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Heme-containing catalase enzyme

The synthesis of ROS can be catalyzed by iron ions, for example. Reaction of O2 with FMN or FAD (see p. 32) also constantly produces ROS. By contrast, reduction of O2 by cytochrome c-oxidase (see p. 140) is clean, as the enzyme does not release the intermediates. In addition to antioxidants (B), enzymes also provide protection against ROS superoxide dismutase [1] breaks down ( dispropor-tionates ) two superoxide molecules into O2 and the less damaging H2O2. The latter is in turn disproportionated into O2 and H2O by heme-containing catalase [2]. [Pg.284]

The bacterium Lactobacillus plantarum and its closest allies are unusual in that they are aerobic organisms but do not produce a superoxide dismutase. This bacterium instead accumulates Mn(II) to an intramolecular level on the order of 25 mM (150-152). In vitro studies indicated that Mn(II) formed a complex with lactate which possessed significant superoxide activity (153). These bacteria are additionally unable to produce heme and, consequently, when grown in the absence of heme, produce a hemeless catalase, or pseudocatalase (154-158). Unlike heme-containing catalases, the enzyme is not inhibited by cyanide or azide, and the addition of either Mn or Fe into the growth medium increased the amount of the pseudocatalase present. However, neither of the metals could be detected in partially purified enzyme assays (157). [Pg.214]

Bacterial SODs typically contain either nonheme iron (FeSODs) or manganese (MnSODs) at their active sites, although bacterial copper/zinc and nickel SODs are also known (Imlay and Imlay 1996 Chung et al. 1999). Catalases are usually heme-containing enzymes that catalyze disproportionation of hydrogen peroxide to water and molecular oxygen (Eq. 10.2) (Zamocky and Koller 1999 Loewen et al. 2000). [Pg.128]

Heme alone can reportedly elicit a catalatic reaction (the reaction mediated by catalase) but at a much reduced, almost negligible, rate compared to the catalatic proteins containing heme, and this may explain the observation of catalase activity in enzymes not normally associated with catalatic activity (4, 5). Other enz5unes have evolved that can catalyze a similar reaction in the absence of heme, but this review will limit itself to a consideration of heme containing proteins with catalatic activity. [Pg.52]

The heme of catalases is deeply buried within the core of the catalase subunit. Protoheme IX or heme b is found in all small-subunit catalases so far characterized. The two large-subunit enzymes HPII and PVC have been characterized biochemically, spectrally, and structurally 91) as containing heme d in which ring HI is oxidized to a cis-hydroxyspirolactone. Heme b is initially bound to both enzymes during assembly, and it is subsequently oxidized by the catalase itself during the early rounds of catalysis 92). [Pg.84]

This process is catalyzed by a variety of catalase enzymes, the most common being the heme catalases, which accomplish the two-electron chemistry of Eq. (12) at a mononuclear heme center. Here, both the iron and its surrounding porphyrin ligand participate to the extent of one electron each in the redox process. Manganese catalases contain a binuclear Mn center and cycle between Mn2(II,II) and Mn2(III,III) oxidation states while carrying out the disproportionation of H2O2. The enzyme can... [Pg.423]

On the basis of the structure of their active site, catalases may be classified as heme or nonheme enzymes. Those that contain heme iron are efficient catalysts, operating close to the diffusion limit, 108M 1sec 1. In iron catalases the metal is coordinated by four heme nitrogens and a proximal Tyr residue, which occupies the fifth coordination site. A catalytically required His is found on the distal side of the heme. In addition, a water molecule has also been observed close to the iron sixth coordination site. [Pg.370]

The heme-containing enzymes catalase and peroxidase are responsible for the removal of long-lived H202 according to the following reactions ... [Pg.168]

Catalase, a heme-containing enzyme with tyrosine as the proximal heme ligand, decomposes hydroperoxides and peracids by this reaction. Catalase is one of the most efficient enzymes known, with maximum turnover numbers on the order of 107 s 1. In... [Pg.226]

The RebD enzyme was characterized as the first member of a new subfamily of heme-containing oxidases [34,36]. The enzyme acted as both a catalase and a CPA synthase, apparently converting two molecules of 7-chloroindole-3-pyruvic acid imine into ll,ll -dichloro-CPA. Formation of CPA by StaD, an enzyme homolog to RebD, was also confirmed for STA biosynthesis [35],... [Pg.630]

Catalase (EC 1.11.1.6) is a heme containing oxidoreductase that acts on peroxides liberating oxygen and water. The enzyme is a very fast biocatalyst, i.e., Pichia pastoris catalase has a turnover number of 3 x 10 H2O2 s [199]. The enzyme consists of multiple subunits containing each heme as active site. [Pg.295]

Catalase is a heme-containing enzyme that uses H202 to oxidize other substrates ... [Pg.327]

Both catalase and ascorbate peroxidase are heme-containing proteins with peroxidase activities. The mechanism by which SA inhibits the activity of both these enzymes appears to be similar [112]. The native ferric form of catalase (Fe III) undergoes a two electron... [Pg.520]

To appreciate the role of thiolate in P450, it is instructive to also look at related heme-containing enzymes like HRP or catalase, where iron is coordinated to imidazole from a histidine side chain or to phenoxyl from a tyrosine side chain. [Pg.51]

Axial ligands of heme-containing enzymes, such as a cysteine thiolate in cytochromes P450 and chloroperoxidases, a histidine imidazole in peroxidases, and a tyrosine phenolate in catalases, are... [Pg.291]


See other pages where Heme-containing catalase enzyme is mentioned: [Pg.492]    [Pg.492]    [Pg.492]    [Pg.492]    [Pg.8]    [Pg.1951]    [Pg.1952]    [Pg.1950]    [Pg.1951]    [Pg.911]    [Pg.56]    [Pg.912]    [Pg.56]    [Pg.198]    [Pg.42]    [Pg.99]    [Pg.361]    [Pg.13]    [Pg.5012]    [Pg.5016]    [Pg.92]    [Pg.446]    [Pg.323]    [Pg.424]    [Pg.323]    [Pg.424]    [Pg.166]    [Pg.279]    [Pg.329]    [Pg.5011]    [Pg.5015]    [Pg.262]    [Pg.147]   
See also in sourсe #XX -- [ Pg.492 ]




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Enzymes containing

Heme enzymes

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