Glycosyltransferases cyclodextrin

Some transferases can directly use and transform oligosaccharides as donors without further activation. The following paragraph will discuss some reactions with non-Leloir glycosyltransferases which are performed on a preparative level. For example, cyclodextrin-al-4-glucosyltransferase (CGT) from Klebsiella pneumonia or from Bacillus macerans are rather versatile enzymes which can catalyze various reactions. 

Amylose may be cyclized to give cyclodextrins, acceptors may be coupled onto cyclodextrins to give acceptor-attached open chain maltooligomer derivatives, or disproportionation reactions between amylose chains of different dp 

Further, various glycosyl fluorides were tested as substrates for CGT [83]. This approach gave novel insights into the specificity of the catalytic site of CGT from Bacillus macerans and new routes for the preparation of regioselectively modified cyclodextrins. 

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Hofmann, B.E., Bender, H., Schulz, G.E. Three-dimensional structure of cyclodextrin glycosyltransferase from Bacillus circulans at 3.4 A resolution. /. Mol. Biol. 209 793-800, 1989. 

Cyclobuxine-D, 2 104 P-Cyclocitral, 24 570 Cyclocitronellene acetate, 24 488 a-Cyclocitrylidenebutanone, 24 565 Cyclodehydrating agents, 20 276 Cyclodemol, 24 488 P-Cyclodextrin, 4 715 Cyclodextrin glucanotransferase, 24 48 Cyclodextrin glycosyltransferase, 4 715 Cyclodextrin inclusions, 74 183 Cyclodextrin inclusion compounds, 74 166-167... 

Bender, H., Siebert, R., Stadler-Szoke, A. (1982). Can cyclodextrin glycosyltransferase be useful for the investigation of the fine structure ofamylopectins Characterisation of highly branched clusters isolated from digests with potato and maize starches. Carbohydr. Res., 110,245-259. 

J. C. M. Uitdehaag, B. A. van der Veen, L. Dijkhuizen, R. Elber, and B. W. Dijkstra (2001) Enzymatic circularization of a malto-octaose linear chain studied by stochastic reaction path calculations on cyclodextrin glycosyltransferase. Proteins Structure Function and Genetics 43, pp. 327-335... 

These cyclodextrin glycosyltransferases are particularly intriguing, since they convert (linear) amylose to 6-, 7- and 8-membered (a, p and y) cyclodextrins. Important interactions occur in the —6 subsites, since the distribution of cyclodextrins can be altered by mutations here, which do not affect the rate of hydrolysis. Remarkably, the cyclodextrins first produced from amylose have between 9 and 60 glucose units in a macrocyclic ring, with the smaller cyclodextrins being produced later. ... 

Cyclodextrin glycosyltransferase is an extracellular enzyme which has been detected in a number of bacteria, mainly Bacillus, but also Paenibaciilus, Klebsiella, Thermoanaerobacterium, Thermoanaerobacter species and Actinomycetes [32], Nearly 30 CGTase genes have been isolated since the first identification of this gene in B. macerans and several of the enzymes have been identified and biochemically characterized [33],... 

Figure 16.3 (a)The three-dimensional structure of cyclodextrin glycosyltransferase and (b) the catalytic (P/ot)8 barrel.(Reproduced with permission from [30]. Copyright (2000) Elsevier). 

Cyclodextrin glycosyltransferase catalyzes the breakdown of starch and linear maltodextrin substrates to produce CDs, while a-amylase converts starch into linear oligosaccharides, resulting in a rapid decrease in viscosity [37]. 

Table 16.2 Influence of organic solvents on the product selectivity of cyclodextrin glycosyltransferase.

Cyclodextrin glycosyltransferase can use a variety of carbohydrates and other compounds as acceptors in the reactions. The synthesis of a number of... 

Glycosyltransferases transfer glycosyl groups from a starch chain to an acceptor. The acceptor may be another starch molecule, phosphoric acid or nucleotides. Most enzymes in this class catalyze reversible reactions some enzymes are involved in the starch biosynthesis. The only glycosyltransferase responsible for starch degradation is the cyclodextrin glycosyltransferase. 

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