Amylase: Difference between revisions
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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>DOI: 10.1021/bi701652t</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>DOI: 10.1021/bi701652t</ref> | ||
Salivary α-Amylase hydrolyzes the (α1-4) glycosidic linkages of starch, separating it into short polysaccharide fragments.<ref> Kuriki T, ImanakaI T. The concept of the α-amylase family: Structural similarity and common catalytic mechanism . Journal of Bioscience and | Salivary α-Amylase hydrolyzes the (α1-4) glycosidic linkages of starch, separating it into short polysaccharide fragments.<ref> 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. The oligosaccharides are referred to as dextrins, which are fragments of amylopectin consisting of (α1-6)branch points. 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. | ||
α-Amylase is regulated through a number of inhibitors. These inhibitors are classified according to six categories, based on their tertiary structures. Inhibitors of α-amylase block the active site of the enzyme. In animals, inhibitors control the conversion of starch to simple sugars during glucose peaks after a meal so that breakdown of glucose occurs at a rate the body can handle. This is particularly important for diabetics, who require low quantities of α-amylase to maintain control over glucose levels. After taking insulin however, pancreatic α-amylase escalates. Plants use these inhibitors as a defence mechanism to inhibit the use of α-amylase in insects, thus protecting themselves from herbivory. | α-Amylase is regulated through a number of inhibitors. These inhibitors are classified according to six categories, based on their tertiary structures. Inhibitors of α-amylase block the active site of the enzyme. In animals, inhibitors control the conversion of starch to simple sugars during glucose peaks after a meal so that breakdown of glucose occurs at a rate the body can handle. This is particularly important for diabetics, who require low quantities of α-amylase to maintain control over glucose levels. After taking insulin however, pancreatic α-amylase escalates. Plants use these inhibitors as a defence mechanism to inhibit the use of α-amylase in insects, thus protecting themselves from herbivory. | ||
