Mucosal C-terminal maltase-glucoamylase hydrolyzes large size starch digestion products that may contribute to rapid postprandial glucose generation.
METHODS
The four mucosal α-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 α-glucan oligomers are digested by each enzyme, and how intermediate α-amylolyzed starches are hydrolyzed, to elucidate a strategy for moderating the glycemic spike of rapidly digestible starchy foods.


RESULTS
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 α-amylase digestion of starch, efficiently to glucose. It is postulated that ctMGAM has the additional capacity to hydrolyze large α-amylase products that are produced immediately on starch digestion in the duodenum and contribute to the rapid generation of glucose from starch-based meals.


CONCLUSIONS
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.
Whistler Center for Carbohydrate Research, Purdue University, West Lafayette, IN, USA; Department of Food Science, Purdue University, West Lafayette, IN, USA.
Byung-Hoo
BH
Lee
Amy Hui-Mei
AH
Lin
Buford L
BL
Nichols
Kyra
K
Jones
David R
DR
Rose
Roberto
R
Quezada-Calvillo
Bruce R
BR
Hamaker
D001786:Blood Glucose / Q000378:metabolism; D004063:Digestion; D004386:Duodenum / Q000378:metabolism; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D006868:Hydrolysis; D008320:Maltose / Q000031:analogs & derivatives / Q000378:metabolism; D009092:Mucous Membrane / Q000378:metabolism; D009844:Oligosaccharides / Q000378:metabolism; D011134:Polysaccharides / Q000378:metabolism; D019518:Postprandial Period; D011994:Recombinant Proteins / Q000378:metabolism; D013213:Starch / Q000737:chemistry*; D000516:alpha-Amylases / Q000378:metabolism; D000520:alpha-Glucosidases / Q000378:metabolism*
D001786:Blood Glucose; D009844:Oligosaccharides; D011134:Polysaccharides; D011994:Recombinant Proteins; C021705:maltooligosaccharides; D008320:Maltose; C008315:maltodextrin; D013213:Starch; C009819:maltotetraose; D000516:alpha-Amylases; D000520:alpha-Glucosidases; D005947:Glucose
Glucogenesis; Glycemic spike; Mucosal α-glucosidases; Starch digestion; ctMGAM