Glycome
Encyclopedia
The glycome is the entire complement of sugar
s, whether free or present in more complex molecule
s, of an organism
. An alternative definition
is the entirety of carbohydrate
s in a cell
. The glycome may in fact be one of the most complex entities in nature
. "Glycomics
, analogous to genomics
and proteomics
, is the systematic study of all glycan structures of a given cell type or organism" and is a subset of glycobiology
.
"Carbohydrate
", "glycan", "saccharide", and "sugar
" are generic terms used interchangeably in this context and includes monosaccharide
s, oligosaccharide
s, polysaccharide
s, and derivatives of these compounds. Carbohydrates consist of “hydrated carbon”, i.e. [CH2O]n. Monosaccharides are a carbohydrate that cannot be hydrolyzed into a simpler carbohydrate and are the building blocks of oligosaccharides and polysaccharides. Oligosaccharides are linear or branched chains of monosaccharides attached to one another via glycosidic linkages. The number of monosaccharide units can vary. Polysaccharides are glycans composed of repeating monosaccharides, generally greater than ten monosaccharide units in length.
The glycome exceeds the complexity of the proteome
as a result of the even greater diversity of the glycome's constituent carbohydrates and is further complicated by the sheer multiplicity of possibilities in the combination and interaction of the carbohydrates with each other and with protein
s. "The spectrum of all glycan structures — the glycome — is immense. In human
s, its size is orders of magnitude greater than the number of proteins that are encoded by the genome, one percent of which encodes proteins that make, modify, localize or bind sugar chains, which are known as glycans."
The outer surface of the cell is a sea of lipids with a fleet of sugar molecules, many of which are attached to proteins, fats or both, that interact with molecules outside the cell and are critical for the communication between cells and the stickiness of a cell. "Glycans are nature's biologic modifiers," says Jamey Marth, a Howard Hughes Medical Institute investigator at the University of California San Diego."Glycans generally don't turn physiologic processes on and off, rather they modify the behavior of the cell by responding to external stimuli."
Sugar
Sugar is a class of edible crystalline carbohydrates, mainly sucrose, lactose, and fructose, characterized by a sweet flavor.Sucrose in its refined form primarily comes from sugar cane and sugar beet...
s, whether free or present in more complex molecule
Molecule
A molecule is an electrically neutral group of at least two atoms held together by covalent chemical bonds. Molecules are distinguished from ions by their electrical charge...
s, of an organism
Organism
In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...
. An alternative definition
Definition
A definition is a passage that explains the meaning of a term , or a type of thing. The term to be defined is the definiendum. A term may have many different senses or meanings...
is the entirety of carbohydrate
Carbohydrate
A carbohydrate is an organic compound with the empirical formula ; that is, consists only of carbon, hydrogen, and oxygen, with a hydrogen:oxygen atom ratio of 2:1 . However, there are exceptions to this. One common example would be deoxyribose, a component of DNA, which has the empirical...
s in a cell
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
. The glycome may in fact be one of the most complex entities in nature
Nature
Nature, in the broadest sense, is equivalent to the natural world, physical world, or material world. "Nature" refers to the phenomena of the physical world, and also to life in general...
. "Glycomics
Glycomics
Glycomics is the comprehensive study of glycomes , including genetic, physiologic, pathologic, and other aspects. Glycomics "is the systematic study of all glycan structures of a given cell type or organism" and is a subset of glycobiology...
, analogous to genomics
Genomics
Genomics is a discipline in genetics concerning the study of the genomes of organisms. The field includes intensive efforts to determine the entire DNA sequence of organisms and fine-scale genetic mapping efforts. The field also includes studies of intragenomic phenomena such as heterosis,...
and proteomics
Proteomics
Proteomics is the large-scale study of proteins, particularly their structures and functions. Proteins are vital parts of living organisms, as they are the main components of the physiological metabolic pathways of cells. The term "proteomics" was first coined in 1997 to make an analogy with...
, is the systematic study of all glycan structures of a given cell type or organism" and is a subset of glycobiology
Glycobiology
Defined in the broadest sense, glycobiology is the study of the structure, biosynthesis, and biology of saccharides that are widely distributed in nature...
.
"Carbohydrate
Carbohydrate
A carbohydrate is an organic compound with the empirical formula ; that is, consists only of carbon, hydrogen, and oxygen, with a hydrogen:oxygen atom ratio of 2:1 . However, there are exceptions to this. One common example would be deoxyribose, a component of DNA, which has the empirical...
", "glycan", "saccharide", and "sugar
Sugar
Sugar is a class of edible crystalline carbohydrates, mainly sucrose, lactose, and fructose, characterized by a sweet flavor.Sucrose in its refined form primarily comes from sugar cane and sugar beet...
" are generic terms used interchangeably in this context and includes monosaccharide
Monosaccharide
Monosaccharides are the most basic units of biologically important carbohydrates. They are the simplest form of sugar and are usually colorless, water-soluble, crystalline solids. Some monosaccharides have a sweet taste. Examples of monosaccharides include glucose , fructose , galactose, xylose...
s, oligosaccharide
Oligosaccharide
An oligosaccharide is a saccharide polymer containing a small number of component sugars, also known as simple sugars...
s, polysaccharide
Polysaccharide
Polysaccharides are long carbohydrate molecules, of repeated monomer units joined together by glycosidic bonds. They range in structure from linear to highly branched. Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure,...
s, and derivatives of these compounds. Carbohydrates consist of “hydrated carbon”, i.e. [CH2O]n. Monosaccharides are a carbohydrate that cannot be hydrolyzed into a simpler carbohydrate and are the building blocks of oligosaccharides and polysaccharides. Oligosaccharides are linear or branched chains of monosaccharides attached to one another via glycosidic linkages. The number of monosaccharide units can vary. Polysaccharides are glycans composed of repeating monosaccharides, generally greater than ten monosaccharide units in length.
The glycome exceeds the complexity of the proteome
Proteome
The proteome is the entire set of proteins expressed by a genome, cell, tissue or organism. More specifically, it is the set of expressed proteins in a given type of cells or an organism at a given time under defined conditions. The term is a portmanteau of proteins and genome.The term has been...
as a result of the even greater diversity of the glycome's constituent carbohydrates and is further complicated by the sheer multiplicity of possibilities in the combination and interaction of the carbohydrates with each other and with protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
s. "The spectrum of all glycan structures — the glycome — is immense. In human
Human
Humans are the only living species in the Homo genus...
s, its size is orders of magnitude greater than the number of proteins that are encoded by the genome, one percent of which encodes proteins that make, modify, localize or bind sugar chains, which are known as glycans."
The outer surface of the cell is a sea of lipids with a fleet of sugar molecules, many of which are attached to proteins, fats or both, that interact with molecules outside the cell and are critical for the communication between cells and the stickiness of a cell. "Glycans are nature's biologic modifiers," says Jamey Marth, a Howard Hughes Medical Institute investigator at the University of California San Diego."Glycans generally don't turn physiologic processes on and off, rather they modify the behavior of the cell by responding to external stimuli."
Further reading
- Bio-IT World a periodical covering glycomics (A proposal to base the glycome project on Caenorhabditis elegansCaenorhabditis elegansCaenorhabditis elegans is a free-living, transparent nematode , about 1 mm in length, which lives in temperate soil environments. Research into the molecular and developmental biology of C. elegans was begun in 1974 by Sydney Brenner and it has since been used extensively as a model...
, a microscopic worm, whose entire genome is already sequenced) - 'GlycoChip'
- Carolyn Bertozzi's iBioSeminar on Chemical Glycobiology