Unexpected High Digestion Rate of Cooked Starch by the Ct-Maltase-Glucoamylase Small Intestine Mucosal α-Glucosidase Subunit

For starch digestion to glucose, two luminal a-amylases and four gut mucosal a-glucosidase subunits are employed. The aim of this research was to investigate, for the first time, direct digestion capability of individual mucosal a-glucosidases on cooked (gelatinized) starch. Gelatinized normal maize starch was digested with Nand C-terminal subunits of recombinant mammalian maltase-glucoamylase (MGAM) and sucrase-isomaltase (SI) of varying amounts and digestion periods. Without the aid of a-amylase, Ct-MGAM demonstrated an unexpected rapid and high digestion degree near 80%, while other subunits showed 20 to 30% digestion. These findings suggest that Ct-MGAM assists a-amylase in digesting starch molecules and potentially may compensate for developmental or pathological amylase deficiencies. Citation: Lin AH-M, Nichols BL, Quezada-Calvillo R, Avery SE, Sim L, et al. (2012) Unexpected High Digestion Rate of Cooked Starch by the Ct-MaltaseGlucoamylase Small Intestine Mucosal a-Glucosidase Subunit. PLoS ONE 7(5): e35473. doi:10.1371/journal.pone.0035473 Editor: Juliet Ann Gerrard, University of Canterbury, New Zealand Received June 5, 2011; Accepted March 18, 2012; Published May 1, 2012 Copyright: 2012 Lin et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This study was supported by internal sources from the Whistler Center for Carbohydrate Research at Purdue University (West Lafayette, IN, U.S.A.) and, for one collaborator (BLN), USDA, Agricultural Research Service, under Cooperative Agreement no. 58-6250-1-003. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: [email protected]