Biocatalysis transferases

A common way to benefit from the ability to combine different molecular orbital methods in ONIOM is to combine a DFT or ab-initio description of the reactive region with a semi-empirical treatment of the immediate protein environment, including up to 1000 atoms. Due to the requirement for reliable semi-empirical parameters, as discussed in Section 2.2.1, this approach has primarily been used for non-metal or Zn-enzymes. Examples include human stromelysin-1 [83], carboxypeptidase [84], ribonucleotide reductase (substrate reaction) [85], farnesyl transferase [86] and cytosine deaminase [87], Combining two ab-initio methods of different accuracy is not common in biocatalysis applications, and one example from is an ONIOM (MP2 HF) study of catechol O-methyltransferase [88],... 

Keywords Biocatalysis Enzymatic polymerization Polyester Polyisoprene Polysaccharide Transferase... 

Enzymes that are suited for application in biocatalysis are mostly hydrolases, bnt also oxidorednctases, lyases and, to a lesser extent, transferases are useful. Obviously, the focus of bulk enzyme producers is different from the main interests of those who want to apply enzymes in biocatalytic applications. Fortunately, a growing number of companies has become active in the field of enzyme prodnction for biotransformations and by now a large nnmber of enzymes suited for biotransformations has become commercially available (Table 5.1). 

Keywords Biocatalysis, Enzyme engineering, Fructosyltransferases, Glucosyl-transferases, Immobilization, Oligosaccharides, Reaction engineering... 

Uridine diphosphate glucose (UDP-Glc) serves as a glucosyl donor in many enzymatic glycosylation processes. A multiple enzyme, one-pot, biocatalytic system was developed for the synthesis of UDP-Glc from low cost raw materials maltodextrin and uridine triphosphate. Three enzymes needed for the synthesis of UDP-Glc (maltodextrin phosphorylase, glucose-l-phosphate thymidyly-transferase, and pyrophosphatase) were expressed in Escherichia coli and then immobilized individually on amino-functionalized magnetic nanoparticles. The conditions for biocatalysis were optimized and the immobilized multiple-enzyme biocatalyst could be easily recovered and reused up to five times in repeated syntheses of UDP-Glc. After a simple purification, approximately 630 mg of crystallized UDP-Glc was obtained from 1 L of reaction mixture, with a moderate yield of around 50% (UTP conversion) at very low cost. ... 

Traditional techniques such as physical adsorption and covalent linkage onto solid supports, entrapment in polymer matrices, and microencapsulation have long been used for immobilizing such enzymes as lipases, proteases, hydantoinases, acylases, amidases, oxidases, isomerases, lyases, and transferases [12-18]. Encapsulation and adsorption have also proved their utility in the immobilization of bacterial, fungal, animal, and plant cells [12-21]. However, as biocatalysis applications have grown, so the drawbacks and limitations of traditional approaches have become increasingly evident. The forefront issues now facing bioimmobilization are indicated in Table 1. 

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