Protein Glycosylation:

Protein Glycosylation is the reaction in that a carbohydrate, example for a glycosyl donor that is attached to a hydroxyl or other functional set of another molecule a glycosyl acceptor. In the biology glycosylation refers to the enzymatic procedure which attaches glycans to lipids, proteins or other organic molecules. This enzymatic procedure produces one of the fundamental biopolymers establish in cells along with DNA, RNA and proteins. Glycosylation is the form of co-translational and post-translational modification. Glycans serve a variety of functional and structural roles in membrane and secreted proteins. The popularity of proteins synthesized in the rough ER undergo glycosylation. It is an enzyme-directed site-specific procedure, as opposed to the non-enzymatic chemical reaction of glycation. The Glycosylation is also present in the cytoplasm and nucleus as the O-GlcNAc modification.

Most plasma-membrane and secretory proteins hold one or more carbohydrate chains; indeed, the subsequent and addition processing of carbohydrates glycosylation is the principal chemical changes to most such proteins. Some glycosylation reactions happens in the lumen of the ER; others, in the lumina of the medial-, cis-, or trans-Golgi cisternae. Therefore the presence of certain carbohydrate residues on proteins gives useful markers for following their movement from the ER and by the Golgi cisternae. In this part we first review the structures of the oligosaccharide chains generally found in glycoproteins and then discuss their function and synthesis.