The structural analysis and enzymic synthesis of a pentasaccharide alpha-limit dextrin formed from amy- lopectin by bacillus subtilis alpha-amylase*

Crystalline Bacillus subtilis alpha-amylase hydrolyses arnylopectin to a mixture Of D-gIUCOSe, maltose, and branched oligosaccharides (alpha-limit dextrins). The smallest such dextrin formed under the conditions of the experiment is a pentasaccharide. A combination of methylation analysis, periodate oxidation, and frag- mentation analysis with acid narrowed the pentasaccharide structure to two possibilities, but failed to distinguish between them. A rigid proof that the dextrin has the structure 6'-a-maltosylmaltotriose was obtained by application of enzymic degradation. Finally, the structure of the pentasaccharide was confirmed by enzymic synthesis. It is shown that the structural analysis of such oligosaccharides, derived from amylopectin, can be made by the use of enzymes alone, without resort to the more time-consuming, less-specific, and less-sensitive methods of chemical analysis. Conclusions are drawn regarding the action pattern of the B. subtilis arnylase.