4,6-α-Glucanotransferase: An enzymatic biocatalyst for the modification of starch and starch-food systems.

The increased demand for healthier, low-calorie foods and ingredients with improved physicochemical properties has increased interest in starch modification strategies aimed at enhancing nutritional and techno-functional properties. Among these strategies, the use of a starch-converting enzyme known as 4,6-α-glucanotransferase (4,6-α-GTase) has attracted considerable attention. 4,6-α-GTase, found in various bacterial sources, most significantly in lactic acid bacteria, converts starch into diverse α-glucans depending on the enzyme type, substrate characteristics and reaction conditions. The resulting products include linear α-(1,6)-linked glucose units, such as isomalto-maltopolysaccharides (IMMP) or a reuteran-like polymer with alternating α-(1,4) and α-(1,6) linkages. These structural modifications have been shown to increase the proportion of slowly digestible and resistant starch while also improving physicochemical and functional attributes in food. This review summarizes current knowledge on 4,6-α-GTase, its catalytic properties, and its potential applications in food systems, offering insights to support further research and development of enzyme modified starch ingredients.