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Mannuronate C-5 epimerases and their use in alginate modification. Essays Biochem 2023; 67:615-627. [PMID: 36876890 DOI: 10.1042/ebc20220151] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Revised: 02/01/2023] [Accepted: 02/02/2023] [Indexed: 03/07/2023]
Abstract
Alginate is a polysaccharide consisting of β-D-mannuronate (M) and α-L-guluronate (G) produced by brown algae and some bacterial species. Alginate has a wide range of industrial and pharmaceutical applications, owing mainly to its gelling and viscosifying properties. Alginates with high G content are considered more valuable since the G residues can form hydrogels with divalent cations. Alginates are modified by lyases, acetylases, and epimerases. Alginate lyases are produced by alginate-producing organisms and by organisms that use alginate as a carbon source. Acetylation protects alginate from lyases and epimerases. Following biosynthesis, alginate C-5 epimerases convert M to G residues at the polymer level. Alginate epimerases have been found in brown algae and alginate-producing bacteria, predominantly Azotobacter and Pseudomonas species. The best characterised epimerases are the extracellular family of AlgE1-7 from Azotobacter vinelandii (Av). AlgE1-7 all consist of combinations of one or two catalytic A-modules and one to seven regulatory R-modules, but even though they are sequentially and structurally similar, they create different epimerisation patterns. This makes the AlgE enzymes promising for tailoring of alginates to have the desired properties. The present review describes the current state of knowledge regarding alginate-active enzymes with focus on epimerases, characterisation of the epimerase reaction, and how alginate epimerases can be used in alginate production.
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2
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Gawin A, Tietze L, Aarstad OA, Aachmann FL, Brautaset T, Ertesvåg H. Functional characterization of three Azotobacter chroococcum alginate-modifying enzymes related to the Azotobacter vinelandii AlgE mannuronan C-5-epimerase family. Sci Rep 2020; 10:12470. [PMID: 32719381 PMCID: PMC7385640 DOI: 10.1038/s41598-020-68789-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Accepted: 07/01/2020] [Indexed: 12/19/2022] Open
Abstract
Bacterial alginate initially consists of 1–4-linked β-D-mannuronic acid residues (M) which can be later epimerized to α-L-guluronic acid (G). The family of AlgE mannuronan C-5-epimerases from Azotobacter vinelandii has been extensively studied, and three genes putatively encoding AlgE-type epimerases have recently been identified in the genome of Azotobacter chroococcum. The three A. chroococcum genes, here designated AcalgE1, AcalgE2 and AcalgE3, were recombinantly expressed in Escherichia coli and the gene products were partially purified. The catalytic activities of the enzymes were stimulated by the addition of calcium ions in vitro. AcAlgE1 displayed epimerase activity and was able to introduce long G-blocks in the alginate substrate, preferentially by attacking M residues next to pre-existing G residues. AcAlgE2 and AcAlgE3 were found to display lyase activities with a substrate preference toward M-alginate. AcAlgE2 solely accepted M residues in the positions − 1 and + 2 relative to the cleavage site, while AcAlgE3 could accept either M or G residues in these two positions. Both AcAlgE2 and AcAlgE3 were bifunctional and could also catalyze epimerization of M to G. Together, we demonstrate that A. chroococcum encodes three different AlgE-like alginate-modifying enzymes and the biotechnological and biological impact of these findings are discussed.
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Affiliation(s)
- Agnieszka Gawin
- Department of Biotechnology and Food Science, NTNU Norwegian University of Science and Technology, Sem Sælandsvei 6/8, 7491, Trondheim, Norway
| | - Lisa Tietze
- Department of Biotechnology and Food Science, NTNU Norwegian University of Science and Technology, Sem Sælandsvei 6/8, 7491, Trondheim, Norway
| | - Olav A Aarstad
- Department of Biotechnology and Food Science, NTNU Norwegian University of Science and Technology, Sem Sælandsvei 6/8, 7491, Trondheim, Norway
| | - Finn L Aachmann
- Department of Biotechnology and Food Science, NTNU Norwegian University of Science and Technology, Sem Sælandsvei 6/8, 7491, Trondheim, Norway
| | - Trygve Brautaset
- Department of Biotechnology and Food Science, NTNU Norwegian University of Science and Technology, Sem Sælandsvei 6/8, 7491, Trondheim, Norway
| | - Helga Ertesvåg
- Department of Biotechnology and Food Science, NTNU Norwegian University of Science and Technology, Sem Sælandsvei 6/8, 7491, Trondheim, Norway.
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3
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Stanisci A, Tøndervik A, Gaardløs M, Lervik A, Skjåk-Bræk G, Sletta H, Aachmann FL. Identification of a Pivotal Residue for Determining the Block Structure-Forming Properties of Alginate C-5 Epimerases. ACS OMEGA 2020; 5:4352-4361. [PMID: 32149266 PMCID: PMC7057702 DOI: 10.1021/acsomega.9b04490] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Accepted: 02/11/2020] [Indexed: 05/13/2023]
Abstract
Alginate is a linear copolymer composed of 1→4 linked β-d-mannuronic acid (M) and its epimer α-l-guluronic acid (G). The polysaccharide is first produced as homopolymeric mannuronan and subsequently, at the polymer level, C-5 epimerases convert M residues to G residues. The bacterium Azotobacter vinelandii encodes a family of seven secreted and calcium ion-dependent mannuronan C-5 epimerases (AlgE1-AlgE7). These epimerases consist of two types of structural modules: the A-modules, which contain the catalytic site, and the R-modules, which influence activity through substrate and calcium binding. In this study, we rationally designed new hybrid mannuronan C-5 epimerases constituting the A-module from AlgE6 and the R-module from AlgE4. This led to a better understanding of the molecular mechanism determining differences in MG- and GG-block-forming properties of the enzymes. A long loop with either tyrosine or phenylalanine extruding from the β-helix of the enzyme proved essential in defining the final alginate block structure, probably by affecting substrate binding. Normal mode analysis of the A-module from AlgE6 supports the results.
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Affiliation(s)
- Annalucia Stanisci
- Department
of Biotechnology and Food Science, NTNU
Norwegian University of Science and Technology, Norwegian Biopolymer
Laboratory (NOBIPOL), Sem Sælands vei 6/8, NO 7491 Trondheim, Norway
| | - Anne Tøndervik
- Department
of Biotechnology and Nanomedicine, SINTEF
Industry, Richard Birkelands
veg 3 B, NO 7491 Trondheim, Norway
| | - Margrethe Gaardløs
- Department
of Biotechnology and Food Science, NTNU
Norwegian University of Science and Technology, Norwegian Biopolymer
Laboratory (NOBIPOL), Sem Sælands vei 6/8, NO 7491 Trondheim, Norway
| | - Anders Lervik
- Department
of Chemistry, NTNU Norwegian University
of Science and Technology, Høgskoleringen 5, NO 7491 Trondheim, Norway
| | - Gudmund Skjåk-Bræk
- Department
of Biotechnology and Food Science, NTNU
Norwegian University of Science and Technology, Norwegian Biopolymer
Laboratory (NOBIPOL), Sem Sælands vei 6/8, NO 7491 Trondheim, Norway
| | - Håvard Sletta
- Department
of Biotechnology and Nanomedicine, SINTEF
Industry, Richard Birkelands
veg 3 B, NO 7491 Trondheim, Norway
| | - Finn L. Aachmann
- Department
of Biotechnology and Food Science, NTNU
Norwegian University of Science and Technology, Norwegian Biopolymer
Laboratory (NOBIPOL), Sem Sælands vei 6/8, NO 7491 Trondheim, Norway
- E-mail: . Phone: +4773593317. Fax: +4773591283
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4
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Alginate esters via chemoselective carboxyl group modification. Carbohydr Polym 2013; 98:1288-96. [DOI: 10.1016/j.carbpol.2013.08.014] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2013] [Revised: 07/29/2013] [Accepted: 08/05/2013] [Indexed: 11/23/2022]
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Tøndervik A, Klinkenberg G, Aachmann FL, Svanem BIG, Ertesvåg H, Ellingsen TE, Valla S, Skjåk-Bræk G, Sletta H. Mannuronan C-5 Epimerases Suited for Tailoring of Specific Alginate Structures Obtained by High-Throughput Screening of an Epimerase Mutant Library. Biomacromolecules 2013; 14:2657-66. [DOI: 10.1021/bm4005194] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Anne Tøndervik
- Department of Biotechnology, SINTEF Materials and Chemistry, N-7465 Trondheim, Norway
| | - Geir Klinkenberg
- Department of Biotechnology, SINTEF Materials and Chemistry, N-7465 Trondheim, Norway
| | - Finn L. Aachmann
- Department of Biotechnology, Norwegian University of Science and Technology, N-7491
Trondheim, Norway
| | - Britt Iren Glærum Svanem
- Department of Biotechnology, Norwegian University of Science and Technology, N-7491
Trondheim, Norway
| | - Helga Ertesvåg
- Department of Biotechnology, Norwegian University of Science and Technology, N-7491
Trondheim, Norway
| | - Trond E. Ellingsen
- Department of Biotechnology, SINTEF Materials and Chemistry, N-7465 Trondheim, Norway
| | - Svein Valla
- Department of Biotechnology, Norwegian University of Science and Technology, N-7491
Trondheim, Norway
| | - Gudmund Skjåk-Bræk
- Department of Biotechnology, Norwegian University of Science and Technology, N-7491
Trondheim, Norway
| | - Håvard Sletta
- Department of Biotechnology, SINTEF Materials and Chemistry, N-7465 Trondheim, Norway
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6
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Goh CH, Heng PWS, Chan LW. Alginates as a useful natural polymer for microencapsulation and therapeutic applications. Carbohydr Polym 2012. [DOI: 10.1016/j.carbpol.2011.11.012] [Citation(s) in RCA: 259] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
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Aarstad OA, Tøndervik A, Sletta H, Skjåk-Bræk G. Alginate Sequencing: An Analysis of Block Distribution in Alginates Using Specific Alginate Degrading Enzymes. Biomacromolecules 2011; 13:106-16. [DOI: 10.1021/bm2013026] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Olav Andreas Aarstad
- Department of Biotechnology, Norwegian University of Science and Technology, NTNU
Sem Sælands vei 6-8, N-7491 Trondheim, Norway
| | - Anne Tøndervik
- Department of Biotechnology, SINTEF Materials and Chemistry, N-7465 Trondheim, Norway
| | - Håvard Sletta
- Department of Biotechnology, SINTEF Materials and Chemistry, N-7465 Trondheim, Norway
| | - Gudmund Skjåk-Bræk
- Department of Biotechnology, Norwegian University of Science and Technology, NTNU
Sem Sælands vei 6-8, N-7491 Trondheim, Norway
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8
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Andreassen T, Buchinger E, Skjåk-Bræk G, Valla S, Aachmann FL. 1H, 13C and 15N resonances of the AlgE62 subunit from Azotobacter vinelandii mannuronan C5-epimerase. BIOMOLECULAR NMR ASSIGNMENTS 2011; 5:147-149. [PMID: 21188559 PMCID: PMC3166602 DOI: 10.1007/s12104-010-9288-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/21/2010] [Accepted: 12/13/2010] [Indexed: 05/30/2023]
Abstract
The 17.7 kDa R2 module from Azotobacter vinelandii mannronan C5-epimerase AlgE6 has been isotopically labeled ((13)C,(15)N) and recombinantly expressed. Here we report the (1)H, (13)C, (15)N resonance assignment of AlgE6R2.
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Affiliation(s)
- Trygve Andreassen
- Department of Biotechnology, Norwegian University of Science and Techology, Sem Sælands vei 6/8, 7491 Trondheim, Norway
| | - Edith Buchinger
- Department of Biotechnology, Norwegian University of Science and Techology, Sem Sælands vei 6/8, 7491 Trondheim, Norway
- Department of Biotechnology, Chemistry and Environmental Engineering, Aalborg University, 9000 Aalborg, Denmark
| | - Gudmund Skjåk-Bræk
- Department of Biotechnology, Norwegian University of Science and Techology, Sem Sælands vei 6/8, 7491 Trondheim, Norway
| | - Svein Valla
- Department of Biotechnology, Norwegian University of Science and Techology, Sem Sælands vei 6/8, 7491 Trondheim, Norway
| | - Finn L. Aachmann
- Department of Biotechnology, Norwegian University of Science and Techology, Sem Sælands vei 6/8, 7491 Trondheim, Norway
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9
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Characterization of three new Azotobacter vinelandii alginate lyases, one of which is involved in cyst germination. J Bacteriol 2009; 191:4845-53. [PMID: 19482920 DOI: 10.1128/jb.00455-09] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Alginates are polysaccharides composed of 1-4-linked beta-D-mannuronic acid and alpha-L-guluronic acid. The polymer can be degraded by alginate lyases, which cleave the polysaccharide using a beta-elimination reaction. Two such lyases have previously been identified in the soil bacterium Azotobacter vinelandii, as follows: the periplasmic AlgL and the secreted bifunctional mannuronan C-5 epimerase and alginate lyase AlgE7. In this work, we describe the properties of three new lyases from this bacterium, AlyA1, AlyA2, and AlyA3, all of which belong to the PL7 family of polysaccharide lyases. One of the enzymes, AlyA3, also contains a C-terminal module similar to those of proteins secreted by a type I secretion system, and its activity is stimulated by Ca(2+). All three enzymes preferably cleave the bond between guluronic acid and mannuronic acid, resulting in a guluronic acid residue at the new reducing end, but AlyA3 also degrades the other three possible bonds in alginate. Strains containing interrupted versions of alyA1, alyA3, and algE7 were constructed, and their phenotypes were analyzed. Genetically pure alyA2 mutants were not obtained, suggesting that this gene product may be important for the bacterium during vegetative growth. After centrifugation, cultures from the algE7 mutants form a large pellet containing alginate, indicating that AlgE7 is involved in the release of alginate from the cells. Upon encountering adverse growth conditions, A. vinelandii will form a resting stage called cyst. Alginate is a necessary part of the protective cyst coat, and we show here that strains lacking alyA3 germinate poorly compared to wild-type cells.
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Mørch YA, Holtan S, Donati I, Strand BL, Skjåk-Braek G. Mechanical properties of C-5 epimerized alginates. Biomacromolecules 2008; 9:2360-8. [PMID: 18702546 DOI: 10.1021/bm8003572] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
There is an increased need for alginate materials with both enhanced and controllable mechanical properties in the fields of food, pharmaceutical and specialty applications. In the present work, well-characterized algal polymers and mannuronan were enzymatically modified using C-5 epimerases converting mannuronic acid residues to guluronic acid in the polymer chain. Composition and sequential structure of controls and epimerized alginates were analyzed by (1)H NMR spectroscopy. Mechanical properties of Ca-alginate gels were further examined giving Young's modulus, syneresis, rupture strength, and elasticity of the gels. Both mechanical strength and elasticity of hydrogels could be improved and manipulated by epimerization. In particular, alternating sequences were found to play an important role for the final mechanical properties of alginate gels, and interestingly, a pure polyalternating sample resulted in gels with extremely high syneresis and rupture strength. In conclusion, enzymatic modification was shown to be a valuable tool in modifying the mechanical properties of alginates in a highly specific manner.
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Affiliation(s)
- Y A Mørch
- Department of Biotechnology, Norwegian University of Science and Technology, Trondheim, Norway.
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12
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Davis TA, Pinheiro JP, Grasdalen H, Smidsrød O, van Leeuwen HP. Stability of lead(II) complexes of alginate oligomers. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2008; 42:1673-1679. [PMID: 18441819 DOI: 10.1021/es702350w] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The current work reports on the Pb(ll) complexes formed with oligomeric uronic acids (carboxylated saccharide residues) found polymerized in the cell walls and envelopes of algae and bacteria alike. The application of partial acid hydrolysis, size-exclusion chromatography (SEC), 1H NMR, and scanned deposition stripping chronopotentiometry (SSCP) has permitted the determination of stability constants for Pb(II) with both mannuronic (M) and guluronic (G) acid oligomers ranging from the dimer to the pentamer. The determined logarithm of the stability constants range between 4.11 +/- 0.05 and 5.00 +/- 0.04 mol(-1) x dm3 for the eight oligomers studied (pH 6; I = 0.1 mol x dm(-3)). Additional experiments under the same experimental conditions employing galacturonic and glucuronic acid oligomers yielded slightly lower values (2.19 +/- 0.10 to 4.02 +/- 0.07 mol(-1) x dm3) that were expected based on their structure, whereby the monomers which were not included in the alginate oligomer series (unavailable by SEC), yielded the lowest stability constants. This work demonstrates the applicability of the SSCP technique for the determination of stability constants for metal-ligand complexes in which the ligands display relatively low molecular mass. Previous studies on heavy metal interaction with the matrix polysaccharide alginate have largely been restricted to the whole polymer that forms a gel upon binding to network bridging ions such as calcium. The results will be discussed in this context with the emphasis being placed on the relevance of these findings to processes occurring at the biointerface and results from the relevant literature.
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Affiliation(s)
- Thomas A Davis
- Laboratory of Physical Chemistry and Colloid Science, Wageningen University, P.O. Box 8038, 6700 EK Wageningen, The Netherlands.
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13
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Holtan S, Bruheim P, Skjåk-Bræk G. Mode of action and subsite studies of the guluronan block-forming mannuronan C-5 epimerases AlgE1 and AlgE6. Biochem J 2006; 395:319-29. [PMID: 16390328 PMCID: PMC1422759 DOI: 10.1042/bj20051804] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
AlgE1, AlgE5 and AlgE6 are members of a family of mannuronan C-5 epimerases encoded by the bacterium Azotobacter vinelandii, and are active in the biosynthesis of alginate, where they catalyse the post-polymerization conversion of beta-D-mannuronic acid (M) residues into alpha-L-guluronic acid residues (G). All enzymes show preference for introducing G-residues neighbouring a pre-existing G. They also have the capacity to convert single M residues flanked by G, thus 'condensing' G-blocks to form almost homopolymeric guluronan. Analysis of the length and distribution of G-blocks based on specific enzyme degradation combined with size-exclusion chromatography, electrospray ionization MS, HPAEC-PAD (high-performance anion-exchange chromatography and pulsed amperometric detection), MALDI (matrix-assisted laser-desorption ionization)-MS and NMR revealed large differences in block length and distribution generated by AlgE1 and AlgE6, probably reflecting their different degree of processivity. When acting on polyMG as substrates, AlgE1 initially forms only long homopolymeric G-blocks >50, while AlgE6 gives shorter blocks with a broader block size distribution. Analyses of the AlgE1 and AlgE6 subsite specificities by the same methodology showed that a mannuronan octamer and heptamer respectively were the minimum substrate chain lengths needed to accommodate enzyme activities. The fourth M residue from the non-reducing end is epimerized first by both enzymes. When acting on MG-oligomers, AlgE1 needed a decamer while AlgE6 an octamer to accommodate activity. By performing FIA (flow injection analysis)-MS on the lyase digests of epimerized and standard MG-oligomers, the M residue in position 5 from the non-reducing end was preferentially attacked by both enzymes, creating an MGMGGG-sequence (underlined and boldface indicate the epimerized residue).
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Affiliation(s)
- Synnøve Holtan
- *Norwegian Biopolymer Laboratory, Department of Biotechnology, The Norwegian University of Science and Technology (NTNU), Trondheim, Norway
| | - Per Bruheim
- †SINTEF Materials and Chemistry, Sem Sælands vei 6/8, N-7491 Trondheim, Norway
| | - Gudmund Skjåk-Bræk
- *Norwegian Biopolymer Laboratory, Department of Biotechnology, The Norwegian University of Science and Technology (NTNU), Trondheim, Norway
- To whom correspondence should be addressed (email )
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Donati I, Draget KI, Borgogna M, Paoletti S, Skjåk-Braek G. Tailor-made alginate bearing galactose moieties on mannuronic residues: selective modification achieved by a chemoenzymatic strategy. Biomacromolecules 2005; 6:88-98. [PMID: 15638508 DOI: 10.1021/bm040053z] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
1-Amino-1-deoxygalactose (12%, mole) has been chemically introduced on a mannuronan sample via an N-glycosidic bond involving the uronic group of the mannuronic acid (M) residues. The unsubstituted M residues in the modified polymer were converted into guluronic moieties (G) by the use of two C-5 epimerases, resulting in an alginate-like molecule selectively modified on M residues. The molecular details of the newly formed polymer, in terms of both composition and molecular dimensions, were disclosed by use of (1)H NMR, intrinsic viscosity, and high-performance size-exclusion chromatography-multiple-angle laser light scattering (HPSEC-MALLS). Circular dichroism has revealed that the modified alginate-like polymer obtained after epimerization was able to bind calcium due to the introduction of alternating and homopolymeric G sequences. The gel-forming ability of this M-selectively modified material was tested and compared with an alginate sample containing 14% galactose introduced on G residues. Mechanical spectroscopy pointed out that the modified epimerized material was able to form stable gels and that the kinetics of the gel formation was similar to that of the unsubstituted sample. In contrast, the G-modified alginate samples showed a slower gel formation, eventually leading to gel characterized by a reduced storage modulus. The advantage of the selective modification on M residues was confirmed by measuring the Young's modulus of gel cylinders of the different samples. Furthermore, due to the high content in alternating sequences, a marked syneresis was disclosed for the modified-epimerized sample. Finally, calcium beads obtained from selectively M-modified alginate showed a higher stability than those from the G-modified alginate, as evaluated upon treatment with nongelling ions.
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Affiliation(s)
- Ivan Donati
- Institute of Biotechnology, Norwegian University of Science and Technology, Sem Saelands vei 6-8, N-7491 Trondheim, Norway.
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15
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Campa C, Holtan S, Nilsen N, Bjerkan T, Stokke B, SKJåK-BRæK G. Biochemical analysis of the processive mechanism for epimerization of alginate by mannuronan C-5 epimerase AlgE4. Biochem J 2004; 381:155-64. [PMID: 15032753 PMCID: PMC1133773 DOI: 10.1042/bj20031265] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2003] [Revised: 03/05/2004] [Accepted: 03/19/2004] [Indexed: 11/17/2022]
Abstract
The enzymes mannuronan C-5 epimerases catalyse the in-chain epimerisation of beta-D-mannuronic acid to alpha-L-guluronic acid in the last step of alginate biosynthesis. The recombinant C-5 epimerase AlgE4, encoded by the soil bacteria Azotobacter vinelandii and expressed in Escherichia coli, exhibits a non-random mode of action when acting on mannuronan and alginates of various monomeric compositions. The observed residue sequence has been suggested previously to be due to either a preferred attack or a processive mode of action. Based on methodologies involving specific degrading enzymes, NMR, electrospray ionisation mass spectrometry and capillary electrophoresis we show here that on average 10 residues are epimerised for each enzyme-substrate encounter. A subsite model for the enzyme is analysed by the same methodology using native and 13C-labelled mannuronan oligomers as substrate for the AlgE4 epimerase. A hexameric oligomer is the minimum size to accommodate activity. For hexa-, hepta- and octameric substrates the third M residue from the non-reducing end is epimerised first.
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Affiliation(s)
- Cristiana Campa
- *Department of Biochemistry, Biophysics and Macromolecular Chemistry, University of Trieste, Italy
| | - Synnøve Holtan
- †Norwegian Biopolymer Laboratory, Department of Biotechnology, The University of Science and Technology NTNU, Trondheim, Norway
| | - Nadra Nilsen
- †Norwegian Biopolymer Laboratory, Department of Biotechnology, The University of Science and Technology NTNU, Trondheim, Norway
| | - Tonje M. Bjerkan
- †Norwegian Biopolymer Laboratory, Department of Biotechnology, The University of Science and Technology NTNU, Trondheim, Norway
| | - Bjørn T. Stokke
- ‡Department of Physics, The University of Science and Technology NTNU, Trondheim, Norway
| | - Gudmund SKJåK-BRæK
- †Norwegian Biopolymer Laboratory, Department of Biotechnology, The University of Science and Technology NTNU, Trondheim, Norway
- To whom correspondence should be addressed (e-mail )
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16
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Bjerkan T, Lillehov B, Strand W, SKJåK-BRæK G, Valla S, ERTESVåG H. Construction and analyses of hybrid Azotobacter vinelandii mannuronan C-5 epimerases with new epimerization pattern characteristics. Biochem J 2004; 381:813-21. [PMID: 15089747 PMCID: PMC1133891 DOI: 10.1042/bj20031580] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2003] [Revised: 04/14/2004] [Accepted: 04/19/2004] [Indexed: 11/17/2022]
Abstract
The secreted mannuronan C-5 epimerases from Azotobacter vinelandii form a family of seven homologous modular type enzymes, which appear to have evolved through duplications and point mutations in the individual modules. The catalytic A modules of these enzymes are responsible for generating the characteristic sequence distribution patterns of G residues in the industrially important polymer alginate by epimerizing M (beta-D-mannuronic acid) moieties to G (alpha-L-guluronic acid). Forty-six different hybrid enzymes were constructed by exchanging parts of the sequences encoding the A modules of AlgE2 (generates consecutive stretches of G residues) and AlgE4 (generates alternating structures). These hybrid enzymes introduce a variety of new monomer-sequence patterns into their substrates, and some regions important for the subsite specificity or processivity of the enzymes were identified. By using time-resolved NMR spectroscopy, it became clear that the rates for introducing alternating structures and consecutive stretches of G residues are different for each enzyme, and that it is the ratio between these rates that determines the overall epimerization pattern. These findings open up new possibilities in biotechnology and in studies of the many biological functions of alginates.
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Affiliation(s)
- Tonje M. Bjerkan
- Department of Biotechnology, Norwegian University of Science and Technology, N-7491 Trondheim, Norway
| | - Bjørn E. Lillehov
- Department of Biotechnology, Norwegian University of Science and Technology, N-7491 Trondheim, Norway
| | - Wenche I. Strand
- Department of Biotechnology, Norwegian University of Science and Technology, N-7491 Trondheim, Norway
| | - Gudmund SKJåK-BRæK
- Department of Biotechnology, Norwegian University of Science and Technology, N-7491 Trondheim, Norway
| | - Svein Valla
- Department of Biotechnology, Norwegian University of Science and Technology, N-7491 Trondheim, Norway
| | - Helga ERTESVåG
- Department of Biotechnology, Norwegian University of Science and Technology, N-7491 Trondheim, Norway
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17
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Bjerkan TM, Bender CL, Ertesvåg H, Drabløs F, Fakhr MK, Preston LA, Skjak-Braek G, Valla S. The Pseudomonas syringae Genome Encodes a Combined Mannuronan C-5-epimerase and O-Acetylhydrolase, Which Strongly Enhances the Predicted Gel-forming Properties of Alginates. J Biol Chem 2004; 279:28920-9. [PMID: 15123694 DOI: 10.1074/jbc.m313293200] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Alginates are industrially important, linear copolymers of beta-d-mannuronic acid (M) and its C-5-epimer alpha-l-guluronic acid (G). The G residues originate from a postpolymerization reaction catalyzed by mannuronan C-5-epimerases (MEs), leading to extensive variability in M/G ratios and distribution patterns. Alginates containing long continuous stretches of G residues (G blocks) can form strong gels, a polymer type not found in alginate-producing bacteria belonging to the genus Pseudomonas. Here we show that the Pseudomonas syringae genome encodes a Ca(2+)-dependent ME (PsmE) that efficiently forms such G blocks in vitro. The deduced PsmE protein consists of 1610 amino acids and is a modular enzyme related to the previously characterized family of Azotobacter vinelandii ME (AlgE1-7). A- and R-like modules with sequence similarity to those in the AlgE enzymes are found in PsmE, and the A module of PsmE (PsmEA) was found to be sufficient for epimerization. Interestingly, an R module from AlgE4 stimulated Ps-mEA activity. PsmE contains two regions designated M and RTX, both presumably involved in the binding of Ca(2+). Bacterial alginates are partly acetylated, and such modified residues cannot be epimerized. Based on a detailed computer-assisted analysis and experimental studies another PsmE region, designated N, was found to encode an acetylhydrolase. By the combined action of N and A PsmE was capable of redesigning an extensively acetylated alginate low in G from a non gel-forming to a gel-forming state. Such a property has to our knowledge not been previously reported for an enzyme acting on a polysaccharide.
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Affiliation(s)
- Tonje M Bjerkan
- Department of Biotechnology, Norwegian University of Science and Technology, N-7491 Trondheim, Norway
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18
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Campa C, Oust A, Skjåk-Braek G, Paulsen BS, Paoletti S, Christensen BE, Ballance S. Determination of average degree of polymerisation and distribution of oligosaccharides in a partially acid-hydrolysed homopolysaccharide: A comparison of four experimental methods applied to mannuronan. J Chromatogr A 2004; 1026:271-81. [PMID: 14763754 DOI: 10.1016/j.chroma.2003.11.045] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The average degree of polymerisation (DP) and distribution of oligosaccharides in partially acid hydrolysed mannuronans were quantitatively evaluated by 1H NMR, electrospray ionisation mass spectrometry (ESI-MS), micellar electrokinetic capillary chromatography with UV detection (MEKC-UV), and high-pressure anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD). Our investigation shows that 1H NMR, MEKC-UV and, in particular, HPAEC-PAD can be used as quantitative tools to aid the investigation of polysaccharide structure, function and synthesis. For the latter two techniques, especially, this represents a significant new development as it enables calculation of the quantity of individual oligomers of nominal DP by direct analysis of a defined oligomer mixture. Appropriate statistical averages of number and weight distributions were also calculated and found to fit very well to predicted Kuhn distributions that assume random depolymerisation.
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Affiliation(s)
- Cristiana Campa
- Department of Biochemistry, Biophysics and Macromolecular Chemistry University of Trieste, 1-34127 Trieste, Italy
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