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

Reaction of chromium(VI) with alpha-lipoic acid (reduced form, also called 1,2-dithiolane-3-pentanoic acid) generated Cr(V) and hydroxyl radical (*OH) as measured by electron spin resonance and ESR spin trapping. 5,5-Dimethyl-1-pyrroline was used as a spin trapping agent. Catalase inhibited the *OH generation and enhanced the Cr(V) formation. Superoxide dismutase had an opposite effect. H2O2 enhanced the *OH generation and decreased the Cr(V) formation in a dose-dependent manner. Metal chelators, EDTA, diethylenetriaminepentaacetic acid, deferoxamine, and 1, 10-phenanthroline inhibited *OH radical generation in the order of EDTA > 1,10-phenanthroline > DTPA > deferoxamine. Oxygen consumption measurements indicated that molecular oxygen was used to generate *OH radical in the mixture of Cr(VI) and alpha-lipoic acid. H2O2 and superoxide radical (O2-) were involved as reactive intermediates. The *OH radical was generated via Cr(V)-mediated Fenton-like reaction (Cr(V) + H2O2 --> Cr(VI) + OH- + *OH). HPLC measurements show that the *OH radical generated by this reaction is capable of generating 8-hydroxyl-2'-deoxyguanosine from 2-deoxyguanosine. Incubation of Cr(VI) with cultured Jurkat cells resulted in an activation of DNA binding activity of the nuclear factor (NF)-kappaB. Addition of alpha-lipoic acid enhanced the NF-kappaB activation, while the *OH radical scavenger, sodium formate, inhibited it, showing that alpha-lipoic acid enhanced Cr(VI)-induced NF-kappaB activation via free radical reactions. The results indicate that while alpha-lipoic acid is considered to be an antioxidant, it may be a cellular one-electron Cr(VI) reductant and could be involved in the mechanism of Cr(VI)-induced carcinogenesis.
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PMID:One-electron reduction of chromium(VI) by alpha-lipoic acid and related hydroxyl radical generation, dG hydroxylation and nuclear transcription factor-kappaB activation. 902 68

Scission of plant cell wall polysaccharides in vivo has generally been assumed to be enzymic. However, in the presence of l-ascorbate, such polysaccharides are shown to undergo non-enzymic scission under physiologically relevant conditions. Scission of xyloglucan by 1 mM ascorbate had a pH optimum of 4.5, and the maximum scission rate was reached after a 10-25-min delay. Catalase prevented the scission, whereas added H2O2 (0.1-10 mM) increased the scission rate and shortened the delay. Ascorbate caused detectable xyloglucan scission above approx. 5 microM. Dehydroascorbate was much less effective. Added Cu2+ (>0.3 microM) also increased the rate of ascorbate-induced scission; EDTA was inhibitory. The rate of scission in the absence of added metals appeared to be attributable to the traces of Cu (2.8 mg.kg-1) present in the xyloglucan. Ascorbate-induced scission of xyloglucan was inhibited by radical scavengers; their effectiveness was proportional to their rate constants for reaction with hydroxyl radicals (.OH). It is proposed that ascorbate non-enzymically reduces O2 to H2O2, and Cu2+ to Cu+, and that H2O2 and Cu+ react to form .OH, which causes oxidative scission of polysaccharide chains. Evidence is reviewed to suggest that, in the wall of a living plant cell, Cu+ and H2O2 are formed by reactions involving ascorbate and its products, dehydroascorbate and oxalate. Systems may thus be in place to produce apoplastic .OH radicals in vivo. Although .OH radicals are often regarded as detrimental, they are so short-lived that they could act as site-specific oxidants targeted to play a useful role in loosening the cell wall, e.g. during cell expansion, fruit ripening and organ abscission.
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PMID:Oxidative scission of plant cell wall polysaccharides by ascorbate-induced hydroxyl radicals. 960 Oct 81

When rat brain homogenate was incubated without adding iron, lipid peroxidation occurred temperature dependently between 27 degrees C and 42 degrees C. When homogenates of liver and heart were incubated under the same conditions, lipid peroxidation did not occur. The brain, compared with other organs, seems to be very vulnerable to oxidative damage with fever. Catalase promoted lipid peroxidation. The ability of dihydrolipoic acid and alpha-tocopherol to inhibit lipid peroxidation was very weak. In contrast, iron chelators, such as bathophenanthroline, desferrioxamine and EDTA, strongly inhibited lipid peroxidation, indicating that endogenous iron is involved in lipid peroxidation. Dialysis of brain homogenate depressed the temperature-dependent lipid peroxidation by about 30%. Then, the iron content of the homogenate decreased by about 35%. On the other hand, dialysis of EDTA-treated homogenate completely depressed the lipid peroxidation and the iron content of the homogenate decreased by about 87%. Adding iron to the homogenate dialyzed after EDTA treatment remarkably increased the lipid peroxidation, but the peroxidation reaction proceeded temperature independently. Our results suggest that endogenous iron, which may bind to cell components, causes temperature dependent lipid peroxidation by a site-specific mechanism.
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PMID:Temperature-dependent lipid peroxidation of rat brain homogenate. 964 25

To investigate DNA damage induced by Pb2+ and its prevention by scavengers, we determined DNA strand breakage and the formation of 8-hydroxydeoxyguanosine (8-OHdG) in DNA using plasmid relaxation assay and HPLC with electrochemical detection, respectively. Lead acetate induced DNA strand breakage in 10 mM of Hepes buffer, pH 6.8, in a time- and dose-dependent manner. Compared with lead, zinc acetate did not significantly induce DNA breakage. The singlet oxygen scavengers NaN3 and 2,2,6,6-tetramethyl-4-piperidone (TEMP) inhibited lead-induced DNA breakage more efficiently than the hydroxyl radical scavengers mannitol and DMPO. Deuterium oxide (D2O), a singlet oxygen enhancer, potentiated lead-induced DNA breakage. At low ratios to Pb2+, NADPH, glutathione, and 2-mercaptoethanol enhanced lead-induced DNA breakage, whereas high ratios of these agents protected it. Catalase and superoxide dismutase (SOD) did not protect DNA breaks induced by Pb2+. Lead-induced DNA breakage was markedly enhanced by H2O2, and this induction was inhibited by NaN3, TEMP, EDTA, catalase, BSA, and glutathione. In contrast, mannitol and SOD potentiated Pb2+/H2O2-induced DNA breaks. The results indicate that singlet oxygen, lead, and H2O2 are all involved in the reaction system, whereas hydroxyl radical and superoxide did not. Lead could cause a small amount of 8-OHdG formation in calf thymus DNA and dose-dependently induced the formation of this adduct in the presence of H2O2. Singlet oxygen scavengers were more effective than hydroxyl radical scavengers in protection from lead/H2O2-induced 8-OHdG adducts. Taken together, these results suggest that lead may induce DNA damage through a Fenton-like reaction and that singlet oxygen is the principal species involved.
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PMID:Singlet oxygen is the major species participating in the induction of DNA strand breakage and 8-hydroxydeoxyguanosine adduct by lead acetate. 1033 21

Electron spin resonance (ESR) spin trapping measurements provide evidence for the generation of hydroxyl radicals (*OH) in the reduction of Cr(VI) by glutathione reductase (GSSG-R) in the presence of NADPH as a cofactor. Catalase inhibited the *OH generation, while the addition of H2O2 enhanced it, indicating that the *OH radical generation involves a Fenton-like reaction. The metal chelator, deferoxamine, inhibited the *OH generation with a concomitant generation of a deferoxamine nitroxide radical. EDTA and 1,10-phenanthroline also inhibited the *OH generation. Experiments performed under argon atmosphere decreased the yield of the *OH formation, showing that molecular oxygen plays a critical role. ESR spin trapping and measurements of fluorescence change of scopoletin in the presence of horseradish peroxidase show that reduction of Cr(VI) by GSSG-R/NADPH generates superoxide anion radicals (O2*-) as well as H2O2. It can be concluded that *OH radical is generated by the reaction of H2O2 with Cr(V), which is produced by enzymatic one-electron reduction of Cr(VI). H2O2 is produced by the reduction of molecular oxygen via O2*- as an intermediate. The *OH radicals generated by these reactions are capable of causing DNA strand breaks, which can be inhibited by catalase, formate, and experiments performed under argon.
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PMID:Role of molecular oxygen in the generation of hydroxyl and superoxide anion radicals during enzymatic Cr(VI) reduction and its implication to Cr(VI)-induced carcinogenesis. 1090 8

Catalase (CAT, EC 1.11.1.6) activity was measured in flesh tissue of six apple cultivars (Malus domestica Borkh. cvs. Braeburn, Gala, Jonagold, McIntosh, Red Delicious, and Spartan). Activity of CAT was determined for fresh and frozen tissue of the same fruit. Freezing resulted in reductions of 50 to 90% in CAT activity compared with the activity measured in crude extracts from fresh tissues. The rate of freezing had an impact on the level of reduction of CAT activity, with slower freezing procedures leading to greater losses in activity. Six additives to the extraction buffer were tested to evaluate their potential to reduce the inactivation of CAT from frozen tissue, but only EDTA and Tween 20 showed any benefit. However, EDTA and Tween 20 provided only partial recovery in CAT activity. In contrast, crude extracts prepared from fresh tissue showed no appreciable loss in CAT activity after frozen storage for two weeks at -80 degrees C. Gel electrophoresis and immunological analysis indicated that the loss in CAT activity from tissue freezing could be attributed to loss of both the tetrameric CAT enzyme structure and total CAT protein. The implications of using freezing to preserve apple tissue samples prior to catalase activity analysis is discussed.
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PMID:Effect of freezing on the activity of catalase in apple flesh tissue. 1108 15

Polyphenols in several oxidation systems gained amine oxidase-like activity, probably due to the formation of the corresponding quinones. In the presence of Cu(II), o- and p-phenolic compounds exhibited amine oxidase-like activity, whereas only the o-phenolic compounds showed the activity in the presence of 1,1-diphenyl-2-picrylhydrazyl radical. The activity was determined by measuring the conversion of benzylamine to benzaldehyde by HPLC. Moreover, gallic acid, chlorogenic acid, and caffeic acid, which are plant polyphenols, converted the lysine residue of bovine serum albumin to alpha-amino-adipic semialdehyde residue, indicating lysyl oxidase-like activity. We also characterized the activity of pyrocatechol, hydroquinone, and pyrogallol in the presence of Cu(II). The oxidative deamination was accelerated at a higher pH, and required O2 and transition metal ions. Furthermore, EDTA markedly inhibited the reaction but not beta-aminopropionitrile, which is a specific inhibitor of lysyl oxidase. Catalase significantly inhibited the oxidation, implying the participation of hydroxyl radical in the reaction, but superoxide dismutase stimulated the oxidation, probably due to its radical formation activity. We discussed the mechanism of the oxidative deamination by polyphenols and the possible significance of the activity for biological systems.
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PMID:Amine oxidase-like activity of polyphenols. Mechanism and properties. 1127 17

2-Nitropropane (2-NP), a widely used industrial solvent, is carcinogenic to rats. To clarify the mechanism of carcinogenesis by 2-NP, we investigated DNA damage by 2-NP metabolites, N-isopropylhydroxylamine (IPHA) and hydroxylamine-O-sulfonic acid (HAS), using 32P-5'-end-labelled DNA fragments obtained from genes that are relevant to human cancer. In the presence of Fe(III) EDTA, both IPHA and HAS caused DNA damage at every nucleotide position without marked site preference. The damage was inhibited by free hydroxyl radical (-*OH) scavengers, catalase and deferoxamine mesilate, an iron chelating agent. These results suggest that the DNA damage was caused by -*OH generated via H(2)O(2) by both IPHA and HAS. In contrast, in the presence of Cu(II), IPHA frequently caused DNA damage at thymine. The Cu(II)-mediated DNA damage caused by IPHA was inhibited by catalase, methional and bathocuproine, a Cu(I)-specific chelator, suggesting the involvement of H(2)O(2) and Cu(I). These results suggest that the DNA damage induced by IPHA in the presence of Cu(II) was caused by a reactive oxygen species like the Cu(I)-hydroperoxo complex. On the other hand, HAS most frequently induced DNA damage at 5'-TG-3', 5'-GG-3' and 5'-GGG-3' sequences. Catalase and methional only partly inhibited the Cu(II)-mediated DNA damage caused by HAS, suggesting that the reactive oxygen species and another reactive species participate in this process. Formation of 8-oxodG by IPHA or HAS increased in the presence of metal ions. This study suggests that metal-mediated DNA damage caused by 2-NP metabolites plays an important role in the mutagenicity and the carcinogenicity of 2-NP.
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PMID:Mechanism of metal-mediated DNA damage induced by metabolites of carcinogenic 2-nitropropane. 1147 Apr 85

Green tea catechins, especially (-)-epigallocatechin gallate (EGCG), are believed to mediate much of the cancer chemopreventive effects of tea. However, it was reported that green tea catechins enhanced colon carcinogenesis in rats. Experiments using 32P-labeled DNA fragments obtained from human cancer-related genes showed that catechins induced DNA damage in the presence of metals such as Cu(II) and Fe(III) complexes. In the presence of Fe(III)EDTA, the order of DNA damaging ability was EGCG approximately (-)-epigallocatechin>(-)-epicatechin gallate>>catechin. Catechins plus Fe(III)EDTA caused DNA damage at every nucleotide, most likely due to *OH generation from H(2)O(2). In the presence of Cu(II), the order was (-)-epigallocatechin>catechin>EGCG>(-)-epicatechin gallate. Cu(II)-mediated DNA damage by EGCG occurred most frequently at T and G residues, especially of 5'-TG-3' and GG sequences. Catalase and bathocuproine inhibited the Cu(II)-mediated DNA damage, suggesting the involvement of H(2)O(2) and Cu(I). In the presence of metal ions, increased amounts of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) were found in DNA treated with EGCG. Furthermore, EGCG increased amounts of 8-oxodG in HL-60 cells, but not in the H(2)O(2)-resistant clone HP100. When GSH was reduced by L-buthionine-[S, R]-sulfoximine, a low concentration of EGCG increased amounts of 8-oxodG in HL-60 cells, further supporting the involvement of H(2)O(2) in cellular DNA damage. It is concluded that EGCG can induce H(2)O(2) generation and subsequent damage to isolated and cellular DNA, and that oxidative DNA damage may mediate the potential carcinogenicity of EGCG.
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PMID:(-)-Epigallocatechin gallate causes oxidative damage to isolated and cellular DNA. 1456 87

1. The current study examined the hypothesis that endothelial production of hydrogen peroxide (H2O2) mediates relaxations to acetylcholine (ACh) in aorta and small mesenteric arteries (SMA) from mice. 2. Relaxations to ACh (0.01-10 microM) and H2O2 (0.1-1000 microM) were produced in aorta and SMA isolated from wild-type C57BL/6 mice and type II diabetic mice (db/db). In SMA, relaxations to ACh were produced in the presence of N omega-nitro-L-arginine methyl ester (100 microM) and indomethacin (Indo, 10 microM). 3. 1-H[1,2,4]oxadiazolo[4,3-]quinoxalin-1-one (10 microM) significantly reduced ACh-induced relaxations in SMA, abolished responses in aorta, but had no effect on relaxations induced by H2O2. Catalase (2500 U ml-1) abolished responses to H2O2, but did not alter relaxations to ACh in the SMA and only caused a small rightward shift in responses to ACh in the aorta. 4. ACh-, but not H2O2-, mediated relaxations were significantly reduced by tetraethylammonium (10 mM), the combination of apamin (1 microM) and charybdotoxin (100 nM), and 25 mm potassium chloride (KCl). Higher KCl (60 mM) abolished relaxations to both ACh and H2O2. Polyethylene glycolated superoxide dismutase (100 U ml-1), the catalase inhibitor 3-amino-1,2,4-triazole (3-AT, 50 mM) and treatment with the copper chelator diethyldithiolcarbamate (3 mM) did not affect relaxations to ACh. 5. H2O2-induced relaxations were endothelium-independent and were not affected by ethylene diamine tetraacetic acid (EDTA 0.067 mM), 4-aminopyridine (1 mM), ouabain (100 microM) and barium (30 microM), 3-AT or Indo. 6. Although the data from this study show that H2O2 dilates vessels, they do not support the notion that H2O2 mediates endothelium-dependent relaxations to ACh in either aorta or SMA from mice.
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PMID:Catalase has negligible inhibitory effects on endothelium-dependent relaxations in mouse isolated aorta and small mesenteric artery. 1459 98


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