Maltase-glucoamylase (MGAM) and sucrase-isomaltase (SI) (MGAM, SI)

α-Glucosidase enzymes, particularly maltase-glucoamylase (MGAM) and sucrase-isomaltase (SI), are membrane-bound enzymes located in the brush border of small intestinal epithelial cells that catalyze the final hydrolytic step in dietary carbohydrate digestion. They cleave terminal non-reducing α(1→4) glycosidic bonds in oligosaccharides (e.g., maltose, maltotriose) and disaccharides (e.g., sucrose) produced by upstream pancreatic α-amylase, releasing free glucose for intestinal absorption.[1][3][4] These enzymes belong to glycoside hydrolase families GH31 (MGAM, SI) and feature (β/α)8-barrel catalytic domains with conserved Asp nucleophiles and Glu acid/base catalysts that execute a double-displacement retaining mechanism.[1][5] In disease, their hyperactivity contributes to rapid postprandial glucose spikes in type 2 diabetes; thus, they are key therapeutic targets for α-glucosidase inhibitors (AGIs) like acarbose, miglitol, and voglibose, which competitively occupy the -1 subsite of the active site to block substrate binding and slow glucose release.[1][3][7] AGIs are FDA-approved adjuncts to diet/exercise or metformin for glycemic control in diabetes, lowering HbA1c by 0.5-1% with primary use in patients prone to GI intolerance.[1][3] Structural differences between MGAM's N- and C-terminal domains allow preferential hydrolysis of short vs. longer substrates, influencing inhibitor potency.[1] Note that lysosomal acid α-glucosidase (GAA, encoded by GAA gene) is distinct, involved in glycogen breakdown, and deficient in Pompe disease, not a digestive or antidiabetic target.[2][4][7]

Other names

α-glucosidasealpha-glucosidaseα-D-glucoside glucohydrolaseintestinal glucosidasessucrase-isomaltasemaltase-glucoamylase

Competitive inhibition of α-glucosidase active sites, preventing cleavage of α(1→4) glycosidic linkages in oligosaccharides and disaccharides, delaying glucose absorption and reducing postprandial blood glucose spikes