Oglycosidases

O-glycosidases are a subset of glycoside hydrolases that catalyze the hydrolysis of O-glycosidic bonds, releasing sugar residues from O-linked glycoconjugates. They act on linkages in glycoproteins and glycolipids where a sugar is attached to the hydroxyl group of serine or threonine residues, or on related O-linked oligosaccharides.

Substrate scope varies by enzyme. Some O-glycosidases specifically target mucin-type O-glycans, while others act on defined disaccharide or short-chain structures. Many enzymes used in laboratory glycomics require prior removal of sialic acids with neuraminidase to expose the core O-glycosidic bond before cleavage.

Biochemical properties and mechanisms differ among enzymes. Activities may require metal ions or operate via retaining or inverting catalytic mechanisms, depending on the glycoside hydrolase family. O-glycosidases originate from bacteria, fungi, and mammals, reflecting diverse roles in carbohydrate metabolism and host–microbe interactions.

Applications include analytical release of O-linked glycans for mass spectrometry and other glycomic analyses, preparation of mucin-derived oligosaccharides, and structural studies of O-glycosylation patterns. A well-known example is an O-glycosidase from Flavobacterium meningosepticum, which has been used in conjunction with neuraminidase to release O-glycans from glycoproteins for detailed analysis.

Limitations include substrate specificity constraints and sensitivity to assay conditions such as pH and co-factors. O-glycosidases complement N-glycosidases in glycan analysis workflows, contributing to the broader understanding of glycobiology and protein glycosylation.