Enzymes that cleave glycosidic bonds, with a few exceptions, are almost all compiled in the carbohydrate-active enzymes (CAZy) database [1, 2]. Many families have been created for enzyme classes of glycoside hydrolases (GHs), polysaccharide lyases (PLs), carbohydrate esterases (CEs), and auxiliary activities (AAs) that cleave polysaccharides by oxidation, such as lytic polysaccharide monooxygenase (LPMO) (Fig. 21.1). Polysaccharide-degrading enzymes include not only amylases and cellulases but also enzymes produced by intestinal bacteria that degrade dietary fibers and human-derived glycans. In the case of glycosidases for glycoconjugates, endoglycosidases that cleave glycans from glycoproteins (endo-β-N-acetylglucosaminidases and peptide:N-glycanases) are known as representative examples. Various exoglycosidases are involved in the biosynthesis of glycosides, such as processing in the endoplasmic reticulum and the Golgi apparatus. Because a large number and variety of enzymes are known, it has become a huge and diverse field of research [3].