Molecularly imprinted protein matrices for catalysis

Substrate selectivity and stereoselectivity of enzyme catalysis are known to be influenced by the reaction media. As has been mentioned in the preceding section, a profound feature of the behaviour of enzymes in an anhydrous organic medium is the conformational stability, which leads to enhanced thermal stability and the ligand memory property. These features of enzymes have been exploited to impart novel catalytic characteristics that are absent in the native biopolymers. 

TRANSESTERIFICATION REACTION OF VINYL BUTYRATE WITH BENZYL ALCOHOL IN ANHYDROUS CARBON TETRACHLORIDE CATALYSED BY DIFFERENT HYDROLYTIC ENZYMES IMPRINTED WITH THE SUBSTRATE ANALOGUE V-ACETYL-L-PHENYLALANINE AMIDE  

Enzyme Initial reaction rate, v (/iM/h/mg) imprinted/ non-imprinted 

A systematic and in-depth study involving bio-imprinted subtilisin using nucleophilic substrates as the templates has been reported by Rich and Dordrick [19]. They allowed subtilisin Carlsberg to interact with thymidine (the template) in an aqueous buffer solution and the resulting complex was lyophilised. After removing the template, catalytic activity of the imprinted enzyme was studied by the acylation reaction of thymidine. Compared to the control (enzyme lyophilised from the aqueous solution in the absenee of the nucleotide template), the imprinted enzyme 

Another novel approach to prepare catalytically active bio-imprinted enzymes has been reported by Braco and co-workers [20]. This approach, known as interfacial activation , involves lyophilisation of lipolytic enzymes in the presence of phospholipid-based liposomes as the template. The efficacy of this imprinting process is controlled by the interface between the liposomes and the enzymes. This strategy to prepare bio-imprinted enzymes is illustrated in Fig. 10.2. It was found that the amphiphiles do not provide mere lyoprotection, rather they are responsible for generating imprinting-induced conformationally rigid active sites. This technique was tested with a number of lipases and the resulting imprinted enzymes showed enhanced catalytic activity in anhydrous media [21]. 

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