ARS | Publication request: Specific starch digestion of maize alpha-limit dextrins by recombinant mucosal glucosidase enzymes

Submitted to: Journal of Federation of American Societies for Experimental Biology
Publication Type: Abstract Only
Publication Acceptance Date: April 6, 2010
Publication Date: April 6, 2010
Citation: Lin, A.H., Nichols, B.L., Quezada-Calvillo, R., Rose, D.R., Sim, L., Hamaker, B.R. 2010. Specific starch digestion of maize alpha-limit dextrins by recombinant mucosal glucosidase enzymes [abstract]. Journal of Federation of American Societies for Experimental Biology. 24:231.6.

Technical Abstract: Starch digestion requires two luminal enzymes, salivary and pancreatic alpha-amylase (AMY), and four small intestinal mucosal enzyme activities from the N- and C-terminals of maltase-glucoamylase (MGAM) and sucrose-isomaltase (SI) complexes. AMY is not a requirement for starch digestion to glucose but dramatically amplifies {alpha}-glucogenesis by producing {alpha}-limit dextrins(LDx) as favored substrates for the mucosal enzymes. The aim of this study was to study substrate specificity of {alpha}-glucogenesis by four recombinant MGAM and SI subunits. Recombinant {alpha}-glucosidase domains were produced in drosophila (N-) or baculovirus (C-) cell lines and purified by histags. LDx was produced with AMY from normal maize and three mutant cultivars with different amylopectin structures: normal, waxy, ae waxy and du waxy. Glucose released in vitro was measured by GOPOD. N-MGAM subunit releases glucose from shortest linear oligomers while the other three subunits digest longer chains or branched molecules. This is the first time that the individual {alpha}-glucogenic activities of all four mucosal enzyme subunits have been tested. The individual {alpha}-glucosidase subunits had different activities for each cultivar LDx substrate and selective affinities for LDx from different cultivars. Combinations of {alpha}-glucosidase subunits thus provide a broader spectrum of {alpha}-glucogenic activities from structurally varied starch LDx.