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

The reaction of p-hydroxyanisole with oxyhemoglobin was investigated using electron spin resonance spectroscopy (ESR) and visible spectroscopy. As a reactive reaction intermediate we found the p-methoxyphenoxyl radical, the one-electron oxidation product of p-hydroxyanisole. Detection of this species required the rapid flow device elucidating the instability of this radical intermediate. The second reaction product formed is methemoglobin. Catalase or SOD had no effect upon the reaction kinetics. Accordingly, reactive oxygen species such as hydroxyl radicals or superoxide could not be observed although the spin trapping agent DMPO was used to make these short-lived species detectable. When the sulfhydryl blocking agents N-ethylmaleimide or mersalyl acid were used, an increase of the methemoglobin formation rate and of the phenoxyl radical concentration were observed. We have interpreted this observation in terms of a side reaction of free radical intermediates with thiol groups.
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PMID:Formation of methemoglobin and phenoxyl radicals from p-hydroxyanisole and oxyhemoglobin. 164 74

The process of oxyhemoglobin oxidation initiated by hydrogen peroxide in low (10(-7) M) concentrations was investigated. It was found, that H2O2 in this concentration is able to induce the process of chain oxidation of oxyhemoglobin to methemoglobin. The following observations indicate that the process is essentially the chain reaction: 1) The amount of the methemoglobin in haem groups, produced in the reaction, exceed by 20 times the quantity of hydrogen, added initially, to induce the oxidation. 2) Catalase stopped this process at any stage of the reaction. This fact implies that the chain process involves generation of new molecules of H2O2 in the course of oxidation of oxyhemoglobin. The chain reaction proceeded only in the presence of oxygen. But if oxygen was introduced into hemoglobin solution, preincubated with H2O2 in vacuum, than again the oxidation of hemoglobin developed. Apparently, H2O2 in low concentrations appears, mainly, as an inductor of the oxyhemoglobin autooxidation.
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PMID:[Mechanism of oxyhemoglobin oxidation induced by hydrogen peroxide]. 179 52

The oxidative reactivities of four tryptophan metabolites in the kynurenine pathway were examined as a potential mechanism for their reported neurotoxicities and carcinogenicities. Neither quinolinic acid, a neurotoxin, nor its monocarboxylic analogue, picolinic acid, auto-oxidized over a wide pH range. However, 3-hydroxyanthranilic acid (3-HAT), a carcinogen, readily auto-oxidized and the reaction rate increased exponentially with increasing pH. 3-HAT auto-oxidation likely involves two steps: auto-oxidation of 3-HAT to the semiquinoneimine (anthranilyl radical) which oxidizes to the quinoneimine, followed by condensation and oxidation reactions to yield a second carcinogen, cinnabarinic acid. 3-HAT auto-oxidation to cinnabarinate required molecular oxygen and generated superoxide radicals and H2O2. Superoxide dismutase (SOD) accelerated 3-HAT auto-oxidation 4-fold, probably by preventing back reactions between superoxide and either the anthranilyl radical or the quinoneimine formed during the initial step of auto-oxidation. Catalase did not accelerate 3-HAT auto-oxidation, but it did prevent destruction of cinnabarinate by H2O2. Interconversion between oxyhemoglobin and methemoglobin occurred during 3-HAT auto-oxidation, although neither form of hemoglobin altered rates of 3-HAT auto-oxidation. Mn2+, Mn3+ and Fe3+-EDTA did not directly catalyze cinnabarinate formation in the absence of O2, but they did accelerate cinnabarinate formation under aerobic conditions.
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PMID:Oxidative reactivity of the tryptophan metabolites 3-hydroxyanthranilate, cinnabarinate, quinolinate and picolinate. 294 52

The mechanism of activation of soluble guanylate cyclase purified from bovine lung by phenylhydrazine is reported. Heme-deficient and heme-containing forms of guanylate cyclase were studied. Heme-deficient enzyme was activated 10-fold by NO but was not activated by phenylhydrazine. Catalase or methemoglobin enabled phenylhydrazine to activate guanylate cyclase 10-fold and enhanced activation by NO to over 100-fold. Heme-containing enzyme was activated only 3-fold by phenylhydrazine but over 100-fold by NO. Added hemoproteins enhanced enzyme activation by phenylhydrazine to 12-fold without enhancing activation by NO. Reducing or anaerobic conditions inhibited, whereas oxidants enhanced enzyme activation by phenylhydrazine plus catalase, and KCN had no effect. In contrast, enzyme activation by NO and NaN3 was inhibited by oxidants or KCN. NaN3 required native catalase, whereas phenylhydrazine also utilized heat-denatured catalase for enzyme activation. Thus, the mechanism of guanylate cyclase activation by phenylhydrazine differed from that by NO or NaN3. Guanylate cyclase activation by phenylhydrazine resulted from an O2-dependent reaction between phenylhydrazine and hemoproteins to generate stable iron-phenyl hemoprotein complexes. These complexes activated guanylate cyclase in the absence of O2, but lost activity after acidification, basification, or heating. Gel filtration of prereacted mixtures of [U-14C]phenylhydrazine plus hemoproteins resulted in co-chromatography of radioactivity, protein, and guanylate cyclase stimulating activity, and yielded a phenyl-hemoprotein binding stoichiometry of four under specified conditions (one phenyl/heme). [14C]Phenyl bound to heme-containing but not heme-deficient guanylate cyclase and binding correlated with enzyme activation. Moreover, reactions between enzyme and iron-[14C] phenyl hemoprotein complexes resulted in the exchange or transfer of iron-phenyl heme to guanylate cyclase and this correlated with enzyme activation.
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PMID:Guanylate cyclase from bovine lung. Evidence that enzyme activation by phenylhydrazine is mediated by iron-phenyl hemoprotein complexes. 614 58

Oxidation of oxyhemoglobin by nitrite is characterized by the presence of a lag phase followed by the autocatalysis. In phosphate buffer, an asymmetric ESR signal is detected at g = 2.005 (hereafter referred to as the g = 2 radical) during the oxidation which is similar to that of the methemoglobin free radical generated from methemoglobin and H2O2. Catalase and KCN prolong the oxidation, indicating the involvement of H2O2 and methemoglobin in the reaction. Superoxide dismutase, on the other hand, does not modify the oxidation. The present results suggest a chain reaction mechanism for the oxidation in which the g = 2 radical catalyzes the formation of NO.2 from NO-2 by a peroxidase action and NO.2 oxidizes oxyhemoglobin. However, in N,M-bis(2-hydroxyethyl)iminotris(hydroxymethyl)methane (bistris) buffer, superoxide dismutase markedly elongates the lag phase and accelerates the autocatalysis: bistris scavenges the g = 2 radical and a radical derived from bistris reduces O2 to O-2.
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PMID:Mechanism of autocatalytic oxidation of oxyhemoglobin by nitrite. 632 65

Catalase promotes the H2O2-dependent oxidation of phenylhydrazine to benzene but simultaneously is subject to a pseudo-first order inactivation process. Each inactivation event is subtended by catalytic turnover of three molecules of phenylhydrazine and 52 molecules of H2O2. The dimethyl ester of N-phenylprotoporphyrin IX is extracted with acidic methanol from the inactivated enzyme, but the prosthetic heme with a phenyl sigma-bonded to the iron atom is obtained by gentle extraction with 2-butanone. The absolute chirality of N-ethylprotoporphyrin IX isolated from catalase inactivated with ethylhydrazine confirms that the prosthetic heme has the same chiral orientation in the active site as it does in hemoglobin. The known inactivation of methemoglobin by phenylhydrazine is shown to depend on H2O2 but not oxygen. The results demonstrate that the H2O2-dependent oxidation of phenylhydrazine by catalase and other hemoproteins results in sigma-coordination of a phenyl residue to the prosthetic heme iron. This process may play a role not only in phenylhydrazine-mediated erythrocyte lysis but also in the activation of guanylate cyclase.
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PMID:Inactivation of catalase by phenylhydrazine. Formation of a stable aryl-iron heme complex. 688 92

21-aminosteroids ("lazaroids") have recently excited much interest by virtue of their ability to inhibit lipid peroxidation in vitro and to protect against neural injury in vivo. We tested the effect of these compounds in models of heme protein-mediated renal injury in vitro and in vivo. We devised an in vitro model of heme protein-induced toxicity in which renal epithelial cells were exposed to heme proteins for one hour, after which they were subjected to glutathione depletion by 1-chloro-2,4-dinitrobenzene (CDNB). This model was associated with more than a threefold increase in lipid peroxidation (as measured by thiobarbituric acid reactive substances, TBARS) and a marked reduction in cellular glutathione content. In this model, 21-aminosteroids virtually prevented cytotoxicity as measured by the 51-chromium release assay, and significantly reduced TBARS in a dose-dependent manner. Catalase was partially protective in this model, thereby indicating hydrogen peroxide-dependent toxicity. While pursuing mechanisms accounting for enhanced cellular generation of hydrogen peroxide, we uncovered the first direct evidence that the heme prosthetic group per se directly stimulates cellular generation of hydrogen peroxide; complementing these findings is the remarkable efficacy of 21-aminosteroids in protecting against cytotoxicity induced by hydrogen peroxide. We also tested the capacity of 21-aminosteroids to protect against heme protein-mediated renal injury in vivo. Prior administration of 21-aminosteroids attenuated reductions in GFR and renal blood flow rates following the systemic infusion of methemoglobin in normal rats. 21-aminosteroids also attenuated renal injury observed over three successive days in the glycerol model of heme protein-mediated injury when this model was induced at a higher dose of glycerol (8 ml/kg body wt) but not at a lower dose (5 ml/kg body wt). We conclude that 21-aminosteroids protect against heme protein-mediated renal injury in vitro and in vivo. We suggest that these compounds are potentially useful in such clinical conditions as rhabdomyolysis, intravascular hemolysis and renal injury associated with hemoglobin-based red blood cell substitutes.
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PMID:Heme protein-mediated renal injury: a protective role for 21-aminosteroids in vitro and in vivo. 772 46

Bed rest is an integral part of treatment of numerous diseases. Typical examples are bone fractures of lower extremities and pelvis. Temporary immobilization is necessary also, e.g., in heart diseases (stroke), backbone and imminent abortion. The sick organism spares energy during the bed rest wich is beneficial. However, bed rest results in many alterations which are disadavantageous. They concern the function of almost all organs and systems but affect most significantly the locomotor and ciruclatory systems. Bed rest brings also about changes in the composition of peripheral blood and functions of the morphotic elements of blood. Red blood cells are subjected to the action of large amounts of reactive oxygen species (ROS). During oxidation of hemoglobin to methemoglobin superoxide radical anion (O2-) is formed: HbFe2+ + O2 --> MetHbFe3+ + O2- (1) Ferrous and ferric ions present in the cytoplasm of red blood cells may be catalysts of the Fenton reaction leading to the production of the hydroxyl radical: O2- + Fe3+ --> O2- + Fe2+ (2) Fe2+ + H2O2 --> Fe3+ + OH + HO- (3) OH shows a tremendous reactivity. It may react with lipids, proteins, nucleic acids and carbohydrates. The process of lipid peroxidation is best understood. It concerns mainly polyunsaturated fatty acids present in cell membranes. Peroxidation of membrane lipids decreases membrane fluidity and impairs its barrier function. The lowered membrane fluidity compromises erythrocyte deormability which in turn disturbs oxygen delivery to the tissues. End productions of lipid peroxidation are low-molecular wieght compounds, among them carbohydrates (ethane and pentane) and aldehydes, e.g. malondialdehyde (MDA). MDA concentration is an acknowldeged marker of the intensity of lipid peroxidation. Erythrocytes contain a complex system of protection against the action of ROS. It includes various enzymatic and non-enzymatic mechanism. The most important antioxidative enzymes of the red blood cells are superoxide dismutase (Cu,Zn-SOD, EC 1.15.1.1) catalase (CAT, EC 1.11.1.6) and glutathione peroxidase (GSH-Px, EC 1.11.1.9). Cu,Zn-SOD catalyzes the dismuation of O2- to hydrogen peroxide (H2O2). Catalase and peroxidase remove H2O2 and, moreover, GSH-Px can reduce lipid peroxides. Under normal conditions an equilibrium exists between the formation and removal ROS. If ROS are formed in excess or the defensive antioxidative mechanism are inefficient, oxidative stress develops. Derangement of the equilibrium between the formation and removal of ROS is important in the pathosgenesis of many diseases, e.g. atherosclerosis, diabetes, Down syndrome and Alzheimer disease. There are literature data on disturbances of enzymatic antioxidant defense mechanism of blood plateless during bed rest. This study was aimed at an examination of the post-traumatic bed rest on the enzymatic antioxidative defense mechanisms and lipid peroxidation in erythrocytes.
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PMID:Effect of long term bed rest in men on enzymatic antioxidative defence and lipid peroxidation in erythrocytes. 1154 39

A scheme of development of nitrite-induced oxyhemoglobin oxidation in erythrocytes based on the analysis of experimental data is proposed. It was found that, contrary to widespread opinion, direct oxidative-reductive interaction between hemoglobin and nitrite is absent or negligible under physiological conditions. The driving stage of this process is methemoglobin-catalyzed peroxidase oxidation of nitrite. The product of the oxidation (presumably NO2*) directly oxidizes oxyhemoglobin to methemoglobin-peroxide complex without hydrogen peroxide release into the environment. The oxidant itself is reduced to nitrite or oxidized to nitrate as a result of interaction with another NO2* molecule. Thus, the stoichiometry of the process depends on the ratio of rates of these two reactions. Substances that are able to compete with nitrite for peroxidase and therefore to prevent the nitrite oxidation effectively protect hemoglobin from oxidation. Catalase is not able to destroy methemoglobin-peroxide complexes, but it can prevent their production in the course of interaction of methemoglobin and free peroxide by destroying the latter.
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PMID:Proposed mechanism of nitrite-induced methemoglobinemia. 1589 15

The effect of in vitro exposure of human erythrocytes to micromolar concentrations of hydroquinone and copper simultaneously on oxidative status-related biochemical parameters was studied. Hydroquinone is a component of cigarette smoke and serum copper level is increased in smokers. Copper forms a complex with hydroquinone and enhances its auto-oxidation to benzoquinone which covalently binds to sulfhydryl group containing compounds like reduced glutathione. In this study, copper increased H(2)O(2) production by hydroquinone. Hydroquinone either alone or in the presence of copper produced a decrease of reduced glutathione level without altering methemoglobin concentration and erythrocyte lipid peroxidation. Catalase inhibition by sodium azide depleted reduced glutathione level further. Copper-hydroquinone complex mediated glutathione depletion in the catalase containing RBC was not decreased by antioxidant, butylated hydroxytoluene. From the known facts and above findings, it is suggested that depletion of reduced glutathione by hydroquinone in the presence of copper in catalase active RBC may be due to the formation of 1, 4 benzoquinone adduct of reduced glutathione and to some extent due to binding of copper to the thiol group of reduced glutathione rather than conversion to oxidized glutathione via reactive oxygen species. Depletion of reduced glutathione by N-ethylmaleimide pretreatment followed by copper-hydroquinone treatment had no effect on methemoglobin level or lipid peroxidation. Furthermore, copper-hydroquinone complex did not increase erythrocyte susceptibility to oxidative stress. This suggests hydroquinone in the presence of copper does not contribute to erythrocyte membrane lipid peroxidation seen in smokers. Criteria for ideal antioxidant supplementation in smokers were suggested.
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PMID:Effect of copper-hydroquinone complex on oxidative stress-related parameters in human erythrocytes (in vitro). 1977 51


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