Peroxidase enzymatic activity

Oliveira, J. C., Silva, D. M., Teixeira, A. A., Amorim, H. V., Enzymatic activity of polyphenoloxidase, peroxidase and catalase in beans of Coffea arabica L. related to the beverage quality, Turrialba 27, 75, 1977. (CA87 51839j)... 

Effect of standardized P. ginseng extract G115 after exhaustion exercise glutathion peroxidase (GPX) enzymatic activity (red gastrocnemius) "mitochondrial fraction."... 

Kinetic studies have shown that the product formed in the reaction of the fully oxidized enzyme with hydrogen peroxide is catalytically inactive. Reaction of the half-reduced enzyme with hydrogen peroxide leads to an enzymatically active compound, in which the Fe" heme is oxidized to Fe, and the FeIU heme is oxidized to the FeIV ferryl species. No stoichiometric formation of a radical species is observed, unlike the case for other peroxidases. The peroxide-oxidized enzyme will then oxidize two molecules of reduced cytochrome c. Mechanistic details are still unclear, particularly with regard to the interaction between the two heme groups, a phenomenon revealed by ESR studies.1373... 

Characterization of the enzymatic activity of the parasite and snail recombinant TPx are in progress, and the recombinant snail enzyme BgTPx has been found to be enzymatically active in an in vitro assay (Sayed and Williams, 2004). It remains to be seen whether the results obtained showing the transcript corresponding to BgTPx to be upregulated in parasite-exposed snails, compared to uninfected controls, correlates with enhanced thioredoxin peroxidase activity in infected snails. 

Wash, hand-peel, chop and lyophilize each plant tissue material for 3-4 h at 25°C (e.g., soybean (Table 17.1), potato, banana, eggplant, sweet potato and artichoke (Table 17.2). Grind the dry tissue to obtain a fine powder and select the particle size using sieves of lower than 200 pm mesh. Store the dry powder in a desiccator at 25°C and use it as the enzymatic source of PPO or peroxidase in the preparation of biosensor. Determine enzymatic activity and total protein content as described in Procedure 22 (in CD accompanying this book). Prepare the carbon paste electrode with dry tissue as described in the same procedure. 

Ruggiero et al. (1989) investigated the ability of a natural silt loam soil and the clay minerals, montmorillonite (Mte) and kaolinite (Kte), to immobilize laccase. They compared the catalytic abilities of the soil-enzyme and clay-enzyme complexes to degrade 2,4-dichlorophenol. They found that the immobilized laccase remains active in removing the substrate even after 15 repeated cycles of substrate addition (Figure 2.24). However, Claus and Filip (1988) found that the activity of tyrosinase, laccase, and peroxidase is inhibited by immobilization on bentonite. The type of saturating cations on clay surfaces also substantially influences enzymatic activity (Claus and Filip, 1990). 

Besides using the bioactive agent to detect the ion of interest, another approach can include monitoring an ion by its inhibitory effect upon enzymatic activity. For example, horseradish peroxidase (HRP) can be immobilised onto one gate of a REFET [107] allowing the presence of cyanide ion to be measured at concentrations of 10 3-10 7 M. The approach used here is to monitor the inhibition of the enzymatic HRP effect, by the cyanide ion, on ascorbic acid. Even lower levels (10 10 M) of detection can be obtained using a polyphenol oxidase/clay composite immobilised on carbon, with no interference from chloride, nitrate or bromide [108]. 

Enzymatic activity is dependent upon several variables, such as enzyme and substrate concentrations, pH, salt concentration of the buffer milieu, temperature and light. Many enzymes also possess non proteinaceous chemical portions termed prosthetic groups. Typical prosthetic groups are the iron protoporphyrin of peroxidase, and biotin of carboxy transferases. In addition, many enzymes require the presence of metal ions such as Mg++, Mn++, and Zn++, which function as electrophilic (electron attracting) agents. 

Adsorbed horseradish peroxidase (HRP) on silica mesoporous materials The immobilized HRP on FSM-16 and MCM-41 with pore diameter of 50 A showed the highest enzymatic activity in toluene and thermostability in aqueous solution at a temperature of 70°C [4]... 

Wang Z, King TL, Branagan SP et al (2009) Enzymatic activity of surface-immobilized horseradish peroxidase confined to micrometer-to nanometer-scale structures in nanocapillary array membranes. Analyst 134 851-859... 

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