sialylierte

Sialylated refers to molecules that carry sialic acid residues at the outer ends of their glycan chains, typically found on glycoproteins and glycolipids. Sialylation is the enzymatic process by which sialic acid, usually N-acetylneuraminic acid (Neu5Ac) in humans, is attached to galactose or N-acetyllactosamine units by sialyltransferases in the Golgi apparatus. The common linkage types are alpha-2,3; alpha-2,6; and alpha-2,8, producing structurally diverse glycans that influence molecular interactions and stability.

In humans, Neu5Ac is the predominant sialic acid, and the enzyme CMAH that produces Neu5Gc is inactive, leaving Neu5Gc largely absent from endogenous glycans. Neu5Gc can be incorporated from certain dietary sources and may provoke immune responses in some contexts.

Biological significance includes extending the circulatory half-life of glycoproteins by reducing clearance by hepatic receptors, and modulating interactions with lectins, selectins, and Siglecs. These interactions affect cell adhesion, signaling, immune recognition, and receptor function. Sialylation patterns are dynamic and can change with development, tissue type, and disease.

Clinical and research relevance: aberrant sialylation is associated with several diseases, notably cancer, where increased sialylation can promote metastasis and immune evasion. Conversely, glycoengineering to tailor sialylation can improve the pharmacokinetics and efficacy of therapeutic proteins and antibodies.

Detection and study methods include lectin binding assays, enzymatic desialylation, and mass spectrometry-based glycomics. Sialidases (neuraminidases) are used to study the functional consequences of sialylation.