Peroxidase treatment

Considerable efforts have aimed at optimizing the reactor configuration in which the peroxidase-catalyzed removal of phenols can be carried out. Much of this work has focused on maximizing the efficiency of enzyme use since the majority of the operating cost associated with peroxidase treatment is likely to be that of the enzyme itself [24]. Improvements in the useful life of the enzyme, with a corresponding reduction in treatment cost, have been accomplished through the selection of an appropriate reactor configuration... 

In contrast to the previous examples, oxidative treatments may promote positive consequences in some other cases, as they decrease concentrations in phenolic acids (and other phenolics) and limit subsequent oxidations. Therefore, hyperoxidation of musts during wine processing has sometimes been proposed, and this process particularly affected HCA derivatives [27]. In addition, a peroxidasic treatment allowed the dimerization of ferulic acid in wheat bran tissues and consequently decreased arabinoxylan solubility and increased mechanical strength of the tissue [58]. 

Fig. 8. Activation of the PO binding with P, infestans cell walls (glucan-specific ) under pathogen inoculation and treatment with salicylic (SA) and jasmonic (JA) acids (A) Peroxidase activity in stomata guard cells and intercellular spaces of adjoining epidermal leaf cells and on the surface of mycelium contacting with the stomata (B). (1) Non-treated control (2) infection (3) treatment with SA (4) treatment with SA + infection (5) treatment with JA (6) treatment with JA + infection (7) treatment with SA + JA (8) treatment with SA + JA + infection g - gifs of P. infestans s - stomata guard cell. Specific to P, infestans cell walls, PO is highlighted.

Selenium is required, but levels must fall into a narrow window. Both deficiency and toxicity symptoms occur. The element is also used therapeutically in cancer treatment. It is the co-factor of the enzyme glutathione peroxidase which is thought to play an important role in oxygen toxicity. The determination of Se in blood or serum is not easy, as many incorrect, inaccurate and imprecise methods have been published (Magee and James 1994). A suggested procedure for Se in body fluids is based on GF-AAS (Thomassen et al. 1994)- For tissues SS-AAS may be used (Fler-ber 1994a). Recent developments by Turner et al. (1999) show that LC-ICP-MS is sensitive and reproducible at low levels. 

Black tea quality as determined by theaflavin levels is also affected by storage conditions. Low temperatures, low moisture levels, and low oxygen availability retard theaflavin loss. Residual peroxidase activity, which accelerates theaflavin loss on storage, is diminished by acid treatment during fermentation.94... 

Zhang, G. and Nicell, J.A., Treatment of aqueous pentachlorophenol by horseradish peroxidase and hydrogen peroxide, Water Res., 34, 1629-1637, 2000. 

Figure 8.1 The results of IHC of two experiments using Dynabeads (Dynal, New York, NY) coated with biotinylated anti-mouse IgG (first experiment) and protein S-100 (second experiment), (a) Positive control showing red color (S-100) localized in the melanoma cells, (b) Strong positive red color circles all beads coated with biotinylated anti-mouse antibody after the heating AR treatment (first experiment), (c) Using the heating AR treatment, S-100-coated polymer beads show positive red color around the beads as circles (second experiment), (d) Negative control of the first experiment. No red color could be seen for polymer beads (arrows) that had been treated with exactly the same protocol as that of slide (b), but omitting the avidin-biotin-peroxidase (label). Bar = 50pm. Reproduced with permission from Shi et al., J. Histochem. Cytochem. 2005 53 1167-1170. See color insert.

Observations Table 1 shows the activity of the antioxidant enzymes of tomato roots after 72 h of exposure of allelochemical stress caused by S. deppei. Catalase (CAT) activity increases by 1.5 fold Ascorbate Peroxidase (APX) decreases 2.3 fold Glutathione reductase (GR) activity does not change with the treatment and Superoxide dismutase (SOD) decreases 1.3 fold. 

The role of N-acetoxy arylamides as metabolically formed ultimate carcinogens jji vivo also appears to be limited. Their enzymatic formation via peroxidation of N-hydroxy arylamides can be excluded since tissues containing high levels of peroxidases such as the rat mammary gland (83) and the dog urinary bladder (84) do not form acetylated carcinogen-DNA adducts in vivo (63). Their non-enzymatic formation by reaction of acetyl coenzyme A with N-hydroxy arylamides (6 ) cannot be excluded however, even if formed, their direct reaction with cellular DNA appears unlikely as treatment of cultured cells with synthetic N-acetoxy AAF (85,86) results primarily in deacetylated arylamine-DNA adducts, apparently due to rapid N-deacetylation to form the reactive N-acetoxy arylamine (V). 

Sanders et al. [133] found that although quercetin treatment of streptozotocin diabetic rats diminished oxidized glutathione in brain and hepatic glutathione peroxidase activity, this flavonoid enhanced hepatic lipid peroxidation, decreased hepatic glutathione level, and increased renal and cardiac glutathione peroxidase activity. In authors opinion the partial prooxidant effect of quercetin questions the efficacy of quercetin therapy in diabetic patients. (Antioxidant and prooxidant activities of flavonoids are discussed in Chapter 29.) Administration of endothelin antagonist J-104132 to streptozotocin-induced diabetic rats inhibited the enhanced endothelin-1-stimulated superoxide production [134]. Interleukin-10 preserved endothelium-dependent vasorelaxation in streptozotocin-induced diabetic mice probably by reducing superoxide production by xanthine oxidase [135]. 

Acyl nitroso compounds (3, Scheme 7.2) contain a nitroso group (-N=0) directly attached to a carbonyl carbon. Oxidation of an N-acyl hydroxylamine derivative provides the most direct method for the preparation of acyl C-nitroso compounds [10]. Treatment of hydroxamic acids, N-hydroxy carbamates or N-hydroxyureas with sodium periodate or tetra-alkyl ammonium periodate salts results in the formation of the corresponding acyl nitroso species (Scheme 7.2) [11-14]. Other oxidants including the Dess-Martin periodinane and both ruthenium (II) and iridium (I) based species efficiently convert N-acyl hydroxylamines to the corresponding acyl nitroso compounds [15-18]. The Swern oxidation also provides a useful alternative procedure for the oxidative preparation of acyl nitroso species [19]. Horseradish peroxidase (HRP) catalyzed oxidation of N-hydroxyurea with hydrogen peroxide forms an acyl nitroso species, which can be trapped with 1, 3-cyclohexanone, giving evidence of the formation of these species with enzymatic oxidants [20]. 

Indicine IV-oxide (169) (Scheme 36) is a clinically important pyrrolizidine alkaloid being used in the treatment of neoplasms. The compound is an attractive drug candidate because it does not have the acute toxicity observed in other pyrrolizidine alkaloids. Indicine IV-oxide apparently demonstrates increased biological activity and toxicity after reduction to the tertiary amine. Duffel and Gillespie (90) demonstrated that horseradish peroxidase catalyzes the reduction of indicine IV-oxide to indicine in an anaerobic reaction requiring a reduced pyridine nucleotide (either NADH or NADPH) and a flavin coenzyme (FMN or FAD). Rat liver microsomes and the 100,000 x g supernatant fraction also catalyze the reduction of the IV-oxide, and cofactor requirements and inhibition characteristics with these enzyme systems are similar to those exhibited by horseradish peroxidase. Sodium azide inhibited the TV-oxide reduction reaction, while aminotriazole did not. With rat liver microsomes, IV-octylamine decreased... 

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