The mechanisms of hydrolysis of glycosides and their revelance to enzyme-catalysed reactions

Abstract Glycoside hydrolysis can be formally represented by (I). where the group OR (R is alkyl, aryl or a carbohydrate) is displaced from the C1 or C2 atom of an aldose or ketose sugar (or sugar derivative) respectively; the ring system being either five- or six-membered. Like the analogous hydrolysis of acetals, glycoside hydrolysis shows specific catalysis by hydrogen ions and, except where R is an aryl residue, base catalysis is absent. A number of enzymes* catalysing the hydrolysis of particular glycosides have been characterized: all show a high degree of specificity towards the carbohydrate structures present in the substrates. Both the acid-catalysed and the enzyme-catalysed reactions have been much studied, but whereas the former are now reasonably well understood, the mechanisms involved in the latter are still largely unknown.