Peroxidase artificial

The electrochemical rate constants for hydrogen peroxide reduction have been found to be dependent on the amount of Prussian blue deposited, confirming that H202 penetrates the films, and the inner layers of the polycrystal take part in the catalysis. For 4-6 nmol cm 2 of Prussian blue the electrochemical rate constant exceeds 0.01cm s-1 [12], which corresponds to the bi-molecular rate constant of kcat = 3 X 103 L mol 1s 1 [114], The rate constant of hydrogen peroxide reduction by ferrocyanide catalyzed by enzyme peroxidase was 2 X 104 L mol 1 s 1 [116]. Thus, the activity of the natural enzyme peroxidase is of a similar order of magnitude as the catalytic activity of our Prussian blue-based electrocatalyst. Due to the high catalytic activity and selectivity, which are comparable with biocatalysis, we were able to denote the specially deposited Prussian blue as an artificial peroxidase [114, 117]. 

A.A. Karyakin and E.E. Karyakina, Prussian Blue-based artificial peroxidase as a transducer for hydrogen peroxide detection. Application to biosensors. Sens. Actuators, B B57, 268-273 (1999). 

The plasma membranes of plant cells possess several redox activities that can be related to both plant nutrition and cell wall formation and lignification (Liithje et al., 1997 Berczi and Mpller, 2000). In this context, it has been shown that in oat roots, HMS humic fractions inhibited NADH oxidation in either the presence or absence of an artificial electron acceptor (ferricyanide), whereas LMS fractions inhibited this oxidase only if the electron donor (NADH) and acceptor (ferricyanide) were added at the same time (Pinton et al., 1995). While the first effect could be related to the activity of surface peroxidases that can be involved in cell wall formation and thickening (Vianello and Macri, 1991), the second seems to be exerted on a different redox system with an unknown function (Nardi et al., 2002). 

For example, Hayashi et al. (73) recently reported an enhancement of the peroxidase activity of Mb by modification of two heme-propionate side chains. They prepared an artificial hemin having two benzene moieties linked at each terminal carboxylate of the heme-propionates in protoheme IX, as shown in Fig. 18. The modified hemin was then inserted into the horse heart apoMb to yield a reconstituted Mb. The characterization of the reconstituted Mb was carried out by ultraviolet-visible (UV-vis), NMR, and electronspray ionization-mass spectrometry (ESI-MS). Particularly, the UV-vis spectrum of the reconstituted Mb is comparable with that observed for the native Mb, suggesting that the artificial hemin is located in the normal position of the heme pocket. 

Makino R, Yamazaki I (1972) Effects of 2,4-substituents of deuterohemin upon peroxidase functions. I. Preparation and some properties of artificial enzymes. J Biochem 72 655-664... 

Fig. 12. Diagram showing sequence for detecting viral antibody by the peroxidase-antiperoxidase (PAP) method of Stemberger et al. This method uses a bridging antibody (anti-primate antibody) between the human and simian antibody. Artificial (chemical) linkage of enzyme with antibody is replaced by an antigen-antibody reaction.

To explain the formation of viniferins in vitro during the peroxidase-catalyzed oxidation, it is assumed that these artificial oligomers are synthesized from frons-resveratrol through a radical coupling mode (Mp + Mo4 ) (Scheme XVI) to give a quinone-methide intermediate followed by cyclization. 

Nolte et al 46) produced an artificial enzyme based on the T4 replisome and applied it to the epoxidation of double bonds in synthetic polymers. Smith et al 51) reported that horseradish peroxidase catalyzes the oxidative polymerization of glucuronic acid. In recent literature, many biomimetic macromolecules with enzyme-like structures or functions have been reported including those that are dendrimers 64-66), those that have specified three-dimensional structures or recognition elements created by molecular imprinting 67), and other enzyme mimics 68). 

Karyakin and Karyakina have developed a hydrogen peroxide sensor, based on Prussian Blue deposited on glassy carbon electrodes. Prussian Blue was considered an artificial peroxidase due to its high catalytic activity and selectivity, which could be compared with biocatalysis. The application of Prussian Blue modified electrodes enabled the sensing of H2O2 at around 0 V vs. SCE. The electrocatalytic reduction of H2O2 in the presence of O2 was found to be better for Prussian Blue deposited on glassy carbon electrodes than for platinum covered electrodes. Furthermore, these electrodes were more stable and active and less expensive than the platinum and peroxidase modified electrodes. The response was linear up to 0.1-100 pM and the detection limit found to be 10 M. 

From the standpoint of blood clotting on the surfaces of artificial organs, the activity and structural changes of proteins bound on surfaces have been studied (36-41). The enzyme used in our studies were thrombin, plasmin, trypsin, phosphatase and peroxidase. Thrombin and plasmin are, respectively, key components of the coagulation and fibrinolytic systems. Kinetic parameters were obtained by direct measurement of the activities of enzymes bound on porous glass by mixing the porous glass with solutions of the substrate. 

Artificial peroxidases have also been designed using the catalytic antibody strategy. The groups of Schultz and Harada initiated the field of antibody-metalloporphyrin complexes.Immunization with me.so-tetrakis(4-carboxyphenyl)porphyrin (TCPP) provides an antibody which binds very strongly to Mn -TCPP or to Fe TCPP. ... 

---