glycosylation

Definition

Target type: biologicalprocess

The covalent attachment and further modification of carbohydrate residues to a substrate molecule. [GOC:hjd, GOC:mah]

Glycosylation is a fundamental biological process that involves the addition of carbohydrate molecules, known as glycans, to proteins or lipids. This modification significantly influences the structure, function, and fate of these biomolecules. The process is catalyzed by enzymes known as glycosyltransferases, which transfer specific sugars from donor molecules to acceptor molecules.

Glycosylation occurs in the endoplasmic reticulum (ER) and Golgi apparatus of eukaryotic cells. The process can be broadly classified into two main types: N-glycosylation and O-glycosylation.

N-glycosylation involves the attachment of a complex oligosaccharide to the nitrogen atom of an asparagine residue within a specific consensus sequence (Asn-X-Ser/Thr) in a protein. The oligosaccharide precursor is assembled in the ER and then transferred en bloc to the protein. This process is initiated by the synthesis of a lipid-linked oligosaccharide precursor, GlcNAc2Man9Glc3, on a dolichol phosphate carrier. Subsequently, this precursor undergoes a series of modifications, including trimming and the addition of additional sugars, before being transferred to the protein.

O-glycosylation involves the attachment of sugars to the oxygen atom of serine or threonine residues in a protein. This type of glycosylation is more diverse than N-glycosylation, with a wide variety of sugar modifications and branching patterns. O-glycosylation is often initiated by the addition of N-acetylgalactosamine (GalNAc) to a serine or threonine residue. Further modifications can then occur, depending on the specific protein and cell type.

Glycosylation plays crucial roles in various cellular processes, including:

- Protein folding and stability: Glycans can promote proper protein folding and prevent aggregation.
- Cell-cell interactions: Glycans mediate interactions between cells, allowing them to recognize and communicate with each other.
- Immune response: Glycosylation is involved in the recognition of pathogens by the immune system.
- Signal transduction: Glycans can influence the activation and signaling of various receptors.
- Protein trafficking: Glycans can direct proteins to their specific locations within the cell.

Disruptions in glycosylation can lead to a variety of diseases, including cancer, genetic disorders, and immune deficiencies. Understanding the complex nature of glycosylation is therefore crucial for developing new therapeutic strategies and diagnostics.'
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Proteins (1)

Compounds (21)