Glycosylation and carbohydrate processing by the liver

Glycosylation is the process by which a carbohydrate is covalently attached to a target macromolecule, typically proteins and lipids. This modification serves various functions.^[4]

For instance, some proteins do not fold correctly unless they are glycosylated.^[1] In other cases, proteins are not stable unless they contain oligosaccharides linked at the amide nitrogen of certain asparagine. The influence of glycosylation on the folding and stability of glycoprotein is twofold. Firstly, the highly soluble glycans may have a direct physicochemical stabilisation effect. Secondly, N-linked glycan mediate a critical quality control check point in glycoprotein folding in the endoplasmic reticulum.^[5]

Glycosylation also plays a role in cell-cell adhesion (a mechanism employed by cells of the immune system) via sugar-binding proteins called lectins, which recognize specific carbohydrate moieties.^[1] Glycosylation is an important parameter in the optimization of many glycoprotein-based drugs…