Peroxidase peroxide

Peroxidases peroxidize a variety of substrates at the expense of hydrogen peroxide. These peroxidases oxidize amines, AH2, for which product analysis has suggested a free radical intermediate (2). The currently accepted valency changes of the enzyme can be represented by the scheme in Reactions 2-5. Reaction 2 represents the conversion... 

The studies on horse-radish peroxidase were conducted at high concentrations in synthetic wastewaters. Most of the aforementioned studies were conducted at 100 mg/L of aromatic and 100 to 1000 units/L of peroxidase. One aromatic amine has been studied as low as 0.5 mg/L, showing no effect of substrate concentration [7 ]. Thus, the peroxidase-peroxide system may have potential in drinking-water treatment for removal of problem aromatic compounds at low levels. 

Gerberick GF, Troutman JA, Foertsch LM, Vassallo JD, Quijano M, Dobson RL, Goebel C, Lepoittevin JP (2009) Investigation of peptide reactivity of pro-hapten skin sensitizers using a peroxidase-peroxide oxidation system. Toxicol Sci 112 164-174... 

Peroxidase Peroxidation, epoxidation No cofactor H2O2 sensitive... 

Above pH 8.8, where further decrease of hydrogen ion concentration leads to increased formation of alkaline peroxidase, peroxide complex formation is suppressed, which indicates that peroxides cannot replace the covalently bound hydroxyl group. There is an interesting parallel here in the case of methemoglobin where Haurowitz claimed that the alkaline form cannot give a peroxide complex (44). 

Since two electrons and protons are ultimately transferred to each molecule of hydrogen peroxide, the peroxidase-peroxide complex must undergo two-step reduction with one-electron donors. Saunders and his students have published a series of papers on the products... 

Early work from this group led to a theory according to which (a) the donor loses a hydrogen atom, (b) the radical so formed enters into a loose combination with a hydroxyl radical (from peroxidase-peroxide) and (c) the unchanged donor displaces a loosely bound hydroxyl radical. Loose combinations between such intermediate radicals are difficult to envisage, and a later hypothesis (372) is more acceptable. Aromatic amines, for example, lose an electron and proton to peroxidase-peroxide, the radical so formed being a hybrid of several canonical structures (structures A-C), which pair to give products appropriate to the particular amine (equation 32). When... 

Chance (16a) recently demonstrated the formation of an intermediate compound of catalases and hydrogen peroxide. The compound had many properties in common with the intermediate compound of hydrogen peroxide and peroxidase. The spectrum could be determined in the region of the Soret band showing a small shift of the band toward the red. The rate of formation of this compound was 3 X lO liter mole sec, exceeding the value required by the Michaelis theory for catalase activity. Without the addition of acceptor the compound decomposed slowly at about the same rate as the peroxidase-peroxide compound. The catalase activity increases the equilibrium constant to 1 X 10 mole liter h The inter-... 

Horse-radish peroxidase, HRP turnip peroxidase, TP dihydroxyfumaric acid (previously misnamed dioxymaleic acid), DHF peroxidase donors, AH and BH free radicals, AH, DHF, etc. indoleacetic acid, lAA peroxidase peroxide compounds I, II, and III, Compounds I, II, and III, respectively. 

Chance, (1952a) showed that hydroquinone is actually inhibitory to the Mn++-stimulated peroxidase reaction. He attributed this to competition between DHF and hydroquinone for the peroxidase peroxide compounds. It is now clear that his result was fortuitous, as it depended upon the choice of competing hydrogen donor. Even in the peroxidatic reaction, stimulation as well as competitive inhibition may occur. Thus Chance (1949b), following up an observation of Huszak (1937), found that the peroxidatic oxidation of ascorbate was stimulated by phenols, the oxidation products of the latter acting as cyclic catalysts (cf. Eq. (20) below). 

The two adjectives derive from Yamazaki s theory of peroxidase activity, that the oxidogenic donors generate radicals with oxidizing ability and the redogenic donors radicals with reducing power, after their reaction with peroxidase peroxide compounds. This extension of George s idea (Section II.A above) will be examined together with some other theories in Section II.E below. 

The Fenton s reagent is not as close to model hydroxylases as the other systems. Aniline and p-cresol are oxidized to condensed products by the peroxidase-peroxide system and by Fenton s reagent, whereas the other hydroxylating systems form only simple hydroxylated derivatives. This means that no free radicals of °OH are formed under those circumstances. 

This enzyme Is widely distributed, more particularly in plants. Three important sources of the enzyme are horse-radish, turnips and milk. Peroxidase is capable of activating both hydrogen peroxide and a suitable substrate so that the latter is oxidised, although hydrogen peroxide alone may be incapable of affecting this change. It sometimes happens that hydrogen pcr-... 

Other substances can activate hydrogen peroxide, for example, ferrous iron (p 352)- The products however are usually less well defined and different from those obtained when using peroxidase. 

Detecting the presence of small, even invisible, amounts of blood is routine. Physical characteristics of dried stains give minimal information, however, as dried blood can take on many hues. Many of the chemical tests for the presence of blood rely on the catalytic peroxidase activity of heme (56,57). Minute quantities of blood catalyze oxidation reactions between colorless materials, eg, phenolphthalein, luco malachite green, luminol, etc, to colored or luminescent ones. The oxidant is typically hydrogen peroxide or sodium perborate (see Automated instrumentation,hematology). 

Chemiluminescent Immunoassay. Chemiluminescence is the emission of visible light resulting from a chemical reaction. The majority of such reactions are oxidations, using oxygen or peroxides, and among the first chemicals studied for chemiluminescence were luminol (5-amino-2,3-dihydro-l,4-phthalazinedione [521-31-3]) and its derivatives (see Luminescent materials, chemiluminescence). Luminol or isoluminol can be directly linked to antibodies and used in a system with peroxidase to detect specific antigens. One of the first appHcations of this approach was for the detection of biotin (31). 

In the most common method for chemiluminescent immunoassay (GLIA), after the immunological reaction and any necessary separation steps, the labeled compounds or complexes react with an oxidizer, eg, hydrogen peroxide, and an enzyme, eg, peroxidase, or a chelating agent such as hemin or metal... 

N—Fe(IV)Por complexes. Oxo iron(IV) porphyrin cation radical complexes, [O—Fe(IV)Por ], are important intermediates in oxygen atom transfer reactions. Compound I of the enzymes catalase and peroxidase have this formulation, as does the active intermediate in the catalytic cycle of cytochrome P Q. Similar intermediates are invoked in the extensively investigated hydroxylations and epoxidations of hydrocarbon substrates cataly2ed by iron porphyrins in the presence of such oxidizing agents as iodosylbenzene, NaOCl, peroxides, and air. 

Reaction takes place ia aqueous solution with hydrogen peroxide and catalysts such as Cu(II), Cr(III), Co(II), ferricyanide, hernia, or peroxidase. Chemiluminescent reaction also takes place with oxygen and a strong base ia a dipolar aprotic solvent such as dimethyl sulfoxide. Under both conditions Qcis about 1% (light emission, 375—500 am) (105,107). 

Chemiluminescence and bioluminescence are also used in immunoassays to detect conventional enzyme labels (eg, alkaline phosphatase, P-galactosidase, glucose oxidase, glucose 6-phosphate dehydrogenase, horseradish peroxidase, microperoxidase, xanthine oxidase). The enhanced chemiluminescence assay for horseradish peroxidase (luminol-peroxide-4-iodophenol detection reagent) and various chemiluminescence adamantyl 1,2-dioxetane aryl phosphate substrates, eg, (11) and (15) for alkaline phosphatase labels are in routine use in immunoassay analyzers and in Western blotting kits (261—266). 

A method of detecting herbicides is proposed the photosynthetic herbicides act by binding to Photosystem II (PS II), a multiunit chlorophyll-protein complex which plays a vital role in photosynthesis. The inhibition of PS II causes a reduced photoinduced production of hydrogen peroxide, which can be measured by a chemiluminescence reaction with luminol and the enzyme horseradish peroxidase (HRP). The sensing device proposed combines the production and detection of hydrogen peroxide in a single flow assay by combining all the individual steps in a compact, portable device that utilises micro-fluidic components. 

Peroxidase An enzyme that breaks down the hydrogen peroxide, H2O2 + NADH + H+ 2H2O + NAD+. 

Horse radish peroxidase, H2O2 or Laccase, pH 4, 2% DMSO or DMF. Cleavage occurs by the formation of a phenyldiimide, which decomposes to the acid, nitrogen, and benzene. The laccase method is compatible with the readily oxidized tryptophan and methionine because it does not use peroxide. ... 

Tamaoku and colleagues presented an efficient enzymatic photometric determination of hydrogen peroxide ffiat is essentially a color reaction resulting from the oxidative condensation of A/-ethyl-A/-(2-hydroxy-3-sulfopropyl)aniline derivatives wiffi 4-aminoantipyrine in the presence of hydrogen peroxide and peroxidase (82CPB2492). A similar calorimetric detection of hydrogen peroxide has been patented (83GEP3301470). 

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