Title: Unexpected high digestion rate of cooked starch by the Ct-Maltase-Glucoamylase small intestine mucosal alpha-glucosidase subunit Authors
|Lin, Amy Hui-Mei -|
|Nichols, Buford -|
|Quezada-Calvillo, Roberto -|
|Avery, Stephen -|
|Sim, Lyann -|
|Rose, David -|
|Naim, Hassan -|
|Hamaker, Bruce -|
Submitted to: PLoS One
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 18, 2012
Publication Date: May 1, 2012
Citation: Lin, A., Nichols, B.L., Quezada-Calvillo, R., Avery, S.E., Sim, L., Rose, D.R., Naim, H.Y., Hamaker, B.R. 2012. Unexpected high digestion rate of cooked starch by the Ct-Maltase-Glucoamylase small intestine mucosal alpha-glucosidase subunit. PLoS One. 7(5;e35473):1-7. Interpretive Summary: Starches are the main source of human dietary glucose (sugar). For food starch to form glucose, producing enzymes (amylases) are required. The development of pancreatic amylases is normally delayed until a child is about 6 months old. Thus, the Women, Infants, and Children Program of Texas (WIC) recommends delaying the feeding of starches until that age. To investigate direct digestion in the gut wall, cooked corn starch was used in 4 subunits of maltase-glucoamylase (MGAM) and sucrase-isomaltase. Without any pretreating with amylase, MGAM alone demonstrated adequate digestion of starch to free glucose. It seems that MGAM can adequately replace pancreatic amylase for digesting food starches in very young infants. Our finding suggests that infants can be fed cooked starches from birth.
Technical Abstract: For starch digestion to glucose, two luminal alpha-amylases and four gut mucosal alpha-glucosidase subunits are employed. The aim of this research was to investigate, for the first time, direct digestion capability of individual mucosal alpha-glucosidases on cooked (gelatinized) starch. Gelatinized normal maize starch was digested with N- and C-terminal subunits of recombinant mammalian maltase-glucoamylase (MGAM) and sucrase-isomaltase (SI) of varying amounts and digestion periods. Without the aid of alpha-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 alpha-amylase in digesting starch molecules and potentially may compensate for developmental or pathological amylase deficiencies.