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Alpha-glucosidase | |||||||||
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Identifiers | |||||||||
EC no. | 3.2.1.20 | ||||||||
CAS no. | 9001-42-7 | ||||||||
Databases | |||||||||
IntEnz | IntEnz view | ||||||||
BRENDA | BRENDA entry | ||||||||
ExPASy | NiceZyme view | ||||||||
KEGG | KEGG entry | ||||||||
MetaCyc | metabolic pathway | ||||||||
PRIAM | profile | ||||||||
PDB structures | RCSB PDB PDBe PDBsum | ||||||||
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Maltase (EC 3.2.1.20, alpha-glucosidase , glucoinvertase, glucosidosucrase, maltase-glucoamylase, alpha-glucopyranosidase, glucosidoinvertase, alpha-D-glucosidase, alpha-glucoside hydrolase, alpha-1,4-glucosidase, alpha-D-glucoside glucohydrolase) is one type of alpha-glucosidase enzymes located in the brush border of the small intestine. [1] [2] This enzyme catalyzes the hydrolysis of disaccharide maltose into two simple sugars of glucose. Maltase is found in plants, bacteria, yeast, humans, and other vertebrates. It is thought to be synthesized by cells of the mucous membrane lining the intestinal wall. [3]
Digestion of starch requires six intestinal enzymes. Two of these enzymes are luminal endo-glucosidases named alpha-amylases. The other four enzymes have been identified as different maltases, exo-glucosidases bound to the luminal surface of enterocytes. Two of these maltase activities were associated with sucrase-isomaltase (maltase Ib, maltase Ia). The other two maltases with no distinguishing characteristics were named maltase-glucoamylase (maltases II and III). The activities of these four maltases are also described as alpha-glucosidase because they all digest linear starch oligosaccharides to glucose. [4] [2]
In most cases, it is equivalent to alpha-glucosidase, but the term "maltase" emphasizes the disaccharide nature of the substrate from which glucose is cleaved, and "alpha-glucosidase" emphasizes the bond, whether the substrate is a disaccharide or polysaccharide.[ citation needed ]
Vampire bats are the only vertebrates known to not exhibit intestinal maltase activity. [5]
Maltase is part of a group of intestinal enzymes called FamilyGH13 (Glycoside hydrolase family 13) that are responsible for breaking apart the α-glucosidase linkages of complex carbohydrates into simple to use glucose molecules. [6] The glucose molecules would then be used as a sort of "food" for cells to produce energy (Adenosine triphosphate) during Cellular respiration. The following are genes that can code for maltase:
The mechanism of all FamilyGH13 enzymes is to break a α-glucosidase linkage by hydrolyzing it. Maltase focuses on breaking apart maltose, a disaccharide that is a link between 2 units of glucose, at the α-(1->4) bond. The rate of hydrolysis is controlled by the size of the substrate (carbohydrate size). [9]
Alpha-amylase has an important function in degradation of starches, so it is used frequently in the baking industry. It is mostly used a means of flavor enhancing to improve bread quality. [7] Without alpha-amylase, yeast would not be able to ferment. [1]
Maltose-glucoamylase is commonly used as a fermentation source as it is able to cut starch into maltose, which is then used for brewing beers and sake. [7]
Other than brewing, maltose glucoamylase has been studied by introducing specific inhibitors to stop the hydrolysis of the α-glucosidase linkages. By inhibiting the cleave of the linkages, scientists are hoping to devise a drug that is more efficient and less toxic to treating diabetes. [10]
The history of maltase discovery began when Napoleon Bonaparte declared a continental blockade in his “Berlin decree” in 1806. This initiated the search for alternative sources of sugar. In 1833 French chemists Anselm Payen and Jean-Francois Persoz discovered a malt extract that converted starch into glucose which they called diastase at the time. [11] In 1880, H.T. Brown discovered mucosal maltase activity and differentiated it from diastase, now called amylase. [2] In the 1960s advances in protein chemistry allowed Arne Dahlqvist and Giorgio Semenza to fractionate and characterize small intestinal maltase activities. Both groups showed there were four major fractions of maltase activity that were intrinsic to two different peptide structures, sucrase-isomaltase and maltase-glucoamylase. [4] [2] [11] [9] Fifty years later entering the genomic age, cloning and sequencing of the mucosal starch hydrolase confirmed Dahlqvist and Semenza's findings. [11]
Acid maltase deficiency (AMD) also known as Pompe disease was first described by Dutch pathologist JC Pompe in 1932. [12] [13] AMD is a non sex linked autosomal recessive condition in which excessive accumulation of glycogen build up within lysosome vacuoles in nearly all types of cells all over the body. [12] [13] [14] It is one of the more serious glycogen storage diseases affecting muscle tissue. [15]
AMD is categorized into three separate types based on the age of onset of symptoms in the affected individual. Infantile (Type a), childhood (Type b), and adulthood (Type c). The type of AMD is determined by the type of gene mutation localized on 17q23. Mutation type will determine production level of acid maltase. AMD is extremely fatal. Type a generally die of heart failure prior to age one. Type b die of respiratory failure between ages three to twenty-four. Type c die of respiratory failure 10–20 years of the onset of symptoms. [15]
A disaccharide is the sugar formed when two monosaccharides are joined by glycosidic linkage. Like monosaccharides, disaccharides are simple sugars soluble in water. Three common examples are sucrose, lactose, and maltose.
A diastase is any one of a group of enzymes that catalyses the breakdown of starch into maltose. For example, the diastase α-Amylase degrades starch to a mixture of the disaccharide maltose; the trisaccharide maltotriose, which contains three α (1-4)-linked glucose residues; and oligosaccharides, known as dextrins, that contain the α (1-6)-linked glucose branches.
An amylase is an enzyme that catalyses the hydrolysis of starch into sugars. Amylase is present in the saliva of humans and some other mammals, where it begins the chemical process of digestion. Foods that contain large amounts of starch but little sugar, such as rice and potatoes, may acquire a slightly sweet taste as they are chewed because amylase degrades some of their starch into sugar. The pancreas and salivary gland make amylase to hydrolyse dietary starch into disaccharides and trisaccharides which are converted by other enzymes to glucose to supply the body with energy. Plants and some bacteria also produce amylase. Specific amylase proteins are designated by different Greek letters. All amylases are glycoside hydrolases and act on α-1,4-glycosidic bonds.
Maltose, also known as maltobiose or malt sugar, is a disaccharide formed from two units of glucose joined with an α(1→4) bond. In the isomer isomaltose, the two glucose molecules are joined with an α(1→6) bond. Maltose is the two-unit member of the amylose homologous series, the key structural motif of starch. When beta-amylase breaks down starch, it removes two glucose units at a time, producing maltose. An example of this reaction is found in germinating seeds, which is why it was named after malt. Unlike sucrose, it is a reducing sugar.
Glycogen storage disease type II, also called Pompe disease, formerly known as GSD-IIa and LGMD2V. It is an autosomal recessive metabolic disorder which damages muscle and nerve cells throughout the body. It is caused by an accumulation of glycogen in the lysosome due to deficiency of the lysosomal acid alpha-glucosidase enzyme. GSD-II and Danon disease are the only glycogen storage diseases with a defect in lysosomal metabolism, and Pompe disease was the first glycogen storage disease to be identified, in 1932 by the Dutch pathologist J. C. Pompe.
Acarbose (INN) is an anti-diabetic drug used to treat diabetes mellitus type 2 and, in some countries, prediabetes. It is a generic sold in Europe and China as Glucobay, in North America as Precose, and in Canada as Prandase.
Disaccharidases are glycoside hydrolases, enzymes that break down certain types of sugars called disaccharides into simpler sugars called monosaccharides. In the human body, disaccharidases are made mostly in an area of the small intestine's wall called the brush border, making them members of the group of "brush border enzymes".
The glycogen debranching enzyme, in humans, is the protein encoded by the gene AGL. This enzyme is essential for the breakdown of glycogen, which serves as a store of glucose in the body. It has separate glucosyltransferase and glucosidase activities.
Isomaltase is an enzyme that breaks the bonds linking saccharides, which cannot be broken by amylase or maltase. It digests polysaccharides at the alpha 1-6 linkages. Its substrate, alpha-limit dextrin, is a product of amylopectin digestion that retains its 1-6 linkage. The product of the enzymatic digestion of alpha-limit dextrin by isomaltase is maltose.
1,4-alpha-glucan-branching enzyme, also known as brancher enzyme or glycogen-branching enzyme is an enzyme that in humans is encoded by the GBE1 gene.
β-Amylase is an enzyme with the systematic name 4-α-D-glucan maltohydrolase. It catalyses the following reaction:
Acid alpha-glucosidase, also called acid maltase, is an enzyme that helps to break down glycogen in the lysosome. It is functionally similar to glycogen debranching enzyme, but is on a different chromosome, processed differently by the cell and is located in the lysosome rather than the cytosol. In humans, it is encoded by the GAA gene. Errors in this gene cause glycogen storage disease type II.
α-Glucosidase (EC 3.2.1.20, is a glucosidase located in the brush border of the small intestine that acts upon α bonds:
In biochemistry, glycoside hydrolases are a class of enzymes which catalyze the hydrolysis of glycosidic bonds in complex sugars. They are extremely common enzymes, with roles in nature including degradation of biomass such as cellulose (cellulase), hemicellulose, and starch (amylase), in anti-bacterial defense strategies, in pathogenesis mechanisms and in normal cellular function. Together with glycosyltransferases, glycosidases form the major catalytic machinery for the synthesis and breakage of glycosidic bonds.
Sucrose intolerance or genetic sucrase-isomaltase deficiency (GSID) is the condition in which sucrase-isomaltase, an enzyme needed for proper metabolism of sucrose (sugar) and starch, is not produced or the enzyme produced is either partially functional or non-functional in the small intestine. All GSID patients lack fully functional sucrase, while the isomaltase activity can vary from minimal functionality to almost normal activity. The presence of residual isomaltase activity may explain why some GSID patients are better able to tolerate starch in their diet than others with GSID.
Sucrase-isomaltase is a bifunctional glucosidase located on the brush border of the small intestine, encoded by the human gene SI. It is a dual-function enzyme with two GH31 domains, one serving as the isomaltase, the other as a sucrose alpha-glucosidase. It has preferential expression in the apical membranes of enterocytes. The enzyme’s purpose is to digest dietary carbohydrates such as starch, sucrose and isomaltose. By further processing the broken-down products, energy in the form of ATP can be generated.
α-Amylase is an enzyme that hydrolyses α bonds of large, α-linked polysaccharides, such as starch and glycogen, yielding shorter chains thereof, dextrins, and maltose, through the following biochemical process:
Glucan 1,4-α-glucosidase is an enzyme located on the brush border of the small intestine with systematic name 4-α-D-glucan glucohydrolase. It catalyses the following chemical reaction
Maltase-glucoamylase, intestinal is an enzyme that in humans is encoded by the MGAM gene.
Neopullulanase is an enzyme of the alpha-amylase family with systematic name pullulan 4-D-glucanohydrolase (panose-forming). This enzyme principally catalyses the following chemical reaction by cleaving pullulan's alpha-1,4-glucosidic bonds:
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