Glykoproteiny

Glykoproteiny, known in English as glycoproteins, are proteins that have carbohydrate chains covalently attached. The carbohydrate portion, or glycan, is typically linked to the protein through N-glycosidic bonds to asparagine residues (N-linked glycosylation) or through O-glycosidic bonds to serine or threonine residues (O-linked glycosylation). Glycosylation occurs mainly in the endoplasmic reticulum and Golgi apparatus during protein maturation.

Most glycoproteins are secreted or cell-surface proteins; many are membrane-anchored or secreted into extracellular fluids. The glycans influence folding, stability, solubility, and trafficking, and play key roles in cell–cell recognition, receptor binding, and immune interactions. Examples include immunoglobulins, mucins, hormones such as erythropoietin, and many receptors and enzymes.

Glycosylation is diverse; N-linked glycans start with a common core and are processed to complex, hybrid, or high-mannose forms; O-linked glycans are more variable. Biosynthesis begins in the endoplasmic reticulum and continues in the Golgi. Glycan structures can be altered in disease; congenital disorders of glycosylation arise from genetic defects in glycosylation pathways, and cancer and inflammation often show changes in glycosylation patterns that affect adhesion and signaling.

In biotechnology, glycosylation is a critical attribute of therapeutic glycoproteins, affecting efficacy and half-life; efforts such as glycoengineering aim to control glycan structures.

Distinction: glycoproteins are proteins with attached glycans, whereas proteoglycans combine glycosaminoglycan chains with a protein core and are more heavily carbohydrate-rich.