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Glucosidases are the glycoside hydrolase enzymes categorized under the EC number 3.2.1. [1]
| | This article needs additional citations for verification .(September 2021) |
Glucosidases are the glycoside hydrolase enzymes categorized under the EC number 3.2.1. [1]
Alpha-glucosidases are enzymes involved in breaking down complex carbohydrates such as starch and glycogen into their monomers. [2]
They catalyze the cleavage of individual glucosyl residues from various glycoconjugates including alpha- or beta-linked polymers of glucose. This enzyme convert complex sugars into simpler ones.
Different sources include different members in this class. Members marked with a "#" are considered by MeSH to be glucosidases.
| Name | EC | Description |
| α-Amylase | EC 3.2.1.1 | is a digestive enzyme in mammals |
| β-Amylase | EC 3.2.1.2 | is a plant enzyme to break down starch |
| γ-Amylase | EC 3.2.1.3 | is a digestive enzyme |
| Cellulase # | EC 3.2.1.4 | breaks down cellulose from plant material |
| Sucrase-isomaltase | EC 3.2.1.10 | - |
| Mannosyl-oligosaccharide glucosidase # | EC 3.2.1.106 | catalyzes the first trimming step of the N-glycosylation pathway; is associated with Congenital Disorder of Glycosylation type IIb |
| Acid α-glucosidase # | EC 3.2.1.20 | is associated with Glycogen storage disease type II |
| Beta-glucosidase # | EC 3.2.1.21 | is associated with Gaucher's disease |
| Lactase | EC 3.2.1.23 | one member of the β-galactosidase family, breaks down milk sugars, and its absence in adulthood causes lactose intolerance |
| Debranching enzyme # | EC 3.2.1.33 | in mammals, yeast and some bacteria, combines transferase and glucosidase activity in glycogen breakdown |
| Pullulanase | EC 3.2.1.41 | has been used as a detergent |
Alpha-glucosidases are targeted by alpha-glucosidase inhibitors such as acarbose and miglitol to control diabetes mellitus type 2.
Maltase is one type of alpha-glucosidase enzymes located in the brush border of the small intestine. 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.
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. It is cheap and popular in China, but not in the U.S. One physician explains the use in the U.S. is limited because it is not potent enough to justify the side effects of diarrhea and flatulence. However, a recent large study concludes "acarbose is effective, safe and well tolerated in a large cohort of Asian patients with type 2 diabetes." A possible explanation for the differing opinions is an observation that acarbose is significantly more effective in patients eating a relatively high carbohydrate Eastern diet.
Sucrase is a digestive enzyme that catalyzes the hydrolysis of sucrose to its subunits fructose and glucose. One form, sucrase-isomaltase, is secreted in the small intestine on the brush border. The sucrase enzyme invertase, which occurs more commonly in plants, also hydrolyzes sucrose but by a different mechanism.
Pullulanase is a specific kind of glucanase, an amylolytic exoenzyme, that degrades pullulan. It is produced as an extracellular, cell surface-anchored lipoprotein by Gram-negative bacteria of the genus Klebsiella. Type I pullulanases specifically attack α-1,6 linkages, while type II pullulanases are also able to hydrolyse α-1,4 linkages. It is also produced by some other bacteria and archaea. Pullulanase is used as a processing aid in grain processing biotechnology.
A debranching enzyme is a molecule that helps facilitate the breakdown of glycogen, which serves as a store of glucose in the body, through glucosyltransferase and glucosidase activity. Together with phosphorylases, debranching enzymes mobilize glucose reserves from glycogen deposits in the muscles and liver. This constitutes a major source of energy reserves in most organisms. Glycogen breakdown is highly regulated in the body, especially in the liver, by various hormones including insulin and glucagon, to maintain a homeostatic balance of blood-glucose levels. When glycogen breakdown is compromised by mutations in the glycogen debranching enzyme, metabolic diseases such as Glycogen storage disease type III can result.
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.
Alpha-glucosidase inhibitors (AGIs) are oral anti-diabetic drugs used for diabetes mellitus type 2 that work by preventing the digestion of carbohydrates. Carbohydrates are normally converted into simple sugars (monosaccharides) by alpha-glucosidase enzymes present on cells lining the intestine, enabling monosaccharides to be absorbed through the intestine. Hence, alpha-glucosidase inhibitors reduce the impact of dietary carbohydrates on blood sugar.
α-Glucosidase is a glucosidase located in the brush border of the small intestine that acts upon α(1→4) bonds:
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
Limit dextrinase is an enzyme with systematic name dextrin 6-alpha-glucanohydrolase. This enzyme catalyses the hydrolysis of (1->6)-alpha-D-glucosidic linkages in alpha- and beta-limits dextrins of amylopectin and glycogen, in amylopectin and pullulan.
Sucrose alpha-glucosidase is an enzyme with systematic name sucrose-alpha-D-glucohydrolase. This enzyme catalyses the following chemical reaction
Glucan 1,3-beta-glucosidase is an enzyme with systematic name 3-beta-D-glucan glucohydrolase. This enzyme catalyses the following chemical reaction
Glucan endo-1,3-alpha-glucosidase is an enzyme with systematic name 3-alpha-D-glucan 3-glucanohydrolase. The enzyme catalyses the following chemical reaction
Glucan 1,6-alpha-glucosidase is an enzyme with systematic name glucan 6-alpha-D-glucohydrolase. This enzyme catalyses the following chemical reaction:
Glucan 1,3-alpha-glucosidase is an enzyme with systematic name 3-alpha-D-glucan 3-glucohydrolase. This enzyme catalyses the following chemical reaction
3alpha(S)-strictosidine beta-glucosidase (EC 3.2.1.105) is an enzyme with systematic name strictosidine beta-D-glucohydrolase. This enzyme catalyses the following chemical reaction
Mannosyl-oligosaccharide glucosidase (MOGS) (EC 3.2.1.106, processing alpha-glucosidase I,Glc3Man9NAc2 oligosaccharide glucosidase, trimming glucosidase I, GCS1) is an enzyme with systematic name mannosyl-oligosaccharide glucohydrolase. MOGS is a transmembrane protein found in the membrane of the endoplasmic reticulum of eukaryotic cells. Biologically, it functions within the N-glycosylation pathway.
Branched-dextran exo-1,2-alpha-glucosidase is an enzyme with systematic name (1->2)-alpha-D-glucosyl-branched-dextran 2-glucohydrolase. This enzyme catalyses the following chemical reaction
Glycoprotein endo-alpha-1,2-mannosidase is an enzyme with systematic name glycoprotein glucosylmannohydrolase. This enzyme catalyses the following chemical reaction
Hesperidin 6-O-alpha-L-rhamnosyl-beta-D-glucosidase (EC 3.2.1.168) is an enzyme with systematic name hesperetin 7-(6-O-alpha-L-rhamnopyranosyl-beta-D-glucopyranoside) 6-O-alpha-rhamnopyranosyl-beta-glucohydrolase. This enzyme catalyses the following chemical reaction
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