Stereochemical course and structure of the products of the enzymic action of endo-1,3-1,4-β-D-glucan 4-glucanohydrolase from Bacillus licheniformis

The stereochemical course of the reaction catalysed by endo-1,3-1,4-β-D-glucan 4-glucanohydrolase (EC 3.2.1.73) has been determined by ¹H n.m.r. The enzyme-catalysed hydrolysis of barley β-glucan proceeds with overall retention of the anomeric configuration, indicating that the enzyme operates through a double-displacement mechanism. The structures of the final oligo-saccharide products, 3-β-O-cellobiosyl D-glucopyranoside and 3-β-O-cellotriosyl D-glucopyranoside, have been completely assigned by ¹H- and ¹³C-n.m.r. spectroscopy.