CD Analogue Enzyme

Enzyme is a kind of protein with special functions. It exhibits substrates and its reaction specificity could specifically catalyze some chemical reactions under mild conditions. Due to the unusual supermolecule interaction between enzyme and 

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CD derivatives have wide applications in analogue enzyme and analysis chemistry. CD derivative with special functional group can be used as a simple enzyme model which is convenient for studying the action mode and functional groups of the enzyme. The fluorescent and chromophore groups linked to the CDs can be seen as an indicator or a probe which are beneficial for separating the isomers and enantiomers. 

Peptides, coenzymes, amino acids are special functional biological molecules. They became a hot topic while studying the analogue enzymes. For example, the ALT model was formed by connecting the cofactor pyridoxamine phosphate (pyridoxamine, vitamin Be amine) and ethylenediamine to y3-CD. The two functional groups were located through the intermediate positioning process. 

Tripeptide Ser-His-Asp had been introduced to the CD for simulating the chymotrypsin by the following method. Mix 2-amino ethyl mercaptan salts, 6-0-tosyl-/3-CD and NH4HCO3 with DMF/H2O (1 3) solution under nitrogen protection at 60 C for 4h. After vacuum concentration, separate the product by Sephadex G-10 column. The yield is about 43%. Mix the above product with Boc-Ser (Ot-Bu) -His-Asp (Ot-Bu) OH, dicyclohexyl carbodiimide, 1-hydroxy triazole in DMF solution to obtain 6-[Boc-Ser (Ot-Bu) -His-Asp (Ot-Bu) NHCH2CH2S]-/3-CD. Then treat with the TFA/CH2C12(9 1) mixed solution, vacuum concentrate and freeze-dry. This modified CD can be used as an analogue enzyme to hydrolyze nitrophenol esters. 

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

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]. 

Metal ions could play an important role in many electro transferring systems, which was frequently used as super acid catalyst and had directional function. Thus, metal ions were introduced into analogue enzyme model in order to increase its catalyzing efficiency. The earliest CD and metal complex was carboxypeptidase... 

The metal ions can be replaced by other divalent metal ions, although exchanging one or both of the zinc ions with Mg +, Co +, or Mn + results in considerably reduced activity. Substitution of both zinc ions by Cd severely hinders hydrolysis of the phosphoserine intermediate, allowing its isolation. The structure of this species has been determined, as well as those of the native AP enzyme, both in the free state and complexed with inorganic phosphate (10). In addition, the complex of the native enzyme with the transition state analogue vanadate has... 

Tetradecylthioacetic acid (TTA) is a fatty acid analogue in which a sulfur atom substitutes theP-methylene group of the alkyl chain. The analogue closely resembles normal fatty acids except that it is unable to be metabolized by 3-oxidation. cd-3 fatty acids, especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are also poorly oxidized and it has been reported that they inhibit proliferation of cancer cells in culture. Other similarities between TTA and o>-3 fatty acids are induction of several enzymes involved in mitochondrial and peroxisomal 3-oxidation. Moreover, they have hypotriglyceridemic effects, but TTA is much more potent than EPA. ... 

Muehlbacher M, Poulter CD. Isopentenyl-diphosphate isomerase Inactivation of the enzyme with active-site-directed irreversible inhibitors and transition-state analogues. Biochemistry-USA, 1988 27 7315-7328. 

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