The Glycoside Hydrolases
DOI link for The Glycoside Hydrolases
The Glycoside Hydrolases book
Enzymes are highly selective for compounds that bind into the active site and are converted to product. Two different enzymes can hydrolyze the glycosidic bond of sucrose; one enzyme recognizes the glucose moiety and the other the fructose moiety. Glucoamylase is an exo-splitting enzyme that removes glucose units consecutively from the nonreducing end of the substrate chains. Glucoamylase hydrolyzes α-1,4 glucosidic linkages but the product is β-glucose, so there is an inversion of configuration as in the case of ß-amylase. In biosynthesis of disaccharides most of the reactions involve nucleoside diphosphate glycosides as donors. In glycoside derivatives of the monosaccharides, the conformation is the chair structure. In a number of cases, the thioglycoside is a competitive inhibitor of the enzyme, indicating that it can be bound in the active site. The β-glucosidases hydrolyze cellobiose much more rapidly than cellohexaose, whereas the reverse is true for the exoglucohydrolases.