Peroxidases biocatalytic systems

In biocatalytic systems, catalase is mainly used in immobilized state. High activity of immobilized catalase was achieved on its sorption immobilization on cellulose [6], on silica gel modified with fatty acids or phospholipids [7] as well as on activated carbon fibres and brics/tissues/ [8]. Biocatalytic activity of catalase immobilized on cellulose was also studied in nonaqueous solvents [9,10]. In [9] it was found that unlike the enzyme dissolved in water-dimethylformamide medium, on the oxidation of o-dianisidine in the presence of dimethylfonnamide the immobilized catalase does not show any peroxidase activity. It was used [10] for working out an organic-phase amperometric biosensor by immobilizing the enzyme in a polymeric film on a glass-carbon surface. 

Synthesized biocatalytic systems on the basis of horseradish peroxidase and mushroom tyrosinase were found to be highly active and stable in catalytic oxidations of phenols including sewage treatment and industrial waste products. The catalysts obtained can be used for sewage and industrial waste biocatalytic treatment as they allow transfering dangerous phenolic compounds to harmless melanin-type polymers. 

The use of hydrogen peroxide as an oxidant is not compatible with the operation of a biocatalytic fuel cell in vivo, because of low levels of peroxide available, and the toxicity associated with this reactive oxygen species. In addition peroxide reduction cannot be used in a membraneless system as it could well be oxidized at the anode. Nevertheless, some elegant approaches to biocatalytic fuel cell electrode configuration have been demonstrated using peroxidases as the biocatalyst and will be briefly reviewed here. 

Bioelectrocatalysis involves the coupling of redox enzymes with electrochemical reactions [44]. Thus, oxidizing enzymes can be incorporated into redox systems applied in bioreactors, biosensors and biofuel cells. While biosensors and enzyme electrodes are not synthetic systems, they are, essentially, biocatalytic in nature (Scheme 3.5) and are therefore worthy of mention here. Oxidases are frequently used as the biological agent in biosensors, in combinations designed to detect specific target molecules. Enzyme electrodes are possibly one of the more common applications of oxidase biocatalysts. Enzymes such as glucose oxidase or cholesterol oxidase can be combined with a peroxidase such as horseradish peroxidase. 

The results of investigations of enzymatic activity in the immobilized state. When laccase, peroxidase, and other enzymes are adsorbed on dispersive electroconductive carriers, their enzymatic activity perceptibly declines, thus indicating a denaturing of part of the macromolecules. In this case, however, there is a sufficient quantity of denatured enzyme molecules strongly bonded with the carrier, which display a specific biocatalytic activity in model reactions of the substrates. It is these molecules of the enzyme, as will be seen further, that are responsible also for the electrocatalytic activity of the system. 

Abstract The in vitro enzyme-mediated polymerization of vinyl monomers is reviewed with a scope covering enzymatic polymerization of vitamin C functionalized vinyl monomers, styrene, derivatives of styrene, acrylates, and acrylamide in water and water-miscible cosolvents. Vitamin C functionalized polymers were synthesized via a two-step biocatalytic approach where vitamin C was first regioselectively coupled to vinyl monomers and then subsequently polymerized. The analysis of this enzymatic cascade approach to functionalized vinyl polymers showed that the vitamin C in polymeric form retained its antioxidant property. Kinetic and mechanistic studies revealed that a ternary system (horseradish peroxidase, H2O2, initiator fS-diketone) was required for efficient polymerization and that the initiator controls the characteristics of the polymer. The main attributes of enzymatic approaches to vinyl polymerization when compared with more traditional synthetic approaches include facile ambient reaction environments of temperature and pressure, aqueous conditions, and direct control of selectivity to generate functionalized materials as described for the ascorbic acid modified polymers. 

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