Glycogen intestinal digestion

We typically consume in our diets a generous amount of starch and a smaller amount of glycogen. These complex carbohydrates must be converted into simpler carbohydrates for absorption by the intestine and transport in the blood. Starch and glycogen are digested primarily by the pancreatic enzyme a-amylase and to a lesser extent by salivary ot-amylase. Amylase cleaves the a-1,4 bonds of starch and glycogen, but not the ot-1,6 bonds. The products are the di- and trisaccharides maltose and maltotriose. The material not digestible because of the a -1,6 bonds is called the limit dextrin. 

Glycogen and starch ingested in the diet are hydrolyzed by a-amylases, enzymes in saliva and intestinal secretions that break (al—>4) glycosidic bonds between glucose units. Most animals cannot use cellulose as a fuel source, because they lack an enzyme to hydrolyze the (fil—>4) linkages. Termites readily digest cellulose... 

The principal sites of dietary carbohydrate digestion are the mouth and intestinal lumen. Salivary a-amylase acts on dietary starch (glycogen, amylose, amylopectin), producing oligosaccharides. Pancreatic a-amylase continues the process of starch digestion. 

Digestion of dietary glycogen and starch in the human body begins with the salivary and pancreatic amylases, which cleave a-1,4 linkages at random. It continues with a glucoamylase found in the brush border membranes of the small intestine where it occurs as a complex with maltase.74 Carbohydrases are discussed in Chapter 12, Section B. 

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