Polymer synthesis oxidoreductases

Peroxidases belong to the class of oxidoreductases containing iron (111) and protoporphyrin IX as the prosthetic groups. Peroxidases catalyze the reduction of peroxides and the oxidation of many organic and inorganic compounds. These enzymes are widely used for the removal of phenolic compounds, decolorization of synthetic dyes, deodorization of swine manure, in enzyme immunoassays, for biofuel production and organic and polymer synthesis (Hamid and Rehman, 2009). Peroxidases have also been used for the surface modification of poly-p-phenylene-2,6-benzo-bisthiazole (PBO), polyethylene, and grafting of acrylamide onto kevlar fibers. 

Thus far, oxidoreductases are mostly engaged in polymer synthesis in two major areas. First, they are employed for the polymerization of phenols and anilines. In the former case, the products include polyphenols (39) and polyCphenylene oxide) (40). In the latter case, wata -soIuble polyaniline polymers can be made (41). Secondly, oxidoreductases are employed for the free-radical polymerization of vinyl monomers (42). 

Oxidoreductases comprise a large class of enzymes that catalyze biological oxidation/reduction reactions. Because so many chemical transformation processes involve oxidation/reduction processes, the idea of developing practical applications of oxidoreductase enzymes has been a very attractive, but quite elusive, goal for many years [83], Applications have been sought for the production of pharmaceuticals, synthesis and modification of polymers, and the development of biosensors for a variety of clinical and analytical applications [83], In recent years, the use of oxido-reductive enzymes to catalyze the removal of aromatic compounds from... 

Since the beginning of enzyme catalysis in microemulsions in the late 1970s, several biocatalytic transformations of various hydrophilic and hydrophobic substrates have been demonstrated. Examples include reverse hydrolytic reactions such as peptide synthesis [44], synthesis of esters through esterification and transesterification reactions [42,45-48], resolution of racemic amino acids [49], oxidation and reduction of steroids and terpenes [50,51], electron-transfer reactions, [52], production of hydrogen [53], and synthesis of phenolic and aromatic amine polymers [54]. Isolated enzymes including various hydrolytic enzymes (proteases, lipases, esterases, glucosidases), oxidoreductases, as well as multienzyme systems [52], were anployed. 

Also laccases, oxidoreductases with a Cu atom in the active center, have been successfully applied to the synthesis of phenol polymers. For example, phenol and several derivatives were polymerized by laccase from Pycnoporus coccineus (PCL) in aqueous organic solvents to yield the corresponding polymers [149]. The same enzyme was used to produce PPO from syringic acid (79) and from 2,6-dimethylphenol. Laccase from Myceliophthore (MPL) was found to catalyze the polymerization of syringic acid to PPO [135-137]. Lac-... 

For the last decades, enzymatic synthesis of phenolic polymers has been extensively investigated [1-10]. In living cells, various oxidoreductases play an important role in maintaining the metabolism of living systems. So far, several oxidoreductases—peroxidase, laccase, bilirubin oxidase etc.—have been reported to catalyze an oxidative polymerization of phenol derivatives, and among them, peroxidase is most often used. The enzymatically synthesized phenolic polymers are expected to become an alternative to conventional phenolic resins, which have limitations of their preparation and use due to concerns over the toxicity of formaldehyde. 

All enzymes are categorized into six groups (1) oxidoreductases, (2) transferases, (3) hydrolases, (4) lyases, (5) isomerases, and (6) Hgases. They show respective catalytic functions specific to the substrate group in vivo. In this volume, however, each chapter is organized on the basis not of the enzyme category but on the class of polymers synthesized. Enzymatic synthesis of polymers (often referred to as enzymatic polymerization) is operated by in vitro enzymatic catalysis, which is close to or very similar to in vivo enzymatic catalysis depending on the reaction. 

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