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Research Project: Pediatric Clinical Nutrition

Location: Children's Nutrition Research Center

Title: Mucosal C-terminal maltase-glucoamylase hydrolyzes large size starch digestion products that may contribute to rapid postprandial glucose generation

item LEE, BYUNG-HOO - Purdue University
item LIN, AMY HUI-MEI - Purdue University
item NICHOLS, BUFORD - Children'S Nutrition Research Center (CNRC)
item JONES, KYRA - University Of Waterloo
item ROSE, DAVID - Children'S Nutrition Research Center (CNRC)
item QUEZADA-CALVILLO, ROBERTO - Autonomous University Of San Luis Potosi
item HAMAKER, BRUCE - Purdue University

Submitted to: Molecular Nutrition and Food Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2013
Publication Date: 5/1/2014
Citation: Lee, B., Lin, A., Nichols, B.L., Jones, K., Rose, D.R., Quezada-Calvillo, R., Hamaker, B.R. 2014. Mucosal C-terminal maltase-glucoamylase hydrolyzes large size starch digestion products that may contribute to rapid postprandial glucose generation. Molecular Nutrition and Food Research. 58(5):1111-1121.

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 four purified surface enzymes were tested individually. The free end enzyme of maltase-glucoamylase, called glucoamylase, were the most active on converting long starch fragments to glucose. Inhibitors of glucoamylase in food may slow starch digestion to glucose.

Technical Abstract: The four mucosal alpha-glucosidases, which differ in their digestive roles, generate glucose from glycemic carbohydrates and accordingly can be viewed as a control point for rate of glucose delivery to the body. In this study, individual recombinant enzymes were used to understand how alpha-glucan oligomers are digested by each enzyme, and how intermediate alpha-amylolyzed starches are hydrolyzed, to elucidate a strategy for moderating the glycemic spike of rapidly digestible starchy foods. The C-terminal maltase-glucoamylase (ctMGAM, commonly termed glucoamylase) was able to rapidly hydrolyze longer maltooligosaccharides, such as maltotetraose and maltopentaose, to glucose. Moreover, it was found to convert larger size maltodextrins, as would be produced early in alpha-amylase digestion of starch, efficiently to glucose. It is postulated that ctMGAM has the additional capacity to hydrolyze large alpha-amylase products that are produced immediately on starch digestion in the duodenum and contribute to the rapid generation of glucose from starch-based meals. In conclusion, the findings suggest that partial inhibition of ctMGAM, such as by natural inhibitors found in foods, might be used to moderate the early stage of high glycemic response, as well as to extend digestion distally; thereby having relevance in regulating glucose delivery to the body.