Showing papers on "Catalase published in 1975"
TL;DR: It would seem clear from these and other studies that the granulo cyte elaborates O2- as a concomitant of the respiratory burst that occurs with phagocytosis, and a requirement for .OH in thephagocytic bactericidal event might explain the apparent requirement for both O1- and H2O2 for such activity.
Abstract: The capacity of human phagocytes to generate superoxide anion (O2-), a free radical of oxygen, and a possible role for this radical or its derivatives in the killing of phagocytized bacteria were explored using leukocytes from normal individuals and patients with chronic granulomatous disease (CGD). Superoxide dismutase, which removes O2-, consistently inhibited phagocytosis-associated nitroblue tetrazolium (NBT) reduction indicating the involvement of O2- in this process. Similarly, superoxide dismutase inhibited the luminescence that occurs with phagocytosis, implicating O2- in this phenomenon, perhaps through its spontaneous dismutation into singlet oxygen. Subcellular fractions from homogenates of both normal and CGD leukocytes generated O2- effectively in the presence of NADH as substrate. However, O2- generation by intact cells during phagocytosis was markedly diminished in nine patients with CGD. Leukocytes from mothers determined to be carriers of X-linked recessive CGD by intermediate phagocytic reduction of NBT elaborated O2- to an intermediate extent, further demonstrating the interrelationship between NBT reduction and O2- generation in phagocytizing cells. Activity of superoxide dismutase, the enzyme responsible for protecting the cell from the damaging effects of O2-, was approximately equal in homogenates of normal and CGD granulocytes. Polyacrylamide electrophoresis separated this activity into a minor band that appeared to be the manganese-containing superoxide dismutase associated with mitochondria and a more concentrated, cyanide-sensitive, cytosol form of the enzyme with electrophoretic mobility that corresponded to that of erythrocyte cuprozinc superoxide dismutase. Superoxide dismutase inhibited the phagocytic killing of Escherichia coli, Staphylococcus aureus, and Streptococcus viridans. A similar inhibitory effect was noted with catalase which removes hydrogen peroxide. Neither enzyme inhibited the ingestion of bacteria. Peroxide and O2- are believed to interact to generate the potent oxidant, hydroxyl radical (.OH). A requirement for .OH in the phagocytic bactericidal event might explain the apparent requirement for both O2- and H2O2 for such activity. In agreement with this possibility, benzoate and mannitol, scavengers of .OH, inhibited phagocytic bactericidal activity. Generation of singlet oxygen from O2- and .OH also might explain these findings. It would seem clear from these and other studies that the granulo cyte elaborates O2- as a concomitant of the respiratory burst that occurs with phagocytosis. To what extent the energy inherent in O2- is translated into microbialdeath through O2- itself, hydrogen peroxide, .OH, singlet oxygen, or some other agent remains to be clearly defined.
705 citations
TL;DR: These findings, combined with oxygen consumption studies on resting and stimulated PMN in the presence or absence of NADH, indicate that NADH oxidase is a surface enzyme in human PMN, which is internalized duringphagocytosis and retains its peroxide-generating capacity within the phagocytic vacuole.
Abstract: The ultrastructural localization of NADH oxidase, a possible enzyme in the increased oxidative activity of polymorphonuclear leukocytes (PMN) during phagocytosis, was studied. A new cytochemical technique for the localization of H2O2, a product of NADH oxidase activity, was developed. Cerous ions, in the presence of peroxide, form an electron-dense precipitate. Resting and phagocytically stimulated PMN were exposed to cerous ions at pH 7.5 to demonstrate sites of NADH-dependent, cyanide-insensitive H2O2 production. Resting PMN exhibites slight activity on the plasma membrane; phagocytizing PMN had extensive deposits of reaction product localized within the phagosome and on the plasma membrane. Peroxide involvement was demonstrated by the inhibitory effect of catalase on cerium precipitation; the surface localization of the enzyme responsible was confirmed by using nonpenetrating inhibitors of enzymatic activity. A correlative study was performed with an NADH-dependent, tetrazolium-reduction system. As with cerium, formazan deposition on the surface of the cell was NADH dependent, cyanide insensitive, and stimulated by phagocytosis. Superoxide dismutase did not inhibit tetrazolium reduction, as observed cytochemically, indicating direct enzymatic dye reduction without superoxide interposition. These findings, combined with oxygen consumption studies on resting and stimulated PMN in the presence or absence of NADH, indicate that NADH oxidase is a surface enzyme in human PMN. It is internalized during phagocytosis and retains its peroxide-generating capacity within the phagocytic vacuole.
459 citations
TL;DR: H2O2 was determined by two methods that are applicable to conditions existing during microsomal mixed function oxidation reactions, provided that contaminating catalase activity is inhibited by azide and that interference by other mixedfunction oxidation reactions can be excluded.
327 citations
TL;DR: Findings suggest that catalase may be a significant staphylococcal virulence factor and protects intraphagocytic microbes by destroying hydrogen peroxide produced by the phagocyte.
Abstract: Since oxygen-free polymorphonuclear neutrophils (PMN) cannot kill Staphylococcus aureus normally, the usual mechanisms for PMN bactericidal activity probably involve hydrogen peroxide or superoxide. Catalase can destroy hydrogen peroxide, and superoxide dismutase breaks down superoxide. Experiments were performed to study the influence of these enzymes (which are found in staphylococci) on virulence for mice or on leukocyte-bacterial interaction. 15 staphylococcal strains were injected i.p. into mice to quantitate virulence. There was good correlation between staphylococcal catalase activity and mouse lethality (r equals 0.88) but no correlation between staphylococcal superoxide dismutase activity and mouse lethality (r equals 0.14). Exogenous catalase (10,000 U/ml) increased the virulence of low-catalase staphylococci, but exogenous superoxide dismutase (200 mug/ml) did not alter the virulence of staphyloccal strains. C14=labeled high-catalase or low-catalase staphylococci were ingested equally well by PMN, with or without the addition of exogenous catalase. A high-catalase staphylococcal strain was killed relatively poorly by PMN, and addition of exogenous catalase (but not superoxide dismutase) decreased the ability of PMN to kill a low-catalase strain. Iodination of bacterial proteins by PMN is related to hydrogen peroxide, and a high-catalase staphylococcal strain was iodinated only 63% as much as a low-catalase strain. Addition of exogenous catalase decreased iodination of the low-catalase strain by 23%. These findings suggest that staphylococcal catalase protects intraphagocytic microbes by destroying hydrogen peroxide produced by the phagocyte. Thus, catalase may be a significant staphylococcal virulence factor.
317 citations
TL;DR: Isolated human polymorphonuclear leukocytes engaged in phagocytosis liberate superoxide radical and hydrogen peroxide into the surrounding medium, which may partially explain the observed anti-inflammatory activity of superoxide dismutase.
Abstract: Isolated human polymorphonuclear leukocytes engaged in phagocytosis liberate superoxide radical and hydrogen peroxide into the surrounding medium. These two chemical species react to produce the hydroxyl radical, which attacks the leukocyte and leads to premature death of the cell. The hydroxyl radical may be scavenged by mannitol, or its formation can be prevented by the addition of superoxide dismutase or catalase to the medium, thereby eliminating the premature death of the cells. This phenomenon may partially explain the observed anti-inflammatory activity of superoxide dismutase.
276 citations
Journal Article•
TL;DR: Findings indicate that neither O2- nor H2O2 were able to kill S. epidermidis under the experimental conditions, but that the bactericidal agent was the product of a reaction between O 2- and H2 O2.
206 citations
TL;DR: Oxygen reduction during photosynthesis under conditions where light is rate limiting is seen as important in supplying the ATP which is needed for CO2 reduction but is not provided during electron transport to NADP.
189 citations
TL;DR: The results suggest that matrix extraction and increased soluble enzyme activities result from transmembrane passage of peroxisomal proteins, and suggest that the trophic effect of the drug used, Su-13437, is more active than CPIB, another per oxisome proliferation-inducing drug.
Abstract: Peroxisome proliferation has been induced with 2-methyl-2-(p-[1,2,3,4-tetrahydro-1-naphthyl]-phenoxy)-propionic acid (Su-13437). DNA, protein, cytochrome oxidase, glucose-6-phosphatase, and acid phosphatase concentrations remain almost constant. Peroxisomal enzyme activities change to approximately 165%, 50%, 30%, and 0% of the controls for catalase, urate oxidase, L-alpha-hydroxy acid oxidase, and D-amino acid oxidase, respectively. For catalase the change results from a decrease in particle-bound activity and a fivefold increase in soluble activity. The average diameter of peroxisome sections is 0.58 +/- 0.15 mum in controls and 0.73 +/- 0.25 mum after treatment. Therefore, the measured peroxisomal enzymes are highly diluted in proliferated particles. After tissue fractionation, approximately one-half of the normal peroxisomes and all proliferated peroxisomes show matric extraction with ghost formation, but no change in size. In homogenates submitted to mechanical stress, proliferated peroxisomes do not reveal increased fragility; unexpectedly, Su-13437 stabilizes lysosomes. Our results suggest that matrix extraction and increased soluble enzyme activities result from transmembrane passage of peroxisomal proteins. The changes in concentration of peroxisomal oxidases and soluble catalase after Su-13437 allow the calculation of their half-lives. These are the same as those found for total catalase, in normal and treated rats, after allyl isopropyl acetamide: about 1.3 days, a result compatible with peroxisome degradation by autophagy. A sequential increase in liver RNA concentration, [14C]leucine incorporation into DOC-soluble proteins and into immunoprecipitable catalase, and an increase in liver size and peroxisomal volume per gram liver, characterize the trophic effect of the drug used. In males, Su-13437 is more active than CPIB, another peroxisome proliferation-inducing drug; in females, only Su-13437 is active.
156 citations
TL;DR: The results indicae that metabolically derived hydrogen peroxide, spared from decomposition by catalase inhibition, oxidizes reduced NADPH required as the oxidant in the pentose pathway of glucose use.
Abstract: Germination of some dormant seeds is promoted by solutions of thiourea, sodium nitrite, and hydroxylamine salts. The promotions are accompanied by irreversible inhibition of catalase (EC 1.11.1.6) in extracts from the seeds. The seeds are also promoted in germination by catechol and pyrogallol solutions. These effects are recorded for lettuce (Lactuca sativa L. cv. Grand Rapids) and pigweed (Amaranthus albus L.) seeds. The results indicae that metabolically derived hydrogen peroxide, spared from decomposition by catalase inhibition, oxidizes reduced NADPH required as the oxidant in the pentose pathway of glucose use. The metabolic system for such use of H2O2 involves the enzymes, peroxidase (EC 1.11.1.7) and pyridine nucleotide quinone oxidoreductase (EC 1.6.99.2), which are present in the dormant seed prior to imbibition of water.
122 citations
TL;DR: In the presence of Fe3+-ADP and NADPH, washed rat liver microsomes at 37 degrees and at pH 7.5 emitted ultraweak light with the peroxidative cleavage of endogenous lipid, suggesting that superoxide anion and OH are involved in the generation of singlet oxygen in the present system.
122 citations
TL;DR: It is concluded from the presented experiments that a combination of the protonated form of the superoxide radical (HO-2 and H2O2 do inactivate DNA.
TL;DR: The spectrophotometric determination of the catalase-H2O2 intermediate was extended to the liver in situ in anaesthetized rats and found to be approx.
Abstract: The spectrophotometric determination of the catalase-H2O2 intermediate (Compound I) was extended to the liver in situ in anaesthetized rats. The rate of H2O2 production was determined for the liver in situ with endogenous substrates, and in the presence of excess of glycollate. Glycollate infusion doubled H2O2 production rate in the liver of air-breathing rats, and caused a fourfold increase when rats breathed O2 at 1 times 10(5) Pa. Hyperbaric O2 up to 6 times 10(5) Pa did not increase H2O2 generation supported by endogenous substrates, nor did it increase H2O2 production above that produced by 1 times 10(5) Pa O2 in glycollate-supplemented rats. The rates of ethanol oxidation via hepatic catalase and via alcohol dehydrogenase in the whole body were separately measured. The contribution of hepatic catalase to ethanol oxidation was found to be approx. 10 percent in endogenous conditions and increased to 30 percent or more of the total ethanol oxidation in rats supplemented with glycolate.
TL;DR: Microbodies, designated as peroxisomes because of their enzyme complement, have been isolated from methanol-grown cells of Candida boidinii and demonstrated that it contained only two predominant protein bands consistent with alcohol oxidase and catalase.
Abstract: Microbodies, designated as peroxisomes because of their enzyme complement, have been isolated from methanol-grown cells of Candida boidinii. Spheroplast lysates were separated on non-continuous Ficoll density gradients, resulting in a mitochondrial fraction and a peroxisome fraction. Estimates of purity using the mitochondrial enzyme markers suggested that the contamination of mitochondria in the peroxisome fraction was about 2-3 %. As shown by electron microscopy the peroxisomes were 0.4-0.6 μm in diameter and contained crystalloid inclusions.
Alcohol oxidase and catalase, which catalyse the oxidation of methanol to formaldehyde in Candida boidinii, could be localized within the peroxisomes. Gel-electrophoretic studies of the peroxisome fraction demonstrated that it contained only two predominant protein bands consistent with alcohol oxidase and catalase. No alcohol oxidase and catalase activity was found in mitochondria.
TL;DR: During the demethylation reaction of aminopyrine, no change in H2O2 production was detected by the present method; thus microsomal H2o2 production observed in isolated subcellular fractions appeared not to contribute significantly to the H2 O2 production in the whole organ.
Abstract: The properties of H2O2 production in the "haemoglobin-free", "non-circulatory" perfused liver of rats were examined. The H2O2 production with 1 mM-lactate and 0.15 mM-pyruvate was 82nmol/min per g of liver or 333nmol/min per 100g body wt. in the liver of fed rats at 30 degrees C. This rate decreased to almost half in the livers of starved and phenobarbital-pretreated rats. When H2O2 production was stimulated by urate infusion, almost all of the H2O2 produced by the uricase reaction was decomposed by the catalase reaction. During the demethylation reaction of aminopyrine, no change in H2O2 production was detected by the present method; thus microsomal H2O2 production observed in isolated subcellular fractions appeared not to contribute significantly to the H2O2 production in the whole organ. Whereas the rate of the glycolate-dependent H2O2 production was halved at an intracellular O2 concentration that caused a 10 percent increase in the reduction state of cytochrome c, the half-maximal rate of H2O2 production with lactate and pyruvate was observed at an O2 concentration that caused a 40 percent increase in the reduction state of cytochrome c in the liver. No further increase in the rates of H2O2 production was obtained by increasing O2 pressure up to 5 times 10(5) Pa. The rate of ethanol oxidation through the catalase "peroxidatic" reaction varied, depending on the substrate availability. The maximal capability of this pathway in ethanol oxidation reached approx. 1.5 mumol/min per g of liver, when a mixture of urate, glycollate and octanoate was infused to enhance H2O2 production.
Journal Article•
TL;DR: Reaction rates and the failure of catalase to inhibit the reaction demonstrated that hydrogen peroxide is of no importance, and the lag phase of the reaction suggests that oxidation products of 4-dimethylaminophenol produced by the reaction between oxyhemoglobin and 4-Dimethylam inophenol are essential intermediates.
Abstract: The rate of oxidation by hydrogen peroxide of human hemoglobin, virtually free from catalase, glutathione peroxidase, and superoxide dismutase, was found to be proportional to the concentrations of hemoglobin and hydrogen peroxide, the second-order rate constant at pH 7.4 and 37° being k = 125 M-1 sec-1. Formation of ferrihemoglobin by reduced glutathione in air was found to be slow, gaining its maximal velocity after a lag phase. Kinetic data and the effect of catalase or glutathione peroxidase demonstrated that hydrogen peroxide is an essential intermediate which produces ferrihemoglobin in solutions of hemoglobin and reduced glutathione. The much higher rate of ferrihemoglobin formation by phenylhydroxylamine than by hydrogen peroxide and the failure of catalase to inhibit the reaction showed that hydrogen peroxide is not an important intermediate in the formation of ferrihemoglobin by phenylhydroxylamine. The reaction rate was found to be proportional to the concentrations of phenylhydroxylamine and hemoglobin. The second-order rate constant was calculated to be k = 2350 M-1 sec-1. With the formation of ferrihemoglobin by 4-dimethylaminophenol also, reaction rates and the failure of catalase to inhibit the reaction demonstrated that hydrogen peroxide is of no importance. The lag phase of the reaction suggests that oxidation products of 4-dimethylaminophenol produced by the reaction between oxyhemoglobin and 4-dimethylaminophenol are essential intermediates.
TL;DR: The specific activity of catalase in Salmonella typhimurium and other enteric bacteria decreased during the logarithmic phase of growth and increased at the onset and during the stationary phase and maintenance of the pH at a constant neutral value did not alter the typical pattern of synthesis.
Abstract: The specific activity of catalase in Salmonella typhimurium and other enteric bacteria decreased during the logarithmic phase of growth and increased at the onset and during the stationary phase. The increase in catalase synthesis at the end of the exponential phase in S. typhimurium cells coincided with the lowest pH value reached by the culture. Maintenance of the pH at a constant neutral value did not alter the typical pattern of synthesis in contradiction of the results previously reported (McCarthy and Hinshelwood. 1959). A sudden decrease in the pH value of an S. typhimurium culture during exponential growth by addition of HC1 did not cause an alteration in the catalase synthesis pattern. Addition of hydrogen peroxide to S. typhimurium cultures within the range 1 muM TO 2MM during the exponential growth phase stimulated catalase synthesis. The extent of catalase synthesis depended on the concentration of hydrogen peroxide; the maximum stimulation was observed at 80 muM. Increased catalase synthesis was not detected for 10 to 15 min after hydrogen peroxide addition. Hydrogen peroxide was produced by S. typhimurium cultures during the exponential and stationary growth phases. However, no direct relationship between hydrogen peroxide accumulation and synthesis of catalase was observed.
TL;DR: Although chicken polymorphonuclear leukocytes were found to possess a substantial capacity to catalyze the cyanide-insensitive oxidation of either NADH or NADPH, the total or specific activities of such processes were not demonstrably affected by phagocytosis.
Abstract: Polymorphonuclear leukocytes isolated from chicken peritoneal exudates have been found to catalyze cyanide-insensitive stimulation of respiration and the hexose monophosphate shunt upon exposure to heat-inactivated Staphylococcus aureus. However, there was no demonstrable formate oxidation concomitant with phagocytosis in either the presence or absence of exogenous catalase. Moreover, chicken polymorphonuclear leukocytes failed to oxidize scopoletin concomitant with phagocytosis in the presence of horseradish peroxidase. While oxygen uptake was increased 2- to 3-fold by the stimulus of phagocytosis, the oxidation of [1-(14)C]glucose was increased approximately 20-fold. The cells contain two mechanisms, a glutathione reductase-glutathione peroxidase system and an NADPH-NAD+ transhydrogenase, each of which is present in sufficient capacity to accommodate the enhanced shunt activity. Although chicken polymorphonuclear leukocytes were found to possess a substantial capacity to catalyze the cyanide-insensitive oxidation of either NADH or NADPH, the total or specific activities of such processes were not demonstrably affected by phagocytosis.
TL;DR: Results are presented which strongly suggest that the species formed during the oxidation of dialuric acid which is active toward the cell is neither superoxide ion nor hydrogen peroxide nor a product of these substances.
TL;DR: The results are compatible with the hypothesis that the agent that mediates platelet aggregation by arachidonic acid is a popoperoxide, requiring the presence of H2O2 or of a similarly catalase-sensitive substance to be generated.
TL;DR: The enzyme functions as a protective agent in the male reproductive tract by oxidizing potentially damaging physiological sulfhydryl groups and thereby preserving sperm structure and function and if an inhibitor of this enzyme can be found it would make an effective male contraceptive.
TL;DR: In this article, peroxidase from Mycobacterium tuberculosis H37Rv was purified to homogeneity, and the homogeneous protein exhibits catalase and Y (Youatt's)-enzyme activities.
Abstract: Peroxidase from Mycobacterium tuberculosis H37Rv was purified to homogeneity. The homogeneous protein exhibits catalase and Y (Youatt's)-enzyme activities in addition to peroxidase activity. Further confirmation that the three activities are due to a single enzyme was accomplished by other criteria, such as differential thermal inactivation, sensitivity to different inhibitors, and co-purification. The Y enzyme (peroxidase) was separated from NADase (NAD+ glycohydrolase) inhibitor by gel filtration on Sephadex G-200. The molecular weights of peroxidase and NADase inhibitor, as determined by gel filtration, are 240000 and 98000 respectively. The Y enzyme shows two Km values for both isoniazid (isonicotinic acid hydrazide) and NAD at low and high concentrations. Analysis of the data by Hill plots revealed that the enzyme has one binding site at lower substrate concentrations and more than one at higher substrate concentration. The enzyme contains 6g-atoms of iron/mol. Highly purified preparations of peroxidases from different sources catalyse the Y-enzyme reaction, suggesting that the nature of the reaction may be a peroxidatic oxidation of isoniazid. Moreover, the Y-enzyme reaction is enhanced by O2. Isoniazid-resistant mutants do not exhibit Y-enzyme, peroxidase or catalase activities, and do not take up isoniazid. The Y-enzyme reaction is therefore implicated in the uptake of the drug.
TL;DR: It was shown that the enzyme is capable of oxidizing methanol, formaldehyde and formate in the presence of hydrogen peroxide, and the physiological significance of these reactions in the transduction of energy from the oxidation of meethanol in yeasts is discussed.
Abstract: Catalase has been partially purified from cell-free extracts of methanol-grown Hansenula polymorpha and its peroxidative properties were studied. It was shown that the enzyme is capable of oxidizing methanol, formaldehyde and formate in the presence of hydrogen peroxide. The physiological significance of these reactions in the transduction of energy from the oxidation of methanol in yeasts is discussed.
TL;DR: Formation of Nitrite from Hydroxylamine in the presence of illuminated chloroplast lamellae is inhibited by superoxide dismutase but not by catalase, indicating that the superoxide free radical ion and not H2O2 is responsible for the oxidation of hydroxyamine.
Abstract: Formation of Nitrite from Hydroxylamine in the presence of illuminated chloroplast lamellae is inhibited by superoxide dismutase but not by catalase, indicating that the superoxide free radical ion and not H₂O₂ is responsible for the oxidation of hydroxylamine. Decarboxylation of α-keto acids on the other hand is strongly inhibited by catalase but only slightly by superoxide dismutase. Light-dependent hydroxylamine oxidation and decarboxylation of α-keto acids can be used, therefor, as specific and sensitive probes for the determination of either the superoxide free radical ion or hydrogen peroxide, respectively.Photosynthetic oxygen reduction in the presence of ferredoxin, (monitored by the above method) yields both H₂O₂ and O₂·⁻. The addition of an oxygen reducing factor (ORF, solubilized by heat - treatment of washed chloroplast lamellae) instead of ferredoxin, however, stimulates only the production of H₂O₂ , while O₂·⁻ - formation is not observed. The cooperation of ferredoxin and ORF during photosynthetic oxygen reduction by chloroplast lamellae apparently produces H₂O₂ not only by dismutation of O₂·⁻, but also by a separate mechanism involving ORF.
TL;DR: It was observed that CMP-sialic acid, together with microsomal extract, protected the supernatant pool of catalase from inactivation upon storage; and that the pattern of multiplicity which was exhibited by the purified enzyme on isoelectric focusing, was considerably altered by incubation with neuraminidase.
TL;DR: The extraordinary stability of superoxide dismutase before and after singlet oxygen treatment was demonstrated by the identical parameters obtained from circular dichroism, electron paramagnetic resonance and X-ray photoelectron spectroscopy.
TL;DR: Two catalase-negative strains of Lactobacillus plantarum and a strain producing the atypical, nonheme catalasing strain were studied to determine if the ability to produce the Atypical Catalase conferred any growth advantage upon the producing strain.
Abstract: Two catalase-negative strains of Lactobacillus plantarum and a strain producing the atypical, nonheme catalase were studied to determine if the ability to produce the atypical catalase conferred any growth advantage upon the producing strain. Both catalase-negative strains grew more rapidly than the catalase-positive strain under aerobic or anaerobic conditions in a glucose-containing, complex medium. Upon exhaustion of glucose from the medium, all three strains continued growth under aerobic but not under anaerobic conditions. The continued aerobic growth was accompanied by production of acetic acid in addition to the lactic acid produced during growth on glucose. Oxygen was taken up by exponential phase-cell suspensions grown on glucose when glucose or glycerol were used as substrates. Cells harvested from glucose-exhausted medium oxidized glucose, glycerol, and pyruvate. Oxygen utilization by a catalase-negative strain increased as did the specific activity of reduced nicotinamide adenine dinucleotide peroxidase during late growth in the glucose-exhausted medium. The catalase-positive strain and the catalase-negative strain tested both possessed low but readily detectable levels of superoxide dismutase throughout growth. The growth responses are discussed in terms of the presence of enzymes which would allow the cells to remove potentially damaging reduction products of O2.
TL;DR: Cell-free extracts from very young primary leaves of parsley plants catalyse the oxidation of naringenin (5,7,4′-trihydroxyflavanone) to apigenin (4,2′, 4′-Trihydroxychalcone), which is not H 2 O 2 -dependent and is not inhibited by catalase, cyanide, or 1.4·10 −2 m mercaptoethanol.
TL;DR: In vitro inactivation of Neurospora crassa nitrite reductase can be obtained by preincubation of the enzyme with reduced pyridine nucleotide plus FAD, and it is revealed that oxygen is required in order to obtain complete inactivation.
TL;DR: Hydrogen peroxide may not be the sole or primary product of the NADH-cytochrome o oxidase reaction, and this result suggests that hydrogen peroxide is an intermediate that can be trapped efficiently under the conditions of the fluorometric assay, whereas under theconditions of the first two assays most of the hydrogenperoxide generated undergoes further reaction.