Peroxidase system

Bateman, Jr. R. C. Evans, J. A. Using the Glucose Oxidase/Peroxidase Systems in Enzyme Kinetics, /. Chem. Educ. 1995, 72, A240-A241. 

Monooxygenases. Under nonlignolytic conditions, arene monooxygenase and epoxide hydrolase systems may function to produce trani-dihydrodiols. Hydrogen abstraction mediated by the lipid peroxidase system may operate, for example, in the formation of fluorene-9-one from fluorene by Ph. chrysosporium (Bogan et al. 1996). 

As compounds exhibiting enhancing effects on CL reactions, a variety of phenols, e.g., firefly luciferin and 6-hydroxybenzothiazole derivatives [12,13], 4-iodophe-nol [14], 4-(4-hydroxyphenyl)thiazole [15], 2-(4,-hydroxy-3 -methoxy-benzyli-dene)-4-cyclopentene-l,3-dione (KIH-201) [16], and 2-(4-hydroxyphenyl)-4,5-diphenylimidazole (HDI) and 2-(4-hydroxyphenyl)-4,5-di(2-pyridyl)imidazole (HPI)[17] (Fig. 6A), and phenylboronic acid derivatives, e.g., 4-phenylylboronic acid [18], 4-iodophenylboronic acid [19], and4-[4,5-di(2-pyridyl)-l //-imidazol-2-yl]phenylboronic acid (DPPA) [20] (Fig. 6B), in the luminol/hydrogen peroxide/peroxidase system are well known. Rhodamine B and quinine are used as sensitizers in the CL-emitting reaction between cerium (IV) and thiol compounds. This CL reaction was successfully applied to the sensitive determination of various thiol drugs [21-32],... 

Figure 6 Representative (A) phenol-type and (B) phenylboronic acid-type enhancers for luminol/hydrogen peroxide/peroxidase system. KIH-201, 2-(4 -hydroxy-3 -methoxy-benzylidene)-4-cyclopentene-1,3-dione HDI, 2-(4-hydroxyphenyl)-4,5-diphenylimida-zole HPI, 2-(4-hydroxyphenyl)-4,5-di(2-pyridyl)imidazole DPPA, 4-[4,5-di(2-pyridyl)-lH-imidazol-2-yl]phenylboronic acid).

However, subsequent studies demonstrated that the formation of hydroxyl radicals, even if it takes place during lipid peroxidation, is of no real importance. Beloqui and Cederbaum [11] have found that although the glutathione-glutathione peroxidase system suppressed hydroxyl radical generation during the oxidation of 4-methylmercapto-2-oxo-butyrate, it exhibited a much smaller effect on microsomal lipid peroxidation. Therefore, hydroxyl radical formation is apparently unimportant in this process. Other authors also pointed out at an unimportant role of hydroxyl radicals in the initiation of microsomal lipid peroxidation [12 14], For example, it has been shown that Fe(EDTA), a most efficient catalyst of hydroxyl radical formation by the Fenton reaction, inhibited microsomal and liposomal lipid peroxidation, while the weak catalysts of this reaction Fe(ADP) and Fe(ATP) enhanced it [13]. 

Peroxidases, 9 379-380 10 303-304 Peroxidase systems, 10 284 Peroxide bleaching, 22 49 of recycled pulp, 22 51... 

Chow, C. K., C. J. Dillard, and A. L. Tappel. Glutathione peroxidase system and lysozyme in rats exposed to ozone or nitrogen dioxide. Environ. Res. 7 311-319. 

In addition to the many enzyme systems available, there are with each a series of chromogenic substrate solutions that can be used to create different colors and locations of reaction products. For the peroxidase system, there are numerous oxidizable compounds that precipitate as a permanent color. The most common and still widely used is 3,3 diaminobenzidine tetrahydro-chloride (DAB). This compound precipitates to a golden brown color when in solution with peroxidase and hydrogen peroxide. This brown color has many subtleties and readily stands out in a tissue section. With practice, it is possible to differentiate specific from nonspecific staining patterns just by examining the characteristics of the precipitated pigment. This material is also insoluble in alcohol and xylene, and therefore the tissue may be routinely dehydrated and cleared without loss of chromogen. 

HU. Hill, J. B., and Kessler, G., An automated determination of glucose utilizing a glucose oxidase-peroxidase system. J. Lab. Clin. Med. 57, 970-980 (1961). 

This drug has a pronounced thyrostatic effect and canses reduced thyroxine synthesis in the thyroid gland. It inhibits the process of iodination of thyroglobnUn, reduces formation of the active form of iodine in the thyroid gland, and blocks the peroxidase system. Propylthionracil is nsed for hyperthyrosis, thyrotoxic crises, and on thyrodectomia. Synonyms of this dmg are propycil and tireostat. 

Bjorck, L., Rosen, C., Marshall, V., and Reiter, B. (1975). Antibacterial activity of the lacto-peroxidase system in milk against pseudomonads and other gram-negative bacteria. Appl. Microbiol. 30, 199-204. 

Most of the work reported with these complexes has been concerned with kinetic measurements and suggestions of possible mechanisms. The [Ru(HjO)(EDTA)] / aq. HjOj/ascorbate/dioxane system was used for the oxidation of cyclohexanol to cw-l,3-cyclohexanediol and regarded as a model for peroxidase systems kinetic data and rate laws were derived [773], Kinetic data were recorded for the following systems [Ru(Hj0)(EDTA)]702/aq. ascorbate/dioxane/30°C (an analogue of the Udenfriend system cyclohexanol oxidation) [731] [Ru(H20)(EDTA)]70j/water (alkanes and epoxidation of cyclic alkenes - [Ru (0)(EDTA)] may be involved) [774] [Ru(HjO)(EDTA)]702/water-dioxane (epoxidation of styrenes - a metallo-oxetane intermediate was postulated) [775] [Ru(HjO)(EDTA)]7aq. H O /dioxane (ascorbic acid to dehydroascorbic acid and of cyclohexanol to cyclohexanone)... 

First of all, the behavior of the enzymes in the membrane differs markedly from the behavior of the unbound enzymes in solution. It is pertinent to note that the medium in which the enzyme bound to a membrane acts might be determined not only by the composition and structure of the membrane itself, but also by the local concentration distribution of substrate and products. The microenvironment in the membranes is the result of a balance between the flow of matter and enzyme reactions. The substrate and product concentrations in the membrane differ from point to point across the membrane and also from those at the outer solution. By electron microscopy this was experimentally demonstrated beyond doubt with the DAB-peroxidase system by Barbotin and Thomas.16 The effects of these profiles were studied with... 

In its biochemical functions, ascorbic acid acts as a regulator in tissue respiration and tends to serve as an antioxidant in vitro by reducing oxidizing chemicals. The effectiveness of ascorbic acid as an antioxidant when added to various processed food products, such as meats, is described in entry on Antioxidants. In plant tissues, the related glutathione system of oxidation and reduction is fairly widely distributed and there is evidence that election transfer reactions involving ascorbic acid are characteristic of animal systems. Peroxidase systems also may involve reactions with ascorbic acid In plants, either of two copper-protein enzymes are commonly involved in the oxidation of ascorbic acid. 

A successive report from the same group [50] discussed the influence of molecular recognition on the substrate binding, and therefore catalytic activity, in the peroxidase system previously developed. The authors reached the conclusion that the haemin played a role not only in the catalytic cycle but it was also essential in the molecular recognition of the substrate, by cooperating with the other co-monomers, 4-vinyl-pyridine and acrylamide. Moreover, imprinting efficiency was demonstrated by showing that the catalytic activity of the MIP was enhanced 7.6 times with respect to the NIP. 

Similar examples of the dependence of intramolecular transfer rates on protein primary gtructure are found in reactions in the cytc/cytc peroxidase system. 

Figure 8. Transplanted kidney stained for C4d using (a) an ultrasensitive polymer detection system (EnVision) and (b) standard strepavidin-biotin peroxidase system. There was clear staining of peritubular capillaries in (b) compared to the polymer system where the stain extended into the intertubular interstitium masking the capillaries.

At pH < 6 or at higher peroxide concentrations, other GSH adducts were also formed but have not yet been identified. Presumably they are formed by further oxidation of GS-CH2-AB and/or GSH adduct formation with other MAB oxidation products. Under optimal conditions in the H202 peroxidase system, 83% of the MAB could be recovered as GS-CH2 AB as calculated from a molar extinction coefficient for GS-CH2 AB of 22,600 M at 395 nm in methanol water 1 1. 

Table IV. Dietary Vitamin E and GSH Peroxidase System in the Lungs of Cigarette-Smoked Rats ...

The dihydrodimer D4, by contrast, is inactive in the peroxidase system. Summing up, the oxidation of the dimers 3 by 02, H202 and the peroxidase system proceeds via formation of an intermediate diradical, i.e. mechanism (a). 

When catalase activity is absent, H2O2 can be monitored directly spectrophotometrically (29) or by coupling to a peroxidase system (30). The weak n tt transition of the carbonyl group is present in the oc-keto acid products of the amino acid oxidase reactions and can also be utilized under special conditions (31), However, all these methods present far more serious technical problems than the O2 electrode technique and are used only in special circumstances. 

---