Glycome

The glycome is the entire complement of sugars, whether free or present in more complex molecules, of an organism. An alternative definition is the entirety of carbohydrates 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. [ [http://www.cshlpress.com/default.tpl?action=full&--eqskudatarq=666 Cold Spring Harbor Laboratory Press] Essentials of Glycobiology, Second Edition]

"Carbohydrate", "glycan", "saccharide", and "sugar" are generic terms used interchangeably in this context and includes monosaccharides, oligosaccharides, polysaccharides, 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. [ [http://72.14.205.104/search?q=cache:8MLUoA_FVYgJ:grtc.ucsd.edu/lecture1.pps Essentials of Glycobiology] ]

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 proteins. "The spectrum of all glycan structures — the glycome — is immense. In humans, 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." [ [http://www.nature.com/nrg/journal/v7/n7/abs/nrg1894.html Nature Reviews Genetics] article "Genetic defects in the human glycome" Nature Reviews Genetics 7, 537-551 (July 2006) | doi:10.1038/nrg1894 ]

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." [ [http://www.genomenewsnetwork.org/articles/05_01/Glycome_project.shtml genomenewsnetwork] article "The glycome project - A sugar-coated proposal] By Bijal P. Trivedi published May 14, 2001]

ee also

*cell adhesion
*List of omics topics in biology

ources and notes

Further reading

* [http://www.bio-itworld.com/ "Bio-IT World"] a periodical covering glycomics
* [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11680876&dopt=Abstract Glycome project: concept, strategy and preliminary application to Caenorhabditis elegans] (A proposal to base the glycome project on "Caenorhabditis elegans", a microscopic worm, whose entire genome is already sequenced)
* [http://www.glycochip.com/ 'GlycoChip']