Dietary carbohydrates influence the structure and function of the intestinal alpha-glucosidases

Chegeni, Mohammad. Ph.D., Purdue University, May 2015. Dietary Carbohydrates Influence the Structure and Function of the Intestinal α-Glucosidases. Major Professor: Bruce R. Hamaker. As the primary products of starch digestion by pancreatic α-amylase, maltooligosaccharides (including maltose) are the main substrates for the α-glucosidases at the intestinal brush border. Here, maltose was shown to induce the formation of a higher molecular weight (HMW) sucrase-isomaltase (SI) species in Caco-2 cells that sorts more quickly to the enterocyte surface to act as a digestive enzyme. As this finding suggested a maltose sensing ability of small intestinal enterocytes, molecular mechanisms associated with the maturation and trafficking of HMW SI were further investigated. A pulse-chase experiment using [S]-methionine revealed a higher rate of early trafficking and maturation of the HMW SI species in cells treated with maltose. Endoglycosidase treatment of immunoprecipitated SI showed that increased molecular weight is a consequence of additional Nand O-glycosylation of the enzyme. In comparison to the control, the HMW SI was found to be more associated with lipid rafts at the membrane surface which was related to the higher apical sorting of these species. Thus, maltose sensing of small intestinal enterocytes triggers the intracellular processing of HMW SI, speculatively to enhance its digestive property. Study on the sweet taste receptor subunits (T1R2 and T1R3) by qRT-PCR showed that the expression of T1R2 and T1R3 increased in presence of maltose compared to glucose. It appeared also that