Morten Tovborg Jensen

Chemical Synthesis of a Dual Branched Malto-Decaose: A Potential Substrate for α-Amylases

A convergent block strategy for general use in efficient synthesis of complex α‐(1→4)‐ and α‐(1→6)‐malto‐oligosaccharides is demonstrated with the first chemical synthesis of a malto‐oligosaccharide, the decasaccharide 6,6′′′′‐bis(α‐maltosyl)‐maltohexaose, with two branch points. Using this chemically defined branched oligosaccharide as a substrate, the cleavage pattern of seven different α‐amylases were investigated. α‐Amylases from human saliva, porcine pancreas, barley α‐amylase 2 and recombinant barley α‐amylase 1 all hydrolysed the decasaccharide selectively. This resulted in a branched hexasaccharide and a branched tetrasaccharide. α‐Amylases from Asperagillus oryzae, Bacillus licheniformis and Bacillus sp. cleaved the decasaccharide at two distinct sites, either producing two branched pentasaccharides, or a branched hexasaccharide and a branched tetrasaccharide. In addition, the enzymes were tested on the single‐branched octasaccharide 6‐α‐maltosyl‐maltohexaose, which was prepared from 6,6′′′′‐bis(α‐maltosyl)‐maltohexaose by treatment with malt limit dextrinase. A similar cleavage pattern to that found for the corresponding linear malto‐oligosaccharide substrate was observed.