AJP - Gastrointestinal and Liver Physiology, Vol 249, Issue 4 510-G518, Copyright © 1985 by American Physiological Society
Nature of elevated rat intestinal carbohydrase activities after high-carbohydrate diet feeding
K. K. Tsuboi, L. K. Kwong, K. Yamada, P. Sunshine and O. Koldovsky
Adult rats that were maintained on a low-carbohydrate intake showed rapid
increase in the activities of sucrase, maltase, and lactase along the
length of the small intestine when they were fed a high-starch diet. In the
present study, we have identified these activity increases, and showed that
they reflect proportional accumulations in enzyme-protein of
sucrase-isomaltase (EC 3.2.1.10, 3.2.1.48), maltase-glucoamylase (EC
3.2.1.20), and neutral lactase (EC 3.2.1.23). It was determined that each
of these enzymes exists in adult rat intestine in single immunoreactive
form and accounts as a group for all sucrase, cellobiase, and most maltase
and lactase activities. Dietary change from low to high carbohydrate
(starch) resulted in an increase in [3H]leucine accumulation in each of the
enzymes, without a change in the amount of label accumulation in total
intestinal proteins. The increase in label accumulation in the brush-border
carbohydrase pools was matched generally by proportional elevation in the
pool concentrations of sucrase-isomaltase and lactase but not maltase.
These studies suggest that the elevation of intestinal carbohydrase
concentrations induced by high-carbohydrate feeding may involve selective
stimulation of their synthesis.
