Retention of anomeric form in lysozyme-catalyzed reaction

A lysozyme-catalyzed reaction is initiated by a cleavage of the beta-1, 4-glucosaminide linkage, followed by hydration and transglycosylation. Since all glycosides produced by transglycosylation have beta-glycosidic linkages between the sugar and the acceptor moieties, the lysozyme-catalyzed reaction has been classified as an anomer-retention reaction. However, there is no experimental evidence on the anomer retention of the new reducing residue produced by the hydrolysis of the substrate. In the present study, an attempt was made to determine the anomeric form of the GlcNAc residue at the reducing end in nascent hydrolytic products. The anomeric forms of the enzymatic products were separated and quantitatively analyzed by high-performance liquid chromatography. The amounts of alpha- and beta-anomers in the product were plotted against the reaction time. Computer analysis of the experimental data indicated that the nascent hydrolytic product takes only the beta-anomeric form and that the alpha-anomer is formed from beta-anomer by mutarotation.