Starch source influences dietary glucose generation at the mucosal α-glucosidase level

J Biol Chem. 2012 Oct 26;287(44):36917-21. doi: 10.1074/jbc.M112.378331. Epub 2012 Sep 17.


The quality of starch digestion, related to the rate and extent of release of dietary glucose, is associated with glycemia-related problems such as diabetes and other metabolic syndrome conditions. Here, we found that the rate of glucose generation from starch is unexpectedly associated with mucosal α-glucosidases and not just α-amylase. This understanding could lead to a new approach to regulate the glycemic response and glucose-related physiologic responses in the human body. There are six digestive enzymes for starch: salivary and pancreatic α-amylases and four mucosal α-glucosidases, including N- and C-terminal subunits of both maltase-glucoamylase and sucrase-isomaltase. Only the mucosal α-glucosidases provide the final hydrolytic activities to produce substantial free glucose. We report here the unique and shared roles of the individual α-glucosidases for α-glucans persisting after starch is extensively hydrolyzed by α-amylase (to produce α-limit dextrins (α-LDx)). All four α-glucosidases share digestion of linear regions of α-LDx, and three can hydrolyze branched fractions. The α-LDx, which were derived from different maize cultivars, were not all equally digested, revealing that the starch source influences glucose generation at the mucosal α-glucosidase level. We further discovered a fraction of α-LDx that was resistant to the extensive digestion by the mucosal α-glucosidases. Our study further challenges the conventional view that α-amylase is the only rate-determining enzyme involved in starch digestion and better defines the roles of individual and collective mucosal α-glucosidases. Strategies to control the rate of glucogenesis at the mucosal level could lead to regulation of the glycemic response and improved glucose management in the human body.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Carbohydrate Metabolism*
  • Dextrins / chemistry*
  • Glucose / chemistry*
  • Humans
  • Hydrolysis
  • Kinetics
  • Mice
  • Molecular Weight
  • Mucous Membrane / enzymology*
  • Protein Subunits / chemistry
  • Starch / chemistry
  • Zea mays / chemistry
  • alpha-Amylases / chemistry
  • alpha-Glucosidases / chemistry*


  • Dextrins
  • Protein Subunits
  • Starch
  • alpha-Amylases
  • alpha-Glucosidases
  • Glucose