Preparation mechanism of CD analogue enzyme

Analogue enzyme is a kind of non-protein molecule which is similar to the function of native enzyme but its structure is much simpler. Analogue enzyme could be taken as a model to analog the combination of enzyme with substrate in order to increase reaction and stereoscopic selectivity. Research of analogue enzyme is an important content in the field of supermolecule chemistry [12]. 

To sum up, CDs have the following characteristics of an ideal analogue enzyme  

CD molecule itself is able to catalyze some chemical reactions due to the hydrophobic cavity similar to the native enzyme, for example, ester hydrolysis. 

Groups with special conformation were introduced into CD. This could get analogue enzyme model with stereoscopic selectivity. For example, pyridoxamine (PM) was bonded to the first hydroxyl group of p CD. The obtained modified CD could catalyze amino transfer reaction of a-ketone add. The reaction speed was 100 fold that of PM as catalyst and the stereoselectivity was shown during the catalysis [16]. If the PM group was linked to the main surface of -CD through double bonds, the transaminase model would be obtained. It was indicated from studies that when PM group was located on one side of CD, the substrate of meta substituted phenyl pyruvic add would be Unked as priority selection when it was located above the cavity of CD, the substrate of p-substituted phenyl pyruvic acid would be linked as priority selection [17]. 

In addition, after the CD units were bridged by some functional groups, two adjacent CDs cavities were able to synergisticaUy partidpate in the inclusion and complexation of guest molecules with the suited shape and size. More stable supramolecular complexes would be formed to better analog the biological enzyme. Based on this, a series of CD polymers have been synthesized by researchers [18]. 

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