Horseradish peroxidase, oxidation

M16. Michon, T., Chenu, M., Kellershon, N., Desmadril, M., and Gueguen, J., Horseradish peroxidase oxidation of tyrosine-containing peptides and their subsequent polymerization A kinetic study. Biochemistry 36, 8504-8513 (1997). 

The emission yield from the horseradish peroxidase (HRP)-catalyzed luminol oxidations can be kicreased as much as a thousandfold upon addition of substituted phenols, eg, -iodophenol, -phenylphenol, or 6-hydroxybenzothiazole (119). Enhanced chemiluminescence, as this phenomenon is termed, has been the basis for several very sensitive immunometric assays that surpass the sensitivity of radioassay (120) techniques and has also been developed for detection of nucleic acid probes ia dot-slot. Southern, and Northern blot formats (121). 

Catalytic oxidation of isobutyraldehyde with air at 30—50°C gives isobutyric acid [79-31-2] ia 95% yield (5). Certain enzymes, such as horseradish peroxidase, cataly2e the reaction of isobutyraldehyde with molecular oxygen to form triplet-state acetone and formic acid with simultaneous chemiluminescence (6). 

According to Reichl et al. (2000), the oxidation of pholasin by compound I or II of horseradish peroxidase induces an intense light emission, whereas native horseradish peroxidase shows only a small effect. The luminescence of pholasin by native myeloperoxidase (verdoperoxidase) is diminished by preincubation with catalase, which is interpreted as the result of the removal of a trace amount of naturally occurring H2O2 in the buffer (about 10-8 M) that forms compound I... 

One of the most used systems involves use of horseradish peroxidase, a 3-diketone (mosl commonly 2,4-pentandione), and hydrogen peroxide." " " Since these enzymes contain iron(II), initiation may involve decomposition of hydrogen peroxide by a redox reaction with formation of hydroxy radicals. However, the proposed initiation mechanism- involves a catalytic cycle with enzyme activation by hydrogen peroxide and oxidation of the [3-diketone to give a species which initiates polymerization. Some influence of the enzyme on tacticity and molecular... 

Martmez-Parra, J. and Munoz, R., An approach to the characterization of betanine oxidation catalyzed by horseradish peroxidase, J. Agric. Food Chem., 45, 2984, 1997. 

Martmez-Parra, J. and Munoz, R., An approach to the characterization of betanine oxidation catalyzed by horseradish peroxidase, J. Agric. Food Chem., 45, 2984, 1997. Martmez-Parra, J. and Munoz, R., Characterization of betacyanin oxidation catalyzed by a peroxidase from Beta vulgaris L. roots, J. Agric. Food Chem., 49, 4064, 2001. Ashie, l.N.A. Simpson, B.K., and Smith, J.P., Mechanisms for controlling enzymatic reactions in foods, Crit. Rev. Food Sci. Nutr., 36, 1, 1996. 

Kobayashi, T. Taguchi, H. Shigematsu, M. Tanahashi, M. Substituent effects of 3,5-disubstituted p-coumaryl alcohols on their oxidation using horseradish peroxidase-H202 as the oxidant. J. Wood Sci. 2005, 51, 607-614. 

N. Narawane, Oxidative and hormonal control of horseradish peroxidase transytosis across the pigmented rabbit conjunctiva, Ph.D. thesis, University of Southern California, 1993. 

Choi, Y.J., Chae, H.J., and Kim, E.Y., Steady-state oxidation model by horseradish peroxidase for the estimation of the non-inactivation zone in the enzymatic removal of pentachlorophenol, J. Biosci. Bioeng., 88, 368-373, 1999. 

Kazunga, C., Aitken, M.D., and Gold, A., Primary product of the horseradish peroxidase-catalyzed oxidation of pentachlorophenol, Environ. Sci. Technol., 33, 1408-1412, 1999. 

Extensive studies have established that the catalytic cycle for the reduction of hydroperoxides by horseradish peroxidase is the one depicted in Figure 6 (38). The resting enzyme interacts with the peroxide to form an enzyme-substrate complex that decomposes to alcohol and an iron-oxo complex that is two oxidizing equivalents above the resting state of the enzyme. For catalytic turnover to occur the iron-oxo complex must be reduced. The two electrons are furnished by reducing substrates either by electron transfer from substrate to enzyme or by oxygen transfer from enzyme to substrate. Substrate oxidation by the iron-oxo complex supports continuous hydroperoxide reduction. When either reducing substrate or hydroperoxide is exhausted, the catalytic cycle stops. 

Answers to these questions were initiated over a decade ago during our studies on catalase (CAT) and horseradish peroxidase (HRP) (30). Both native enzymes are ferric hemoproteins and both are oxidized by hydrogen peroxide. These oxidations cause the loss of two electrons and generate active enzymatic intermediates that can be formally considered as Fe + complexes. 

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