New Approach to the Metabolism of Hydrogenated Starch Hydrolysate: Hydrolysis by the Maltase/Glucoamylase Complex of the Rat Intestinal Mucosa

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Abstract
The maltase (EC 3.2.1.20)/glucoamylase (EC 3.2.1.3) complex from rat small intestine brush border, which is able to split α (1→4) glucose-sorbitol linkage, was isolated and purified by chromatography on DEAE-Trisacryl M and Sepharose 6B. The complex was homogeneous on polyacrylamide gel electrophoresis. Kinetic parameters were studied on two substrates: maltose and maltitol (Km: 1.3 mM and 30 mM, Vmax: 200 nmol·min-1 and 15 nmol·min-1, respectively). Inhibition studies were performed with maltose and maltitol as substrates and isomaltitol and δ-gluconolactone as inhibitors. Crossed-inhibition reactions were also performed. The results support the existence of one single catalytic site and this fact was confirmed by physicochemical properties. Similar results were obtained with germ-free rats as well as with conventional rats adapted over 6–12 months to Lycasin® 80/55 as the sole source of sugar. Lycasin® 80/55, hydrogenated starch hydrolysate, was converted by purified maltase/glucoamylase complex in glucose and sorbitol.

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