Amylase: Difference between revisions
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==Function== | ==Function== | ||
In the human body, α-amylase is part of digestion with the breakdown of carbohydrates in the diet.The mechanism involved includes catalyzing substrate hydrolysis by a double replacement mechanism, forming a covalent glycosyl-enzyme intermediate and hydrolyzed through oxocarbenium ion-like transition states. One of the carboxylic acids in the active site acts as the catalytic nucleophile during the formation of the intermediate. A second carboxylic acid operates as the acid/base catalyst supporting the stabilization of the transition states during the hydrolysis.<ref> | In the human body, α-amylase is part of digestion with the breakdown of carbohydrates in the diet.The mechanism involved includes catalyzing substrate hydrolysis by a double replacement mechanism, forming a covalent glycosyl-enzyme intermediate and hydrolyzed through oxocarbenium ion-like transition states. One of the carboxylic acids in the active site acts as the catalytic nucleophile during the formation of the intermediate. A second carboxylic acid operates as the acid/base catalyst supporting the stabilization of the transition states during the hydrolysis.<ref name="human">Robert Maurus, Anjuman Begum, Leslie K. Williams, Jason R. Fredriksen, Ran Zhang, Stephen G. Withers, Gary D. Brayer. Alternative Catalytic Anions Differentially Modulate Human α-Amylase Activity and Specificity.Biochemistry 2008 47 (11), 3332-3344 | ||
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Salivary α-Amylase hydrolyzes the (α1-4) glycosidic linkages of starch, separating it into short polysaccharide fragments.<ref name="Japan"> Kuriki T, ImanakaI T. The concept of the α-amylase family: Structural similarity and common catalytic mechanism . Journal of Bioscience and Bioengineerin.1999 Mar;87(5): 557-565</ref> Once the enzyme reaches the stomach, it becomes inactivated due to the acidic pH. Further breakdown of starch occurs by secretion of a second form of the enzyme by the pancreas. Pancreatic juice enters the duodenum and pancreatic α-amylase further cleaves starch to yield maltose, maltotriose and oligosaccharides.<ref name="Japan"/> The oligosaccharides are referred to as dextrins, which are fragments of amylopectin consisting of (α1-6)branch points.<ref name="Japan"/> Microvilli of the intestinal epithelia break maltose and dextrins into glucose, which gets absorbed into the circulatory system. Glycogen has a relatively similar structure as starch, and thus proceeds in the same digestive pathway. | Salivary α-Amylase hydrolyzes the (α1-4) glycosidic linkages of starch, separating it into short polysaccharide fragments.<ref name="Japan"> Kuriki T, ImanakaI T. The concept of the α-amylase family: Structural similarity and common catalytic mechanism . Journal of Bioscience and Bioengineerin.1999 Mar;87(5): 557-565</ref> Once the enzyme reaches the stomach, it becomes inactivated due to the acidic pH. Further breakdown of starch occurs by secretion of a second form of the enzyme by the pancreas. Pancreatic juice enters the duodenum and pancreatic α-amylase further cleaves starch to yield maltose, maltotriose and oligosaccharides.<ref name="Japan"/> The oligosaccharides are referred to as dextrins, which are fragments of amylopectin consisting of (α1-6)branch points.<ref name="Japan"/> Microvilli of the intestinal epithelia break maltose and dextrins into glucose, which gets absorbed into the circulatory system. Glycogen has a relatively similar structure as starch, and thus proceeds in the same digestive pathway. | ||
