Coimobilization of superoxide dismutase, catalase and peroxidase

For preparationing the polyenzyme antioxidant complex, containing superoxide dismutase (SOD), catalase and horseradish peroxidase (HRP), the different successivities of those enzymes co-immobilization were compared. The optimum successivity is provided by simultaneous co-immobilization of covalently bound HRP with the SOD and catalase. The catalytic enzyme activity and the catalase operational stability was kinetically characterized in various samples. For one sample, the influence of ascorbate, glutathione and ethanol on the catalase kinetic parameters was studied. A possible scheme of different processes at the H2O2 decomposition in the presence of co-immobilized SOD, catalase, HRP and the substrates-reductans was discussed.     

Ferric Ion and Oxygen Reduction at the Surface of Protoplasts and Cells of Acer pseudoplatanus

This work was undertaken to verify whether surface NADH oxidases or peroxidases are involved in the apoplastic reduction of Fe(III). The reduction of Fe(III)-ADP, linked to NADH-dependent activity of horseradish peroxidase (HRP), protoplasts and cells of Acer pseudoplatanus, was measured as Fe(II)-bathophenanthrolinedisulfonate (BPDS) chelate formation. In the presence of BPDS in the incubation medium (method 1), NADH-dependent HRP activity was associated with a rapid Fe(III)-ADP reduction that was almost completely inhibited by superoxide dismutase (SOD), while catalase only slowed down the rate of reduction. A. pseudoplatanus protoplasts and cells reduced extracellular Fe(III)-ADP in the absence of exogenously supplied NADH. The addition of NADH stimulated the reduction. SOD and catalase only inhibited the NADH-dependent Fe(III)-ADP reduction. Mn(II), known for its ability to scavenge O^?₂, inhibited both the independent and NADH-dependent Fe(III)-ADP reduction. The reductase activity of protoplasts and cells was also monitored in the absence of BPDS (method 2). The latter was added only at the end of the reaction to evaluate Fe(II) formed. Also, in this case, both preparations reduced Fe(III)-ADP. However, the addition of NADH did not stimulate Fe(III)-ADP reduction but, instead, lowered it. This may be related to a re-oxidation of Fe(II) by H₂O₂ that could also be produced during NADH-dependent peroxidase activity. Catalase and SOD made the Fe(III)-ADP reduction more efficient because, by removing H₂O₂ (catalase) or preventing H₂O₂ formation (SOD), they hindered the re-oxidation of Fe(II) not chelated by BPDS. As with the result obtained by method 1, Mn(II) inhibited Fe(III)-ADP reduction carried out in the presence or absence of NADH. The different effects of SOD and Mn(II), both scavengers of O^?₂, may depend on the ability of Mn(II) to permeate the cells more easily than SOD. These results show that A. pseudoplatanus protoplasts and cells reduce extracellular Fe(III)-ADP. Exogenously supplied NADH induces an additional reduction of Fe(III) by the activity of NADH peroxidases of the plasmalemma or cell wall. However, the latter can also trigger the formation of H₂O₂ that, reacting with Fe(II) (not chelated by BPDS), generates hydroxyl radicals and converts Fe(II) to Fe(III) (Fenton's reaction).     

Continuous conversion of sucrose to fructose and gluconic acid by immobilized yeast cell multienzyme complex

A multienzyme complex consisting of invertase, glucose oxidase, and catalase was reconstituted by binding glucose oxidase using concanavalin A (Con A) to the cell wall of Sacchararomyces cerevisiae, previously induced for maximal activities of invertase and catalase. The cell flocculate obtained was stabilized by entrapment in polyacrylamide using γ irradiation at 100 kR. This complex showed a shortening of the lag period and enhancement in gluconic acid production as compared to a similar mixture of soluble enzymes. The efficacy of the multienzyme complex has been compared with that of mixed multienzyme system composed of individually immobilized enzymes. The immobilized multienzyme complex in a continuous-flow stirred-tank reactor system could be operated for continuous conversion of sucrose to fructose and gluconic acid. The reactor system did not show any loss in efficiency in a continuous operation over 20 days.     

Competing two enzymatic reactions realizing one‐step preparation of cell‐enclosing duplex microcapsules

The usefulness of cell‐enclosing microcapsules in biomedical and biopharmaceutical fields is widely recognized. In this study, we developed a method enabling the preparation of microcapsules with a liquid core in one step using two enzymatic reactions, both of which consume H₂O₂ competitively. The microcapsule membrane prepared in this study is composed of the hydrogel obtained from an alginate derivative possessing phenolic hydroxyl moieties (Alg‐Ph). The cell‐enclosing microcapsules with a hollow core were obtained by extruding an aqueous solution of Alg‐Ph containing horseradish peroxidase (HRP), catalase, and cells into a co‐flowing stream of liquid paraffin containing H₂O₂. Formation of the microcapsule membrane progressed from the surface of the droplets through HRP‐catalyzed cross‐linking of Ph moieties by consuming H₂O₂ supplied from the ambient liquid paraffin. A hollow core structure was induced by catalase‐catalyzed decomposition of H₂O₂ resulting in the center region being at an insufficient level of H₂O₂. The viability of HeLa cells was 93.1% immediately after encapsulation in the microcapsules with about 250 µm diameter obtained from an aqueous solution of 2.5% (w/v) Alg‐Ph, 100 units mL^?1 HRP, 9.1 × 10⁴ units mL^?1 catalase. The enclosed cells grew much faster than those in the microparticles with a solid core. In addition, the thickness of microcapsule membrane could be controlled by changing the concentrations of HRP and catalase in the range of 13–48 µm. The proposed method could be versatile for preparing the microcapsules from the other polymer derivatives of carboxymetylcellulose and gelatin. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29:1528–1534, 2013     

Novel palladium(II) and Zinc(II) Schiff base complexes: Synthesis,biophysical studies,and anticancer activity investigation

BackgroundSchiff base metal complexes are considered promising chemotherapeutic agents due to their potential application in cancer therapy.MethodsThe current work sought to synthesize a brand-new Schiff base ligand obtained from 2-hydroxybenzohydrazide and (E)− 1-(2-(p-tolyl)hydrazono)propan-2-one with metal ions which included Pd(II) and Zn(II) ions. Elemental analyses, FT-IR, mass spectra, 1H NMR, UV-Vis spectrometer, and computational analysis characterized the compound's structure. In vitro, the breast cancer cell line (MCF-7) was tested for its sensitivity to Schiff base (HL) and its Pd(II) and Zn(II) complexes. The half-maximal inhibitory concentration IC₅₀ of the compounds was determined and used to perform the comet assay, which was carried out to reveal the photo-induced DNA damaging ability of the compounds of individual cells. Moreover, the compounds' effects on antioxidant defense systems of enzymes in cells: superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activities and oxidant Malondialdehyde (MDA) were examined in MCF-7 cells.ResultsThe Pd(II) complex displayed approximately the same IC₅₀ as Cisplatin, while Zn(II) complex had better activity than Cisplatin with very low IC₅₀, 1.40 μg/ml. Significant alterations in SOD, CAT, GPx, and MDA production were discovered, inducing oxidative stress, enlarging ROS production, and reducing the antioxidant amount. This change was approximately similar in most compounds. Consequently, it promoted apoptosis, particularly the Zn(II) complex, which demonstrated an improved impact because of its ability to influence the antioxidant defense systems of enzymes, mostly SOD and GPx, besides increasing MDA levels.ConclusionIt can be concluded that Zn(II) complex is the most effective anticancer drug since it induced a very similar genotoxic effect as Cisplatin and has a very low IC₅₀ value.     

A discrepancy in superoxide scavenging activity between the ESR-spin trapping method and the luminol chemiluminescence method

In a previous study of ours, the superoxide scavenging activity of aqueous extracts from dinophycean red tide flagellates was detected by an electron spin resonance (ESR)-spin trapping method, but not by an L-012 (luminol analog)-dependent chemiluminescence (CL) method. To investigate the discrepancy between the two methods, the effect of ferric-protein complexes on superoxide scavenging activity was examined. The reduced signal intensity of 5,5-dimethyl-1-pyrroline-N-oxide (DMPO)-OOH due to superoxide dismutase (SOD) did not change with the addition of horseradish peroxidase (HRP), while the reduced CL response due to SOD was restored by the addition of different concentrations of HRP. Since HRP is a ferric-protein complex, the effects of other ferric-protein complexes, catalase and hemoglobin, on the reduced CL response due to SOD were examined, and similar results were obtained. As is the case with SOD, the reduced CL response activity due to an aqueous extract from a raphidophycean red tide flagellate, Chattonella ovata, was also enhanced by HRP, catalase, and hemoglobin. ESR spectra analyzed at 77 K indicated that aqueous extracts of Gymnodinium impudicum and Alexandrium affine, both of which are dinophycean red tide flagellates, contained a ferric-protein complex, and that an extract of C. ovata did not. These results suggest that the presence of such a ferric-protein complex is a causative factor in the discrepancy between the ESR and luminol CL methods when determining superoxide scavenging activity.     

Response of antioxidant enzymes to high NaCl concentration in different salt-tolerant plants

The effects of NaCl on the H₂O₂ content and the activities of catalase (CAT) and superoxide dismutase (SOD) were studied in diverse group of plants, such as a unicellular alga, Chlorella sp., an aquatic macrophyte, Najas graminea, and a mangrove plant, Suaeda maritima, all showing high tolerance to NaCl. Significant accumulation of H₂O₂ was observed in all the tested plants upon their exposure to 255 mM NaCl. The activity of both CAT and SOD increased significantly in response to the NaCl treatment. Growing the plants in presence of 255 mM NaCl also resulted in the synthesis of new isoforms of both CAT and SOD.     

Comparative biochemistry of oxygen toxicity in lactic acid-forming aquatic fungi

Taxonomically diverse aquatic fungi ranging in oxidative capabilities from obligate aerobes to aerotolerant anaerobes were examined for growth under hyperbaric (0.9 atm) O₂, and for the ability to degrade H₂O₂ and O ₂ ^- . The results support the presumption that several Oomycetes and Chytridiomycetes are biochemically adapted to environments low in O₂. Results further indicate significant differences between Oomycetes and Chytridiomycetes in the enzymatic means of dealing with O ₂ ^- and H₂O₂, supporting the recent concept of a great evolutionary divergence between the groups. In general, facultative anaerobes and aerotolerant anaerobes were more severely inhibited by hyperbaric O₂, and they exhibited lower superoxide dismutase (SOD), catalase and peroxidase activities than did strongly-oxidative species. SOD activity, which was detected in all isolates, was insensitive to cyanide in Oomycetes but cyanide sensitive in the Blastocladiales (Chytridiomycetes). All strongly-oxidative Oomycetes exhibited readily-detectable catalase and peroxidase activities, while activities were very low or absent in strongly-fermentative species. As with the Oomycetes, peroxidase activities among the Blastocladiales were high in aerobes and low in strong fermenters. Surprisingly, however, none of the Blastocladiales, including strongly-oxidative species, exhibited substantial catalase activity. Catalase and SOD activities in faculatively anaerobic Oomycetes increased with increasing O₂ concentration; but even in hyperbaric (0.5 atm) O₂, activities for both enzymes in the aerotolerant anaerobe Aqualinderella fermentans were very low compared with activities in aerobes.Abbreviation SOD Superoxide dismutase     

Kidney glomerular explants in serum-free media: Demonstration of intracellular antioxidant enzymes and active oxygen metabolites

Summary Guinea pig glomeruli were grown for 22 d in a serum-free medium composed of Waymouth's MB 752/1 supplemented with sodium pyruvate, nonessential amino acids, and antibiotics (the basic medium). Intracellular cellular activity of the antioxidant enzymes superoxide dismutase (SOD; both copper-zinc [Cu,Zn] and manganese [Mn] forms) and catalase, and intracellular active oxygen metabolites (hydrogen peroxide [H₂O₂] and superoxide [O_{2 −} ^· ]) were measured with time in culture. The results were compared to results obtained from glomeruli grown in different serum-free media, including the basic medium plus fibronectin (FN), the basic medium plus transferrin and FN, and a complex medium containing insulin, transferrin, selenium (Se), triiodothyronine, and FN (complete medium). In general, although the intracellular activity of antioxidant enzymes and active oxygen metabolites varied over time in culture in all media, there were only a few statistically significant differences among different media. Both CuZn SOD and Mn SOD activity were demonstrated, in isolated glomeruli. The CuZn SOD activity per DNA ratio decreased slightly with time in culture in all media tested except the complete medium, in which CuZn SOD activity per DNA ratio remained more constant. The Mn SOD activity per DNA ratio did not vary significantly over time in culture. Catalaselike activity was very low in isolated glomeruli and declined sharply with time in culture in all media except the complete medium. Both H₂O₂ and O_{2 −} ^· were detected intracellularly in glomerular culture. Our results indicate that intracellular antioxidant enzymes and active oxygen metabolites in glomeruli vary with time in culture and, in some instances, with culture conditions. Supported by grants to Dr. Terry Oberley from the University of Wisconsin Graduate School and by the Veterans Administration. Mr. Steinert was a predoctoral fellow supported by National Institutes of Health training grant 5-T32 ES0715.     

Possible accumulation of non-active molecules of catalase and superoxide dismutase in S. cerevisiae cells under hydrogen peroxide induced stress

The effect of hydrogen peroxide on the activities of catalase and superoxide dismutase (SOD) in S. cerevisiae has been studied under different experimental conditions: various H₂O₂ concentrations, time exposures, yeast cell densities and media for stress induction. The yeast treatment with 0.25–0.50 mM H₂O₂ led to an increase in catalase activity by 2–3-fold. At the same time, hydrogen peroxide caused an elevation by 1.6-fold or no increase in SOD activity dependently on conditions used. This effect was cancelled by cycloheximide, an inhibitor of protein synthesis in eukaryotes. Weak elevation of catalase and SOD activities in cells treated with 0.25–0.50 mM H₂O₂ found in this study does not correspond to high level of synthesis of the respective enzyme molecules observed earlier by others. It is well known that exposure of microorganisms to low sublethal concentrations of hydrogen peroxide leads to the acquisition of cellular resistance to a subsequent lethal oxidative stress. Hence, it makes possible to suggest that S. cerevisiae cells treated with low sublethal doses of hydrogen peroxide accumulate non-active stress-protectant molecules of catalase and SOD to survive further lethal oxidant concentrations.     

Effect of hydrogen peroxide on antioxidant enzyme activities in Saccharomyces cerevisiae is strain-specific

The effect of hydrogen peroxide on the survival and activity of antioxidant and associated enzymes in Saccharomyces cerevisiae has been studied. A difference found in the response of wild-type yeast strains treated with hydrogen peroxide was probably related to the different protective effects of antioxidant enzymes in these strains. Exposure of wild-type YPH250 cells to 0.25 mM H₂O₂ for 30 min increased activities of catalase and superoxide dismutase (SOD) by 3.4-and 2-fold, respectively. However, no activation of catalase in the EG103 strain, as well as of SOD in the YPH98 and EG103 wild strains was detected, which was in parallel to lower survival of these strains under oxidative stress. There is a strong positive correlation (R ² = 0.95) between activities of catalase and SOD in YPH250 cells treated with different concentrations of hydrogen peroxide. It is conceivable that catalase would protect SOD against inactivation caused by oxidative stress and vice versa. Finally, yeast cell treatment with hydrogen peroxide can lead to either a H₂O₂-induced increase in activities of antioxidant and associated enzymes or their decrease depending on the H₂O₂ concentration used or the yeast strain specificity. Published in Russion in Biokhimiya, 2006, Vol. 71, No. 9, pp. 1243–1252.     

Electrically Contacted Bienzyme‐Functionalized Mesoporous Carbon Nanoparticle Electrodes: Applications for the Development of Dual Amperometric Biosensors and Multifuel‐Driven Biofuel Cells

The capping of electron relay units in mesoporous carbon nanoparticles (MPC NPs) by crosslinking of different enzymes on MPC NPs matrices leads to integrated electrically contacted bienzyme electrodes acting as dual biosensors or as functional bienzyme anodes and cathodes for biofuel cells. The capping of ferrocene methanol and methylene blue in MPC NPs by the crosslinking of glucose oxidase (GOx) and horseradish peroxidase (HRP) yields a functional sensing electrode for both glucose and H₂O₂, which also acts as a bienzyme cascaded system for the indirect detection of glucose. A MPC NP matrix, loaded with ferrocene methanol and capped by GOx/lactate oxidase (LOx), is implemented for the oxidation and detection of both glucose and lactate. Similarly, MPC NPs, loaded with 2,2′‐azino‐bis(3‐ethylbenzo­thiazoline‐6‐sulphonic acid), are capped with bilirubin oxidase (BOD) and catalase (Cat), to yield a bienzyme O₂ reduction cathode. A biofuel cell that uses the bienzyme GOx/LOx anode and the BOD/Cat cathode, glucose and/or lactate as fuels, and O₂ and/or H₂O₂ as oxidizers is assembled, revealing a power efficiency of ≈90 μW cm^?2 in the presence of the two fuels. The study demonstrates that multienzyme MPC NP electrodes may improve the performance of biofuel cells by oxidizing mixtures of fuels in biomass.     

Peroxisomal participation in the cellular response to the oxidative stress of endotoxin

Exposure to a sublethal dose of endotoxin offers protection against subsequent oxidative stresses. The cellular mechanisms involved in generating this effect are not well understood. We evaluated the effect of endotoxin on antioxidant enzymes in liver peroxisomes. Peroxisomes have recently been shown to contain superoxide dismutase (SOD) and glutathione peroxidase (GPX) in addition to catalase. Peroxisomes were isolated from liver homogenates by differential and density gradient centrifugations. Endotoxin treatment increased the specific activity of SOD and GPX in peroxisomes to 208% and 175% of control activity, respectively. These findings correlated with increases in peroxisomal SOD and GPX proteins observed by immunoblot. Although the quantity of catalase protein was increased when assessed by immunoblot analysis, the specific activity of catalase was decreased to 68% of control activity. Activation of catalase with ethanol only restored catalase activity to control levels suggesting that catalase had undergone irreversible inactivation. The observed increase in GPX activity may represent a compensatory mechanism triggered by accumulating H₂O₂. The data presented here suggest for the first time that mammalian peroxisomal antioxidant enzymes are altered during the oxidative injury of endotoxin treatment.     

Antioxidant defenses and oxidative stress parameters in tissues of mud crab (Scylla serrata) with reference to changing salinity

The effects of salinity (10, 17 and 35 ppt) on O₂ consumption, CO₂ release and NH₃ excretion by crabs and oxidative stress parameters and antioxidant defenses of its tissues were reported. An increase in salinity caused a decrease in O₂ consumption and CO₂ release and an increase in ammonia excretion by crabs. Lipid peroxidation, protein carbonyl, H₂O₂ levels and total antioxidant capacity of the tissues elevated significantly at 35 ppt salinity except in abdominal muscle where H₂O₂ content was low. Ascorbic acid content of tissues was higher at 17 ppt salinity than at 10 and 35 ppt salinities. With increasing salinity, a gradual decrease in SOD, an increase in catalase, no change in GPx and a decrease followed by an increase in GR activities were recorded for abdominal muscle. While for hepatopancreas, an increase followed by a decrease in SOD and catalase, decrease in GPx and GR activities were noticed with increasing salinity. In the case of gills, a decrease followed by an increase in SOD, a decrease in catalase and GPx and an increase in GR activities were noted when the salinity increased from 10 ppt to 35 ppt. These results suggest that salinity modulation of oxidative stress and antioxidant defenses in Scylla serrata is tissue specific.     

Catalase catalyzes nitrotyrosine formation from sodium azide and hydrogen peroxide

Sodium azide (NaN₃) is known as an inhibitor of catalase, and a nitric oxide (NO) donor in the presence of catalase and H₂O₂. We showed here that catalase-catalyzed oxidation of NaN₃ can generate reactive nitrogen species which contribute to tyrosine nitration in the presence of H₂O₂. The formation of free-tyrosine nitration and protein-bound tyrosine nitration by the NaN₃/catalase/H₂O₂ system showed a maximum level at pH 6.0. Free-tyrosine nitration induced by peroxynitrite was inhibited by ethanol and dimethyl-sulfoxide (DMSO), and augmented by superoxide dismutase (SOD). However, free-tyrosine nitration induced by the NaN₃/catalase/H₂O₂ system was not affected by ethanol, DMSO and SOD. NO^-₂ and NO donating agents did not affect free-tyrosine nitration by the NaN₃/catalase/H₂O₂ system. The reaction of NaN₃ with hydroxyl radical generating system showed free-tyrosine nitration, but no formation of nitrite and nitrate. The generation of nitrite (NO^-₂) and nitrate (NO^-₃) by the NaN₃/catalase/H₂O₂ system was maximal at pH 5.0. These results suggested that the oxidation of NaN₃ by the catalase/H₂O₂ system generates unknown peroxynitrite-like reactive nitrogen intermediates, which contribute to tyrosine nitration.     

Flooding-induced membrane damage, lipid oxidation and activated oxygen generation in corn leaves

Flooding effects on membrane permeability, lipid peroxidation and activated oxygen metabolism in corn (Zea mays L.) leaves were investigated to determine if activated oxygens are involved in corn flooding-injury. Potted corn plants were flooded at the 4-leaf stage in a controlled environment. A 7-day flooding treatment resulted in a significant increase in chlorophyll breakdown, lipid peroxidation (malondialdehye content), membrane permeability, and the production of superoxide (O ₂ ^- ) and hydrogen peroxide (H₂O₂) in corn leaves. The effects were much greater in older leaves than in younger ones. Spraying leaves with 8-hydroxyquinoline (an O ₂ ^- scavenger) and sodium benzoate (an .OH scavenger) reduced the oxidative damage and enhanced superoxide dismutase (SOD) activity. A short duration flooding treatment elevated the activities of SOD, catalase, ascorbate peroxidase (AP), and glutathione reductase (GR), while further flooding significantly reduced the enzyme activities but enhanced the concentrations of ascorbic acid and reduced form glutathione (GSH). It was noted that the decline in SOD activity was greater than that in H₂O₂ scavengers (AP and GR). The results suggested that O ₂ ^- induced lipid peroxidation and membrane damage, and that excessive accumulation of O ₂ ^- is due to the reduced activity of SOD under flooding stress.     

Induction of H2O2 and related enzymes in tomato roots infected with root knot nematode (M. javanica) by several chemical and microbial elicitors

The effects of chemical and microbial elicitors such as β-aminobutyric acid (BABA), Salicylic acid (SA), and Pseudomonas fluorecens CHAO on hydrogen peroxide generation and activity of the enzymes related to its metabolism, i.e., superoxide dismutase (SOD), guaiacol peroxidase (GPOX), and catalase (CAT) were investigated in tomato roots infected with root-knot nematode (Meloidogyne javanica). Results of this study show that treating the tomato seedlings with the above elicitors significantly reduces the nematode infection level. Among the tested elicitors, BABA has reduced the nematode galls, number of egg masses per plant and number of eggs per individual egg mass more than the others. Additionally, the amount of H₂O₂, a product of oxidative stress, SOD and GPOX specific activities were significantly increased in the elicitor treated plants in comparison to control. Our observation shows that BABA also increases the H₂O₂ accumulation and the SOD and GPOX activities more as compared with the other tested elicitors. Such increases have occurred in two phases and maximum levels of them were observed at 5 days after treatment. In contrast with the increase in SOD and GPOX activities, the CAT activity doesnot show any significant increase in treated plants as compared with the control and other tested elicitors. It can be concluded that BABA, SA, and Pseudomonas fluorescens CHAO induce oxidative stress in tomato roots through generation of reactive oxygen species (ROS) and the enzymes related to their metabolism.     

Interaction between lanthanum ion and horseradish peroxidase in vitro

The interaction between lanthanum ion (La³⁺) and horseradish peroxidase (HRP) in vitro was investigated using a combination of biophysical and biochemical methods. When the molar ratio of La³⁺ and HRP is low, it was found that the interaction between La³⁺ and HRP mainly depends on the electrostatic attraction, van der waals force and hydrogen bond etc. Thus, the interaction is weak and the La–HRP complex cannot be formed in vitro. As expected, the interaction can change the conformation of HRP molecule, leading to the increase in the non-planarity of the porphyrin ring in the heme group of HRP molecule, and then in the exposure degree of the active center, Fe(III) of the porphyrin ring of HRP molecule. Therefore, the catalytic activity of HRP for the H₂O₂ reduction is improved. When the molar ratio of La³⁺ and HRP is high, La³⁺ can strongly coordinate with O and/or N in the amide group of the polypeptide chain of HRP molecule, forming the La–HRP complex. The formation of the La–HRP complex causes the change in the conformation of HRP molecule, leading to the decrease in the non-planarity of the porphyrin ring in the heme group of HRP molecule, and then in the exposure degree of the active center, Fe(III) of the porphyrin ring of HRP molecule. Thus, the catalytic activity of HRP for the H₂O₂ reduction is decreased comparing with that of HRP in the absence of La³⁺. The results can provide some references for understanding the interaction mechanism between trace elements ions and peroxidase in living organisms.     

Induction of heat tolerance in wheat coleoptiles by calcium ions and its relation to oxidative stress

Effects of Ca²⁺ ions on the intensity of lipid peroxidation, activities of guaiacol peroxidase, superoxide dismutase (SOD), and catalase, as well as on heat resistance of winter wheat (Triticum aestivium L.) coleoptiles were examined. A preliminary incubation of coleoptile segments in a 5 mM CaCl₂ solution was shown to improve their survival rates after an injuring heat treatment (43.5°C). The effect of Ca²⁺ was suppressed by the inhibitor of Ca²⁺ channels (1 mM LaCl₃). An incubation of coleoptiles in the presence of 5 mM CaCl₂ prior to the stress treatment elevated the content of lipid peroxidation product, malondialdehyde (MDA) and stimulated the activities of guaiacol peroxidase, SOD, and catalase. After the heat exposure of untreated and Ca²⁺-treated seedlings, differential changes in MDA content and in activities of guaiacol peroxidase, SOD, and catalase were observed. It is concluded that a short-term oxidative stress arising in Ca²⁺-enriched plant tissues after the heat treatment is unrelated to their irreversible damage.Translated from Fiziologiya Rastenii, Vol. 52, No. 2, 2005, pp. 227–232.Original Russian Text Copyright © 2005 by Kolupaev, Akinina, Mokrousov.This revised version was published online in April 2005 with a corrected cover date.