环糊精葡萄糖基转移酶CGTase

Cyclodextrin
Cyclodextrins are torus-shaped molecules of cyclic α (1-4)-linked oligosaccharides mainly consisting of six , seven, or eight glucose residues (α- ， β- ，or γ cyclodextrin, respectively).
Introduction
Its main products when acting on starch are cyclodextrins and highly branched highmolecular-weight dextrins (CGTase limit dextrins). CGTase have been characterized from both mesophilic and thermophilic sources. The optimum temperature for activity is about 90℃.The optimum pH for activity is generally around pH 5–6.
Proposed modelof substrate binding in cyclization reaction ofCGTase
Cyclization
Scheme of the cyclization reaction of CGTase

Application
Cyclodextrin
Construction of CGTase
Fig . 2 Stereo-view of the structure of Bacillus circulans strain 251 cyclodextrin glycosyltransferase
Comparison
Comparison
Cat Schematic representation of the CGTase -catalyzed reactions
Catalyzed reactions
The different reactions catalyzed by CGTase
Cyclization
Food field
Application in food additives and modification of functional ingredients
Application in baking bread
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Application
a、Modification of Vc
Vc is very unstable in aqueous solution, and easily oxidized by oxygen in the air and other oxidizing agents. VC will quickly degrade when exposed to neutral pH, heat, light and heavy metal.
Hydrolyzed starch Produced cyclodextrin
Application in baking bread
CGTase be applied in baking bread, can improve the quality of bread, such as increase volume, improve the texture of bread and delay aging.
b、Improvement of sweeteners
Stevioside is a compound with a bitter taste and a low solubility. Glycosylation reactions can reduce the bitterness of stevioside and increase its solubility .
Cyclodextrin Glycosyltransferase
Contents
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Introduction Construction Catalytic mechanism
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Application
Introduction
Cyclodextrin glycosyltransferase(EC 2.4.1.19) (CGTase) is a member of the α-amylase family of glycoside hydrolases(family 13). CGTase has been identified in bacteria belonging to the genera Bacillus ,Clostridium , Klebsiella, Micrococcus ,Thermoanaerobacter , and Thermoanaerobacterium , and in a single archaeon,Thermococcus.