glycosidase

Glycosidases, or glycoside hydrolases, are enzymes that catalyze the hydrolysis of glycosidic bonds, which link sugar units within polysaccharides, disaccharides, or between a sugar and a non-sugar moiety. They are found across all forms of life and play essential roles in digestion, metabolism, and cellular turnover. The enzymes are classified by the enzyme commission as hydrolases acting on glycosyl compounds (EC 3.2).

Glycosidases can be categorized by substrate specificity (for example, alpha- or beta-linkages; exoglycosidases that trim residues from the ends, and endoglycosidases that cleave internal bonds). They also differ in their catalytic mechanisms: many retain a glycosyl-enzyme intermediate in two steps, while others invert the glycosidic bond in a single displacement. Regardless of mechanism, the reaction releases a free sugar moiety and an aglycone.

Physiological roles include human digestive enzymes such as lactase (β-galactosidase), sucrase-isomaltase, and maltase-glucoamylase, which hydrolyze dietary carbohydrates. Alpha-amylases act on starch in the digestive tract, and lysosomal glycosidases such as acid alpha-glucosidase participate in glycogen breakdown. Deficiency or malfunction of specific glycosidases can cause disease, for example lactose intolerance from lactase deficiency and Pompe disease from acid alpha-glucosidase deficiency.

Industrial and research uses include biomass conversion, food processing, and the synthesis of defined oligosaccharides. Glycosidases enable cellulose and other polysaccharide breakdown in biofuel production and are employed in glycoprotein remodeling and analytical glycomics. The diversity of glycosidases is reflected in many protein families cataloged in the CAZy database, underscoring broad substrate specificities and evolutionary adaptation.