Contribution of the Individual Small Intestinal α-Glucosidases to Digestion of Unusual α-Linked Glycemic Disaccharides

The mammalian mucosal α-glucosidase complexes, maltase-glucoamylase (MGAM) and sucrase-isomaltase (SI), have two catalytic subunits (N- and C-termini). Concurrent with the desire to modulate glycemic response, there has been a focus on di-/oligosaccharides with unusual α-linkages that are digested to glucose slowly by these enzymes. Here, we look at disaccharides with various possible α-linkages and their hydrolysis. Hydrolytic properties of the maltose and sucrose isomers were determined using rat intestinal and individual recombinant α-glucosidases. The individual α-glucosidases had moderate to low hydrolytic activities on all α-linked disaccharides, except trehalose. Maltase (N-terminal MGAM) showed a higher ability to digest α-1,2 and α-1,3 disaccharides, as well as α-1,4, making it the most versatile in α-hydrolytic activity. These findings apply to the development of new glycemic oligosaccharides based on unusual α-linkages for extended glycemic response. It also emphasizes that mammalian mucosal α-glucosidases must be used in in vitro assessment of digestion of such carbohydrates.