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Heme peroxidases myeloperoxidase

Interestingly, unlike the heme-containing peroxidases myeloperoxidase and chloroperoxidase, the vanadium enzyme does not catalyze the direct disproportionation of H2O2 in the absence of bromide or iodide... [Pg.85]

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)... [Pg.75]

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... [Pg.543]

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. [Pg.95]

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... 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...
The direct interactions between metals and ONOO- can catalyze modifications. For example, the metals in Cu,Zn SOD and FeEDTA (EDTA = ethyl-enediaminetetraacetic acid) enhance nitration reactions (229). Heme-containing enzymes such as myeloperoxidase (6 x 106A/-1 s-1) and lactoperoxidase (3.3 x 105M-1s-1) also react with ONOO- (230) such that compound II [FeIV(P+)0] is formed. In contrast, horseradish peroxidase (3.2 x 106M-1 s-1) is converted to compound I (FevO) by ONOO-. Floris et al. (230) proposed an interesting mechanism by which compound I is initially produced and then rapidly oxidizes NO-f to N02. In the presence of NO, a number of nitrosation reactions would subsequently be facilitated by subsequent formation of N2O3 (Eq. 32). [Pg.373]

Aside from the classical examples of hemoglobin and myoglobin, reaction of ferrous heme iron with O2 in hemeperoxidases has been reported for myeloperoxidase [60], horseradish peroxidase C [62], bovine liver catalase [68], lignin peroxidase [46], and lactoperoxidase [61]. With the exception of lactoperoxidase, the binding of O2 is irreversible and CIII engages in one or more of the decay pathways described below. [Pg.296]

Peroxidases fall into two superfamilies (plant and mammalian) and a third, indistinct group that includes chloroperoxidase (a P450-like hybrid) and di-heme cytochrome c peroxidase from Pseudomonas aeruginosa. The plant peroxidase superfamily contains enzymes of plant, fungal, and bacterial origin [126], Mammalian peroxidases make up the second superfamily, and include lactoperoxidase, myeloperoxidase, and prostaglandin H synthase. Both families have been the focus of numerous excellent reviews, several of which have discussed the differences between the plant and mammalian peroxidases [126-130], Here, recent experimental investigations focused on the plant peroxidases will be discussed. [Pg.1748]

Horseradish peroxidase, which is the most fully characterized of the heme(Fe )-centered enzymes for the activation of HOOH, has an axial histidine ligand this also is the case for myeloperoxidase (uses HOOH and CF to form HOCl). In contrast, the catalase protein (catalyzes the harmless destruction of HOOH into O2 and H2O) has an axial tyrosine ligand in place of the histidine... [Pg.115]

Another endogenous HNO source relies on the oxidation of hydroxylamine (HA), or other alcohol amine, such as hydroxyurea or A -hydroxy arginine. In vivo, such a process is postulated to depend on the activity of several heme proteins, which are able to stabilize oxo ferryl species (compound I and compound II), such as peroxidases. Recently, Donzelli et al. evaluated HNO production by this mechanism (22), with a newly developed selective assay in which the reaction products, GS(0)NH, in the presence of reduced glutathione (GSH) are quantified by HPLC. Their results showed that metmyoglobin, horse radish peroxidase, and myeloperoxidase were efficient HNO producers using hydroxylamine as substrate. However, there are several remaining unresolved questions concerning the proposed mechanism (which is outlined below, Eq. (2)). [Pg.101]

M. Sono, A.M. Bracete, A.M. Huff, M. Ikeda-Saito, and J.H. Dawson, Evidence that a formyl-substituted iron porphyrin is the prosthetic group of myeloperoxidase magnetic circular dichroism similarity of the peroxidase to Spirographis heme-reconstituted myoglobin, Proc. Natl. Acad. Sci. USA 88 11148 (1991). [Pg.284]


See other pages where Heme peroxidases myeloperoxidase is mentioned: [Pg.733]    [Pg.734]    [Pg.704]    [Pg.360]    [Pg.50]    [Pg.39]    [Pg.1948]    [Pg.2099]    [Pg.2154]    [Pg.704]    [Pg.80]    [Pg.1947]    [Pg.2098]    [Pg.2153]    [Pg.6849]    [Pg.261]    [Pg.257]    [Pg.111]    [Pg.346]    [Pg.78]    [Pg.48]    [Pg.116]    [Pg.65]    [Pg.296]    [Pg.205]    [Pg.1948]    [Pg.2987]    [Pg.673]    [Pg.743]    [Pg.743]    [Pg.114]    [Pg.65]    [Pg.1947]    [Pg.2986]    [Pg.540]    [Pg.6]    [Pg.204]   
See also in sourсe #XX -- [ Pg.88 , Pg.89 ]




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