The catalytic mechanism of CGTase

CGTase is a kind of glycoside hydrolases, and according to the deference in the conformation of the anomeric carbon atom of glycosidic bonds subjected to hydrolysis, there are two kinds of enzyme catalytic mechanisms One is conformation inversion type (Fig. 2.2(a)), and the other is conformation keeping 

Glycosylation transfer reaction catalyzed by GGTase is divided into four types hydrolysis reaction, cychzation reaction, couphng reaction and disproportionation reaction, in which the coupling reaction in some documents is also known as the open-loop reaction. The direction of glycosylation reaction catalyzed by the GGTase depends on the reaction rate constant of the four types of reaction. Typically, the rate constant of cychzation reaction is greater than that of the hydrolysis reaction, and therefore the direction of the reaction is mainly to produce GD (Fig. 2.3). 

Fig- 2.4. The mechanism of the four kinds of reaction catalyzed by CGTase [6]. 

In the GM study of CGTase, the research on evolution of product-specificity of the enzyme is the most mentioned. Those amino acid residues for substrate binding in the CGTase active site are considered to have an important influence 

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