Action of [Beta]-amylase on branched oligosaccharides

Abstract

<p>Homologous panose coupled branched oligosaccharides have been prepared by the action of macerans amylase on alpha-dextrin and panose. The isomeric fractions B5, B6, and B 7 were separated by the multiple ascent technique of paper chromatography;Isomaltose has been separated from the products of acid hydrolyzed dextran by carbon chromatography. Isomaltose coupled products were prepared by the use of the macerans amylase coupling reaction. The oligosaccharide fractions were separated by multiple ascent paper chromatography into B 4, B5, and B6 groups;The action of beta-amylase on the panose coupled oligosaccharides has been studied. Fractions of the B5 and B6 groups were resistant to the action of beta-amylase. By the use of R-enzyme, it was concluded that the resistant B5 was 0-0-(0-0)-0-, and the resistant B6 was 0-0-(0-0-0)-0-. There might have been a small amount of a resistant B7 with the probable structure 0-0-0-(0-0-0)-0-. A measure of the rate of beta-amylase action on the various fractions has been made. The rate of enzyme action decreased considerably as the branch point (alpha-1,6 linkage) was approached;The action of beta-amylase on the isomaltose coupled oligosaccharides has been studied. Fractions of the B4, B5, and B 6 groups were resistant to the action of the enzyme. The resistant B 4 consisted mainly of 0-0-(0-0)-, but could conceivably have contained 0-0-0-(0)-. The resistant B5 contained both 0-0-(0-0-0)- and 0-0-0-(0-0)-. The resistant B6 consisted of 0-0-0-(0-0-0)-. One chain had an effect on the other as far as the action of the enzyme was concerned. The presence of a single glucose unit on the opposite chain was enough to make a resistant bond out of one which was formerly non-resistant. The rate of beta-amylase action on these fractions was also studied. Again the rate diminished as the branch point was approached;B7 from the salivary amylase hydrolysis of amylopectin was separated by paper chromatography. This preparation consisted of a single oligosaccharide of known structure, 0-0-(0-0-0)-0-0-. Salivary amylase was capable of slowly hydrolyzing this B7 to a B5 and maltose, but the B7 was apparently completely resistant to the action of beta-amylase;The rate of beta-amylase on sweet corn glycogen and maltoheptaose was studied. Two distinct phases of hydrolysis were evident for both of these substrates. The slow phase of each was comparable in rate to that of beta-amylase on B5 from panose and B4 from isomaltose. Evidence was presented which indicated the impracticality of attaining an absolute limit dextrin from a high molecular weight natural molecule such as glycogen or amylopectin.</p>