Enzymes artificially modified

In principle, we could ask of almost any molecule selected for a prominent biochemical role whether its structure is really well suited to its function, or could be designed better. For most structures, however, it is not obvious how to put the question in a concrete testable form. Until we know a great deal more than we do now about how the details of protein structure are related to the fine details of enzyme activity, it will be difficult to know whether the enzymes we have are the best we could possibly have. Certainly, there have been reports that artificially modified enzymes can have higher catalytic activity than their natural counterparts (though not usually by large factors) but this does not prove that they are better, because a real enzyme has more to do than just catalyze a reaction. It has to have the required degree of stability not so stable that it fails to disappear when it is unwanted not so unstable that it... 

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. 

Various bacterial plasmids, bacteriophages, and yeast artificial chromosomes are used as cloning vectors (Brown, 2001). At the heart of the general approach to generating and propagating a recombinant DNA molecule is a set of enzymes which synthesize, modify, cut, and join DNA molecules. 

I Cyclodextrins are excellent enzyme models Catalysis and induced fit. Due to their cavities, which are able to accommodate guest (substrate) molecules, and due to the many hydroxyl groups lining this cavity, cyclodextrins can act catalytically in a variety of chemical reactions and they therefore serve as good model enzymes. Thus, benzoic acid esters are hydrolyzed in I aqueous solution by factors up to 100 times faster if cyclodextrins are added. The reaction in- j volves an acylated cyclodextrin as intermediate which is hydrolyzed in a second step of the j reaction, a mechanism reminiscent of the enzyme chymotrypsin. The catalytic efficiency can. be further enhanced if the cyclodextrins are suitably modified chemically so that a whole range of artificial enzymes have been synthesized [551-555, 556, 563, 564]. 

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