-Amylase

-Amylase cleaves internal (1 - > 4) linkages of starch and glycogen. In the intestine, digestion continues, aided by -amylase secreted by the pancreas. -Amylase degrades amylose to maltose and a little glucose. However, it only partially degrades amylopectin and glycogen, as shown in Figure 13.16, because it cannot cleave the (1 --> 6) linkages found at branch points. The product of exhaustive digestion of amylopectin or glycogen by -amylase is called a limit dextrin; its continued degradation requires the action of a "debranching enzyme," (1 - > 6)-glucosidase (also called isomaltase). This action exposes a new group of (1 -> 4)-linked branches, which can be attacked by -amylase until a new set of (1 -> 6)-linked branches is reached. The end result of the sequential action of these two enzymes is the complete breakdown of starch or glycogen to maltose and some glucose. Maltose is cleaved hydrolytically by maltase, yielding 2 moles of glucose, which is then absorbed into the bloodstream and transported to various tissues for utilization.