Artificial and Modified Enzymes

Two solutions to this problem have been put forward (Fig. 3.8). 

It has to be emphasized that it is difficult to directly compare the different methodologies of enzyme immobilization since enzymes differ in their properties and details of the immobilization of industrial biocatalysts are often not disclosed. 

Synthetic chemists have always admired the unparalleled catalytic efficiency and specificity of enzymes with some envy and have attempted to copy the catalytic principles which were developed by nature during evolution and to adopt them to the needs of chemical synthesis. Two strategies can be distinguished. 

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Poly(HASCL) depolymerases are able to bind to poly(3HB)-granules. This ability is specific because poly(3HB) depolymerases do not bind to chitin or to (crystalline) cellulose [56,57]. The poly(3HB)-binding ability is lost in truncated proteins which lack the C-terminal domain of about 60 amino acids, and these modified enzymes do not hydrolyze poly(3HB). However, the catalytic domain is unaffected since the activity with water-soluble oligomers of 3-hy-droxybutyrate or with artificial water-soluble substrates such as p-nitrophenyl-esters is unaffected [55, 56, 58, 59]. Obviously, the C-terminal domain of poly(3HB) depolymerases is responsible and sufficient for poly(3HB)-binding [poly(3HB)-binding domain]. These results are in agreement ... 

There is another approach that is increasingly part of synthesis the use of enzymes as catalysts. This approach is strengthened by the new ability of chemists and molecular biologists to modify enzymes and change their properties. There is also interest in the use of artificial enzymes for this purpose, either those that are enzyme-like but are not proteins, or those that are proteins but based on antibodies. Catalytic antibodies and nonprotein enzyme mimics have shown some of the attractive features of enzymes in processes for which natural enzymes are not suitable. 

The design of supramolecular catalysts may make use of biological materials and processes for tailoring appropriate recognition sites and achieving high rates and selectivities of reactions. Modified enzymes obtained by chemical mutation [5.70] or by protein engineering [5.71] represent biochemical approaches to artificial catalysts. 

The area of applied bioactive polymeric systems includes such diverse entities as controlled release systems (erodable systems, diffusion controlled systems, mechanical systems and microcapsules), and biologically active polymers, such as natural polymers, synthetic polypeptides, pseudo-enzymes, pseudo-nucleic acids and polymeric drugs. The area can also include immobilized bioactive materials, such as immobilized enzymes, antibodies and other bioactive agents and the area of artificial cells. This Chapter reviews the general field of biologically active synthetic and modified natural macromolecules with an emphasis on their common characteristics, problems and applications. The areas reviewed include both medical and non-medical applications for both controlled release systems and polymers that exhibit direct biological activity. 

Alonso GA, Istamboulie G, Noguer T, Marty J-L, Munoz R (2012) Rapid determination of pesticide mixtures using disposable biosensors based on genetieally modified enzymes and artificial neural networks. Sens Actuators B Chem 164(l) 22-28... 

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