Structure and enzymic degradation of polysaccharides

Abstract

Previous work on the elucidation of structures of dextrans, and their degradation by enzymes, has dealt mainly with those containing the 'branching' linkage. The aim of the present work has been (a) to extend what is known about the fine structures of dextrans containing [alpha]-1-3 'branching' linkages, (b) to study dextrans containing [alpha]-1-4 and [alpha]-1-2 'branching' linkages, and (c) to examine the action pattern of several enzymes capable of degrading such dextrans. Standard techniques used in the structural studies have included infrared analysis, periodate oxidation followed by examination of the fragments left (before and after reduction), acid hydrolysis, acetolysis and methylation. Techniques described which have not previously been used on dextrans are glucamylolysis and catalytic oxidation (followed by a study of the modified dextrans). Since one of the key compounds involved, an aldobiouronic acid containing the linkage, was not previously known, it was necessary to carry out certain studies on the catalytic oxidation of a glycosideof maltose, from which the required compound could be isolated. After completion of the present work the acidhas been isolated by other workers 184 the properties being almost identical with the ones obtained in the present investigation.The work describes the action pattern of three dextranase enzymes on 'branched' dextrans, in particular a dextran containing [alpha]-1-4 'branching'. One dextranase was from a bacterial source (Lactobacillus bifidus) while the other two were from moulds (Penicillium lilacinum, Penicllium funiculosum).