Peroxidase reactions

Figure 20-3. Role of the pentose phosphate pathway in the glutathione peroxidase reaction of erythrocytes. (G-S-S-G, oxidized glutathione G-SH, reduced glutathione Se, selenium cofactor.)...

B. D. Agunda and B. L. Clarke, Bistability in chemical reaction networks Theory and application to the peroxidase reaction. J. Chem. Phys. 87(6), 3461 3469 (1987). 

Subrahmanyam VV, O Brien PJ. 1985. Phenol oxidation products, formed by a peroxidase reaction, that bind to DNA. Xenobiotica 15 873-885. 

Figure 24 Peroxidase reaction catalyzed by 13G10-Fe(ToCPP) and 7G12-Fe(MPIX) porphyrin-antibody complexes and X-ray structure of the 7G12-MPIX complex.

The three best-known examples of biochemical oscillations were found during the decade 1965-1975 [40,41]. These include the peroxidase reaction, glycolytic oscillations in yeast and muscle, and the pulsatile release of cAMP signals in Dictyostelium amoebae (see Section V). Another decade passed before the development of Ca " " fluorescent probes led to the discovery of oscillations in intracellular Ca +. Oscillations in cytosolic Ca " " have since been found in a variety of cells where they can arise spontaneously, or after stimulation by hormones or neurotransmitters. Their period can range from seconds to minutes, depending on the cell type [56]. The oscillations are often accompanied by propagation of intracellular or intercellular Ca " " waves. The importance of Ca + oscillations and waves stems from the major role played by this ion in the control of many key cellular processes—for example, gene expression or neurotransmitter secretion. 

The peroxidase-catalyzed transformations are classified as (1) the peroxidase reaction (Table 2, entries 1 -4), (2) the peroxygenase reaction (Table 2, entries 4-6) [25], and (3) the oxidase reaction (Table 2,entries 7-9). 

We should also note that there are other ways in which substances can luminesce (/.e., produce light). One of the most common nonfluorescent mechanisms is called chemiluminescence. Chemical reactions can produce light when radicals (/.e., atoms or molecules with reactive unpaired electrons) combine to form a covalent bond. Heating of molecules can also cause them to display chemiluminescence. And, of course, there are biological processes that are accompanied by chemiluminescence. The most familiar case is the luciferase reaction associated with fire flies and luminescent marine creatures. Peroxidase reactions also produce faint luminescence. 

Enzymes requiring vanadium for catalytic activity. Perhaps the best studied of these are the vanadium-dependent nitrogenases [EC 1.18.6.1]. Other vanadium-dependent enzymes include vanadium haloperoxidase, vanadium chloroperoxidase, and vanadium bromoper-oxidase. In the vanadium chloroperoxidase and bromo-peroxidase reactions, the vanadium(V) is coordinated in a trigonal bipyramidal site to a histidyl residue, three nonprotein oxygens, and, presumably, to a hydroxide. 

Yamasaki, H., Sakihama, Y., and Ikehara, N., Flavonoid-peroxidase reaction as a detoxification mechanism of plant cells against H2O2, Plant Physiol, 115, 1405, 1997. 

Propylthiouracil (PTU) Inhibit thyroid peroxidase reactions block iodine organification inhibit peripheral deiodination of T4 and T Hyperthyroidism Oral duration of action 6-8 h delayed onset of action Toxicity Nausea, gastrointestinal distress, rash, agranulocytosis, hepatitis,hypothyroidism... 

In spite of a relatively slow rate of superoxide release by peroxidases (Reaction (19), Table... 

The peroxidase reaction is coupled with the formation of free radicals, either directly at the protein backbone or at the porphyrin moiety or both. This topic is borderline to the scope of this review and we will restrict ourselves to those studies which have at least a strong connection with the heme iron situation. We mention however, some relevant articles which have appeared in the period reviewed. Specific interest was given to a bi-functional enzyme from Mycobacterium tuberculosis which has both catalase and peroxidase activity.286-287,288-289 We also mention that a critical role of cations like Ca2+ and K+ has been described.290-291... 

Haloperoxidases. Many specialized peroxidases are active in halogenation reactions. Chloroperoxi-dases from fungi236 237 catalyze chlorination reactions like that of Eq. 16-11 using H202 and Cl as well as the usual peroxidase reaction. 

Incubate at room temperature. Peroxidase reactions take about 5—30 mm to develop P-galactosidase reactions can take longer Judge the reaction time by eye (see Notes 4 and 5). Reactions may be stopped by adding 100 pL of appropriate stop solution to each well (5% SDS for peroxidase, lMNa2C03 for P-galactosidase). The SDS also solubilizes any precipitated products formed in the HRP reaction. 

If the ELISA color development takes more than a few minutes, continue the incubation m the dark p-galactosidase reactions tend to have a lower spontaneous background than peroxidase reactions, but take longer to develop, p-galac-tosidase reactions can be sped up by incubation at 37°C. 

The primary antibody solution can be saved and reused two to three times within the following 2 wk if stored at 4°C, and no bacterial growth is evident. It is not advisable to use sodium azide as an antimicrobial agent, particularly when using HRP-labeled antibodies azide inhibits peroxidase reactions... 

The technique described above is not useful for removing colored peroxidase reaction products (e.g., diaminobenzidine oxidation products) from blots Thus, we avoid detection methods based on these reactions. On the other hand, peroxidase-based luminescent assays (20) do not deposit a chemical reaction product on the blot and are compatible with this erasure method (21). An example of the use of this erasure method (Section 3 3, steps 1-5) after chemiluminescent detection is shown in Fig 2. 

In the peroxidase reaction, Compound I is reduced to the Fe111 resting state via Compound II in two consecutive one-electron transfer steps which results in the formation of two substrate radicals (path B in Scheme 2.11). With respect to the whole catalytic cycle, this behavior can be described by the following equation ... 

The peroxidase reaction of heme peroxidases has found technical uses mainly for the polymerization of phenols and anilines (Scheme 2.13) [206-216] and for waste water treatment [217-220], whereas phenol coupling reactions in the biosynthesis of e.g. vancomycin are carried out by P450-type cytochromes [221],... 

Mediator for peroxidase reaction H2O2+mediator - peroxidase HgO+oxidised mediator -> Monitoring of reduction of oxidised mediator [18]... 

As pointed out by Gorton and co-workers [19,65], this process is usually referred to a direct electron transfer (DET), that is, when an electrode substitutes the electron donor substrates in a common peroxidase reaction cycle (Eqs. (17.8)-(17.10)). When an electron donor (SH), such as phenolic compounds and the catecholamines shown in Tables 17.2 and 17.4, is present in a peroxidase-electrode system, both processes can occur simultaneously [29,30,43,48,52-54] and the oxidized donor S is reduced electrochemically by the electrode as shown in the following reaction ... 

---