- Akshay Vishwanatha
- Department of Studies in Biochemistry, University of Mysore, Manasagangotri, Mysuru 570 006, Karnataka, India
| | - Charalampos Rallis
- Research Department of Genetics, Evolution and Environment, UCL Institute of Healthy Ageing, University College London, London WC1E 6BT, UK
| | - Shubha Bevkal Subramanyaswamy
- Department of Studies in Biochemistry, University of Mysore, Manasagangotri, Mysuru 570 006, Karnataka, India Institute of Cell Biology, University of Bern, Baltzerstrasse 4, CH-3012 Bern, Switzerland
| | | | - Jürg Bähler
- Research Department of Genetics, Evolution and Environment, UCL Institute of Healthy Ageing, University College London, London WC1E 6BT, UK
| | - Martin Ernst Schweingruber
- Department of Studies in Biochemistry, University of Mysore, Manasagangotri, Mysuru 570 006, Karnataka, India
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Ali S, Huang Z, Li H, Bashir MH, Ren S. Antioxidant enzyme influences germination, stress tolerance, and virulence of Isaria fumosorosea. J Basic Microbiol 2013; 53:489-97. [PMID: 23756951 DOI: 10.1002/jobm.201100645] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2011] [Accepted: 05/20/2012] [Indexed: 11/05/2022]
Abstract
Antioxidizing enzymes (superoxide dismutase, catalase, and glutathione peroxidae) are important enzymatic systems used to degrade hydrogen peroxide into water and oxygen, thereby lowering intracellular hydrogen peroxide levels. Entomopathogenic fungi display increased activities of antioxidizing enzymes during growth and germination, which is necessary to counteract the hyperoxidant state produced by oxidative metabolism. We studied the influence of different carbon sources on antioxidizing enzyme production by Isaria fumosorosea to determine the importance of antioxiding enzymes induction in fungal germination, stress tolerance and virulence. Conidia produced by colonies grown on hydrocarbons showed higher rates of enzyme activities compared to the control and the enzyme activities of the conidia produced on n-octacosane were higher than all the other treatments. The lipid peroxidation activities were observed as an indicative marker of oxidative damage to cells and the lowest levels of lipid peroxidation activities were observed for n-octacosane treatment. The increased enzyme activities of n-octacosane- grown conidia were accompanied by higher levels of resistance to exogenous hydrogen peroxide, reduction in germination time and higher virulence against Spodoptera exigua. Our study has helped to identify that increased activities of antioxidizing enzymes can improve the germination and tolerance to antioxidant stress response of I. fumosorosea.
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Affiliation(s)
- Shaukat Ali
- Engineering Research Center of Biological Control, Ministry of Education, College of Natural Resource and Environment, South China Agricultural University, Guangzhou City, PR, China
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6
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Kato H, Kira S, Kawamukai M. The transcription factors Atf1 and Pcr1 are essential for transcriptional induction of the extracellular maltase Agl1 in fission yeast. PLoS One 2013; 8:e80572. [PMID: 24224056 PMCID: PMC3818258 DOI: 10.1371/journal.pone.0080572] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Accepted: 10/04/2013] [Indexed: 11/19/2022] Open
Abstract
The fission yeast Schizosaccharomyces pombe secretes the extracellular maltase Agl1, which hydrolyzes maltose into glucose, thereby utilizing maltose as a carbon source. Whether other maltases contribute to efficient utilization of maltose and how Agl1 expression is regulated in response to switching of carbon sources are unknown. In this study, we show that three other possible maltases and the maltose transporter Sut1 are not required for efficient utilization of maltose. Transcription of agl1 was induced when the carbon source was changed from glucose to maltose. This was dependent on Atf1 and Pcr1, which are highly conserved transcription factors that regulate stress-responsive genes in various stress conditions. Atf1 and Pcr1 generally bind the TGACGT motif as a heterodimer. The agl1 gene lacks the exact motif, but has many degenerate TGACGT motifs in its promoter and coding region. When the carbon source was switched from glucose to maltose, Atf1 and Pcr1 associated with the promoters and coding regions of agl1, fbp1, and gpx1, indicating that the Atf1-Pcr1 heteromer binds a variety of regions in its target genes to induce their transcription. In addition, the association of Mediator with these genes was dependent on Atf1 and Pcr1. These data indicate that Atf1 and Pcr1 induce the transcription of agl1, which allows efficient utilization of extracellular maltose.
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Affiliation(s)
- Hiroaki Kato
- Department of Life Science and Biotechnology, Faculty of Life and Environmental Science, Shimane University, Matsue, Japan
- Department of Biochemistry, Shimane University School of Medicine, Izumo, Japan
- PRESTO, Japan Science and Technology Agency (JST), Saitama, Japan
| | - Shintaro Kira
- Department of Life Science and Biotechnology, Faculty of Life and Environmental Science, Shimane University, Matsue, Japan
| | - Makoto Kawamukai
- Department of Life Science and Biotechnology, Faculty of Life and Environmental Science, Shimane University, Matsue, Japan
- * E-mail:
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7
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Ali S, Huang Z, Li H, Bashir MH, Ren S. Antioxidant enzyme influences germination, stress tolerance and virulence ofIsaria fumosorosea. J Basic Microbiol 2012. [DOI: 10.1002/jobm.201200645] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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8
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Barnett JA. A history of research on yeasts 13. Active transport and the uptake of various metabolites. Yeast 2008; 25:689-731. [PMID: 18951365 DOI: 10.1002/yea.1630] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- James A Barnett
- School of Biological Sciences, University of East Anglia, Norwich, UK.
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Fission yeast SWI/SNF and RSC complexes show compositional and functional differences from budding yeast. Nat Struct Mol Biol 2008; 15:873-80. [PMID: 18622392 PMCID: PMC2559950 DOI: 10.1038/nsmb.1452] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2008] [Accepted: 05/27/2008] [Indexed: 11/26/2022]
Abstract
SWI/SNF chromatin-remodeling complexes have crucial roles in transcription and other chromatin-related processes. The analysis of the two members of this class in Saccharomyces cerevisiae, SWI/SNF and RSC, has heavily contributed to our understanding of these complexes. To understand the in vivo functions of SWI/SNF and RSC in an evolutionarily distant organism, we have characterized these complexes in Schizosaccharomyces pombe. Although core components are conserved between the two yeasts, the compositions of S. pombe SWI/SNF and RSC differ from their S. cerevisiae counterparts and in some ways are more similar to metazoan complexes. Furthermore, several of the conserved proteins, including actin-like proteins, are markedly different between the two yeasts with respect to their requirement for viability. Finally, phenotypic and microarray analyses identified widespread requirements for SWI/SNF and RSC on transcription including strong evidence that SWI/SNF directly represses iron-transport genes.
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10
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Cloning and overexpression of a maltase gene from Schizosaccharomyces pombe in Escherichia coli and characterization of the recombinant maltase. ACTA ACUST UNITED AC 2008; 112:983-9. [PMID: 18556189 DOI: 10.1016/j.mycres.2008.01.024] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2007] [Revised: 12/26/2007] [Accepted: 01/24/2008] [Indexed: 11/22/2022]
Abstract
The Schizosaccharomyces pombe maltase structural gene (SPMAL1(+)) was amplified from genomic DNA of S. pombe by PCR. An open reading frame of 1740bp, encoding a putative 579 amino-acid protein with a calculated molecular mass of 67.7kDa was characterized in the genomic DNA insert of plasmid pQE30. The specific maltase activity in the induced transformants was 21 times higher than that in wild-type. However, the estimated molecular mass of the purified recombinant maltase was 44.3kDa by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). The optimal temperature and pH of the purified recombinant maltase were 40 degrees C and 6, respectively. The recombinant maltase was weakly activated by Mg(2+), Ca(2+), Na(+), and Ba(2+), but was strongly inhibited by Hg(2+), Ag(+) and Cu(2+), EDTA, and PMSF. The purified maltase could actively hydrolyse rho-nitrophenyl glucoside (PNPG), maltose, dextrin, and soluble starch. The results demonstrate that maltase from S. pombe was different from that from other yeasts, and might be usefully exploited in the future by the biotechnology industry or lead to the development of new molecular genetic tools.
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11
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Dietvorst J, Blieck L, Brandt R, Van Dijck P, Steensma HY. Attachment ofMAL32-encoded maltase on the outside of yeast cells improves maltotriose utilization. Yeast 2007; 24:27-38. [PMID: 17192852 DOI: 10.1002/yea.1436] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
The fermentation of maltotriose, the second most abundant fermentable sugar in wort, is often incomplete during high-gravity brewing. Poor maltotriose consumption is due to environmental stress conditions during high-gravity fermentation and especially to a low uptake of this sugar by some industrial strains. In this study we investigated whether the use of strains with an alpha-glucosidase attached to the outside of the cell might be a possible way to reduce residual maltotriose. To this end, the N-terminal leader sequence of Kre1 and the carboxy-terminal anchoring domain of either Cwp2 or Flo1 were used to target maltase encoded by MAL32 to the cell surface. We showed that Mal32 displayed on the cell surface of Saccharomyces cerevisiae laboratory strains was capable of hydrolysis of alpha-1,4-linkages, and that it increased the ability of a strain lacking a functional maltose permease to grow on maltotriose. Moreover, the enzyme was also expressed and found to be active in an industrial strain. These data show that expressing a suitable maltase on the cell surface might provide a means of modifying yeast for more complete maltotriose utilization in brewing and other fermentation applications.
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Affiliation(s)
- J Dietvorst
- Institute of Biology, Leiden University, Wassenaarseweg 64, 2333 AL Leiden, The Netherlands
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12
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Jansen MLA, Krook DJJ, De Graaf K, van Dijken JP, Pronk JT, de Winde JH. Physiological characterization and fed-batch production of an extracellular maltase of Schizosaccharomyces pombe CBS 356. FEMS Yeast Res 2006; 6:888-901. [PMID: 16911511 DOI: 10.1111/j.1567-1364.2006.00091.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
The fission yeast Schizosaccharomyces pombe CBS 356 exhibits extracellular maltase activity. This activity may be of commercial interest as it exhibited a low pH optimum (3.5) and a high affinity for maltose (Km of 7.0+/-1.8 mM). N-terminal sequencing of the protein indicates that it is the product of the AGL1 gene. Regulation of this gene occurs via a derepression/repression mechanism. In sugar- or nitrogen-limited chemostat cultures, the specific rate of enzyme production (q(p)) was independent of the nature of the carbon source (i.e. glucose or maltose), but synthesis was partially repressed by high sugar concentrations. Furthermore, q(p) increased linearly with specific growth rate (mu) between 0.04 and 0.10 h(-1). The enzyme is easily mass-produced in aerobic glucose-limited fed-batch cultures, in which the specific growth rate is controlled to prevent alcoholic fermentation. In fed-batch cultures in which biomass concentrations of 83 g L(-1) were attained, the enzyme concentration reached 58,000 Units per liter culture supernatant. Extracellular maltase may be used as a dough additive in order to prevent mechanisms such as maltose-induced glucose efflux and maltose-hypersensitivity that occur in maltose-consuming Saccharomyces cerevisiae.
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Affiliation(s)
- Mickel L A Jansen
- Kluyver Laboratory of Biotechnology, Delft University of Technology, Delft, The Netherlands
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13
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Yao S, Chi Z, He S. Studies on inositol-mediated expression of MAL gene encoding maltase and phospholipid biosynthesis in Schizosaccharomyces pombe. J Ind Microbiol Biotechnol 2006; 33:417-22. [PMID: 16496115 DOI: 10.1007/s10295-005-0069-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2005] [Accepted: 12/03/2005] [Indexed: 10/25/2022]
Abstract
In this study, the effects of inositol addition on expression of the MAL gene encoding maltase and phosphatidylinositol (PI) biosynthesis in Schizosaccharomyces pombe (a naturally inositol-requiring strain) were examined. We found that specific maltase activity was at its maximum when the concentration of added inositol reached 6 microg ml(-1) in a synthetic medium containing 2.0% (w/v) glucose. When the concentration of added inositol was 1 microg ml(-1) in the medium, repression of MAL gene expression occurred at glucose concentration higher than 0.2% (w/v). However, when S. pombe was cultured in the synthetic medium containing 6 microg ml(-1), repression of maltase gene expression occurred only at initial glucose concentration above 1.0% (w/v). More mRNA encoding maltase was detected in the cells grown in the medium with 6 microg ml(-1) inositol than in those grown in the same medium with 1 microg ml(-1) inositol. These results demonstrate that higher inositol concentrations in the synthetic medium could derepress MAL gene expression in S. pombe. PI content of the yeast cells grown in the synthetic medium with 6 microg ml(-1) of inositol was higher than that of the yeast cells grown in the same medium with 1 microg ml(-1) of inositol. This means that PI may be involved in the derepression of MAL gene expression in S. pombe.
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Affiliation(s)
- Shumin Yao
- College of Marine Life Science, Ocean University of China, 266003, Shandong, Qingdao, China
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14
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The effect of glucose and maltose concentrations on pyruvate and ascorbate production, antioxidant enzyme activities and LPO levels in Fusarium equiseti. Process Biochem 2004. [DOI: 10.1016/s0032-9592(03)00286-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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15
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Flores CL, Rodríguez C, Petit T, Gancedo C. Carbohydrate and energy-yielding metabolism in non-conventional yeasts. FEMS Microbiol Rev 2000; 24:507-29. [PMID: 10978549 DOI: 10.1111/j.1574-6976.2000.tb00553.x] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Sugars are excellent carbon sources for all yeasts. Since a vast amount of information is available on the components of the pathways of sugar utilization in Saccharomyces cerevisiae it has been tacitly assumed that other yeasts use sugars in the same way. However, although the pathways of sugar utilization follow the same theme in all yeasts, important biochemical and genetic variations on it exist. Basically, in most non-conventional yeasts, in contrast to S. cerevisiae, respiration in the presence of oxygen is prominent for the use of sugars. This review provides comparative information on the different steps of the fundamental pathways of sugar utilization in non-conventional yeasts: glycolysis, fermentation, tricarboxylic acid cycle, pentose phosphate pathway and respiration. We consider also gluconeogenesis and, briefly, catabolite repression. We have centered our attention in the genera Kluyveromyces, Candida, Pichia, Yarrowia and Schizosaccharomyces, although occasional reference to other genera is made. The review shows that basic knowledge is missing on many components of these pathways and also that studies on regulation of critical steps are scarce. Information on these points would be important to generate genetically engineered yeast strains for certain industrial uses.
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Affiliation(s)
- C L Flores
- Instituto de Investigaciones Biomédicas Alberto Sols C.S.I.C.-UAM, Unidad de Bioquímica y Genética de Levaduras, 28029, Madrid, Spain
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16
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Heiland S, Radovanovic N, Höfer M, Winderickx J, Lichtenberg H. Multiple hexose transporters of Schizosaccharomyces pombe. J Bacteriol 2000; 182:2153-62. [PMID: 10735857 PMCID: PMC111263 DOI: 10.1128/jb.182.8.2153-2162.2000] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We have identified a family of six hexose transporter genes (Ght1 to Ght6) in the fission yeast Schizosaccharomyces pombe. Sequence homology to Saccharomyces cerevisiae and mammalian hexose transporters (Hxtp and GLUTp, respectively) and secondary-structure predictions of 12 transmembrane domains for each of the Ght proteins place them into the sugar porter subfamily within the major facilitator superfamily. Interestingly, among this sugar porter family, the emerging S. pombe hexose transporter family clusters are separate from monosaccharide transporters of other yeasts (S. cerevisiae, Kluyveromyces lactis, and Candida albicans) and of humans, suggesting that these proteins form a distinct structural family of hexose transporters. Expression of the Ght1, Ght2, Ght5, and Ght6 genes in the S. cerevisiae mutant RE700A may functionally complement its D-glucose uptake-deficient phenotype. Northern blot analysis and reverse transcription-PCR showed that among all Ght's of S. pombe, Ght5 is the most prominently expressed hexose transporter. Ght1p, Ght2p, and Ght5p displayed significantly higher specificities for D-glucose than for D-fructose. Analysis of the previously described S. pombe D-glucose transport-deficient mutant YGS-5 revealed that this strain is defective in the Ght1, Ght5, and Ght6 genes. Based on an analysis of three S. pombe strains bearing single or double mutations in Ght3 and Ght4, we conclude that the Ght3p function is required for D-gluconate transport in S. pombe. The function of Ght4p remains to be clarified. Ght6p exhibited a slightly higher affinity to D-fructose than to D-glucose, and among the Ght's it is the transporter with the highest specificity for D-fructose.
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Affiliation(s)
- S Heiland
- Botanisches Institut, Universität Bonn, 53115 Bonn, Germany
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