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Neoh GKS, Tan X, Chen S, Roura E, Dong X, Gilbert RG. Glycogen metabolism and structure: A review. Carbohydr Polym 2024; 346:122631. [PMID: 39245499 DOI: 10.1016/j.carbpol.2024.122631] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2024] [Revised: 08/15/2024] [Accepted: 08/16/2024] [Indexed: 09/10/2024]
Abstract
Glycogen is a glucose polymer that plays a crucial role in glucose homeostasis by functioning as a short-term energy storage reservoir in animals and bacteria. Abnormalities in its metabolism and structure can cause several problems, including diabetes, glycogen storage diseases (GSDs) and muscular disorders. Defects in the enzymes involved in glycogen synthesis or breakdown, resulting in either excessive accumulation or insufficient availability of glycogen in cells seem to account for the most common pathogenesis. This review discusses glycogen metabolism and structure, including molecular architecture, branching dynamics, and the role of associated components within the granules. The review also discusses GSD type XV and Lafora disease, illustrating the broader implications of aberrant glycogen metabolism and structure. These conditions also impart information on important regulatory mechanisms of glycogen, which hint at potential therapeutic targets. Knowledge gaps and potential future research directions are identified.
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Affiliation(s)
- Galex K S Neoh
- School of Medicine, Shanghai University, Shanghai 200444, China.
| | - Xinle Tan
- Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, Brisbane, Queensland 4072, Australia; Centre for Animal Science, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, Brisbane, Queensland 4072, Australia.
| | - Si Chen
- School of Medicine, Shanghai University, Shanghai 200444, China.
| | - Eugeni Roura
- Centre for Animal Science, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, Brisbane, Queensland 4072, Australia.
| | - Xin Dong
- School of Medicine, Shanghai University, Shanghai 200444, China.
| | - Robert G Gilbert
- Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, Brisbane, Queensland 4072, Australia; Jiangsu Key Laboratory of Crop Genomics and Molecular Breeding/Key Laboratory of Plant Functional Genomics of the Ministry of Education/Jiangsu Key Laboratory of Crop Genetics and Physiology, Agricultural College of Yangzhou University, Yangzhou 225009, China; Jiangsu Co-Innovation Center for Modern Production Technology of Grain Crops, Yangzhou University, Yangzhou 225009, China.
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2
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Thompson EM, Stoker AW. A Review of DUSP26: Structure, Regulation and Relevance in Human Disease. Int J Mol Sci 2021; 22:ijms22020776. [PMID: 33466673 PMCID: PMC7828806 DOI: 10.3390/ijms22020776] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Revised: 01/05/2021] [Accepted: 01/08/2021] [Indexed: 01/10/2023] Open
Abstract
Dual specificity phosphatases (DUSPs) play a crucial role in the regulation of intracellular signalling pathways, which in turn influence a broad range of physiological processes. DUSP malfunction is increasingly observed in a broad range of human diseases due to deregulation of key pathways, most notably the MAP kinase (MAPK) cascades. Dual specificity phosphatase 26 (DUSP26) is an atypical DUSP with a range of physiological substrates including the MAPKs. The residues that govern DUSP26 substrate specificity are yet to be determined; however, recent evidence suggests that interactions with a binding partner may be required for DUSP26 catalytic activity. DUSP26 is heavily implicated in cancer where, akin to other DUSPs, it displays both tumour-suppressive and -promoting properties, depending on the context. Here we review DUSP26 by evaluating its transcriptional patterns, protein crystallographic structure and substrate binding, as well as its physiological role(s) and binding partners, its role in human disease and the development of DUSP26 inhibitors.
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3
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Li C, Hu Z. Is liver glycogen fragility a possible drug target for diabetes? FASEB J 2019; 34:3-15. [PMID: 31914592 DOI: 10.1096/fj.201901463rr] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Revised: 10/08/2019] [Accepted: 10/09/2019] [Indexed: 12/14/2022]
Abstract
Liver glycogen α particles are molecularly fragile in diabetic mice, and readily form smaller β particles, which degrade more rapidly to glucose. This effect is well associated with the loss of blood-glucose homeostasis in diabetes. The biological mechanism of such fragility is still unknown; therefore, there are perceived opportunities that could eventually lead to new means to manage type 2 diabetes. The hierarchical structures of glycogen particles are controlled by the underlying biosynthesis/degradation process that involves various enzymes, including, for example, glycogen synthase (GS) and glycogen-branching enzyme (GBE). Recent studies have shown that fragile glycogen α particles in diabetic mice have longer chains and a higher molecular density compared to wild-type mice, indicating an enhanced enzymatic activity ratio of GS to GBE in diabetes. Furthermore, it has been shown that with an improved blood glucose homeostasis, the glycogen fragility in diabetic mice can be restored by treatment with active ingredients from traditional Chinese medicine, yet the underlying mechanism is unknown. In this review, we summarize recent advances in understandings glycogen fragility from the perspectives of glycogen biosynthesis/degradation, glycogen hierarchical structures, and its relation to diabetes. Importantly, we for the first time set GS/GBE activity ratio as the therapeutic target for diabetes.
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Affiliation(s)
- Cheng Li
- Department of Pharmacy, Renmin Hospital of Wuhan University, Wuhan, China.,School of Medical Instrument and Food Engineering, University of Shanghai for Science and Technology, Shanghai, China.,Joint International Research Laboratory of Agriculture and Agri-Product Safety of Ministry of Education of China, Yangzhou University, Yangzhou, China
| | - Zhenxia Hu
- Department of Pharmacy, Renmin Hospital of Wuhan University, Wuhan, China
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4
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Florio TJ, Lokareddy RK, Gillilan RE, Cingolani G. Molecular Architecture of the Inositol Phosphatase Siw14. Biochemistry 2019; 58:534-545. [PMID: 30548067 DOI: 10.1021/acs.biochem.8b01044] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Siw14 is a recently discovered inositol phosphatase implicated in suppressing prion propagation in Saccharomyces cerevisiae. In this paper, we used hybrid structural methods to decipher Siw14 molecular architecture. We found the protein exists in solution as an elongated monomer that is ∼140 Å in length, containing an acidic N-terminal domain and a basic C-terminal dual-specificity phosphatase (DSP) domain, structurally similar to the glycogen phosphatase laforin. The two domains are connected by a protease susceptible linker and do not interact in vitro. The crystal structure of Siw14-DSP reveals a highly basic phosphate-binding loop and an ∼10 Å deep substrate-binding crevice that evolved to dephosphorylate pyro-phosphate moieties. A pseudoatomic model of the full-length phosphatase generated from solution, crystallographic, biochemical, and modeling data sheds light on the interesting zwitterionic nature of Siw14, which we hypothesized may play a role in discriminating negatively charged inositol phosphates.
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Affiliation(s)
- Tyler J Florio
- Department of Biochemistry and Molecular Biology , Thomas Jefferson University , 233 South 10th Street , Philadelphia , Pennsylvania 19107 , United States
| | - Ravi K Lokareddy
- Department of Biochemistry and Molecular Biology , Thomas Jefferson University , 233 South 10th Street , Philadelphia , Pennsylvania 19107 , United States
| | - Richard E Gillilan
- Macromolecular Diffraction Facility, Cornell High Energy Synchrotron Source (MacCHESS) , Cornell University , 161 Synchrotron Drive , Ithaca , New York 14853 , United States
| | - Gino Cingolani
- Department of Biochemistry and Molecular Biology , Thomas Jefferson University , 233 South 10th Street , Philadelphia , Pennsylvania 19107 , United States.,Institute of Biomembranes and Bioenergetics , National Research Council , Via Amendola 165/A , 70126 Bari , Italy
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5
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Sharma S, Vander Kooi CD, Gentry MS, Vander Kooi CW. Oligomerization and carbohydrate binding of glucan phosphatases. Anal Biochem 2018; 563:51-55. [PMID: 30291838 DOI: 10.1016/j.ab.2018.10.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Revised: 09/20/2018] [Accepted: 10/02/2018] [Indexed: 11/24/2022]
Abstract
Glucan phosphatases are a unique subset of the phosphatase family that bind to and dephosphorylate carbohydrate substrates. Family members are found in diverse organisms ranging from single-cell red algae to humans. The nature of their functional oligomerization has been a source of considerable debate. We demonstrate that the human laforin protein behaves aberrantly when subjected to Size Exclusion Chromotography (SEC) analysis due to interaction with the carbohydrate-based matrix. This interaction complicates the analysis of laforin human disease mutations. Herein, we show that SEC with Multi-Angle static Light Scattering (SEC-MALS) provides a method to robustly define the oligomerization state of laforin and laforin variants. We further analyzed glucan phosphatases from photosynthetic organisms to define if this interaction was characteristic of all glucan phosphatases. Starch EXcess-four (SEX4) from green plants was found to lack significant interaction with the matrix and instead exists as a monomer. Conversely, Cm-laforin, from red algae, exists as a monomer in solution while still exhibiting significant interaction with the matrix. These data demonstrate a range of oligomerization behaviors of members of the glucan phosphatase family, and establish SEC-MALS as a robust methodology to quantify and compare oligomerization states between different proteins and protein variants in this family.
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Affiliation(s)
- Savita Sharma
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY, 40536, USA
| | - Carl D Vander Kooi
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY, 40536, USA
| | - Matthew S Gentry
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY, 40536, USA
| | - Craig W Vander Kooi
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY, 40536, USA; Center for Structural Biology, University of Kentucky, Lexington, KY, 40536, USA.
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6
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7
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Parihar R, Rai A, Ganesh S. Lafora disease: from genotype to phenotype. J Genet 2018; 97:611-624. [PMID: 30027899] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The progressive myoclonic epilepsy of Lafora or Lafora disease (LD) is a neurodegenerative disorder characterized by recurrent seizures and cognitive deficits. With typical onset in the late childhood or early adolescence, the patients show progressive worsening of the disease symptoms, leading to death in about 10 years. It is an autosomal recessive disorder caused by the loss-of-function mutations in the EPM2A gene, coding for a protein phosphatase (laforin) or the NHLRC1 gene coding for an E3 ubiquitin ligase (malin). LD is characterized by the presence of abnormally branched water insoluble glycogen inclusions known as Lafora bodies in the neurons and other tissues, suggesting a role for laforin and malin in glycogen metabolic pathways. Mouse models of LD, developed by targeted disruption of the Epm2a or Nhlrc1 gene, recapitulated most of the symptoms and pathological features as seen in humans, and have offered insight into the pathomechanisms. Besides the formation of Lafora bodies in the neurons in the presymptomatic stage, the animal models have also demonstrated perturbations in the proteolytic pathways, such as ubiquitin proteasome system and autophagy, and inflammatory response. This review attempts to provide a comprehensive coverage on the genetic defects leading to the LD in humans, on the functional properties of the laforin and malin proteins, and on how defects in any one of these two proteins result in a clinically similar phenotype. We also discuss the disease pathologies as revealed by the studies on the animal models and, finally, on the progress with therapeutic attempts albeit in the animal models.
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Affiliation(s)
- Rashmi Parihar
- Department of Biological Sciences and Bioengineering, Indian Institute of Technology Kanpur, Kanpur 208 016, India.
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8
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Nitschke F, Sullivan MA, Wang P, Zhao X, Chown EE, Perri AM, Israelian L, Juana-López L, Bovolenta P, Rodríguez de Córdoba S, Steup M, Minassian BA. Abnormal glycogen chain length pattern, not hyperphosphorylation, is critical in Lafora disease. EMBO Mol Med 2018; 9:906-917. [PMID: 28536304 PMCID: PMC5494504 DOI: 10.15252/emmm.201707608] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Lafora disease (LD) is a fatal progressive epilepsy essentially caused by loss-of-function mutations in the glycogen phosphatase laforin or the ubiquitin E3 ligase malin. Glycogen in LD is hyperphosphorylated and poorly hydrosoluble. It precipitates and accumulates into neurotoxic Lafora bodies (LBs). The leading LD hypothesis that hyperphosphorylation causes the insolubility was recently challenged by the observation that phosphatase-inactive laforin rescues the laforin-deficient LD mouse model, apparently through correction of a general autophagy impairment. We were for the first time able to quantify brain glycogen phosphate. We also measured glycogen content and chain lengths, LBs, and autophagy markers in several laforin- or malin-deficient mouse lines expressing phosphatase-inactive laforin. We find that: (i) in laforin-deficient mice, phosphatase-inactive laforin corrects glycogen chain lengths, and not hyperphosphorylation, which leads to correction of glycogen amounts and prevention of LBs; (ii) in malin-deficient mice, phosphatase-inactive laforin confers no correction; (iii) general impairment of autophagy is not necessary in LD We conclude that laforin's principle function is to control glycogen chain lengths, in a malin-dependent fashion, and that loss of this control underlies LD.
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Affiliation(s)
- Felix Nitschke
- Program in Genetics and Genome Biology, The Hospital for Sick Children Research Institute, Toronto, ON, Canada
| | - Mitchell A Sullivan
- Program in Genetics and Genome Biology, The Hospital for Sick Children Research Institute, Toronto, ON, Canada.,Glycation and Diabetes, Mater Research Institute, Translational Research Institute, The University of Queensland, Brisbane, Qld, Australia
| | - Peixiang Wang
- Program in Genetics and Genome Biology, The Hospital for Sick Children Research Institute, Toronto, ON, Canada
| | - Xiaochu Zhao
- Program in Genetics and Genome Biology, The Hospital for Sick Children Research Institute, Toronto, ON, Canada
| | - Erin E Chown
- Program in Genetics and Genome Biology, The Hospital for Sick Children Research Institute, Toronto, ON, Canada.,Institute of Medical Science, University of Toronto, Toronto, ON, Canada
| | - Ami M Perri
- Program in Genetics and Genome Biology, The Hospital for Sick Children Research Institute, Toronto, ON, Canada
| | - Lori Israelian
- Program in Genetics and Genome Biology, The Hospital for Sick Children Research Institute, Toronto, ON, Canada.,Institute of Medical Science, University of Toronto, Toronto, ON, Canada
| | - Lucia Juana-López
- Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas and Ciber de Enfermedades Raras, Madrid, Spain
| | - Paola Bovolenta
- Centro de Biología Molecular Severo Ochoa, CSIC-UAM and Ciber de Enfermedades Raras, Universidad Autónoma de Madrid, Madrid, Spain
| | - Santiago Rodríguez de Córdoba
- Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas and Ciber de Enfermedades Raras, Madrid, Spain
| | - Martin Steup
- Program in Genetics and Genome Biology, The Hospital for Sick Children Research Institute, Toronto, ON, Canada
| | - Berge A Minassian
- Program in Genetics and Genome Biology, The Hospital for Sick Children Research Institute, Toronto, ON, Canada .,Institute of Medical Science, University of Toronto, Toronto, ON, Canada.,Division of Neurology, Department of Pediatrics, University of Texas Southwestern, Dallas, TX, USA
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9
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Segovia D, Haouz A, Porley D, Olivero N, Martínez M, Mariadassou M, Berois M, André-Leroux G, Villarino A. OH1 from Orf Virus: A New Tyrosine Phosphatase that Displays Distinct Structural Features and Triple Substrate Specificity. J Mol Biol 2017; 429:2816-2824. [PMID: 28754374 DOI: 10.1016/j.jmb.2017.07.017] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2017] [Revised: 07/21/2017] [Accepted: 07/21/2017] [Indexed: 10/19/2022]
Abstract
Viral tyrosine phosphatases such as VH1 from Vaccinia and Variola virus are recognized as important effectors of host-pathogen interactions. While proteins sharing sequence to VH1 have been identified in other viruses, their structural and functional characterization is not known. In this work, we determined the crystal structure of the VH1 homolog in the Orf virus, herein named OH1. Similarly to Variola and Vaccinia VH1, the structure of OH1 shows a dimer with the typical dual-specificity phosphatase fold. In contrast to VH1, the OH1 dimer is covalently stabilized by a disulfide bond involving residue Cys15 in the N-terminal helix alpha-1 of both monomers, and Cys15 is a conserved residue within the Parapoxvirus genus. The in vitro functional characterization confirms that OH1 is a dual-specificity phosphatase and reveals its ability to dephosphorylate phosphatidylinositol 3,5-bisphosphate, a new activity potentially relevant in phosphoinositide recycling during virion maturation.
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Affiliation(s)
- Danilo Segovia
- Sección Bioquímica y Biología Molecular, Facultad de Ciencias, UdelaR, 11400 Montevideo, Uruguay
| | - Ahmed Haouz
- Institut Pasteur, Plate-forme de Cristallographie, CNRS-UMR 3528, 75724 Paris, France
| | - Darío Porley
- Sección Bioquímica y Biología Molecular, Facultad de Ciencias, UdelaR, 11400 Montevideo, Uruguay; Sección Virología, Facultad de Ciencias, UdelaR, 11400 Montevideo, Uruguay
| | - Natalia Olivero
- Sección Virología, Facultad de Ciencias, UdelaR, 11400 Montevideo, Uruguay
| | - Mariano Martínez
- Institut Pasteur, UMS, CNRS-UMR 3528 and Université Paris Diderot, 75724 Paris, France
| | | | - Mabel Berois
- Sección Virología, Facultad de Ciencias, UdelaR, 11400 Montevideo, Uruguay.
| | | | - Andrea Villarino
- Sección Bioquímica y Biología Molecular, Facultad de Ciencias, UdelaR, 11400 Montevideo, Uruguay.
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10
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Janeček Š, Majzlová K, Svensson B, MacGregor EA. The starch-binding domain family CBM41-Anin silicoanalysis of evolutionary relationships. Proteins 2017; 85:1480-1492. [DOI: 10.1002/prot.25309] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Revised: 04/05/2017] [Accepted: 04/17/2017] [Indexed: 12/27/2022]
Affiliation(s)
- Štefan Janeček
- Institute of Molecular Biology, Slovak Academy of Sciences; Bratislava Slovakia
- Department of Biology; Faculty of Natural Sciences, University of SS. Cyril and Methodius; Trnava Slovakia
| | - Katarína Majzlová
- Institute of Molecular Biology, Slovak Academy of Sciences; Bratislava Slovakia
| | - Birte Svensson
- Department of Biotechnology and Biomedicine; Technical University of Denmark; Kgs. Lyngby Denmark
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11
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Janeček Š, Gabriško M. Remarkable evolutionary relatedness among the enzymes and proteins from the α-amylase family. Cell Mol Life Sci 2016; 73:2707-25. [PMID: 27154042 PMCID: PMC11108405 DOI: 10.1007/s00018-016-2246-6] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2016] [Accepted: 04/22/2016] [Indexed: 12/17/2022]
Abstract
The α-amylase is a ubiquitous starch hydrolase catalyzing the cleavage of the α-1,4-glucosidic bonds in an endo-fashion. Various α-amylases originating from different taxonomic sources may differ from each other significantly in their exact substrate preference and product profile. Moreover, it also seems to be clear that at least two different amino acid sequences utilizing two different catalytic machineries have evolved to execute the same α-amylolytic specificity. The two have been classified in the Cabohydrate-Active enZyme database, the CAZy, in the glycoside hydrolase (GH) families GH13 and GH57. While the former and the larger α-amylase family GH13 evidently forms the clan GH-H with the families GH70 and GH77, the latter and the smaller α-amylase family GH57 has only been predicted to maybe define a future clan with the family GH119. Sequences and several tens of enzyme specificities found throughout all three kingdoms in many taxa provide an interesting material for evolutionarily oriented studies that have demonstrated remarkable observations. This review emphasizes just the three of them: (1) a close relatedness between the plant and archaeal α-amylases from the family GH13; (2) a common ancestry in the family GH13 of animal heavy chains of heteromeric amino acid transporter rBAT and 4F2 with the microbial α-glucosidases; and (3) the unique sequence features in the primary structures of amylomaltases from the genus Borrelia from the family GH77. Although the three examples cannot represent an exhaustive list of exceptional topics worth to be interested in, they may demonstrate the importance these enzymes possess in the overall scientific context.
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Affiliation(s)
- Štefan Janeček
- Laboratory of Protein Evolution, Institute of Molecular Biology, Slovak Academy of Sciences, Dúbravská cesta 21, 84551, Bratislava, Slovakia.
- Department of Biology, Faculty of Natural Sciences, University of SS. Cyril and Methodius in Trnava, Nám. J. Herdu 2, 91701, Trnava, Slovakia.
| | - Marek Gabriško
- Laboratory of Protein Evolution, Institute of Molecular Biology, Slovak Academy of Sciences, Dúbravská cesta 21, 84551, Bratislava, Slovakia
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12
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Emanuelle S, Brewer MK, Meekins DA, Gentry MS. Unique carbohydrate binding platforms employed by the glucan phosphatases. Cell Mol Life Sci 2016; 73:2765-2778. [PMID: 27147465 PMCID: PMC4920694 DOI: 10.1007/s00018-016-2249-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2016] [Accepted: 04/22/2016] [Indexed: 12/19/2022]
Abstract
Glucan phosphatases are a family of enzymes that are functionally conserved at the enzymatic level in animals and plants. These enzymes bind and dephosphorylate glycogen in animals and starch in plants. While the enzymatic function is conserved, the glucan phosphatases employ distinct mechanisms to bind and dephosphorylate glycogen or starch. The founding member of the family is a bimodular human protein called laforin that is comprised of a carbohydrate binding module 20 (CBM20) followed by a dual specificity phosphatase domain. Plants contain two glucan phosphatases: Starch EXcess4 (SEX4) and Like Sex Four2 (LSF2). SEX4 contains a chloroplast targeting peptide, dual specificity phosphatase (DSP) domain, a CBM45, and a carboxy-terminal motif. LSF2 is comprised of simply a chloroplast targeting peptide, DSP domain, and carboxy-terminal motif. SEX4 employs an integrated DSP-CBM glucan-binding platform to engage and dephosphorylate starch. LSF2 lacks a CBM and instead utilizes two surface binding sites to bind and dephosphorylate starch. Laforin is a dimeric protein in solution and it utilizes a tetramodular architecture and cooperativity to bind and dephosphorylate glycogen. This chapter describes the biological role of glucan phosphatases in glycogen and starch metabolism and compares and contrasts their ability to bind and dephosphorylate glucans.
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Affiliation(s)
- Shane Emanuelle
- Department of Molecular and Cellular Biochemistry and Center for Structural Biology, University of Kentucky, Lexington, KY 40536 USA
| | - M. Kathryn Brewer
- Department of Molecular and Cellular Biochemistry and Center for Structural Biology, University of Kentucky, Lexington, KY 40536 USA
| | - David A. Meekins
- Division of Biology, Kansas State University, Manhattan, KS 66506 USA
| | - Matthew S. Gentry
- Department of Molecular and Cellular Biochemistry and Center for Structural Biology, University of Kentucky, Lexington, KY 40536 USA
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Adeva-Andany MM, González-Lucán M, Donapetry-García C, Fernández-Fernández C, Ameneiros-Rodríguez E. Glycogen metabolism in humans. BBA CLINICAL 2016; 5:85-100. [PMID: 27051594 PMCID: PMC4802397 DOI: 10.1016/j.bbacli.2016.02.001] [Citation(s) in RCA: 264] [Impact Index Per Article: 33.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Revised: 02/10/2016] [Accepted: 02/16/2016] [Indexed: 12/31/2022]
Abstract
In the human body, glycogen is a branched polymer of glucose stored mainly in the liver and the skeletal muscle that supplies glucose to the blood stream during fasting periods and to the muscle cells during muscle contraction. Glycogen has been identified in other tissues such as brain, heart, kidney, adipose tissue, and erythrocytes, but glycogen function in these tissues is mostly unknown. Glycogen synthesis requires a series of reactions that include glucose entrance into the cell through transporters, phosphorylation of glucose to glucose 6-phosphate, isomerization to glucose 1-phosphate, and formation of uridine 5'-diphosphate-glucose, which is the direct glucose donor for glycogen synthesis. Glycogenin catalyzes the formation of a short glucose polymer that is extended by the action of glycogen synthase. Glycogen branching enzyme introduces branch points in the glycogen particle at even intervals. Laforin and malin are proteins involved in glycogen assembly but their specific function remains elusive in humans. Glycogen is accumulated in the liver primarily during the postprandial period and in the skeletal muscle predominantly after exercise. In the cytosol, glycogen breakdown or glycogenolysis is carried out by two enzymes, glycogen phosphorylase which releases glucose 1-phosphate from the linear chains of glycogen, and glycogen debranching enzyme which untangles the branch points. In the lysosomes, glycogen degradation is catalyzed by α-glucosidase. The glucose 6-phosphatase system catalyzes the dephosphorylation of glucose 6-phosphate to glucose, a necessary step for free glucose to leave the cell. Mutations in the genes encoding the enzymes involved in glycogen metabolism cause glycogen storage diseases.
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Affiliation(s)
- María M. Adeva-Andany
- Nephrology Division, Hospital General Juan Cardona, c/ Pardo Bazán s/n, 15406 Ferrol, Spain
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Biophysical characterization of laforin–carbohydrate interaction. Biochem J 2016; 473:335-45. [DOI: 10.1042/bj20141555] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Accepted: 11/17/2015] [Indexed: 11/17/2022]
Abstract
Laforin, a key regulator of glycogen metabolism, is a low-affinity glycan binder. In the present work, we thoroughly biophysically characterized its glycan interaction.
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