Peroxidase-hydrogen peroxide

Peroxidases are found in milk and in leukocytes, platelets, and other tissues involved in eicosanoid metabolism (Chapter 23). The prosthetic group is protoheme. In the reaction catalyzed by peroxidase, hydrogen peroxide is reduced at the expense of several substances that will act as electron acceptors, such as ascorbate, quinones, and cytochrome c. The reaction catalyzed by peroxidase is complex, but the overall reaction is as follows ... 

Katayama, Y. Fukuzumi, T. Enzymic synthesis of three lignin-related dimers by an improved peroxidase-hydrogen peroxide system. Mokuzai Gakkaishi 1978,24,664-667. 

Subrahmanyam VV, McGirr LG, O Brien PJ. 1990c. Peroxidase/hydrogen peroxide-or bone marrow homogenate/hydrogen peroxide-mediated activation of phenol and binding to protein. Xenobiotica 20 1369-1378. 

Inhibitory effects were seen following bioactivation using a peroxidase/hydrogen peroxide system. 

Henderson JP, Byun J, Mueller DM, Heinecke JW (2001) The Eosinophil Peroxidase-Hydrogen Peroxide-Bromide System of Human Eosinophils Generates 5-Bromouracil, a Mutagenic Thymine Analogue. Biochemistry 40 2052... 

Maeda Y, Morita Y (1967) Mossbauer effect in peroxidase-hydrogen peroxide compounds. Biochem Biophys Res Commun 29 680-685... 

The cytochrome-c peroxidase test offers the advantages of stability of the peroxidase-hydrogen peroxide complex and high specificity for its hydrogen donor, cytochrome c. 

Another aspect of the mode of action of ellipticine and its derivatives that has been intensely scrutinized in recent years is the chemistry of ellipticine quinone imines 6 and 256. The oxidation product of 9-hydroxyellipticine (3), formed by horseradish peroxidase-hydrogen peroxide or chemical (e.g., manganese dioxide) oxidation of 3, undergoes a rich array of chemical reactions. Meunier et al. 

The first successful observation and characterization of the ascorbate free radical was carried out with ESR (14,15). A 1.7-G ESR doublet was reported and it was correctly concluded that the observed spectrum represented the anionic form (A ) of the radical. These measurements (14,15) showed that the enzyme-generated radical (horseradish peroxidase-hydrogen peroxide-ascorbate) was present as a free radical and decayed by second-order kinetics (see Figure 2). Recent experiments (16,17) have shown that ascorbate oxidase and dopamine-monooxygenase also generate unbound ascorbate radicals. 

Yoshikawa, S., Kayes, S.G. and Parker, J.C. (1993). Eosinophils increase lung microvascular permeability via the peroxidase-hydrogen peroxide-halide system. Bronchoconstriction and vasoconstriction unaflFected by eosinophil peroxidase inhibition. Am. Rev. Respir. Dis. 147, 914-920. 

Klebanoff SJ and Shepard CC Toxic Effect of the Peroxidase-hydrogen peroxide-halide Antimicrobial System on Mycobacterium leprae. Infect. Immun. 1984 44(2) 534-6. 

Jhoo et al. reported that the oxidation of theaflavin in either DPPH or the peroxidase-hydrogen peroxide model system leads to the generation of theanaphthoqui-none as the major oxidation product. The proposed radical scavenging mechanism of theaflavin is shown in figure 8.14. Theanaphthoquinone is formed through one-electron oxidation. This indicates that the benzotropolone moiety of theaflavin is the active site for scavenging of radicals. ... 

Many of the enzyme/microorganism mediated dealkylation procedures that have been reported have come from the work of Rosazza and his coworkers as a consequence of their studies on Microbial models on Mammalian metabolism. These studies have largely concerned with demethylation of various alkaloids with bacteria and fungi. 0-deethylation reactions with Streptomyces griseus as with dealkylation of 7-ethoxy coumarin gave very poor yields and therefore was not considered a viable synthetic procedure. The quinone imine(I), has been prepared in 64%isolated yield by horseradish peroxidase/hydrogen peroxide O-demethylation of 9-methoxy-ellipticine(II). Studies with H2 0 as a reaction medium demonstrated that the reaction was not a simple demethylation but rather a replacement of the methoxy group by OH from the solvent (as shown in Fig.l)... 

Mixed-type oligomers of the type 62 can be formed when indoles 1 and 2 are co-oxidized with peroxidase/hydrogen peroxide (93TL885), suggesting that these indoles may co-polymerize in vitro to some extent. 

Horseradish peroxidase, hydrogen peroxide and buffers were purchased from Sigma Chemical Company. Benzidine and alkyl substituted phenols were purchased from Aldrich Chemical Company. Solvents used were high performance liquid chromatography grade and were purchased from Caledon Laboratories. 

---