Dietary Phenolic Compounds Selectively Inhibit the Individual Subunits of Maltase-Glucoamylase and Sucrase-Isomaltase with the Potential of Modulating Glucose Release

In this study, it was hypothesized that dietary phenolic compounds selectively inhibit the individual C- and N-terminal (Ct, Nt) subunits of the two small intestinal α-glucosidases, maltase-glucoamylase (MGAM) and sucrase-isomaltase (SI), for a modulated glycemic carbohydrate digestion. The inhibition by chlorogenic acid, caffeic acid, gallic acid, (+)-catechin, and (−)-epigallocatechin gallate (EGCG) on individual recombinant human Nt-MGAM and Nt-SI and on mouse Ct-MGAM and Ct-SI was assayed using maltose as the substrate. Inhibition constants, inhibition mechanisms, and IC50 values for each combination of phenolic compound and enzymatic subunit were determined. EGCG and chlorogenic acid were found to be more potent inhibitors for selectively inhibiting the two subunits with highest activity, Ct-MGAM and Ct-SI. All compounds displayed noncompetitive type inhibition. Inhibition of fast-digesting Ct-MGAM and Ct-SI by EGCG and chlorogenic acid could lead to a slow, but complete, digestion of starch for improved glycemic response of starchy foods with potential health benefit.