The influence of amylose content on the modification of starches by glycogen branching enzymes

Glycogen branching enzymes (GBEs) have been used to generate new branches in starches for producing slowly digestible starches. The aim of this study was to expand the knowledge about the mode of action of these enzymes by identifying structural aspects of starchy substrates affecting the products generated by different GBEs. The structures obtained from incubating five GBEs (three from glycoside hydrolase family (GH) 13 and two from GH57) on five different substrates exhibited minor but statistically significant correlations between the amount of longer chains (degree of polymerization (DP) 9-24) of the product and both the amylose content and the degree of branching of the substrate (Pearson correlation coefficient of ≤-0.773 and ≥0.786, respectively). GH57 GBEs mainly generated large products with long branches (100-700 kDa and DP 11-16) whereas GH13 GBEs produced smaller products with shorter branches (6-150 kDa and DP 3-10).