Myeloperoxidase peroxidases

According to Reichl et al. (2000), the oxidation of pholasin by compound I or II of horseradish peroxidase induces an intense light emission, whereas native horseradish peroxidase shows only a small effect. The luminescence of pholasin by native myeloperoxidase (verdoperoxidase) is diminished by preincubation with catalase, which is interpreted as the result of the removal of a trace amount of naturally occurring H2O2 in the buffer (about 10-8 M) that forms compound I... 

Brennan M-L and et al. (2002) A tale of two controversies. Defining both the role of peroxidases in nitrotyro-sine formation in vivo using eosinophil peroxidase and myeloperoxidase-deficient mice, and the natnre of the peroxidase-generated reactive nitrogen species. J Biol Chem 277 17415-17427. 

The classic oxidizing systems of human myeloperoxidase and horseradish peroxidase were exploited for their well-known abilities to oxidize phenolic substrates. Under conditions of incubations, the following oxidation pathway was defined (155). Peroxidases are first converted to the oxidized... 

Klebanoff SJ. Myeloperoxidase occurence and biological function. In Everse J, Everse KE, Grisham MB, eds. Peroxidases in Chemistry and Biology. Boca Raton, FL CRC Press 1991. 

Histochemical studies of bone marrow samples show that peroxidase-containing granules are detectable in promyelocytes. The human promyelo-cytic leukaemia cell line HL-60 grows easily in culture, and the cells resemble promyelocytes both structurally and functionally. Furthermore, they can be induced to differentiate in vitro upon addition of various agents, such as retinoic acid and phorbol esters, and these differentiated cells resemble more mature forms of neutrophils. HL-60 cells possess almost the same amount of myeloperoxidase (4.4 fig per 106 cells) as mature neutrophils, and the enzyme purified from these cells has the same subunit structure. The cells thus actively synthesise the enzyme only until they are induced to differentiate. This cell line has been extensively used to study the molecular events controlling the expression of enzymes such as myeloperoxidase, and also to investigate the molecular controls that lead to a cessation of their expression. 

It was therefore somewhat surprising when, in the early 1980s, a number of independent reports worldwide indicated that myeloperoxidase deficiencies may be quite common in the population of apparently-healthy individuals. These observations came from the use of the Hemalog D or Technicon H6000, flow-cytochemical systems intended to automate differential white blood counts. Part of this system uses a peroxidase stain, and hence neutro-... 

Eastmond DA, Smith MT, Ruzo LO, et al. 1986. Metabolic activation of phenol by human myeloperoxidase and horseradish peroxidase. Mol Pharmacol 30 674-679. 

Peroxidases (E.C. 1.11.1.7) are ubiquitously found in plants, microorganisms and animals. They are either named after their sources, for example, horseradish peroxidase and lacto- or myeloperoxidase, or akin to their substrates, such as cytochrome c, chloro- or lignin peroxidases. Most of the peroxidases studied so far are heme enzymes with ferric protoporphyrin IX (protoheme) as the prosthetic group (Fig. 1). However, the active centers of some peroxidases also contain selenium (glutathione peroxidase) [7], vanadium (bromoperoxidase)... 

This heme-dependent enzyme [EC 1.11.1.7] catalyzes the reaction of a donor with hydrogen peroxide to produce an oxidized donor and two water. See also Horseradish Peroxidase Ovoperoxidase Myeloperoxidase... 

HORSERADISH PEROXIDASE LACTOPEROXIDASE LIGNAN PEROXIDASE LYSYL OXIDASE MANGANESE PEROXIDASE MYELOPEROXIDASE OVOPEROXIDASE PEROXIDASE PYRUVATE OXIDASE XANTHINE OXIDASE Hydrogen selenide,... 

HORSERADISH PEROXIDASE OVOPEROXIDASE MYELOPEROXIDASE Perpendicular effect,... 

ATP, adenosine 5 -triphosphate BH4, 5,6,7,8-tetrahydrobiopterin BMPO, 5- er -butoxycarbonyl-5-pyrroline A-oxide DBNBS, 3,5-dibromo-4-nitrosoben-zene sulfonate DEPMPO, 5-diethoxyphosphoryl-5-methyl-l-pyrroline A-ox-ide DMPO, 5,5-dimethyl- 1-pyrroline A-oxide EMPO, 5-ethoxycarbonyl-5-methyl-l-pyrroline A-oxide GSH, glutathione (y-L-glutamyl-L-cysteinyl-glycine) HRP, horseradish peroxidase MNP, 2-methyl-2-nitrosopropane MPO, myeloperoxidase NAD(P)H, fl-nicotinamine adenine dinucleotide (3 -phosphate), reduced from NMDA, A-methyl-D-aspartic acid PBN, N-tert-butyl-a-phenylnitrone PMN, polymorphonuclear lymphocyte POBN, a-(4-pyridyl-l-oxide)-A-fer -butylnitrone SOD, superoxide dismutase TEMP,... 

Peroxidases. Another group of enzymes, which is involved in the oxidation of xenobiotics, is the peroxidase. There are a number of these enzymes in mammalian tissues prostaglandin synthase found in many tissues, but especially seminal vesicles and also the kidney, the lung, the intestine spleen, and blood vessels lactoperoxidase found in mammary glands myeloperoxidase found in neutrophils, macrophages, liver Kupffer cells, and bone marrow cells. 

The heme iron in the peroxidase is oxidized by the peroxide from III+ to V4- in compound I. The compound I is reduced by two sequential one-electron transfer processes giving rise to the original enzyme. A substrate-free radical is in turn generated. This may have toxicological implications. Thus the myeloperoxidase in the bone marrow may catalyze the metabolic activation of phenol or other metabolites of benzene. This may underlie the toxicity of benzene to the bone marrow, which causes aplastic anemia (see below and chap. 6). The myeloperoxidase found in neutrophils and monocytes may be involved in the metabolism and activation of a number of drugs such as isoniazid, clozapine, procainamide, and hydralazine (see below). In in vitro systems, the products of the activation were found to be cytotoxic in vitro. 

Figure 16-12 Linkage of heme to mammalian peroxidases. There are two ester linkages to carboxylate side chains from the protein.220 221 Myeloperoxidase contains a third linkage.222 2223...

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