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Liang J, Nie Y, Ren X, Li R, Xiong Z, Ai L, Tian Y. Gellan Gum Biosynthesis in Microorganisms: Current Status and Future Directions. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2025. [PMID: 40396223 DOI: 10.1021/acs.jafc.5c02818] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2025]
Abstract
Gellan gum is a widely used gel polysaccharide that is gaining market preference because of its unique gel characteristics. Although the biological synthesis of gellan gum dates back to the 1970s, research into its synthetic metabolic pathways has lagged behind that of other polysaccharides because of a lack of clarity. In recent years, driven by growing market demand and advancements in our understanding of metabolic pathways, as well as the rapid development of genetic engineering tools, the biological synthesis of gellan gum has progressed significantly. This article summarizes the developmental history of Sphingomonas paucimobilis ATCC 31461 and the structure of gellan gum, with a particular focus on the metabolic pathway involved in the production of gellan gum by these strains. This review discusses the metabolic engineering and research progress of key genes at different stages of the synthesis pathway. Additionally, this article introduces strategies for obtaining high-titer strains using traditional breeding methods and metabolic engineering approaches. Finally, it addresses the methods for producing low-molecular-weight-gellan gum. We discuss ongoing disputes in the field and highlight promising directions for future research. This review aims to address the bottlenecks in gellan gum production by promoting a greener and more sustainable manufacturing process.
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Affiliation(s)
- Jiayuan Liang
- School of Health Science and Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China
| | - Yupeng Nie
- School of Health Science and Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China
| | - Xuebing Ren
- School of Health Science and Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China
| | - Ruiguo Li
- Shandong Food Ferment Industry Research & Design Institute, Qilu University of Technology, Jinan 250013, China
| | - Zhiqiang Xiong
- School of Health Science and Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China
| | - Lianzhong Ai
- School of Health Science and Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China
| | - Yanjun Tian
- School of Health Science and Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China
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Synthesis of the Microbial Polysaccharide Gellan from Dairy and Plant-Based Processing Coproducts. POLYSACCHARIDES 2021. [DOI: 10.3390/polysaccharides2020016] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
This review examines the production of the microbial polysaccharide gellan, synthesized by Sphingomonas elodea, on dairy and plant-based processing coproducts. Gellan is a water-soluble gum that structurally exists as a tetrasaccharide comprised of 20% glucuronic acid, 60% glucose and 20% rhamnose, for which various food, non-food and biomedical applications have been reported. A number of carbon and nitrogen sources have been tested to determine whether they can support bacterial gellan production, with several studies attempting to optimize gellan production by varying the culture conditions. The genetics of the biosynthesis of gellan has been explored in a number of investigations and specific genes have been identified that encode the enzymes responsible for the synthesis of this polysaccharide. Genetic mutants exhibiting overproduction of gellan have also been identified and characterized. Several dairy and plant-based processing coproducts have been screened to learn whether they can support the production of gellan in an attempt to lower the cost of synthesizing the microbial polysaccharide. Of the processing coproducts explored, soluble starch as a carbon source supported the highest gellan production by S. elodea grown at 30 °C. The corn processing coproducts corn steep liquor or condensed distillers solubles appear to be effective nitrogen sources for gellan production. It was concluded that further research on producing gellan using a combination of processing coproducts could be an effective solution in lowering its overall production costs.
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Kumpf A, Partzsch A, Pollender A, Bento I, Tischler D. Two Homologous Enzymes of the GalU Family in Rhodococcus opacus 1CP- RoGalU1 and RoGalU2. Int J Mol Sci 2019; 20:ijms20225809. [PMID: 31752319 PMCID: PMC6888414 DOI: 10.3390/ijms20225809] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Revised: 11/15/2019] [Accepted: 11/16/2019] [Indexed: 01/15/2023] Open
Abstract
Uridine-5’-diphosphate (UDP)-glucose is reported as one of the most versatile building blocks within the metabolism of pro- and eukaryotes. The activated sugar moiety is formed by the enzyme UDP-glucose pyrophosphorylase (GalU). Two homologous enzymes (designated as RoGalU1 and RoGalU2) are encoded by most Rhodococcus strains, known for their capability to degrade numerous compounds, but also to synthesize natural products such as trehalose comprising biosurfactants. To evaluate their functionality respective genes of a trehalose biosurfactant producing model organism—Rhodococcus opacus 1CP—were cloned and expressed, proteins produced (yield up to 47 mg per L broth) and initially biochemically characterized. In the case of RoGalU2, the Vmax was determined to be 177 U mg−1 (uridine-5’-triphosphate (UTP)) and Km to be 0.51 mM (UTP), respectively. Like other GalUs this enzyme seems to be rather specific for the substrates UTP and glucose 1-phosphate, as it accepts only dTTP and galactose 1-phoshate in addition, but both with solely 2% residual activity. In comparison to other bacterial GalU enzymes the RoGalU2 was found to be somewhat higher in activity (factor 1.8) even at elevated temperatures. However, RoGalU1 was not obtained in an active form thus it remains enigmatic if this enzyme participates in metabolism.
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Affiliation(s)
- Antje Kumpf
- Environmental Microbiology, Institute of Biosciences, TU Bergakademie Freiberg, Leipziger Str. 29, 09599 Freiberg, Germany; (A.P.); (A.P.)
- EMBL Hamburg, Notkestr. 85, 22607 Hamburg, Germany;
- Microbial Biotechnology, Faculty of Biology & Biotechnology, Ruhr University Bochum, Universitätsstr. 150, 44780 Bochum, Germany
- Correspondence: (A.K.); (D.T.); Tel.: +49-234-32-22082 (A.K.); +49-234-32-22656 (D.T.)
| | - Anett Partzsch
- Environmental Microbiology, Institute of Biosciences, TU Bergakademie Freiberg, Leipziger Str. 29, 09599 Freiberg, Germany; (A.P.); (A.P.)
| | - André Pollender
- Environmental Microbiology, Institute of Biosciences, TU Bergakademie Freiberg, Leipziger Str. 29, 09599 Freiberg, Germany; (A.P.); (A.P.)
| | - Isabel Bento
- EMBL Hamburg, Notkestr. 85, 22607 Hamburg, Germany;
| | - Dirk Tischler
- Microbial Biotechnology, Faculty of Biology & Biotechnology, Ruhr University Bochum, Universitätsstr. 150, 44780 Bochum, Germany
- Correspondence: (A.K.); (D.T.); Tel.: +49-234-32-22082 (A.K.); +49-234-32-22656 (D.T.)
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Li H, Li J, Jiao X, Li K, Sun Y, Zhou W, Shen Y, Qian J, Chang A, Wang J, Zhu H. Characterization of the biosynthetic pathway of nucleotide sugar precursor UDP-glucose during sphingan WL gum production in Sphingomonas sp. WG. J Biotechnol 2019; 302:1-9. [PMID: 31199955 DOI: 10.1016/j.jbiotec.2019.06.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Revised: 04/24/2019] [Accepted: 06/10/2019] [Indexed: 10/26/2022]
Abstract
To elucidate the possible biosynthetic pathway of a precursor UDP-glucose of the sphingan WL gum produced by Sphingomonas sp. WG, two enzymes phosphoglucomutase (PGM) and UDP-glucose pyrophosphorylase (UGPase) were bioinformatically analysed, expressed in Escherichia coli BL21 (DE3) and characterized. PGM was in the phosphoglucomutase/phosphomannomutase subclass and UGPase was predicted to be a UDP-glucose pyrophosphatase in a tetrameric structure. Both enzymes were expressed in soluble form, purified to near homogeneity with high activity at 1159 and 796 U/mg, exhibited folding with reasonable secondary structures, and existed as monomer and tetramer, respectively. The optimal pH and temperature of PGM were 9.0 and 50 °C, respectively, and this protein was stable at pH 8.0 and at temperatures ranging from 40 to 50 °C. The optimal pH and temperature of UGPase were 9.0 and 45 °C, respectively, and the protein was stable at pH 8.0 and at temperatures ranging from 30 to 55 °C. A small-scale one-pot biosynthesis of UDP-glucose by combining PGM and UGPase using glucose-6-phosphate and UTP as substrates was also performed, and formation of UDP-glucose was observed by HPLC detection, which confirmed the biosynthetic pathway of UDP-glucose in vitro. PGM and UGPase will be ideal targets for the metabolic engineering to improve WL gum yields in industrial production.
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Affiliation(s)
- Hui Li
- State Key Laboratory of Heavy Oil Processing and Centre for Bioengineering and Biotechnology, China University of Petroleum (East China), 66 Changjiang West Road, Qingdao 266580, People's Republic of China
| | - Jing Li
- State Key Laboratory of Heavy Oil Processing and Centre for Bioengineering and Biotechnology, China University of Petroleum (East China), 66 Changjiang West Road, Qingdao 266580, People's Republic of China
| | - Xue Jiao
- State Key Laboratory of Heavy Oil Processing and Centre for Bioengineering and Biotechnology, China University of Petroleum (East China), 66 Changjiang West Road, Qingdao 266580, People's Republic of China
| | - Kehui Li
- State Key Laboratory of Heavy Oil Processing and Centre for Bioengineering and Biotechnology, China University of Petroleum (East China), 66 Changjiang West Road, Qingdao 266580, People's Republic of China
| | - Yajie Sun
- State Key Laboratory of Heavy Oil Processing and Centre for Bioengineering and Biotechnology, China University of Petroleum (East China), 66 Changjiang West Road, Qingdao 266580, People's Republic of China
| | - Wanlong Zhou
- State Key Laboratory of Heavy Oil Processing and Centre for Bioengineering and Biotechnology, China University of Petroleum (East China), 66 Changjiang West Road, Qingdao 266580, People's Republic of China
| | - Yaling Shen
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, People's Republic of China
| | - Jin Qian
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, People's Republic of China
| | - Aiping Chang
- College of Chemistry and Materials Science, Fujian Normal University, 32 Shangsan Road, Fuzhou 350007, People's Republic of China
| | - Jiqian Wang
- State Key Laboratory of Heavy Oil Processing and Centre for Bioengineering and Biotechnology, China University of Petroleum (East China), 66 Changjiang West Road, Qingdao 266580, People's Republic of China.
| | - Hu Zhu
- State Key Laboratory of Heavy Oil Processing and Centre for Bioengineering and Biotechnology, China University of Petroleum (East China), 66 Changjiang West Road, Qingdao 266580, People's Republic of China; College of Chemistry and Materials Science, Fujian Normal University, 32 Shangsan Road, Fuzhou 350007, People's Republic of China.
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The evolutionary life cycle of the polysaccharide biosynthetic gene cluster based on the Sphingomonadaceae. Sci Rep 2017; 7:46484. [PMID: 28429731 PMCID: PMC5399355 DOI: 10.1038/srep46484] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Accepted: 03/21/2017] [Indexed: 11/08/2022] Open
Abstract
Although clustering of genes from the same metabolic pathway is a widespread phenomenon, the evolution of the polysaccharide biosynthetic gene cluster remains poorly understood. To determine the evolution of this pathway, we identified a scattered production pathway of the polysaccharide sanxan by Sphingomonas sanxanigenens NX02, and compared the distribution of genes between sphingan-producing and other Sphingomonadaceae strains. This allowed us to determine how the scattered sanxan pathway developed, and how the polysaccharide gene cluster evolved. Our findings suggested that the evolution of microbial polysaccharide biosynthesis gene clusters is a lengthy cyclic process comprising cluster 1 → scatter → cluster 2. The sanxan biosynthetic pathway proved the existence of a dispersive process. We also report the complete genome sequence of NX02, in which we identified many unstable genetic elements and powerful secretion systems. Furthermore, nine enzymes for the formation of activated precursors, four glycosyltransferases, four acyltransferases, and four polymerization and export proteins were identified. These genes were scattered in the NX02 genome, and the positive regulator SpnA of sphingans synthesis could not regulate sanxan production. Finally, we concluded that the evolution of the sanxan pathway was independent. NX02 evolved naturally as a polysaccharide producing strain over a long-time evolution involving gene acquisitions and adaptive mutations.
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Wang H, Zhang C, Yang Q, Feng J, Chen H, Gu Z, Zhang H, Chen W, Chen YQ. Production of GDP- l-fucose from exogenous fucose through the salvage pathway in Mortierella alpina. RSC Adv 2016. [DOI: 10.1039/c6ra06031e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
This study is the first to report a comprehensive characterization of GDP-l-fucose pyrophosphorylase (GFPP) in a fungus.
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Affiliation(s)
- Hongchao Wang
- State Key Laboratory of Food Science and Technology
- School of Food Science and Technology
- Jiangnan University
- Wuxi
- P. R. China
| | - Chen Zhang
- State Key Laboratory of Food Science and Technology
- School of Food Science and Technology
- Jiangnan University
- Wuxi
- P. R. China
| | - Qin Yang
- State Key Laboratory of Food Science and Technology
- School of Food Science and Technology
- Jiangnan University
- Wuxi
- P. R. China
| | - Jinghan Feng
- State Key Laboratory of Food Science and Technology
- School of Food Science and Technology
- Jiangnan University
- Wuxi
- P. R. China
| | - Haiqin Chen
- State Key Laboratory of Food Science and Technology
- School of Food Science and Technology
- Jiangnan University
- Wuxi
- P. R. China
| | - Zhennan Gu
- State Key Laboratory of Food Science and Technology
- School of Food Science and Technology
- Jiangnan University
- Wuxi
- P. R. China
| | - Hao Zhang
- State Key Laboratory of Food Science and Technology
- School of Food Science and Technology
- Jiangnan University
- Wuxi
- P. R. China
| | - Wei Chen
- State Key Laboratory of Food Science and Technology
- School of Food Science and Technology
- Jiangnan University
- Wuxi
- P. R. China
| | - Yong Q. Chen
- State Key Laboratory of Food Science and Technology
- School of Food Science and Technology
- Jiangnan University
- Wuxi
- P. R. China
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7
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A comparison of genes involved in sphingan biosynthesis brought up to date. Appl Microbiol Biotechnol 2014; 98:7719-33. [DOI: 10.1007/s00253-014-5940-z] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2014] [Revised: 07/02/2014] [Accepted: 07/03/2014] [Indexed: 10/25/2022]
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A Chimeric UDP-glucose pyrophosphorylase produced by protein engineering exhibits sensitivity to allosteric regulators. Int J Mol Sci 2013; 14:9703-21. [PMID: 23648478 PMCID: PMC3676807 DOI: 10.3390/ijms14059703] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Revised: 04/10/2013] [Accepted: 04/18/2013] [Indexed: 11/17/2022] Open
Abstract
In bacteria, glycogen or oligosaccharide accumulation involves glucose-1-phosphate partitioning into either ADP-glucose (ADP-Glc) or UDP-Glc. Their respective synthesis is catalyzed by allosterically regulated ADP-Glc pyrophosphorylase (EC 2.7.7.27, ADP-Glc PPase) or unregulated UDP-Glc PPase (EC 2.7.7.9). In this work, we characterized the UDP-Glc PPase from Streptococcus mutans. In addition, we constructed a chimeric protein by cutting the C-terminal domain of the ADP-Glc PPase from Escherichia coli and pasting it to the entire S. mutans UDP-Glc PPase. Both proteins were fully active as UDP-Glc PPases and their kinetic parameters were measured. The chimeric enzyme had a slightly higher affinity for substrates than the native S. mutans UDP-Glc PPase, but the maximal activity was four times lower. Interestingly, the chimeric protein was sensitive to regulation by pyruvate, 3-phosphoglyceric acid and fructose-1,6-bis-phosphate, which are known to be effectors of ADP-Glc PPases from different sources. The three compounds activated the chimeric enzyme up to three-fold, and increased the affinity for substrates. This chimeric protein is the first reported UDP-Glc PPase with allosteric regulatory properties. In addition, this is a pioneer work dealing with a chimeric enzyme constructed as a hybrid of two pyrophosphorylases with different specificity toward nucleoside-diphospho-glucose and our results turn to be relevant for a deeper understanding of the evolution of allosterism in this family of enzymes.
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Genome sequence of Sphingomonas elodea ATCC 31461, a highly productive industrial strain of gellan gum. J Bacteriol 2012; 193:7015-6. [PMID: 22123766 DOI: 10.1128/jb.06307-11] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The commercial gelling agent gellan gum is a heteropolysaccharide produced by Sphingomonas elodea ATCC 31461. However, the genes involved in the biosynthesis, regulation, and modification of gellan gum have not been fully characterized. Here we describe the draft genome sequence of stain ATCC 31461 and major findings from its annotation.
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10
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Expression, purification, and characterization of a functionally active Mycobacterium tuberculosis UDP-glucose pyrophosphorylase. Protein Expr Purif 2008; 61:50-6. [DOI: 10.1016/j.pep.2008.05.015] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2008] [Revised: 05/16/2008] [Accepted: 05/27/2008] [Indexed: 11/18/2022]
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11
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Occurrence, production, and applications of gellan: current state and perspectives. Appl Microbiol Biotechnol 2008; 79:889-900. [DOI: 10.1007/s00253-008-1496-0] [Citation(s) in RCA: 160] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2008] [Revised: 04/03/2008] [Accepted: 04/05/2008] [Indexed: 10/22/2022]
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Granja AT, Popescu A, Marques AR, Sá-Correia I, Fialho AM. Biochemical characterization and phylogenetic analysis of UDP-glucose dehydrogenase from the gellan gum producer Sphingomonas elodea ATCC 31461. Appl Microbiol Biotechnol 2007; 76:1319-27. [PMID: 17668199 DOI: 10.1007/s00253-007-1112-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2007] [Revised: 07/03/2007] [Accepted: 07/04/2007] [Indexed: 10/23/2022]
Abstract
Sphingomonas elodea ATCC 31461 synthesizes in high yield the exopolysaccharide gellan, which is a water-soluble gelling agent with many applications. In this study, we describe the cloning and sequence analysis of the ugdG gene, encoding a UDP-glucose dehydrogenase (47.2 kDa; UDPG-DH; EC 1.1.1.22), required for the synthesis of the gellan gum precursor UDP-glucuronic acid. UgdG protein shows homology to members of the UDP-glucose/GDP-mannose dehydrogenase superfamily. The Neighbor-Joining method was used to determine phylogenetic relationships among prokaryotic and eukaryotic UDPG-DHs. UgdG from S. elodea and UDPG-DHs from Novosphingobium, Zymomonas, Agrobacterium, and Caulobacter species form a divergent phylogenetic group with a close evolutionary relationship with eukaryotic UDPG-DHs. The ugdG gene was recombinantly expressed in Escherichia coli with and N-terminal 6-His tag and purified for biochemical characterization. The enzyme has an optimum temperature and pH of 37 degrees C and 8.7, respectively. The estimated apparent K(m) values for UDP-glucose and NAD(+) were 0.87 and 0.4 mM, respectively. DNA sequencing of chromosomal regions adjacent to ugdG gene and sequence similarity studies suggests that this gene maps together with others presumably involved in the biosynthesis of S. elodea cell wall polysaccharides.
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Affiliation(s)
- Ana Teresa Granja
- IBB - Institute for Biotechnology and Bioengineering, Centre for Biological and Chemical Engineering, Instituto Superior Técnico, Av. Rovisco Pais, 1049-001 Lisbon, Portugal
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Aragão D, Fialho AM, Marques AR, Mitchell EP, Sá-Correia I, Frazão C. The complex of Sphingomonas elodea ATCC 31461 glucose-1-phosphate uridylyltransferase with glucose-1-phosphate reveals a novel quaternary structure, unique among nucleoside diphosphate-sugar pyrophosphorylase members. J Bacteriol 2007; 189:4520-8. [PMID: 17434970 PMCID: PMC1913352 DOI: 10.1128/jb.00277-07] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2007] [Accepted: 03/02/2007] [Indexed: 11/20/2022] Open
Abstract
Gellan gum is a widely used commercial material, available in many different forms. Its economic importance has led to studies into the biosynthesis of exopolysaccharide gellan gum, which is industrially prepared in high yields using Sphingomonas elodea ATCC 31461. Glucose-1-phosphate uridylyltransferase mediates the reversible conversion of glucose-1-phosphate and UTP into UDP-glucose and pyrophosphate, which is a key step in the biosynthetic pathway of gellan gums. Here we present the X-ray crystal structure of the glucose-1-phosphate uridylyltransferase from S. elodea. The S. elodea enzyme shares strong monomeric similarity with glucose-1-phosphate thymidylyltransferase, several structures of which are known, although the quaternary structures of the active enzymes are rather different. A detailed comparison between S. elodea glucose-1-phosphate uridylyltransferase and available thymidylyltransferases is described and shows remarkable structural similarities, despite the low sequence identities between the two divergent groups of proteins.
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Affiliation(s)
- David Aragão
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Apartado 127, 2781-901 Oeiras, Portugal
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14
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Silva E, Marques AR, Fialho AM, Granja AT, Sá-Correia I. Proteins encoded by Sphingomonas elodea ATCC 31461 rmlA and ugpG genes, involved in gellan gum biosynthesis, exhibit both dTDP- and UDP-glucose pyrophosphorylase activities. Appl Environ Microbiol 2005; 71:4703-12. [PMID: 16085866 PMCID: PMC1183319 DOI: 10.1128/aem.71.8.4703-4712.2005] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The commercial gelling agent gellan is a heteropolysaccharide produced by Sphingomonas elodea ATCC 31461. In this work, we carried out the biochemical characterization of the enzyme encoded by the first gene (rmlA) of the rml 4-gene cluster present in the 18-gene cluster required for gellan biosynthesis (gel cluster). Based on sequence homology, the putative rml operon is presumably involved in the biosynthesis of dTDP-rhamnose, the sugar necessary for the incorporation of rhamnose in the gellan repeating unit. Heterologous RmlA was purified as a fused His6-RmlA protein from extracts prepared from Escherichia coli IPTG (isopropyl-beta-D-thiogalactopyranoside)-induced cells, and the protein was proven to exhibit dTDP-glucose pyrophosphorylase (Km of 12.0 microM for dTDP-glucose) and UDP-glucose pyrophosphorylase (Km of 229.0 microM for UDP-glucose) activities in vitro. The N-terminal region of RmlA exhibits the motif G-X-G-T-R-X2-P-X-T, which is highly conserved among bacterial XDP-sugar pyrophosphorylases. The motif E-E-K-P, with the conserved lysine residue (K163) predicted to be essential for glucose-1-phosphate binding, was observed. The S. elodea ATCC 31461 UgpG protein, encoded by the ugpG gene which maps outside the gel cluster, was previously identified as the UDP-glucose pyrophosphorylase involved in the formation of UDP-glucose, also required for gellan synthesis. In this study, we demonstrate that UgpG also exhibits dTDP-glucose pyrophosphorylase activity in vitro and compare the kinetic parameters of the two proteins for both substrates. DNA sequencing of ugpG gene-adjacent regions and sequence similarity studies suggest that this gene maps with others involved in the formation of sugar nucleotides presumably required for the biosynthesis of another cell polysaccharide(s).
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Affiliation(s)
- Elisabete Silva
- Biological Sciences Research Group, Centre for Biological and Chemical Engineering, Instituto Superior Técnico, Av. Rovisco Pais, 1049-001 Lisbon, Portugal
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15
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Bonofiglio L, García E, Mollerach M. Biochemical characterization of the pneumococcal glucose 1-phosphate uridylyltransferase (GalU) essential for capsule biosynthesis. Curr Microbiol 2005; 51:217-21. [PMID: 16132460 DOI: 10.1007/s00284-005-4466-0] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2004] [Accepted: 02/16/2005] [Indexed: 11/29/2022]
Abstract
The glucose 1-phosphate uridylyltransferase (GalU) is absolutely required for the biosynthesis of capsular polysaccharide, the sine qua non virulence factor of Streptococcus pneumoniae. The pneumococcal GalU protein was overexpressed in Escherichia coli, and purified. GalU showed a pI of 4.23, and catalyzed the reversible formation of UDP-glucose and pyrophosphate from UTP and glucose 1-phosphate with K(m) values of 0.4 mM: for UDP-glucose, 0.26 mM: for pyrophosphate, 0.19 mM: for glucose 1-phosphate, and 0.24 mM: for UTP. GalU has an optimum pH of 8-8.5, and requires Mg(2+) for activity. Neither ADP-glucose nor TDP-glucose is utilized as substrates in vitro. The purification of GalU represents a fundamental step to provide insights on drug design to control the biosynthesis of the main pneumococcal virulence factor.
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Affiliation(s)
- Laura Bonofiglio
- Cátedra de Microbiología, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Argentina
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16
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Moreira LM, Hoffmann K, Albano H, Becker A, Niehaus K, Sá-Correia I. The Gellan Gum Biosynthetic Genes gelC and gelE Encode Two Separate Polypeptides Homologous to the Activator and the Kinase Domains of Tyrosine Autokinases. J Mol Microbiol Biotechnol 2005; 8:43-57. [PMID: 15741740 DOI: 10.1159/000082080] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The high-molecular-weight exopolysaccharide gellan is an important commercial gelling agent produced in high yield by the Gram-negative bacterium Sphingomonas elodea ATCC 31461. The cluster of genes required for gellan biosynthesis contains the genes gelC and gelE. These encode for two polypeptides homologous to the activator domain and the kinase domain, respectively, of bacterial autophosphorylating tyrosine kinases involved in polysaccharide chain length determination. The GelC/GelE pair is an exception to the biochemically characterized Gram-negative tyrosine autokinases since it consists of two polypeptides instead of a single one. The deletion of gelC or gelE resulted in the abolishment of gellan in the culture medium confirming their role in gellan biosynthesis. In addition, ATP-binding assays confirmed the predicted ATP-binding ability of GelE. Interestingly, GelE contains an unusual Walker A sequence (ASTGVGCS), where the invariant lysine is replaced by a cysteine. This residue was replaced by alanine or lysine and although both mutant proteins were able to restore gellan production by complementation of the gelE deletion mutant to the production level observed with native GelE, only the mutated GelE where the cysteine was replaced by alanine was demonstrated to bind ATP in vitro. The importance of specific tyrosine residues present in the C-terminal domain of GelE in gellan assembly was also determined. The tyrosine residue at position 198 appears to be essential for the synthesis of high-molecular-weight gellan, although other tyrosine residues may additionally contribute to GelE biological function.
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Affiliation(s)
- Leonilde M Moreira
- Centro de Engenharia Biológica e Química, Instituto Superior Técnico, PT-1049-001 Lisboa, Portugal.
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Moreira LM, Videira PA, Sousa SA, Leitão JH, Cunha MV, Sá-Correia I. Identification and physical organization of the gene cluster involved in the biosynthesis of Burkholderia cepacia complex exopolysaccharide. Biochem Biophys Res Commun 2004; 312:323-33. [PMID: 14637140 DOI: 10.1016/j.bbrc.2003.10.118] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Bacteria belonging to the Burkholderia cepacia complex (BCC) are important opportunistic pathogens in patients with cystic fibrosis (CF). Since approximately 80% of the CF isolates examined produce exopolysaccharide (EPS), it was hypothesized that this EPS may play a role in the colonization and persistence of these bacteria in the CF lung. The present study describes the identification and physical organization of the EPS biosynthetic gene cluster. This bce gene cluster was identified following the isolation of three EPS-defective mutants from the highly mucoid CF isolate IST408, belonging to BCC genomovar I, based on random plasposon insertion mutagenesis and comparison of the nucleotide sequence of the interrupted genes with the available genome of Burkholderia cenocepacia J2315. This 16.2 kb cluster includes 12 genes and is located on chromosome 2. Database searches for homologous proteins and secondary structure analysis for the deduced Bce amino acid sequences revealed genes predicted to encode enzymes required for the formation of nucleotide sugar precursors, glycosyltransferases involved in the repeat-unit assembly, and other proteins involved in polymerization and export of bacterial surface polysaccharides.
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Affiliation(s)
- Leonilde M Moreira
- Biological Sciences Research Group, Centro de Engenharia Biológica e Química, Instituto Superior Técnico, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
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