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Title: Branch pattern of starch internal structure influences the glucogenesis by mucosal Nt-maltase-glucoamylase

item LIN, AMY HUI-MEI - Purdue University
item AO, ZIHUA - Purdue University
item QUEZADA-CALVILLO, ROBERTO - Children'S Nutrition Research Center (CNRC)
item NICHOLS, BUFORD - Children'S Nutrition Research Center (CNRC)
item LIN, CHI-TIEN - Providence University
item HAMAKER, BRUCE - Purdue University

Submitted to: Carbohydrate Polymers
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/9/2014
Publication Date: 4/22/2014
Citation: Lin, A., Ao, Z., Quezada-Calvillo, R., Nichols, B.L., Lin, C., Hamaker, B.R. 2014. Branch pattern of starch internal structure influences the glucogenesis by mucosal Nt-maltase-glucoamylase. Carbohydrate Polymers. 111:33-40.

Interpretive Summary: There is very little free glucose in the human diet. Four intestinal surface enzyme activities digest glucose chains in starch and starch fragments to free glucose. The most common forms of food starch (amylopectins) have branched as well as straight linkages. Here we studied digestion of 6 different food starches by the surface bound enzyme maltase. The glucose production by maltase was different among the food starch and was found to be due to the number and closeness of the branches in the starches.

Technical Abstract: To produce sufficient amounts of glucose from food starch, both alpha-amylase and mucosal alpha-glucosidases are required. We found previously that the digestion rate of starch is influenced by its susceptibility to mucosal alpha-glucosidases. In the present study, six starches and one glycogen were pre-hydrolyzed by alpha-amylase for various time periods, and then further hydrolyzed with the mucosal alpha-glucosidase, the N-terminal subunit of maltase-glucoamylase (Nt-MGAM), to generate free glucose. Results showed that alpha-amylase amplified the Nt-MGAM glucogenesis, and that the amplifications differed in various substrates. The amount of branches within alpha-amylase hydrolysate substrates was highly related to the rate of Nt-MGAM glucogenesis. After de-branching, the hydrolysates showed three fractions, Fraction 1, 2, and 3, in size exclusion chromatographs. We found that the alpha-amylase hydrolysates with higher quantity of the Fraction 3 (molecules with relatively short chain-length) and shorter average chain-length of this fraction had lower rates of Nt-MGAM glucogenesis. This study revealed that the branch pattern of alpha-amylase hydrolysates modulates glucose release by Nt-MGAM. It further supported the hypothesis that the internal structure of starch affects its digestibility at the mucosal alpha-glucosidase level.