Luminal Substrate “Brake” on Mucosal Maltase‐glucoamylase Activity Regulates Total Rate of Starch Digestion to Glucose

ABSTRACT Background: Starches are the major source of dietary glucose in weaned children and adults. However, small intestine α‐glucogenesis by starch digestion is poorly understood due to substrate structural and chemical complexity, as well as the multiplicity of participating enzymes. Our objective was dissection of luminal and mucosal α‐glucosidase activities participating in digestion of the soluble starch product maltodextrin (MDx). Patients and Methods: Immunoprecipitated assays were performed on biopsy specimens and isolated enterocytes with MDx substrate. Results: Mucosal sucrase‐isomaltase (SI) and maltase‐glucoamylase (MGAM) contributed 85% of total in vitro α‐glucogenesis. Recombinant human pancreatic α‐amylase alone contributed