Biocatalysts Protein engineering

The biotransformation process has been improved by significant advances in biochemical engineering advances in genetic and protein engineering, microbiological manipulations for the production of enzymes, and the use of biocatalysts in immobilized form and large-scale purification methods. 

The search for and the development of a useful biocatalyst with a suitable yield, specific activity and stability is, in the beginning, the task of microbiologists, biochemists, molecular biologists, protein engineers, etc. However, especially with respect to stability, the process engineer also has means available, among others immobilization, to improve the stability of biocatalysts. 

P. C. Cirino and F. H. Arnold, Protein engineering of oxygenases for biocatalysts, Curr. Opin. Chem. Bid. 2002, 6,130-135. 

The last systematic description of heme peroxidases was published in 1999 by Brian Dunford, from the University of Alberta in Canada. The book Heme peroxidases covers discussion on three-dimensional structure, reaction mechanism, kinetics, and spectral properties of representative enzymes from bacterial, plant, fungal, and animal origin. Since 1999, vast information on basic but also applied aspects of heme peroxidases has been generated. We believe fusion of these two aspects will benefit research of those dedicated to development of biocatalytic process. The aim of this book is to present recent advances on basic aspects such as evolution, structure-function relation, and catalytic mechanism, as well as applied aspects, such as bioreactor and protein engineering, in order to provide the tools for rational design of enhanced biocatalysts and biocatalytic processes. The book does not include an exhaustive listing of references but rather a selected collection to enrich discussion and to allow envisioning future directions for research. 

The characteristics of limited operating regions, substrate or product inhibition, and reactions in aqueous solutions have often been considered as the most serious drawbacks of biocatalysts. Many of these drawbacks, however, turn out to be misconceptions and prejudices.For example, many commercially used enzymes show excellent stability with half-lives of months or even years under process conditions. In addition, there is an enzyme-catalyzed reaction equivalent to almost every type of known organic reaction. Many enzymes can accept non-natural substrates and convert them into desired products. More importantly, almost all of the biocatalyst characteristics can be tailored with protein engineering and metabolic engineering methods (refer to the section Biocatalyst Engineering and see also the entry Protein Design ) to meet the desired process conditions. 

The use of a-transglucosidases in the large-scale manufacture of novel bioderivatives is stiU limited by several factors such as enzyme selectivity, stability, and, in some cases, efficiency. To overcome these Umitations and further enlarge the appUcatimis of these enzymes, the latest protein engineering technologies have been used to tailor biocatalysts with specific properties for novel oligosaccharide. 

With the abundant number (> 16 000) of three-dimensional structures in the Brookhaven Protein Data Bank, a challenging but promising task in protein engineering is the synthesis of novel biocatalysts by assembling individual functional modules (substrate binding sites, catalytic centers etc.), or by introducing a... 

The examples above represent some of the most successful studies in protein engineering. They show that it is possible to enhance protein thermostability rationally, alter cofactor or substrate specificity, regiospecificity, and even change catalytic activity. Furtherm ore, the creation of enzymatic activity from a non-catalytic protein backbone, and the creation of a biocatalyst with an unprecedented catalytic activity not found in nature, have also been achieved. However, the examples published in the literature are probably only a tiny fraction of the many studies that have been, or are still, in progress awaiting positive results. 

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