Toward Transition State Analysis of O-Glycoside Hydrolysis by Human Sucrase/Isomaltase

Abstract

Type 2 diabetes is a major health concern worldwide. One of its complications is postprandial hyperglycemia, i.e., high blood glucose concentrations, caused by glucose fast release from dietary polysaccharides into the bloodstream after meals. α-Glucosidase inhibitor drugs reduce postprandial hyperglycemia by inhibiting maltase/glucoamylase (MGAM) and sucrase/isomaltase (SI). MGAM and SI transform polysaccharides into absorbable monosaccharides, and inhibiting them delays monosaccharide release into the blood. The three commercially available α-glucosidase inhibitors are limited by their absorption abilities, inhibition efficacies, and side effects, which highlights the need for more specific α-glucosidase inhibitors. Because enzymes catalyze their reactions by tightly binding to their cognate transition states (TS), TS analogs can be powerful inhibitors and potential drugs. The measurement and interpretation of kinetic isotope effects (KIEs) is the only method that can directly determine TS structures on large molecules. In this work, methods to prepare radioisotopically labelled maltose were developed, as well as methods to measure KIEs on acid- and enzyme-catalyzed maltose hydrolysis. However, the methods developed did not achieve the required precision for TS analysis. Also, KIEs were calculated computationally for a model reaction of maltose hydrolysis.