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1.
A novel thermo-alkali-stable catalase from Thermus brockianus was purified and characterized. The protein was purified from a T. brockianus cell extract in a three-step procedure that resulted in 65-fold purification to a specific activity of 5300 U/mg. The enzyme consisted of four identical subunits of 42.5 kDa as determined by SDS-PAGE and a total molecular mass measured by gel filtration of 178 kDa. The catalase was active over a temperature range from 30 to 94 degrees C and a pH range from 6 to 10, with optimum activity occurring at 90 degrees C and pH 8. At pH 8, the enzyme was extremely stable at elevated temperatures with half-lives of 330 h at 80 degrees C and 3 h at 90 degrees C. The enzyme also demonstrated excellent stability at 70 degrees C and alkaline pH with measured half-lives of 510 h and 360 h at pHs of 9 and 10, respectively. The enzyme had an unusual pyridine hemochrome spectrum and appears to utilize eight molecules of heme c per tetramer rather than protoheme IX present in the majority of catalases studied to date. The absorption spectrum suggested that the heme iron of the catalase was in a 6-coordinate low spin state rather than the typical 5-coordinate high spin state. A K(m) of 35.5 mM and a V(max) of 20.3 mM/min.mg protein for hydrogen peroxide was measured, and the enzyme was not inhibited by hydrogen peroxide at concentrations up to 450 mM. The enzyme was strongly inhibited by cyanide and the traditional catalase inhibitor 3-amino-1,2,4-triazole. The enzyme also showed no peroxidase activity to peroxidase substrates o-dianisidine and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), a trait of typical monofunctional catalases. However, unlike traditional monofunctional catalases, the T. brockianus catalase was easily reduced by dithionite, a characteristic of catalase-peroxidases. The above properties indicate that this catalase has potential for applications in industrial bleaching processes to remove residual hydrogen peroxide from process streams.  相似文献   

2.
A putative perA gene from Archaeoglobus fulgidus was cloned and expressed in Escherichia coli BL21(DE3), and the recombinant catalase-peroxidase was purified to homogeneity. The enzyme is a homodimer with a subunit molecular mass of 85 kDa. UV-visible spectroscopic analysis indicated the presence of protoheme IX as a prosthetic group (ferric heme), in a stoichiometry of 0.25 heme per subunit. Electron paramagnetic resonance analysis confirmed the presence of ferric heme and identified the proximal axial ligand as a histidine. The enzyme showed both catalase and peroxidase activity with pH optima of 6.0 and 4.5, respectively. Optimal temperatures of 70 degrees C and 80 degrees C were found for the catalase and peroxidase activity, respectively. The catalase activity strongly exceeded the peroxidase activity, with Vmax values of 9600 and 36 U mg(-1), respectively. Km values for H2O2 of 8.6 and 0.85 mM were found for catalase and peroxidase, respectively. Common heme inhibitors such as cyanide, azide, and hydroxylamine inhibited peroxidase activity. However, unlike all other catalase-peroxidases, the enzyme was also inhibited by 3-amino-1,2,4-triazole. Although the enzyme exhibited a high thermostability, rapid inactivation occurred in the presence of H2O2, with half-life values of less than 1 min. This is the first catalase-peroxidase characterized from a hyperthermophilic microorganism.  相似文献   

3.
A simple and sensitive method for the simultaneous visualization of glutathione peroxidase and catalase on polyacrylamide gels is described. The procedure included: (I) running samples on a 7. 5% polyacryla-mide gel, (2) soaking the gel in a certain concentration of reduced glutathione (0.25-2.0 mM). (3) soaking the gel in GSH plus HzOz or cumene hydroperoxide, (4) finally staining with a 1% ferric chloride I% potassium ferricyanide solution. The best concentration of glutathione for simultaneous visualization of glutathione peroxidase and catalase was 0.25rnM; I.5mM glutathione was the best concentration for visualization of glutathione peroxidase alone. The method is sensitive enough to detect catalase and glutathione peroxidase in mouse liver homogenates and also it is specific for glutathione peroxidase since other peroxidases such as lactoperoxidase, horseradish peroxidase and glutathione S-transferase cannot be visualized. Using this method, it was found that unlike catalase. glutathione peroxidase is heat resistant (68°C. 1min), but sensitive to 10mM sodium iodoacetate.  相似文献   

4.
5.
《Free radical research》2013,47(2):67-75
A simple and sensitive method for the simultaneous visualization of glutathione peroxidase and catalase on polyacrylamide gels is described. The procedure included: (I) running samples on a 7. 5% polyacryla-mide gel, (2) soaking the gel in a certain concentration of reduced glutathione (0.25–2.0 mM). (3) soaking the gel in GSH plus HzOz or cumene hydroperoxide, (4) finally staining with a 1% ferric chloride I% potassium ferricyanide solution. The best concentration of glutathione for simultaneous visualization of glutathione peroxidase and catalase was 0.25rnM; I.5mM glutathione was the best concentration for visualization of glutathione peroxidase alone. The method is sensitive enough to detect catalase and glutathione peroxidase in mouse liver homogenates and also it is specific for glutathione peroxidase since other peroxidases such as lactoperoxidase, horseradish peroxidase and glutathione S-transferase cannot be visualized. Using this method, it was found that unlike catalase. glutathione peroxidase is heat resistant (68°C. 1min), but sensitive to 10mM sodium iodoacetate.  相似文献   

6.
A novel cytochrome c and a catalase-peroxidase with alkaline peroxidase activity were purified from the culture supernatant of Bacillus sp. No.13 and characterized. The cytochrome c exhibited absorption maxima at 408 nm (Soret band) in its oxidized state, and 550 (alpha-band), 521 (beta-band), and 415 (Soret band) nm in its reduced state. The native cytochrome c with a relative molecular mass of 15,000 was composed of two identical subunits. The cytochrome c showed over 50 times higher peroxidase activity than those of known c-type cytochromes from various sources. The optimum pH and temperature of the peroxidase activity were about 10.0 and 70 degrees C, respectively. The peroxidase activity is stable in the pH range of 6.0 to 10.8 (30 degrees C, 1-h treatment), and at temperatures up to 80 degrees C (pH 8.5, 20-min treatment). The heme content was determined to be 1 heme per subunit. The amino acid sequence of the cytochrome c showed high homology with those of the c-type cytochromes from Bacillus subtilis and Bacillus sp. PS3. The catalase-peroxidase showed high catalase activity and considerable peroxidase activity, the specific activities being 55,000 and 0.94 micromol/min/mg, respectively. The optimum pH and temperature of the peroxidase activity were in the range of 6.4 to 10.1 and 60 degrees C, respectively. The catalase-peroxidase showed a lower K(m) value (0.67 mM) as to H(2)O(2) than known catalase-peroxidases.  相似文献   

7.
The photosynthetic bacterium, Rhodospirillum rubrum S1, when grown under anaerobic conditions, generated three different types of catalases. In this study, we purified and characterized the highest molecular weight catalase from the three catalases. The total specific catalase activity of the crude cell extracts was 88 U/mg. After the completion of the final purification step, the specific activity of the purified catalase was 1,256 U/mg. The purified catalase evidenced an estimated molecular mass of 318 kDa, consisting of four identical subunits, each of 79 kDa. The purified enzyme exhibited an apparent Km value of 30.4 mM and a Vmax of 2,564 U against hydrogen peroxide. The enzyme also exhibited a broad optimal pH (5.0-9.0), and remained stable over a broad temperature range (20 degrees C-60 degrees C). It maintained 90% activity against organic solvents (ethanol/chloroform) known hydroperoxidase inhibitors, and exhibited no detectable peroxidase activity. The catalase activity of the purified enzyme was reduced to 19% of full activity as the result of the administration of 10 mM 3-amino-1,2,4-triazole, a heme-containing catalase inhibitor. Sodium cyanide, sodium azide, and hydroxylamine, all of which are known heme protein inhibitors, inhibited catalase activity by 50% at concentrations of 11.5 microM, 0.52 microM, and 0.11 microM, respectively. In accordance with these findings, the enzyme was identified as a type of monofunctional catalase.  相似文献   

8.
The effect of elevated light treatment (25 degrees C, PPFD 360 mumol m-2 sec-1) or chilling temperatures combined with elevated light (5 degrees C, PPFD 360 mumol m-2 sec-1) on the activity of six antioxidant enzymes, guaiacol peroxidases, and glutathione peroxidase (GPx, EC 1.11.1.9) protein accumulation were studied in tobacco Nicotiana tabacum cv. Petit Havana SR1. Both treatments caused no photooxidative damage, but chilling caused a transient wilting. The light treatment increased the activities of ascorbate peroxidase (APx, EC 1.11.1.11) and guaiacol peroxidases while catalase (EC 1.11.1.6), superoxide dismutase (SOD, EC 1.15.1.1), monodehydroascorbate reductase (MDHAR, EC 1.6.5.4), dehydroascorbate reductase (DHAR, EC 1.8.5.1), and glutathione reductase (EC 1.6.4.2) were unchanged. In contrast, chilling treatment did not increase any of the antioxidant enzyme activities, but decreased catalase and to a lesser extent DHAR activities. Glutathione peroxidase protein levels increased sporadically under light treatment and constantly under chilling. Both chilling and light stress caused induction of glutathione synthesis and accumulation of oxidised glutathione, although the predominant part of the glutathione pool remained in the reduced form. Antioxidant enzymes from the chilling treated plants were measured at both 25 degrees C and 5 degrees C. Measurements at 5 degrees C revealed a 3-fold reduction in catalase activity, compared with that measured at 25 degrees C, indicating that the overall reduction in catalase after four days of chilling was approximately 10-fold. The overall reduction in activity for the other antioxidant enzymes after four days of chilling was 2-fold for GR and APx, 1.5-fold for MDHAR, 3.5-fold for DHAR. The activity of SOD was the same at 25 and 5 degrees C. These results indicate that catalase and DHAR are most strongly affected by the chilling treatment and may be the rate-limiting factor of the antioxidant system at low temperatures.  相似文献   

9.
Thermostable peroxidase from Bacillus stearothermophilus   总被引:8,自引:0,他引:8  
A peroxidase from Bacillus stearothermophilus was purified to homogeneity. The enzyme (Mr 175,000) was composed of two subunits of equal size, and showed a Soret band at 406 nm. On reduction with sodium dithionite, absorption at 434 nm and 558 nm was observed. The spectrum of reduced pyridine haemochrome showed peaks at 418, 526 and 557 nm; the reduced minus oxidized spectrum of pyridine haemochrome showed peaks of 418, 524 and 556 nm with a trough at 452 nm. These results indicate that the enzyme contained protohaem IX as a prosthetic group. The optimum pH was about 6 and the apparent optimum temperature was 70 degrees C. The enzyme was relatively stable up to 70 degrees C; at 30 degrees C it was stable for a month. The enzyme had peroxidase activity toward a mixture of 2,4-dichlorophenol and 4-aminoantipyrine with a Km for H2O2 of 1.3 mM. It also acted as a catalase with a Km for H2O2 of 7.5 mM.  相似文献   

10.
A significant inactivation of red blood cell glutathione peroxidase (25% less than the physiological value) was observed after exposure of intact erythrocytes to 2 mM divicine (an autoxidizable aminophenol from Vicia faba seeds) and 2 mM ascorbate for 3 h at 37 degrees C. Addition of catalase and conversion of Hb to the carbomonoxy derivative resulted in protection against enzyme inactivation. Oxidation of Hb was a concurrent phenomenon, and augmented the inactivating effect. In hemolysates, much stronger effects were observed at shorter times (2 h); divicine was effective also without ascorbate, and the presence of reductants (ascorbate or glutathione or NADPH) enhanced its inactivating power. Of the other antioxidant enzymes, superoxide dismutase was unaffected under the same experimental conditions. Catalase was found to be much less sensitive to the inactivation; it was almost unaffected in experiments with intact erythrocytes and specifically protected by NADPH in experiments with hemolysates. This specific damage of glutathione peroxidase, apparently involving interaction of H2O2 and HbO2, may be related to the pathogenesis of hemolysis in favism.  相似文献   

11.
If H2O2 is one of the major mediators of the 'oxygen effect' in biological systems then catalase, which enzymically decomposes H2O2 should have a significant influence on radiation damage, particularly under oxygenated conditions. The post-irradiation (300 Gy gamma rays) effect of catalase was, therefore, assessed on barley seeds of about 4 per cent moisture content under oxygenated and oxygen-free conditions at varying temperatures. Catalase affords concentration-dependent radioprotection under oxygenated condition at both 25 degrees C and 4 degrees C. The level of protection at 4 degrees C is less than at 25 degrees C. This is obviously due to a decrease in catalase activity at low temperature. Under oxygen-free conditions, catalase enhances radiation damage at 4 degrees C while at 25 degrees C it has no effect. This has been substantiated by data on the frequency of chromosomal aberrations and on peroxidase activity. Sodium azide, a catalase inhibitor, was found to eliminate the radioprotective action of catalase. The study supports the view that the 'oxygen effect' is mediated largely through peroxides in irradiated biological systems. However, the observations made particularly at 4 degrees C under oxygen-free condition seem to involve physicochemical reactions.  相似文献   

12.
1. The effect of 70 mg/l and 35 mg/l MS 222 an anaesthetic on the enzymes: superoxide dismutase (SOD), catalase (C) and peroxidase (P) were estimated in erythrocytes of Cyprinus carpo, a freshwater fish and Dicentrarchus labrax, a marine fish. 2. The end of the summer, at 16 degrees C MS 222 in concentration 70 mg/l caused an enhancement of the SOD and peroxidase activities and a decrease of the catalase activity. 3. In the autumn at 22 degrees C SOD and peroxidase activities in erythrocytes of Dicentrarchus labrax are normally higher than at 16 degrees C. On the contrary MS 222 causes no significant modification of enzymatic activities measured, but an increase in the dispersion of the results. 4. At 13 degrees C in the spring, MS 222 has no immediate influence on the activity of these enzymes, whilst at the same temperature at the beginning of winter, SOD is the only one activated. 5. It seems that in experiments concerning peroxide metabolism enzymes the use of anaesthetic MS 222 is not advisable.  相似文献   

13.
In this study, an approx. 2.5-kb gene fragment including the catalase gene from Rhodospirillum rubrum S1 was cloned and characterized. The determination of the complete nucleotide sequence revealed that the cloned DNA fragment was organized into three open reading frames, designated as ORF1, catalase, and ORF3 in that order. The catalase gene consisted of 1,455 nucleotides and 484 amino acids, including the initiation and stop codons, and was located 326 bp upstream in the opposite direction of ORF1. The catalase was overproduced in Escherichia coli UM255, a catalase-deficient mutant, and then purified for the biochemical characterization of the enzyme. The purified catalase had an estimated molecular mass of 189 kDa, consisting of four identical subunits of 61 kDa. The enzyme exhibited activity over a broad pH range from pH 5.0 to pH 11.0 and temperature range from 20 degrees C to 60 degrees C. The catalase activity was inhibited by 3-amino-1,2,4-triazole, cyanide, azide, and hydroxylamine. The enzyme's K(m) value and V(max) of the catalase for H2O2 were 21.8 mM and 39,960 U/mg, respectively. Spectrophotometric analysis revealed that the ratio of A406 to A280 for the catalase was 0.97, indicating the presence of a ferric component. The absorption spectrum of catalase-4 exhibited a Soret band at 406 nm, which is typical of a heme-containing catalase. Treatment of the enzyme with dithionite did not alter the spectral shape and revealed no peroxidase activity. The combined results of the gene sequence and biochemical characterization proved that the catalase cloned from strain S1in this study was a typical monofunctional catalase, which differed from the other types of catalases found in strain S1.  相似文献   

14.
Retinoic acid 5,6-epoxidation by hemoproteins   总被引:2,自引:0,他引:2  
Retinoic acid 5,6-epoxidase activity was found in several hemoproteins such as human oxy- and methemoglobin (HbO2 and MetHb), equine skeletal muscle oxy- and metmyoglobin (MbO2 and MetMb), bovine liver catalase, and horseradish peroxidase. Hematin also catalyzed retinoic acid 5,6-epoxidation. The results suggest that the heme moiety participates in the epoxidation. However, neither horse heart cytochrome c, nor free ferrous ion nor free ferric ion exhibited the epoxidase activity. Some hemoproteins (HbO2, MetHb, MbO2, MetMb, catalase, peroxidase, and hematin) exhibited characteristic individual pH dependences of the activity, suggesting that the epoxidase activities of the hemoproteins are influenced by the apoenzymes to some degree. This view is also supported by the finding that preincubation of an HbO2 preparation at various temperatures (37-70 degrees C) reduced its epoxidase activity with increasing temperature, whereas the activity of hematin was unaffected. Active oxygen scavengers such as mannitol, catalase, and superoxide dismutase exhibited no effect on the epoxidase activities of HbO2, MetHb, MbO2, and MetMb. A ligand of heme, CN- (100 mM), inhibited the epoxidase activities but N3- (100 mM) did not. The epoxidase activities were completely inhibited by NADPH, NADH, and/or 2-mercaptoethanol but not by NADP+ and/or NAD+. An intermediate in the epoxidation may be reduced by NADPH, NADH and/or 2-mercaptoethanol. Radical species can be considered as plausible candidates for the intermediate.  相似文献   

15.
The activities of antioxidant enzymes viz. glutathione reductase, GR; superoxide dismutase, SOD; peroxidase, POD; catalase, CAT and glutathione-S-transferase, GST and alkaloid accumulation were investigated in leaf pairs (apical, middle, basal) and in roots of Catharanthus roseus seedlings under the conditions of different nitrogen sources (20 mM KNO(3) and 2 mM NH(4)Cl) and salinity, in the absence (non-saline control) and in the presence of 100 mM NaCl in the nutrient solution. Salinity caused a reduction in plant biomass. The biomass production of ammonium-fed plants was lower than that of nitrate-fed plants. The antioxidant enzymes exhibited higher activity in saline-treated plants. Changes in antioxidant enzyme activity caused by different nitrogen sources differed in all leaf pairs, as well as in roots of C. roseus. Ammonium-fed plants showed higher CAT, GR and GST activity in leaf pairs as well as in roots, while POD and SOD activity were higher in nitrate-fed plants. Higher peroxidase activity concomitant with the increased accumulation of alkaloid was found in all leaf pairs, as well as in roots of C. roseus of NO(3)(-) fed plants as compared to NH(4)(+) fed plants.  相似文献   

16.
A hydroperoxidase purified from the halophilic archaeon Halobacterium halobium exhibited both catalase and peroxidase activities, which were greatly diminished in a low-salt environment. Therefore, the purification was carried out in 2 M NaCl. Purified protein exhibited catalase activity over the narrow pH range of 6.0 to 7.5 and exhibited peroxidase activity between pH 6.5 and 8.0. Peroxidase activity was maximal at NaCl concentrations above 1 M, although catalase activity required 2 M NaCl for optimal function. Catalase activity was greatest at 50 degrees C; at 90 degrees C, the enzymatic activity was 20% greater than at 25 degrees C. Peroxidase activity decreased rapidly above its maximum at 40 degrees C. An activation energy of 2.5 kcal (ca. 10 kJ)/mol was calculated for catalase, and an activation energy of 4.0 kcal (ca. 17 kJ)/mol was calculated for peroxidase. Catalase activity was not inhibited by 3-amino-1,2,4-triazole but was inhibited by KCN and NaN3 (apparent Ki [KiApp] of 50 and 67.5 microM, respectively). Peroxidative activity was inhibited equally by KCN and NaN3 (KiApp for both, approximately 30 microM). The absorption spectrum showed a Soret peak at 404 nm, and there was no apparent reduction by dithionite. A heme content of 1.43 per tetramer was determined. The protein has a pI of 3.8 and an M(r) of 240,000 and consists of four subunits of 60,300 each.  相似文献   

17.
Free radicals are produced continuously by skeletal muscle fibers. Extracellular release of reactive oxygen species (ROS) and nitric oxide (NO) derivatives has been demonstrated, but little is known about intracellular oxidant regulation. We used a fluorescent oxidant probe, 2',7'-dichlorofluorescin (DCFH), to assess net oxidant activity in passive muscle fiber bundles isolated from mouse diaphragm and studied in vitro. We tested the following three hypotheses. 1) Net oxidant activity is decreased by muscle cooling. 2) CO(2) exposure depresses intracellular oxidant activity. 3) Muscle-derived ROS and NO both contribute to overall oxidant activity. Our results indicate that DCFH oxidation was diminished by cooling muscle fibers from 37 degrees C to 23 degrees C (P < 0.001). The rate of DCFH oxidation correlated positively with CO(2) exposure (0-10%; P < 0.05) and negatively with concurrent changes in pH (7.0-8.5; P < 0.05). Separate exposures to anti-ROS enzymes (superoxide dismutase, 1 kU/ml; catalase, 1 kU/ml), a glutathione peroxidase mimetic (ebselen, 30 microM), NO synthase inhibitors (N(omega)-nitro-l-arginine methyl ester, 1 mM; N(omega)-monomethyl-l-arginine, 1 mM), or an NO scavenger (hemoglobin, 1 microM) each inhibited DCFH oxidation (P < 0.05). Oxidation was increased by hydrogen peroxide, 100 microM, an NO donor (NOC-22, 400 microM), or the substrate for NO synthase (l-arginine, 5 mM). We conclude that net oxidant activity in resting muscle fibers is 1) decreased at subphysiological temperatures, 2) increased by CO(2) exposure, and 3) influenced by muscle-derived ROS and NO derivatives to similar degrees.  相似文献   

18.
Two fractions of peroxidase activity, cationic Px-cat and anionic Px-ani, were isolated and partially purified (143.5- and 5.49-fold, respectively) from homogenate of spring cabbage heads. Optimum pH for both fractions is 6.0; however, Px-cat is almost equally active at neutral pH (7.0) while Px-ani reveals high activity in more acidic pHs (with 60% of maximum activity at pH 3.0). Optimal temperature for both fractions was 40 degrees C. Px-ani possessed much higher thermal stability at 40-50 degrees C (60% of remaining activity after 144h of incubation) than Px-cat. The peroxidases remained fully active during 4 weeks of storage at 4 degrees C. Kinetic studies revealed that Px-cat and Px-ani had lower apparent Km values for ABTS (0.0377 and 0.0625mM) and o-dianisidine (0.357 and 0.286mM) than for guaiacol (6.41 and 13.89mM). The best substrate for Px-cat was pyrogallol and for Px-ani-o-dianisidine. Px-cat immobilized on polyanionic PyBA-modified carbon electrode was found to produce linear repetitive signals upon consecutive additions of hydrogen peroxide during at least 1-week period and to work effectively under buffered and non-buffered conditions. These properties were comparable with those of commercially available horseradish peroxidase. Stability of the hybrid bioelectrocatalytic film and low costs of extraction and partial purification of Px-cat make it a highly promising enzyme for practical applications, including construction of bioelectrodes.  相似文献   

19.
20.
Salinity influences the agricultural production all over the world. This constrain, similar to others biotic and abiotic stresses generate the reactive oxygen species such as superoxide, hydrogen peroxide and hydroxyl radicals. In the evolution process of halophyte plants the mechanisms to detoxify ROS, such as antioxidant enzymes, have been developed. Aeluropus littoralis is a special halophyte that selected to our research, so the plants treated with NaCl at different salt concentration (0, 250, 450 and 650 mM) for a period 45 days. Leaves and roots (separately) collected and their proteins extracted for superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and peroxidase (POD) activity assay. Meanwhile the electrolyte leakage of leaves analyzed and increased at 450 and 650 mM of NaCl concentrations. Superoxide dismutase and catalase showed same pattern for changing in enzymatic activities (increasing activity by salt stress in roots and decreasing in shoot at 450 and 650 mM stress), also peroxidase and ascorbate peroxidase activity almost increased in all stress conditions.  相似文献   

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