Starch digestion and absorption in nonruminants.
Starch digestion and absorption is augmented appreciably by physical processing of grain or legume and by heating to 100 degrees C for several minutes before its ingestion. Starch, a polysaccharide composed of alpha 1,4-linked glucose units (amylose) and alpha 1,4-1,6-linked branched structure (amylopectin), is cleaved in the duodenal cavity by secreted pancreatic alpha-amylase to a disaccharide (maltose), trisaccharide (maltotriose), and branched alpha-dextrins. These final oligosaccharides are hydrolyzed efficiently by complimentary action of three integral brush border enzymes at the intestinal surface: glucoamylase (maltase-glucoamylase, amyloglucosidase), sucrase (maltase-sucrase) and alpha-dextrinase (isomaltase). The final monosaccharide glucose product is then cotransported into the enterocyte along with Na+ by a specific brush border 75-kDa transport protein in the rate-limiting step for overall starch assimilation. By virtue of this sequential luminal and membrane digestion followed by glucose transport, starch is assimilated in a very efficient manner in nonruminants.
Gray
G M
GM
Gastroenterology Division, Stanford University School of Medicine, CA 94305.
D000818:Animals; D004040:Dietary Carbohydrates / Q000378:metabolism*; D004063:Digestion / Q000502:physiology*; D005947:Glucose / Q000378:metabolism; D006801:Humans; D013213:Starch / Q000737:chemistry / Q000378:metabolism*
D004040:Dietary Carbohydrates; D013213:Starch; D005947:Glucose