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Nakamura Y. A model for the reproduction of amylopectin cluster by coordinated actions of starch branching enzyme isoforms. PLANT MOLECULAR BIOLOGY 2023:10.1007/s11103-023-01352-6. [PMID: 37294528 DOI: 10.1007/s11103-023-01352-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 03/01/2023] [Accepted: 04/10/2023] [Indexed: 06/10/2023]
Abstract
Amylopectin is a highly branched glucan which accounts for approximately 65-85% of starch in most plant tissues. It is crucially important to understand the biosynthetic process of this glucan in regulating the structure and functional properties of starch granules. Currently, the most accepted ideas of structural feature and biosynthesis of amylopectin are that amylopectin is composed of a branched element called "cluster" and that the essential process of amylopectin biosynthesis is to reproduce a new cluster from the existing cluster. The present paper proposes a model explaining the whole process of amylopectin biosynthesis as to how the new cluster is reproduced by concerted actions of multiple isoforms of starch biosynthetic enzymes, particularly by combinations of distinct roles of starch branching enzyme (BE) isoforms. This model proposes for the first time the molecular mechanism as to how the formation of a new cluster is initiated, and the reason why BEI can play a major role in this step. This is because BEI has a rather broad chain-length preference compared to BEIIb, because a low preference of BEI for the substrate chain-length is advantageous for branching a couple of elongated chains that are not synchronously formed and thus these chains having varied lengths could be safely attacked by this isoform. On the contrary, it is unlikely that BEIIb is involved in this reaction because it can react to only short chains having degree of polymerization of 12-14. BEIIa is possibly able to complement the role of BEI to some extent, because BEIIa can attack basically short chains but its chain-length preference is lower compared with BEIIb. The model implies that the first branches mainly formed by BEI to construct the amorphous lamellae whereas the second branches predominantly formed by BEIIb are located mainly in the crystalline lamellae. This paper provides new insights into the roles of BEI, BEIIb, and BEIIa in amylopectin biosynthesis in cereal endosperm.
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Affiliation(s)
- Yasunori Nakamura
- Starch Technologies Co., Ltd, Akita Prefectural University, Shimoshinjo-Nakano, Akita-City, Akita, 010-0195, Japan.
- Faculty of Bioresource Sciences, Akita Prefectural University, Shimoshinjo-Nakano, Akita-City, Akita, 010-0195, Japan.
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Ryu JJ, Li X, Lee ES, Li D, Lee BH. Slowly digestible property of highly branched α-limit dextrins produced by 4,6-α-glucanotransferase from Streptococcus thermophilus evaluated in vitro and in vivo. Carbohydr Polym 2022; 275:118685. [PMID: 34742415 DOI: 10.1016/j.carbpol.2021.118685] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Revised: 08/16/2021] [Accepted: 09/16/2021] [Indexed: 11/02/2022]
Abstract
Starch molecules are first degraded to slowly digestible α-limit dextrins (α-LDx) and rapidly hydrolyzable linear malto-oligosaccharides (LMOs) by salivary and pancreatic α-amylases. In this study, we designed a slowly digestible highly branched α-LDx with maximized α-1,6 linkages using 4,6-α-glucanotransferase (4,6-αGT), which creates a short length of α-1,4 side chains with increasing branching points. The results showed that a short length of external chains mainly composed of 1-8 glucosyl units was newly synthesized in different amylose contents of corn starches, and the α-1,6 linkage ratio of branched α-LDx after the chromatographical purification was significantly increased from 4.6% to 22.1%. Both in vitro and in vivo studies confirmed that enzymatically modified α-LDx had improved slowly digestible properties and extended glycemic responses. Therefore, 4,6-αGT treatment enhanced the slowly digestible properties of highly branched α-LDx and promises usefulness as a functional ingredient to attenuate postprandial glucose homeostasis.
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Affiliation(s)
- Jae-Jin Ryu
- Department of Food Science and Biotechnology, Gachon University, Seongnam 13120, Republic of Korea
| | - Xiaolei Li
- Key Laboratory of Agro-products Processing Technology at Jilin Provincial Universities, Education Department of Jilin Provincial Government, Changchun University, Changchun 130022, People's Republic of China
| | - Eun-Sook Lee
- Department of Pharmacology, Asan Medical Center, University of Ulsan College of Medicine, Seoul 05505, Republic of Korea
| | - Dan Li
- Key Laboratory of Agro-products Processing Technology at Jilin Provincial Universities, Education Department of Jilin Provincial Government, Changchun University, Changchun 130022, People's Republic of China
| | - Byung-Hoo Lee
- Department of Food Science and Biotechnology, Gachon University, Seongnam 13120, Republic of Korea.
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Tetlow IJ, Bertoft E. A Review of Starch Biosynthesis in Relation to the Building Block-Backbone Model. Int J Mol Sci 2020; 21:E7011. [PMID: 32977627 PMCID: PMC7582286 DOI: 10.3390/ijms21197011] [Citation(s) in RCA: 52] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 09/15/2020] [Accepted: 09/16/2020] [Indexed: 01/31/2023] Open
Abstract
Starch is a water-insoluble polymer of glucose synthesized as discrete granules inside the stroma of plastids in plant cells. Starch reserves provide a source of carbohydrate for immediate growth and development, and act as long term carbon stores in endosperms and seed tissues for growth of the next generation, making starch of huge agricultural importance. The starch granule has a highly complex hierarchical structure arising from the combined actions of a large array of enzymes as well as physicochemical self-assembly mechanisms. Understanding the precise nature of granule architecture, and how both biological and abiotic factors determine this structure is of both fundamental and practical importance. This review outlines current knowledge of granule architecture and the starch biosynthesis pathway in relation to the building block-backbone model of starch structure. We highlight the gaps in our knowledge in relation to our understanding of the structure and synthesis of starch, and argue that the building block-backbone model takes accurate account of both structural and biochemical data.
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Affiliation(s)
- Ian J. Tetlow
- Department of Molecular and Cellular Biology, College of Biological Science, University of Guelph, Guelph, ON N1G 2W1, Canada
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Goren A, Ashlock D, Tetlow IJ. Starch formation inside plastids of higher plants. PROTOPLASMA 2018; 255:1855-1876. [PMID: 29774409 DOI: 10.1007/s00709-018-1259-4] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Accepted: 05/03/2018] [Indexed: 05/09/2023]
Abstract
Starch is a water-insoluble polyglucan synthesized inside the plastid stroma within plant cells, serving a crucial role in the carbon budget of the whole plant by acting as a short-term and long-term store of energy. The highly complex, hierarchical structure of the starch granule arises from the actions of a large suite of enzyme activities, in addition to physicochemical self-assembly mechanisms. This review outlines current knowledge of the starch biosynthetic pathway operating in plant cells in relation to the micro- and macro-structures of the starch granule. We highlight the gaps in our knowledge, in particular, the relationship between enzyme function and operation at the molecular level and the formation of the final, macroscopic architecture of the granule.
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Affiliation(s)
- Asena Goren
- Department of Mathematics and Statistics, University of Guelph, Guelph, ON, N1G 2W1, Canada
| | - Daniel Ashlock
- Department of Mathematics and Statistics, University of Guelph, Guelph, ON, N1G 2W1, Canada
| | - Ian J Tetlow
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of Guelph, Guelph, ON, N1G 2W1, Canada.
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Abstract
The starch-rich endosperms of the Poaceae, which includes wild grasses and their domesticated descendents the cereals, have provided humankind and their livestock with the bulk of their daily calories since the dawn of civilization up to the present day. There are currently unprecedented pressures on global food supplies, largely resulting from population growth, loss of agricultural land that is linked to increased urbanization, and climate change. Since cereal yields essentially underpin world food and feed supply, it is critical that we understand the biological factors contributing to crop yields. In particular, it is important to understand the biochemical pathway that is involved in starch biosynthesis, since this pathway is the major yield determinant in the seeds of six out of the top seven crops grown worldwide. This review outlines the critical stages of growth and development of the endosperm tissue in the Poaceae, including discussion of carbon provision to the growing sink tissue. The main body of the review presents a current view of our understanding of storage starch biosynthesis, which occurs inside the amyloplasts of developing endosperms.
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Abstract
Starch is a major food supply for humanity. It is produced in seeds, rhizomes, roots and tubers in the form of semi-crystalline granules with unique properties for each plant. Though the size and morphology of the granules is specific for each plant species, their internal structures have remarkably similar architecture, consisting of growth rings, blocklets, and crystalline and amorphous lamellae. The basic components of starch granules are two polyglucans, namely amylose and amylopectin. The molecular structure of amylose is comparatively simple as it consists of glucose residues connected through α-(1,4)-linkages to long chains with a few α-(1,6)-branches. Amylopectin, which is the major component, has the same basic structure, but it has considerably shorter chains and a lot of α-(1,6)-branches. This results in a very complex, three-dimensional structure, the nature of which remains uncertain. Several models of the amylopectin structure have been suggested through the years, and in this review two models are described, namely the “cluster model” and the “building block backbone model”. The structure of the starch granules is discussed in light of both models.
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Sawada T, Nakamura Y, Ohdan T, Saitoh A, Francisco PB, Suzuki E, Fujita N, Shimonaga T, Fujiwara S, Tsuzuki M, Colleoni C, Ball S. Diversity of reaction characteristics of glucan branching enzymes and the fine structure of α-glucan from various sources. Arch Biochem Biophys 2014; 562:9-21. [DOI: 10.1016/j.abb.2014.07.032] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Revised: 07/08/2014] [Accepted: 07/10/2014] [Indexed: 11/26/2022]
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Tetlow IJ, Emes MJ. A review of starch-branching enzymes and their role in amylopectin biosynthesis. IUBMB Life 2014; 66:546-58. [PMID: 25196474 DOI: 10.1002/iub.1297] [Citation(s) in RCA: 117] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Revised: 07/31/2014] [Accepted: 08/07/2014] [Indexed: 11/07/2022]
Abstract
Starch-branching enzymes (SBEs) are one of the four major enzyme classes involved in starch biosynthesis in plants and algae, and their activities play a crucial role in determining the structure and physical properties of starch granules. SBEs generate α-1,6-branch linkages in α-glucans through cleavage of internal α-1,4 bonds and transfer of the released reducing ends to C-6 hydroxyls. Starch biosynthesis in plants and algae requires multiple isoforms of SBEs and is distinct from glycogen biosynthesis in both prokaryotes and eukaryotes which uses a single branching enzyme (BE) isoform. One of the unique characteristics of starch structure is the grouping of α-1,6-branch points in clusters within amylopectin. This is a feature of SBEs and their interplay with other starch biosynthetic enzymes, thus facilitating formation of the compact water-insoluble semicrystalline starch granule. In this respect, the activity of SBE isoforms is pivotal in starch granule assembly. SBEs are structurally related to the α-amylase superfamily of enzymes, sharing three domains of secondary structure with prokaryotic Bes: the central (β/α)8 -barrel catalytic domain, an NH2 -terminal domain involved in determining the size of α-glucan chain transferred, and the C-terminal domain responsible for catalytic capacity and substrate preference. In addition, SBEs have conserved plant-specific domains, including phosphorylation sites which are thought to be involved in regulating starch metabolism. SBEs form heteromeric protein complexes with other SBE isoforms as well as other enzymes involved in starch synthesis, and assembly of these protein complexes is regulated by protein phosphorylation. Phosphorylated SBEIIb is found in multienzyme complexes with isoforms of glucan-elongating starch synthases, and these protein complexes are implicated in amylopectin cluster formation. This review presents a comparative overview of plant SBEs and includes a review of their properties, structural and functional characteristics, and recent developments on their post-translational regulation.
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Affiliation(s)
- Ian J Tetlow
- Department of Molecular and Cellular Biology, Science Complex, University of Guelph, Guelph, ON, Canada
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9
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Wu S, Liu Y, Yan Q, Jiang Z. Gene cloning, functional expression and characterisation of a novel glycogen branching enzyme from Rhizomucor miehei and its application in wheat breadmaking. Food Chem 2014; 159:85-94. [DOI: 10.1016/j.foodchem.2014.02.161] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Revised: 01/21/2014] [Accepted: 02/27/2014] [Indexed: 10/25/2022]
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Affiliation(s)
- Eric Bertoft
- Department of Food Science, University of Guelph, Guelph, ON, Canada. Phone: (519) 824-4120, ext. 58054. Fax: (519) 824-6631. E-mail:
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Sawada T, Nakagami T, Utsumi Y, Ohdan T, Suzuki E, Nakamura Y. Special Issue ^|^quot;Starch Metabolism, Structure and Properties^|^quot; Characterization of Starch and Glycogen Branching Enzymes from Various Sources. J Appl Glycosci (1999) 2013. [DOI: 10.5458/jag.jag.jag-2012_011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
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Nakamura Y, Sawada T, Ohdan T, Aihara S, Fujita N. New Assay Method for Starch Branching Enzyme and Starch Synthase by the Chain-length Distribution Analysis. J Appl Glycosci (1999) 2011. [DOI: 10.5458/jag.jag.jag-2010_015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022] Open
Affiliation(s)
- Yasunori Nakamura
- Department of Biological Production, Faculty of Bioresource Sciences, Akita Prefectural University
- Biotechnology Center, Faculty of Bioresource Sciences, Akita Prefectural University
| | - Takayuki Sawada
- Biotechnology Center, Faculty of Bioresource Sciences, Akita Prefectural University
| | - Takashi Ohdan
- Biotechnology Center, Faculty of Bioresource Sciences, Akita Prefectural University
| | - Satomi Aihara
- Department of Biological Production, Faculty of Bioresource Sciences, Akita Prefectural University
| | - Naoko Fujita
- Department of Biological Production, Faculty of Bioresource Sciences, Akita Prefectural University
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Nakamura Y, Utsumi Y, Sawada T, Aihara S, Utsumi C, Yoshida M, Kitamura S. Characterization of the reactions of starch branching enzymes from rice endosperm. PLANT & CELL PHYSIOLOGY 2010; 51:776-94. [PMID: 20305271 DOI: 10.1093/pcp/pcq035] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
To our knowledge the present paper shows for the first time the kinetic parameters of all the three starch branching enzyme (BE) isozymes, BEI, BEIIa and BEIIb, from rice with both amylopectin and synthetic amylose as glucan substrate. The activities of these BE isozymes with a linear glucan amylose decreased with a decrease in the molar size of amylose, and no activities of BEIIa and BEIIb were found when the degree of polymerization (DP) of amylose was lower than at least 80, whereas BEI had an activity with amylose of a DP higher than approximately 50. Detailed analyses of debranched products from BE reactions revealed the distinct chain length preferences of the individual BE isozymes. BEIIb almost exclusively transferred chains of DP7 and DP6 while BEIIa formed a wide range of short chains of DP6 to around DP15 from outer chains of amylopectin and amylose. On the other hand, BEI formed a variety of short chains and intermediate chains of a DP <or=40 by attacking not only outer chains but also inner chains of branched glucan while BEIIa or BEIIb could only scarcely or could not attack inner chains, respectively. The comprehensive in vitro studies revealed different enzymatic characteristics of the three BE isozymes and give a new insight into the distinct roles of individual BE isozymes in amylopectin biosynthesis in the endosperm. Based on these results, the functional distinction and interaction of BE isozymes during amylopectin biosynthesis in cereal endosperm is discussed.
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Affiliation(s)
- Yasunori Nakamura
- Faculty of Bioresource Sciences, Akita Prefectural University, Akita-City, 010-0195 Japan.
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16
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Ohdan T, Sawada T, Nakamura Y. Effects of Temperature on Starch Branching Enzyme Properties of Rice. J Appl Glycosci (1999) 2010. [DOI: 10.5458/jag.jag.jag-2010_014] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
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17
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Hernández JM, Gaborieau M, Castignolles P, Gidley MJ, Myers AM, Gilbert RG. Mechanistic Investigation of a Starch-Branching Enzyme Using Hydrodynamic Volume SEC Analysis. Biomacromolecules 2008; 9:954-65. [DOI: 10.1021/bm701213p] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Javier M. Hernández
- Centre for Nutrition & Food Sciences, School of Land Crop & Food Sciences, University of Queensland, Brisbane, Queensland 4072, Australia, Key Centre for Polymer Colloids, School of Chemistry, University of Sydney, NSW 2006, Australia, Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, Iowa 50011
| | - Marianne Gaborieau
- Centre for Nutrition & Food Sciences, School of Land Crop & Food Sciences, University of Queensland, Brisbane, Queensland 4072, Australia, Key Centre for Polymer Colloids, School of Chemistry, University of Sydney, NSW 2006, Australia, Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, Iowa 50011
| | - Patrice Castignolles
- Centre for Nutrition & Food Sciences, School of Land Crop & Food Sciences, University of Queensland, Brisbane, Queensland 4072, Australia, Key Centre for Polymer Colloids, School of Chemistry, University of Sydney, NSW 2006, Australia, Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, Iowa 50011
| | - Michael J. Gidley
- Centre for Nutrition & Food Sciences, School of Land Crop & Food Sciences, University of Queensland, Brisbane, Queensland 4072, Australia, Key Centre for Polymer Colloids, School of Chemistry, University of Sydney, NSW 2006, Australia, Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, Iowa 50011
| | - Alan M. Myers
- Centre for Nutrition & Food Sciences, School of Land Crop & Food Sciences, University of Queensland, Brisbane, Queensland 4072, Australia, Key Centre for Polymer Colloids, School of Chemistry, University of Sydney, NSW 2006, Australia, Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, Iowa 50011
| | - Robert G. Gilbert
- Centre for Nutrition & Food Sciences, School of Land Crop & Food Sciences, University of Queensland, Brisbane, Queensland 4072, Australia, Key Centre for Polymer Colloids, School of Chemistry, University of Sydney, NSW 2006, Australia, Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, Iowa 50011
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18
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Takata H. Properties and Application of Enzymes for Bacterial Glycogen Biosynthesis and Degradation. J Appl Glycosci (1999) 2004. [DOI: 10.5458/jag.51.55] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
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Viksø-Nielsen A, Hao-Jie Chen P, Larsson H, Blennow A, Møller BL. Production of highly phosphorylated glycopolymers by expression of R1 in Escherichia coli. Carbohydr Res 2002; 337:327-33. [PMID: 11841813 DOI: 10.1016/s0008-6215(01)00326-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The possible involvement of the starch bound R1 protein from potato (Solanum tuberosum L.) in the phosphorylation of starch was investigated by functional expression and characterisation of R1 in Escherichia coli. By expression of R1 in E. coli it is shown that it is possible to produce glycopolymers, e.g., glycogen, with an increased degree of phosphate substitution. The expression of R1 in E. coli resulted in a sixfold increase in glycogen bound phosphate and in an increased accumulation of glycogen leading to a glycogen excess (gex) phenotype. There was an overall shift in the unit-chain length of the isolated glycogen towards smaller degrees of polymerisation. The pleiotropic effects on the glycogen biosynthetic and amylolytic enzyme activities was investigated and showed an increase in ADPglucose pyrophosphorylase activity, as well as a decrease in exo-amylolytic activity. These results are discussed in relation to starch phosphorylation and a possible role of R1 in this respect.
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Affiliation(s)
- Anders Viksø-Nielsen
- Plant Biochemistry Laboratory, Department of Plant Biology, Centre for Molecular Plant Physiology (PlaCe), Royal Veterinary and Agricultural University, Thorvaldsensvej 40, DK-1871 C, Frederiksberg, Denmark
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Matheson N, Caldwell R. α(1-4) Glucan chain disposition in models of α(1-4)(1-6) glucans: comparison with structural data for mammalian glycogen and waxy amylopectin. Carbohydr Polym 1999. [DOI: 10.1016/s0144-8617(99)00054-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Büttcher V, Quanz M, Willmitzer L. Molecular cloning, functional expression and purification of a glucan branching enzyme from Neisseria denitrificans(1). BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1432:406-12. [PMID: 10407163 DOI: 10.1016/s0167-4838(99)00101-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The nucleotide sequence containing the complete structural information for a glucan branching enzyme was isolated from a Neisseria denitrificans genomic library. The gene was expressed in Escherichia coli and the active recombinant protein was purified. The deduced protein of 762 amino acids with a calculated molecular weight of 86313 Da shows similarity to the primary protein sequences of other known glucan branching enzymes. Amino acid sequencing of the isolated protein by Edman degradation confirmed the deduced start codon of the structural gene of the glucan branching enzyme. The purified glucan branching enzyme has a stimulating effect on the Neisseria amylosucrase activity.
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Affiliation(s)
- V Büttcher
- Institut für Genbiologische Forschung GmbH Berlin, Ihnestr. 63, D-14195, Berlin, Germany.
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22
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Abstract
The emphasis of this review is on starch structure and its biosynthesis. Improvements in understanding have been brought about during the last decade through the development of new physicochemical and biological techniques, leading to real scientific progress. All this literature needs to be kept inside the general literature about biopolymers, despite some confusing results or discrepancies arising from the biological variability of starch. However, a coherent picture of starch over all the different structural levels can be presented, in order to obtain some generalizations about its structure. In this review we will focus first on our present understanding of the structures of amylose and amylopectin and their organization within the granule, and we will then give insights on the biosynthetic mechanisms explaining the biogenesis of starch in plants.
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Abstract
This review describes and discusses the implications of recent discoveries about how starch polymers are synthesized and organized to form a starch granule. Three issues are highlighted. 1. The role and importance of ADPglucose pyrophosphorylase in the generation of ADPglucose as the substrate for polymer synthesis. 2. The contributions of isoforms of starch-branching enzyme, starch synthase, and debranching enzyme to the synthesis and ordered packing of amylopectin molecules. 3. The requirements for and regulation of the synthesis of amylose.
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Affiliation(s)
- A. M. Smith
- John Innes Centre, Colney Lane, Norwich NR4 7UH, United Kingdom
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Takata H, Takaha T, Okada S, Hizukuri S, Takagi M, Imanaka T. Structure of the cyclic glucan produced from amylopectin by Bacillus stearothermophilus branching enzyme. Carbohydr Res 1996; 295:91-101. [PMID: 9002186 DOI: 10.1016/s0008-6215(96)90126-3] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The thermostable branching enzyme (BE, EC 2.4.1.18) from Bacillus stearothermophilus TRBE14 produces large cyclic glucans from waxy rice amylopectin similar to those obtained from amylose as described elsewhere [H. Takata, T. Takaha, S. Okada. M. Takagi, and T. Imanaka, J. Bacteriol., 178 (1996) 1600-1606]. The structure of the product (P-1) from the late-stage reaction was analyzed in detail. The weight-average degree of polymerization (dpw) of P-1 was 900. Its chain-length distribution was not significantly changed compared with that of amylopectin, although the amount of long chains (dp > 38) was slightly decreased. The cyclic component of P-1, which was isolated by the extensive action of glucoamylase, had dpw of 49. Three point five alpha-1,6 linkages were directly involved in the formation of the ring structure with several non-cyclic side chains linked to the ring. Based on these results, the action and new roles of BE are discussed.
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Affiliation(s)
- H Takata
- Biochemical Research Laboratory, Ezaki Glico Co., Ltd., Osaka, Japan
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Takata H, Takaha T, Okada S, Takagi M, Imanaka T. Cyclization reaction catalyzed by branching enzyme. J Bacteriol 1996; 178:1600-6. [PMID: 8626287 PMCID: PMC177844 DOI: 10.1128/jb.178.6.1600-1606.1996] [Citation(s) in RCA: 78] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The action of branching enzyme (EC 2.4.l.l8) from Bacillus stearothermophilus on amylose was analyzed. The enzyme reduced the molecular size of amylose without increasing the reducing power. This result could not be explained by the normal branching reaction model. When the product was treated with glucoamylase (an exo++-type amylase), a resistant component remained. The glucoamylase-resistant component was easily digested by an endo-type alpha-amylase or by isoamylase plus glucoamylase. These results suggested that the glucoamylase-resistant component was a cyclic glucan composed of alpha-1,4- and alpha-l,6-glucosidic linkages. In other words, it was suggested that branching enzyme catalyzed cyclization of the alpha-l,4-glucan chain of the amylose molecule to form an alpha-l,6-glucosidic linkage, thereby forming two smaller molecules. Mass spectrometry also supported the cyclic nature of the product.
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Affiliation(s)
- H Takata
- Biochemical Research Laboratory, Ezaki Glico Co., Ltd., Nishiyodogawa-ku, Osaka, Japan
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Baba T, Kimura K, Mizuno K, Etoh H, Ishida Y, Shida O, Arai Y. Sequence conservation of the catalytic regions of amylolytic enzymes in maize branching enzyme-I. Biochem Biophys Res Commun 1991; 181:87-94. [PMID: 1720313 DOI: 10.1016/s0006-291x(05)81385-3] [Citation(s) in RCA: 93] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
We have identified cDNA clones encoding branching enzyme-I (BE-I) from a maize kernel cDNA library. The combined nucleotide sequence of the cDNAs indicates that maize BE-I is initially synthesized as a precursor protein with a putative 64-residue transit peptide at the amino terminus, and that the mature enzyme contains 759 amino acid residues with a calculated molecular mass of 86,236 Da. The four regions, which constitute the catalytic site of amylolytic enzymes, are conserved in the sequences of BE-I and bacterial branching enzymes. This result demonstrates that branching enzyme belongs to a family of the amylolytic enzymes. The BE-I gene is highly expressed in the early stages of kernel development, and the level of the message concentration decreases slowly as kernel maturation proceeds.
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Affiliation(s)
- T Baba
- Institute of Applied Biochemistry, University of Tsukuba, Ibaraki, Japan
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Relationship between the distribution of the chain length of amylopectin and the crystalline structure of starch granules. Carbohydr Res 1985. [DOI: 10.1016/s0008-6215(00)90461-0] [Citation(s) in RCA: 407] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Rollings JE, Thompson RW. Kinetics of enzymatic starch liquefaction: Simulation of the high-molecular-weight product distribution. Biotechnol Bioeng 1984; 26:1475-84. [DOI: 10.1002/bit.260261212] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Palmer TN, Macaskie LE, Grewel KK. The unit-chain distribution profiles of branched (1→4)-α- d -glucans. Carbohydr Res 1983. [DOI: 10.1016/0008-6215(83)88205-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Bender H, Siebert R, Stadler-Szöke A. Can cyclodextrin glycosyltransferase be useful for the investigation of the fine structure of amylopectins?: Characterisation of highly branched clusters isolated from digests with potato and maize starches. Carbohydr Res 1982. [DOI: 10.1016/0008-6215(82)84006-8] [Citation(s) in RCA: 37] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Baba T, Arai Y, Ono T, Munakata A, Yamaguchi H, Itoh T. Branching enzyme from amylomaize endosperms. Carbohydr Res 1982. [DOI: 10.1016/s0008-6215(00)80540-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Abstract
Many types of amylases are found throughout the animal, vegetable and microbial kingdoms. They have evolved along different pathways to enable the organism to convert insoluble starch (or glycogen) into low molecular weight, water soluble dextrins and sugars. Alpha amylases are dextrinogenic and can attack the interior of starch molecules. The products retain the alpha anomeric configuration. Beta amylases act only at the non-reducing chain ends and liberate only beta maltose. Both alpha and beta amylases exhibit multiple (repetitive) attack, that is, after the initial catalytic cleavage, the enzyme may remain attached to the substrate and lead to several more cleavages before dissociation of the enzyme-substrate complex. Amylases have extended substrate binding sites, in the range 4-9 glucose units. This enables the enzyme to stress the substrate and lower the activation energy for hydrolysis. Similarly the enzyme exerts a torsion on the glucose unit at the catalytic site, inducing a transition state conformation (oxycarbonium ion). Alpha and beta amylases differ in the stereospecific hydration of the oxycarbonium ion, in the sequence of liberation of the right-hand vs the left-hand product, and the direction of motion of the retained substrate to give multiple attack.
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