DEGRADATION OF DEXTRANS BY ENZYMES OF INTESTINAL BACTERIA

Abstract

A soluble enzyme system, capable of hydrolyzing dextrans to glucose as the sole or major product, was obtained from an unidentified intestinal species of Bacteriodes. This system evidently contains 2 different dextranases, since it can either "liquiefy" or "saccharify" dextrans. (At pH 5.0-5.5, the principal effect is rapid lowering of viscosity; at pH 7.0-7.5, the major effect is rapid release of glucose). At pH 7.4, the system hydrolyzed both the alpha-1,6- and alpha-l,4-glucosidic bonds of oligosaccharides, and caused the complete or nearly complete hydrolysis of dextrans containing 90-95% "terminal plus 1,6-linked" glucose units. Dextrans with smaller proportions of such units (as well as amylopectins and glycogens) were partly hydrolyzed to glucose under the same conditions. Since these incompletely hydrolyzed substances, with one exception, yielded polysaccharide residues readily precipitated by alcohol, it would appear that the enzymic attack was generally limited to the outer portions of the molecules.