Glycomics

 Vertebrates synthesize N- and O-glycans, glycosaminoglycans, and glycosylphosphatidylinositol (GPI) anchors covalently attached to proteins, as well as lipid-linked glycans and free glycans, such as hyaluronan. As with the proteome, each cell type has its own distinct glycome that is governed by local cues and the metabolic state of the cell. Other organisms have distinct glycomes; those of plants and prokaryotes are distinctly different from the vertebrate and invertebrate glycomes . The size of any particular glycome has not yet been established, but the combinatorial possibilities that can occur with numerous glycans on multiple glycosylation sites on each protein (the glycoproteome), means that determining a “complete” glycome is not straightforward.     The notion that glycans should be studied as a totality (glycomics), as well as simply one glycan or glycoprotein at a time, developed when it became apparent that glycans form patterns on cells that change during development , cancer progression, infection , and many other diseases. Many glycan-binding proteins, such as lectins, are oligomerized on the cell surface and interact with multivalent arrays of glycans on opposing cells . Sometimes, multiple discrete glycans work together to engage two cells or to deliver a signal from one cell to the other. Thus, the term “glycomics” was coined to describe the many aspects of glycobiology that can be understood only with a systems-level analysis. No systems-level analysis of a biological process is complete without interrogating the glycome and the glycoproteome in addition to the genome, transcriptome, and proteome. Methods for systemic analysis of the total cellular glycolipids, glycophospholipids ,free glycans , plant glycans and prokaryotic are mentioned in the respective chapters.