Amylases and related glycoside hydrolases with transglycosylation activity used for the production of isomaltooligosaccharides

Abstract

Abstract Isomaltooligosaccharides (IMOS) are sugars with health promoting properties that make them relevant for the pharmaceutical and food industries. IMOS have ample chemical diversity achieved by different α-glucosidic linkages and polymerization degrees, forming linear, branched and cyclic structures. Enzymatic synthesis of these compounds can be carried out by glycoside hydrolases (GHs) with transglycosylating activity. Different substrates are used for the synthesis: combinations of disaccharides and monosaccharides, or polymeric carbohydrates such as starch or dextran, which are converted to IMOS by a combination of hydrolysis and transglucosylation. In this review, the structural features of different enzyme families (GH31, GH13, GH70, GH57 and GH66) involved in IMOS synthesis are analysed. Focus is placed on structural traits that affect substrate and product specificity, and on the relative efficiency of transglucosylation and hydrolysis. Information resulting from site-directed mutagenesis and sequence alignments complements structural data to understand the role of specific residues in the performance of the enzymes. Altogether, these studies provide a frame of knowledge which may be used to design new enzymes with improved properties