Glykoosylaatio

Glykoosylaatio, commonly referred to in English as glycosylation, is the enzymatic process by which carbohydrate groups (glycans) are covalently attached to proteins or lipids. This modification produces glycoproteins and glycolipids and is a fundamental post-translational modification in many organisms. In eukaryotes, glykoosylaatio largely occurs in the endoplasmic reticulum and the Golgi apparatus, where the glycan chains are built and processed before the mature molecules are trafficked to their cellular destinations. Prokaryotes and some archaea also exhibit glycosylation pathways, but with different enzymes and glycan structures.

There are several major forms of glykoosylaatio. N-linked glycosylation attaches glycans to the asparagine residue within a specific consensus sequence, often co-translationally in the ER. O-linked glycosylation attaches glycans to serine or threonine residues, typically in the Golgi. Other forms include cytosolic and nuclear O-GlcNAcylation and various specialized glycosylations seen in bacteria and archaea. The process is driven by glycosyltransferases, using activated sugar donors such as dolichol-linked sugars in the ER and nucleotide-activated sugars in the Golgi.

Functions of glykoosylaatio are diverse. It influences protein folding and stability, quality control, membrane targeting, and cell surface recognition. Glycosylation patterns modulate immune responses and cell signaling, and they can affect the pharmacokinetics and efficacy of therapeutic proteins. Aberrations in glykoosylaatio cause congenital disorders of glycosylation and are implicated in cancer progression, infectious disease, and inflammatory conditions.

Analytical approaches include mass spectrometry, high-performance liquid chromatography, and glycoproteomics, often complemented by lectin-based assays. In biotechnology, glykoosylaatio is manipulated through glycoengineering to optimize therapeutic proteins and antibodies.