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Transforming Glycoscience: A Roadmap for the Future (2012)

Chapter: Appendix E: Glossary

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Suggested Citation:"Appendix E: Glossary." National Research Council. 2012. Transforming Glycoscience: A Roadmap for the Future. Washington, DC: The National Academies Press. doi: 10.17226/13446.
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Appendix E

Glossary
1

Amino sugar: A monosaccharide in which an alcoholic hydroxyl group is replaced by an amino group.

Anomeric carbon: The carbon atom of a monosaccharide that bears the hemiacetal functionality (C-1 for most sugars; C-2 for sialic acids).

Anomers: Stereoisomers of a monosaccharide that differ only in configuration at the anomeric carbon of the ring structure.

Carbohydrate: Generic term used interchangeably in this report with sugar, saccharide, or glycan. This term includes monosaccharides, oligosaccharides, and polysaccharides as well as derivatives of these compounds.

Carbohydrate recognition domain: The domain of a polypeptide that is specifically involved in binding to a carbohydrate. In lectins it is often a highly evolutionarily conserved region of the polypeptide.

Cellulose: A repeating homopolymer of β1–4-linked glucose residues.

Chemoenzymatic synthesis: Glycan synthesis that uses both chemical and enzymatic transformations to obtain the desired product.

Chitin: A repeating homopolymer of β1–4-linked N-acetyl-glucosamine residues. It is the main component of the cell walls of fungi and the exoskeletons of arthopods, among other functions.

_______________

1Adapted from Essentials of Glycobiology, 2nd ed., A. Varki et al., eds., Cold Spring Harbor Laboratory Press, Cold Spring Harbor, NY, 2009; used with permission.

Suggested Citation:"Appendix E: Glossary." National Research Council. 2012. Transforming Glycoscience: A Roadmap for the Future. Washington, DC: The National Academies Press. doi: 10.17226/13446.
×

Complex glycan: A glycan containing more than one type of monosaccharide.

Deoxy sugar: A monosaccharide in which a hydroxyl group is replaced by a hydrogen atom.

Epimers: Two isomeric monosaccharides differing only in the configuration of a single chiral carbon. For example, mannose is the C-2 epimer of glucose.

Furanose: Five-membered (four carbons and one oxygen; i.e., an oxygen heterocycle) ring form of a monosaccharide named after the structural similarity to the compound furan.

Galectins: S-type (sulfhydryl-dependent) β-galactoside-binding lectins, usually occurring in a soluble form, expressed by a wide variety of animal cell types and distinguishable by the amino acid sequence of their carbohydrate recognition domains.

Genome: The complete genetic sequence of one set of chromosomes.

Glycan: Generic term for any sugar or assembly of sugars, in free form or attached to another molecule, used interchangeably in this report with saccharide or carbohydrate.

Glycan array: A collection of glycans attached to a surface in a spatially addressed manner.

Glycan-binding proteins: Proteins that recognize and bind to specific glycans and mediate their biological function.

Glycobiology: Study of the structure, chemistry, biosynthesis, and biological functions of glycans and their derivatives.

Glycocalyx: The cell coat consisting of glycans and glycoconjugates surrounding animal cells that is seen as an electron-dense layer by electron microscopy.

Glycoconjugate: A molecule in which one or more glycan units are covalently linked to a noncarbohydrate entity.

Glycoforms: Different molecular forms of a glycoprotein, resulting from variable glycan structure and/or glycan attachment site occupancy.

Glycogen: A polysaccharide comprising α1–4- and α1–6-linked glucose residues that functions in short-term energy storage in animals; sometimes referred to as animal starch.

Glycolipid: General term denoting a molecule containing a glycan linked to a lipid aglycone. In higher organisms most glycolipids are glycosphingolipids, but glycoglycerolipids and other types exist.

Suggested Citation:"Appendix E: Glossary." National Research Council. 2012. Transforming Glycoscience: A Roadmap for the Future. Washington, DC: The National Academies Press. doi: 10.17226/13446.
×

Glycome: The total collection of glycans synthesized by a cell, a tissue, or an organism under specified conditions of time, space, and environment.

Glycomics: Systematic analysis of the glycome.

Glycomimetics: Noncarbohydrate compounds that mimic the properties of glycans.

Glycopeptide: A peptide having one or more covalently attached glycans. Glycoprotein: A protein with one or more covalently bound glycans.

Glycoproteomics: The systems-level analysis of glycoproteins, including their protein identities, sites of glycosylation, and glycan structures.

Glycosaminoglycans: Polysaccharide side chains of proteoglycans or free complex polysaccharides composed of linear disaccharide repeating units, each composed of a hexosamine and a hexose or a hexuronic acid.

Glycosidase: An enzyme that catalyzes the hydrolysis of glycosidic bonds in a glycan.

Glycoside: A glycan containing at least one glycosidic linkage to another glycan or an aglycone.

Glycosidic linkage: Linkage of a monosaccharide to another residue via the anomeric hydroxyl group. The linkage generally results from the reaction of a hemiacetal with an alcohol (e.g., a hydroxyl group on another monosaccharide or amino acid) to form an acetal. Glycosidic linkages between two monosaccharides have defined regiochemistry and stereochemistry.

Glycosyl acceptor: The nucleophile in a glycosylation reaction, usually containing a free hydroxyl group.

Glycosylation: The enzyme-catalyzed covalent attachment of a carbohydrate to a polypeptide, lipid, polynucleotide, carbohydrate, or other organic compound, generally catalyzed by glycosyltransferases, utilizing specific sugar nucleotide donor substrates.

Glycosyl donor: The electrophile in a glycosylation reaction; the nucleotide sugar in an enzymatic glycosylation reaction.

Glycosyltransferase: The enzyme that catalyzes transfer of a sugar from a sugar nucleotide donor to a substrate.

Heparan sulfate: A glycosaminoglycan defined by the disaccharide unit (GlcNAcα1–4GlcAβ1–4/IdoAα1–4), containing N- and O-sulfate esters at various positions, and typically found covalently linked to a proteoglycan core protein.

Heparin: A type of heparan sulfate made by mast cells that has the highest amount of iduronic acid and N- and O-sulfate residues. Pharmaceutical heparin binds and activates antithrombin.

Suggested Citation:"Appendix E: Glossary." National Research Council. 2012. Transforming Glycoscience: A Roadmap for the Future. Washington, DC: The National Academies Press. doi: 10.17226/13446.
×

Heteropolysaccharide: A polysaccharide containing more than one type of monosaccharide.

Hexosamine: Hexose with an amino group in place of the hydroxyl group at the C-2 position. Common examples found in vertebrate glycans are the N-acetylated sugars, N-acetylglucosamine, and N-acetylgalactosamine.

Hexose: A six-carbon monosaccharide typically with an aldehyde (or potential aldehyde) at the C-1 position (aldo-hexose) and hydroxyl groups at all other positions. Common examples in vertebrate glycans are mannose, glucose, and galactose.

Homopolysaccharide: A polysaccharide composed of only one type of monosaccharide.

Lectin: A protein (other than a glycan-specific antibody) that specifically recognizes and binds to glycans without catalyzing a modification of the glycan.

Ligand: A molecule that is recognized by a specific receptor. In the case of lectins the ligands are partly or completely glycan based and are sometimes called counterreceptors.

Methylation analysis: A method for carbohydrate structure analysis based on the acid stability of methyl ethers and the acid lability of glycosidic linkages; used to determine the linkage positions of monosaccharide residues in an oligosaccharide chain.

Microheterogeneity: Structural variations in a glycan at any given glycosylation site on a protein (one source of glycoforms).

Monosaccharide: A carbohydrate that cannot be hydrolyzed into a simpler carbohydrate. It is the building block of oligosaccharides and polysaccharides. Simple monosaccharides are polyhydroxyaldehydes or polyhydroxyketones with three or more carbon atoms.

N-Glycan: A glycan covalently linked to an asparagine residue of a polypeptide chain in the consensus sequence: -Asn-X-Ser/ Thr. Unless otherwise stated, the term N-glycan is used generically in this report to denote the most common linkage region, Manβ1–4GlcNAcβ1–4GlcNAcβ1-N-Asn.

Nucleotide sugars: Activated forms of monosaccharides, such as UDP-Gal, GDP-Fuc, and CMP-Sia, typically used as donor substrates by glycosyltransferases.

Suggested Citation:"Appendix E: Glossary." National Research Council. 2012. Transforming Glycoscience: A Roadmap for the Future. Washington, DC: The National Academies Press. doi: 10.17226/13446.
×

O-Glycan: A glycan glycosidically linked to the hydroxyl group of the amino acids serine, threonine, tyrosine, or hydroxylysine. Unless otherwise stated, the term O-glycan is used in this report to denote the common linkage GalNAcα1-O-Ser/Thr.

Oligosaccharide: A linear or branched chain of monosaccharides attached to one another via glycosidic linkages. The number of monosaccharide units can vary; the term polysaccharide is usually reserved for large glycans with repeating units.

Polysaccharide: A glycan composed of repeating monosaccharides, generally greater than 10 monosaccharide units in length.

Protecting group: A chemical moiety commonly used in glycan synthesis that masks hydroxyl groups in order to prevent them from reacting with other chemical reagents.

Proteome: The total collection of proteins in a cell, tissue, or organism, under specific conditions of time, space, and environment.

Pyranose: Six-membered (five carbons and one oxygen; i.e., an oxygen heterocycle) ring form of a monosaccharide; the most common form found for hexoses and pentoses. The name is based on the structural similarity to the compound “pyran.”

Saccharide: Generic term for any carbohydrate or assembly of carbohydrates, in free form or attached to another molecule, used interchangeably in this report with carbohydrate and glycan.

Sialic acids: Family of acidic sugars with a nine-carbon backbone, of which the most common is N-acetylneuraminic acid, in vertebrates.

Siglecs: Sialic acid–binding proteins that are members of the I-type lectin family and have an amino-terminal V-set domain with typical conserved residues.

Sugar: Generic term often used to refer to any carbohydrate but most frequently to low molecular weight carbohydrates that are sweet in taste. Table sugar, sucrose, is a nonreducing disaccharide (Fruβ21αGlc). Oligosaccharides are sometimes called “sugar chains,” and individual monosaccharides in a sugar chain are sometimes referred to as “sugar residues.”

Transcriptome: The total collection of RNA transcripts in a cell, a tissue, or an organism, under specific conditions of time, space, and environment.

Suggested Citation:"Appendix E: Glossary." National Research Council. 2012. Transforming Glycoscience: A Roadmap for the Future. Washington, DC: The National Academies Press. doi: 10.17226/13446.
×

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Suggested Citation:"Appendix E: Glossary." National Research Council. 2012. Transforming Glycoscience: A Roadmap for the Future. Washington, DC: The National Academies Press. doi: 10.17226/13446.
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Suggested Citation:"Appendix E: Glossary." National Research Council. 2012. Transforming Glycoscience: A Roadmap for the Future. Washington, DC: The National Academies Press. doi: 10.17226/13446.
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Suggested Citation:"Appendix E: Glossary." National Research Council. 2012. Transforming Glycoscience: A Roadmap for the Future. Washington, DC: The National Academies Press. doi: 10.17226/13446.
×
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Suggested Citation:"Appendix E: Glossary." National Research Council. 2012. Transforming Glycoscience: A Roadmap for the Future. Washington, DC: The National Academies Press. doi: 10.17226/13446.
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Suggested Citation:"Appendix E: Glossary." National Research Council. 2012. Transforming Glycoscience: A Roadmap for the Future. Washington, DC: The National Academies Press. doi: 10.17226/13446.
×
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Suggested Citation:"Appendix E: Glossary." National Research Council. 2012. Transforming Glycoscience: A Roadmap for the Future. Washington, DC: The National Academies Press. doi: 10.17226/13446.
×
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A new focus on glycoscience, a field that explores the structures and functions of sugars, promises great advances in areas as diverse as medicine, energy generation, and materials science, this report finds. Glycans--also known as carbohydrates, saccharides, or simply as sugars--play central roles in many biological processes and have properties useful in an array of applications. However, glycans have received little attention from the research community due to a lack of tools to probe their often complex structures and properties.

Transforming Glycoscience: A Roadmap for the Future presents a roadmap for transforming glycoscience from a field dominated by specialists to a widely studied and integrated discipline, which could lead to a more complete understanding of glycans and help solve key challenges in diverse fields.

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