• Haem peroxidases (or heme peroxidases) are haem-containing enzymes that use hydrogen peroxide as the electron acceptor to catalyse a number of oxidative reactions. (wikipedia.org)
  • Collectively, the data show that all three members of the class I heme peroxidases can support radical formation on the distal tryptophan and that the reactivity of this radical can be controlled either by the protein structure or by the nature of the compound I intermediate. (bris.ac.uk)
  • Exposure to Se or mimosine exhibited a differential response in the mitochondrial catalase and ascorbate peroxidase (Asc-Px) activities. (typeset.io)
  • Peroxidase activity registered a significant increase by threefold in mitochondria and fourfold in soluble fraction in both Se and mimosine groups. (typeset.io)
  • 2011 ). On the other side, plants have developed some enzymatic systems including superoxide dismutases (SOD), catalases (CAT), ascorbate peroxidases (APX), peroxiredoxins and non-enzymatic mechanisms to protect against oxidative damage caused by these ROS (Agrawal et al. (springeropen.com)
  • Fe3+ + H2O + oxidized substrate In this mechanism, the enzyme reacts with one equivalent of H2O2 to give [Fe4+=O]R' (compound I). This is a two-electron oxidation/reduction reaction in which H2O2 is reduced to water, and the enzyme is oxidized. (wikipedia.org)
  • Antioxidants are compounds that inhibit oxidation (usually occurring as autoxidation ), a chemical reaction that can produce free radicals . (wikipedia.org)
  • One oxidizing equivalent resides on iron, giving the oxyferryl intermediate, and in many peroxidases the porphyrin (R) is oxidized to the porphyrin pi-cation radical (R'). Compound I then oxidizes an organic substrate to give a substrate radical and Compound II, which can then oxidize a second substrate molecule. (wikipedia.org)
  • 2007) Biochemistry 46, 2174-2180] that reaction of APX with peroxide leads, over long time scales, to formation of a covalent link with the distal tryptophan (Trp41) in a mechanism that proceeds through initial formation of a compound I species bearing a porphyrin π-cation radical followed by radical formation on Trp41, as implicated in the KatG enzymes. (bris.ac.uk)
  • Formation of such a covalent link in CcP has never been reported, and we proposed that this could be because compound I in CcP uses Trp191 instead of a porphyrin π-cation radical. (bris.ac.uk)
  • To test this, we have examined the reactivity of the W191F variant of CcP with H2O2, in which formation of a porphyrin π-cation radical occurs. (bris.ac.uk)
  • Autoxidation leads to degradation of organic compounds, including living matter. (wikipedia.org)
  • In the expression and possible role of the major antioxidant enzymes (AOEs), the manganese superoxide dismutase (MnSOD), catalase, and mechanisms closely related to glutathione (GSH) metabolism were investigated in the biopsies of Malignant Pleural Mesothelioma and/or cell lines in culture. (charismaticplanet.com)
  • They, however, also contained higher intracellular GSH levels and catalase than mesothelioma cells and had elevated levels of γ-glutamylcysteine synthetase (γGCS). (charismaticplanet.com)
  • Based on this mechanism, both activities should be mutually antagonistic and peroxidatic electron donors should inhibit the catalase activity. (auburn.edu)
  • In fact, it has been established that the common peroxidatic electron donor o-dianisidine does inhibit the catalase activity of KatG from Escherichia coli at pH 7.5. (auburn.edu)
  • The role of GSH and catalase were also investigated by treating the Malignant Pleural Mesothelioma cells and A549 adenocarcinoma cells with buthionine sulfoximine (BSO), to block glutathione synthesis, and aminotriazole (ATZ) to inhibit catalase. (charismaticplanet.com)
  • The results revealed that photosynthetic pigments, accumulation of catalase (CAT), phenolic contents, polyphenol oxidase, and flavanols are higher in the IAA and SL3-treated plants than in the non-inoculated plants. (bvsalud.org)
  • Catalase activity is optimal near neutral pH (i.e., pH ~ 7.5), whereas peroxidase activity is optimal under acidic conditions (i.e., pH ~ 4.5) and requires an exogenous electron donor. (auburn.edu)
  • The stimulatory effect was most prominent under conditions favorable to peroxidase activity (i.e., acidic pH and low H2O2 concentrations). (auburn.edu)
  • We analyzed the vector directionalities of the lone pairs of the nitrogen common to these molecules, and the acidic hydrogen of phenols (in aminoindanes, aminotetralins, apomorphines, p-phenol-piperazines, octahydrobenzo(g)quinolines, octahydrobenzo(f)quinolines, and benzazepines) or of nitrogen (in ergoline-type compounds and related structures). (nih.gov)
  • The regression analysis of log KD with respect to the distances of the vectors of the acidic hydrogen support the hypothesis that these compounds bind to the receptor as donors in hydrogen bond formation. (nih.gov)
  • However, the peroxidase reaction is completed by the subsequent reduction of compound I to compound II (i.e. (auburn.edu)
  • KatGs are heme-dependent enzymes and are primarily known as H2O2 scavengers. (auburn.edu)
  • Conversely, catalase activity can sustain high concentrations of H2O2 without the enzyme inactivation. (auburn.edu)
  • Evaluation of the dominant enzyme intermediates by stopped-flow spectroscopy revealed that a compound III-like (i.e. (auburn.edu)
  • Polyphenols are the major plant compounds with antioxidant activity, although they are not the only ones. (dadospdf.com)
  • The aim of this review, after presenting general aspects about natural antioxidants, is to focus on the extraction of antioxidant compounds (mainly polyphenols) from agricultural and industrial wastes, as well as to summarize available data on the factors a ecting their antioxidant activity and stability, and, in some cases, the reported major active compounds identi®ed. # 2001 Elsevier Science Ltd. All rights reserved. (dadospdf.com)
  • This is far less than the amount expected for normal peroxidatic turnover where two equivalents of oxidized donor is anticipated for every equivalent of H2O2 consumed. (auburn.edu)
  • Clearly, the catalase mechanism and the interrelationship between the catalase and peroxidase functions of KatG are much more complex than has been previously appreciated, and pH plays an important factor in both activities. (auburn.edu)
  • The ability of one activity to dominate over the other depends on several factors including: pH, the concentration of H2O2, and the availability of an appropriate exogenous electron donor. (auburn.edu)
  • Strikingly, in this dissertation, we report the dramatic stimulation of the catalase activity of KatG from Mycobacterium tuberculosis (MtKatG) by up to 14-fold, in the presence of several common peroxidatic electron donors. (auburn.edu)
  • In particular, we observed that aromatic amines were better stimulators than other donors like pyrogallol and ascorbate. (auburn.edu)
  • 1. Introduction The oxidative deterioration of fats and oils in foods is responsible for rancid odours and ¯avours, with a consequent decrease in nutritional quality and safety caused by the formation of secondary, potentially toxic, compounds. (dadospdf.com)
  • intermediate dominated during electron donor-stimulated catalase activity of MtKatG, and this intermediate converted directly to the ferric state upon depletion of H2O2. (auburn.edu)
  • More so, peroxidase activity is favorable at low H2O2 concentrations. (auburn.edu)
  • Clearly, conditions which favor the peroxidase activity do not coincide with those that favor the catalase activity. (auburn.edu)
  • In the absence of a peroxidatic electron donor, we observed a "low-KM" and "high-KM" component for catalase activity at pH 5.0. (auburn.edu)
  • During stimulated catalase activity, very little of the donor (0.008 eq. (auburn.edu)
  • It is thought that catalase-peroxidase provides protection to cells under oxidative stress. (wikipedia.org)
  • Mesothelioma cell line expressing the highest MnSOD (10 fold compared to non-malignant mesothelial cells) levels also had the highest levels of GSH, glutathione S-transferase (GST), and catalase, and was the most resistant cell line to oxidants and cytotoxic drugs. (charismaticplanet.com)
  • This model, when expressed as distances from that of the reference compound pergolide, correlates with the dopaminergic binding affinity observed in compounds previously reported to act on the dopaniergic system in the central nervous system (CNS). (nih.gov)
  • As the name suggests, they catalyze the decomposition of H2O2 by catalatic and peroxidatic mechanisms using a single active site. (auburn.edu)