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

The mammalian mucosal alpha-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 alpha-linkages that are digested to glucose slowly by these enzymes. Here, we look at disaccharides with various possible alpha-linkages and their hydrolysis. Hydrolytic properties of the maltose and sucrose isomers were determined using rat intestinal and individual recombinant alpha-glucosidases. The individual alpha-glucosidases had moderate to low hydrolytic activities on all alpha-linked disaccharides, except trehalose. Maltase (N-terminal MGAM) showed a higher ability to digest alpha-1,2 and alpha-1,3 disaccharides, as well as alpha-1,4, making it the most versatile in alpha-hydrolytic activity. These findings apply to the development of new glycemic oligosaccharides based on unusual alpha-linkages for extended glycemic response. It also emphasizes that mammalian mucosal alpha-glticosidases must be used in in-vitro assessment of digestion of such carbohydrates.