Cyclodextrin glycosyl transferase or CGTase for short (EC 2.4.1.19) is a bacterialenzyme belonging to the same family of the Alpha-amylase specifically known as glycosyl-hydrolase family 13. This peculiar enzyme is capable of catalyzing more than one reaction with the most important being the synthesis of non-reducing cyclic dextrins known as cyclodextrins starting from starch, amylose, and other polysaccharides. CGTase is an enzyme common to many bacterial species, in particular of the Bacillusgenus (e.g. B. circulans, B. macerans and B. stearothermophilus), as well as to some archaea, but it is not known to be present in any other species. EC numbers (Enzyme Commission numbers) are a numerical classification scheme for enzymes, based on the chemical reactions they catalyze. ... Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ... Ribbon diagram of the catalytically perfect enzyme TIM. Factor D enzyme crystal prevents the immune system from inappropriately running out of control. ... α-Amylase Amylase (EC 3. ... Dextrins are a group of carbohydrates produced by the hydrolysis of starch. ... Starch is a complex carbohydrate which is insoluble in water. ... Amylose is a linear polymer of glucose linked with α(1→4) bonds. ... Polysaccharides (sometimes called glycans) are relatively complex carbohydrates. ... In biology, a genus (plural genera) is a grouping in the classification of living organisms having one or more related and morphologically similar species. ... Phyla / Classes Phylum Crenarchaeota Phylum Euryarchaeota Halobacteria Methanobacteria Methanococci Methanopyri Archaeoglobi Thermoplasmata Thermococci Phylum Korarchaeota Phylum Nanoarchaeota The Archaea are a major group of prokaryotes. ...
Catalytic activities
All of the CGTases can catalyze up to four reactions: cyclization, coupling, disproportionation and hydrolysis. All these activities share the same catalytic mechanism which is common to all glycosyl-hydrolases.
Cyclization is the process through which a linear polysaccharidic chain is cleaved and the two ends of the cleaved fragment are joined to produce a circular dextrin (cyclodextrin or CD): on the basis of the number of sugar residues this circular product is made of three main type of cyclodextrins can be distinguished, Alpha-CD with six residues, Beta-CD with seven residues and Gamma-CD with eight residues. Alpha-cyclodextrin is a chemical compound belonging to a group of circular oligoglucosides generally called cyclodextrins. ...
The coupling reaction can be easily described as the reverse process of cyclization: the enzyme cleaves a cyclodextrin to produce a linear dextrin which is subsequently joined to a linear oligosaccharide.
Disproportionation is very similar to coupling, but the cleaved dextrin is not a cyclodextrin, but a linear oligosaccharide that is then joined to a second oligosaccharide.
CGTase also has a weak hydrolyzing activity which consists in cleaving the longer polisaccharidic chains into shorter fragments.
References
Biwer A, Antranikian G, Heinzle E. Enzymatic production of cyclodextrins. Appl Microbiol Biotechnol 2002;59:609-17. PMID 12226716.
van der Veen BA, Uitdehaag JC, Penninga D, van Alebeek GJ, Smith LM, Dijkstra BW, Dijkhuizen L. Rational design of cyclodextrin glycosyltransferase from Bacillus circulans strain 251 to increase alpha-cyclodextrin production. J Mol Biol 2000;296:1027-38. PMID 10686101.
Cyclodextrins have a specific toroidal shape: a tight conical cylinder with a hydrophilic exterior (due to the presence of hydroxyl radicals) and a hydrophobic cavity of a specific size.
Cyclodextrin inclusion is a molecular phenomenon in which usually only one guest molecule interacts with the cavity of a Cyclodextrin molecule to become entrapped and form a stable association.
Cyclodextrins are able to form inclusion complexes with broad range hydrophobic molecules as poorly soluble drugs, rapidly deteriorating flavours, volatile fragrances, toxic pesticides or dangerous explosives, even gases; entrapping these substances in their inner cavities.
Mosi, R., Sham, H., Uitdehaag, J.C.M., Ruiterkamp, R., Dijkstra, B.W., and Withers, S.G. Reassessment of acarbose as a transition state analogue inhibitor of cyclodextringlycosyltransferase.
Sin, K.A., Nakamura, A., Kobayashi, K., Masaki, H., and Uozumi, T. Cloning and sequencing of a cyclodextrin glucanotransferase gene from Bacillus ohbensis and its expression in Escherichia coli.
Uitdehaag, J.C.M., van der Veen, B.A., Dijkhuizen, L., Elber, R., and Dijkstra, B.W. Enzymatic circularization of a malto-octaose linear chain studied by stochastic reaction path calculations on cyclodextringlycosyltransferase.
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