Studies on the transport of glucose from disaccharides by hamster small intestine in vitro. I. Evidence for a disaccharidase-related transport system

Abstract

In the presence of saturating concentrations of free d-glucose, total glucose uptake was enhanced beyond the theoretical V for free glucose uptake when disaccharides were incubated with intestinal rings. This phenomenon was not seen when glucose 1-phosphate was the substrate. Analogs of d-glucose transport system, galactose and β-methyl glucoside, had an inhibitory effect on glucose uptake from sucrose and their uptake was in turn inhibited by the disaccharide. This inhibition was non-competitive. The effect of phlorizin on glucose uptake from sucrose was 2-fold, competitive at low concentrations and non-competitive at high concentrations. Sucrose did not induce counterflow of the preloaded β-methyl glucoside. These observations indicate that with a disaccharide as the substrate, there is a component of glucose transport which is in addition to the monoscaccharide-transport system and that this could arise as a consequence of the association of disaccharidases with the brush border membrane.