ABSTRACT
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.
