Stereochemical course of glucan hydrolysis by barley (1 → 3)- and (1 → 3,1 → 4)-β-glucanases

Abstract

The stereochemical course of hydrolysis of Laminaria digitata laminarin and barley (1 → 3,1 → 4)-β-glucan by barley (1 → 3)-β-glucanase (E.C. 3.2.1.39) isoenzyme GII and (1 → 3,1 → 4)-β-glucanase (EC 3.2.1.73) isoenzyme EII, respectively, has been determined by 1H-NMR. Both enzymes catalyse hydrolysis with retention of anomeric configuration (e → e) and may therefore operate via a double displacement mechanism. We predict that all other members of Family 17 of β-glycosyl hydrolases also follow this stereochemical course of hydrolysis.