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Query: UNIPROT:P04040 (Catalase)
 3,577 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Oxidative stress responses were tested in the unicellular cyanobacterium synechococcus PCC 7942 (R-2). Cells were exposed to hydrogen peroxide, cumene hydroperoxide and high light intensities. The extent and time course of oxidative stress were related to the activities of ascorbate peroxidase and catalase. Ascorbate peroxidase was found to be the major enzyme involved in the removal of hydrogen peroxide under the tested oxidative stress. Catalase activity was inhibited in cells, treated with high H2O2 concentrations, and was not induced under photooxidative stress. Catalase was specifically induced in cells treated with cumene hydroperoxide. Superoxide dismutase activity increased under conditions generating superoxide, such as high light intensities. The induction of the antioxidative enzymes was light dependent and was inhibited by chloramphenicol.
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PMID:Oxidative stress responses in the unicellular cyanobacterium Synechococcus PCC 7942. 190 71

It has been claimed that the sole H(2)O(2)-scavenging system in the cyanobacterium Synechococcus sp. PCC 7942 is a cytosolic catalase-peroxidase. We have measured in vivo activity of a light-dependent peroxidase in Synechococcus sp. PCC 7942 and UTEX 625. The addition of small amounts of H(2)O(2) (2.5 microM) to illuminated cells caused photochemical quenching (qP) of chlorophyll fluorescence that was relieved as the H(2)O(2) was consumed. The qP was maximal at about 50 microM H(2)O(2) with a Michaelis constant of about 7 microM. The H(2)O(2)-dependent qP strongly indicates that photoreduction can be involved in H(2)O(2) decomposition. Catalase-peroxidase activity was found to be almost completely inhibited by 10 microM NH(2)OH with no inhibition of the H(2)O(2)-dependent qP, which actually increased, presumably due to the light-dependent reaction now being the only route for H(2)O(2)-decomposition. When (18)O-labeled H(2)O(2) was presented to cells in the light there was an evolution of (16)O(2), indicative of H(2)(16)O oxidation by PS 2 and formation of photoreductant. In the dark (18)O(2) was evolved from added H(2)(18)O(2) as expected for decomposition by the catalase-peroxidase. This evolution was completely blocked by NH(2)OH, whereas the light-dependent evolution of (16)O(2) during H(2)(18)O(2) decomposition was unaffected.
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PMID:The photoreduction of H(2)O(2) by Synechococcus sp. PCC 7942 and UTEX 625. 1085 92

Catalase-peroxidases (KatGs) are multifunctional heme peroxidases exhibiting an overwhelming catalase activity and a substantial peroxidase activity of broad specificity. Here, we show that catalase-peroxidases are also haloperoxidases capable of oxidizing chloride, bromide, and iodide in a peroxide- and enzyme-dependent manner. Recombinant KatG and the variants R119A, W122F, and W122A from the cyanobacterium Synechocystis PCC 6803 have been tested for their halogenation activity. Halogenation of monochlorodimedon (MCD), formation of triiodide and tribromide, and bromide- and chloride-mediated oxidation of glutathione have been tested. Halogenation of MCD by chloride, bromide, and iodide was shown to be catalyzed by wild-type KatG and the variant R119A. Generally, rates of halogenation increased in the order Cl(-) < Br(-) < I(-) and/or by decreasing pH. The halogenation activity of R119A was about 7-9% that of the wild-type enzyme. Upon exchange of the distal Trp122 by Phe and Ala, both the catalase and halogenation activities were lost but the overall peroxidase activity was increased. The findings suggest that the same redox intermediate is involved in H(2)O(2) and halide oxidation and that distal Trp122 is involved in both two-electron reactions. That halides compete with H(2)O(2) for the same redox intermediate is also emphasized by the fact that the polarographically measured catalase activity is influenced by halides, with bromide being more effective than chloride.
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PMID:Catalase-peroxidase from synechocystis is capable of chlorination and bromination reactions. 1156 49

The inactivation of glutamine synthetase (GS; EC 6.3.1.2) by metal-catalyzed oxidation (MCO) systems was studied in several Prochlorococcus strains, including the axenic PCC 9511. GS was inactivated in the presence of various oxidative systems, either enzymatic (as NAD(P)H+NAD(P)H-oxidase+Fe(3+)+O(2)) or non-enzymatic (as ascorbate+Fe(3+)+O(2)). This process required the presence of oxygen and a metal cation, and is prevented under anaerobic conditions. Catalase and peroxidase, but not superoxide dismutase, effectively protected the enzyme against inactivation, suggesting that hydrogen peroxide mediates this mechanism, although it is not directly responsible for the reaction. Addition of azide (an inhibitor of both catalase and peroxidase) to the MCO systems enhanced the inactivation. Different thiols induced the inactivation of the enzyme, even in the absence of added metals. However, this inactivation could not be reverted by addition of strong oxidants, as hydrogen peroxide or oxidized glutathione. After studying the effect of addition of the physiological substrates and products of GS on the inactivation mechanism, we could detect a protective effect in the case of inorganic phosphate and glutamine. Immunochemical determinations showed that the concentration of GS protein significantly decreased by effect of the MCO systems, indicating that inactivation precedes the degradation of the enzyme.
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PMID:Regulation of glutamine synthetase by metal-catalyzed oxidative modification in the marine oxyphotobacterium Prochlorococcus. 1178 30

A catalase-negative mutant of the yeast Hansenula polymorpha consumed methanol in the presence of glucose when the organism was grown in carbon-limited chemostat cultures. The organism was apparently able to decompose the H(2)O(2) generated in the oxidation of methanol by alcohol oxidase. Not only H(2)O(2) generated intracellularly but also H(2)O(2) added extracellularly was effectively destroyed by the catalase-negative mutant. From the rate of H(2)O(2) consumption during growth in chemostat cultures on mixtures of glucose and H(2)O(2), it appeared that the mutant was capable of decomposing H(2)O(2) at a rate as high as 8 mmol . g of cells . h. Glutathione peroxidase (EC 1.11.1.9) was absent under all growth conditions. However, cytochrome c peroxidase (CCP; EC 1.11.1.5) increased to very high levels in cells which decomposed H(2)O(2). When wild-type H. polymorpha was grown on mixtures of glucose and methanol, the CCP level was independent of the rate of methanol utilization, whereas the level of catalase increased with increasing amounts of methanol in the substrate feed. Also, the wild type decomposed H(2)O(2) at a high rate when cells were grown on mixtures of glucose and H(2)O(2). In this case, an increase of both CCP and catalase was observed. When Saccharomyces cerevisiae was grown on mixtures of glucose and H(2)O(2), the level of catalase remained low, but CCP increased with increasing rates of H(2)O(2) utilization. From these observations and an analysis of cell yields under the various conditions, two conclusions can be drawn. (i) CCP is a key enzyme of H(2)O(2) detoxification in yeasts. (ii) Catalase can effectively compete with mitochondrial CCP for hydrogen peroxide only if hydrogen peroxide is generated at the site where catalase is located, namely in the peroxisomes.
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PMID:Hydrogen peroxide metabolism in yeasts. 1634 19

Catalase-peroxidases or KatGs from seven different organisms, including Archaeoglobus fulgidus,Bacillus stearothermophilus, Burkholderia pseudomallei, Escherichia coli, Mycobacterium tuberculosis, Rhodobacter capsulatus and Synechocystis PCC 6803, have been characterized to provide a comparative picture of their respective properties. Collectively, the enzymes exhibit similar turnover rates with the catalase and peroxidase reactions varying between 4900 and 15,900s(-1) and 8-25s(-1), respectively. The seven enzymes also exhibited similar pH optima for the peroxidase (4.25-5.0) and catalase reactions (5.75), and high sensitivity to azide and cyanide with IC50 values of 0.2-20muM and 50-170muM, respectively. The K(M)s of the enzymes for H2O2 in the catalase reaction were relatively invariant between 3 and 5mM at pH 7.0, but increased to values ranging from 20 to 225mM at pH 5, consistent with protonation of the distal histidine (pKa approximately 6.2) interfering with H2O2 binding to Cpd I. The catalatic k(cat) was 2- to 3-fold higher at pH 5 compared to pH 7, consistent with the uptake of a proton being involved in the reduction of Cpd I. The turnover rates for the INH lyase and isonicotinoyl-NAD synthase reactions, responsible for the activation of isoniazid as an anti-tubercular drug, were also similar across the seven enzymes, but considerably slower, at 0.5 and 0.002s(-1), respectively. Only the NADH oxidase reaction varied more widely between 10(-4) and 10(-2)s(-1) with the fastest rate being exhibited by the enzyme from B. pseudomallei.
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PMID:Comparative study of catalase-peroxidases (KatGs). 1817 43

Cyanobacterium Synechococcus sp. PCC 7002 contains a single gene (glbN) coding for GlbN, a protein of the 2/2 hemoglobin lineage. The precise function of GlbN is not known, but comparison to similar 2/2 hemoglobins suggests that reversible dioxygen binding is not its main activity. In this report, the results of in vitro and in vivo experiments probing the role of GlbN are presented. Transcription profiling indicated that glbN is not strongly regulated under any of a large number of growth conditions and that the gene is probably constitutively expressed. High levels of nitrate, used as the sole source of nitrogen, and exposure to nitric oxide were tolerated better by the wild-type strain than a glbN null mutant, whereas overproduction of GlbN in the null mutant background restored the wild-type growth. The cellular contents of reactive oxygen/nitrogen species were elevated in the null mutant under all conditions and were highest under NO challenge or in the presence of high nitrate concentrations. GlbN overproduction attenuated these contents significantly under the latter conditions. The analysis of cell extracts revealed that the heme of GlbN was covalently bound to overproduced GlbN apoprotein in cells grown under microoxic conditions. A peroxidase assay showed that purified GlbN does not possess significant hydrogen peroxidase activity. It was concluded that GlbN protects cells from reactive nitrogen species that could be encountered naturally during growth on nitrate or under denitrifying conditions. The solution structure of covalently modified GlbN was determined and used to rationalize some of its chemical properties.
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PMID:Functional and structural characterization of the 2/2 hemoglobin from Synechococcus sp. PCC 7002. 2066 34