Myeloperoxidase-Halide-Hydrogen Peroxide Antibacterial System

An antibacterial effect of myeloperoxidase, a halide, such as iodide, bromide, or chloride ion, and H(2)O(2) on Escherichia coli or Lactobacillus acidophilus is described. When L. acidophilus was employed, the addition of H(2)O(2) was not required; however, the protective effect of catalase suggested that, in this instance, H(2)O(2) was generated by the organisms. The antibacterial effect was largely prevented by preheating the myeloperoxidase at 80 C or greater for 10 min or by the addition of a number of inhibitors; it was most active at the most acid pH employed (5.0). Lactoperoxidase was considerably less effective than was myeloperoxidase when chloride was the halide employed. Myeloperoxidase, at high concentrations, exerted an antibacterial effect on L. acidophilus in the absence of added halide, which also was temperature- and catalase-sensitive. Peroxidase was extracted from intact guinea pig leukocytes by weak acid, and the extract with peroxidase activity had antibacterial properties which were similar, in many respects, to those of the purified preparation of myeloperoxidase. Under appropriate conditions, the antibacterial effect was increased by halides and by H(2)O(2) and was decreased by catalase, as well as by cyanide, azide, Tapazole, and thiosulfate. This suggests that, under the conditions employed, the antibacterial properties of a weak acid extract of guinea pig leukocytes is due, in part, to its peroxidase content, particularly if a halide is present in the reaction mixture. A heat-stable antibacterial agent or agents also appear to be present in the extract.     

硫氧还蛋白依赖性过氧化物还原酶在中医肝阳化风证的表达及其意义

目的:比较硫氧还蛋白依赖性过氧化物还原酶(Thioredoxin-dependent peroxide reductase,又称PRX3)在中医肝阳化风证中的表达及意义.方法:按照西医诊断标准及中医辨证标准收集脑出血、脑梗塞、颈椎病、帕金森病四种肝阳化风证患者40例(每病10例)及健康人10例,采用RT-PCR方法检测外周血淋巴细胞硫氧还蛋白依赖性过氧化物还原酶的基因表达情况.结果:较对照组相比.四病肝阳化风证组PRX3表达显著下降(P＜0.05),而四病肝阳化风证组间表达无差异.结论:肝阳化风证硫氧还蛋白依赖性过氧化物还原酶表达下调与提示与氧化应激有关和异病同证具有相同物质基础,可能成为肝阳化风证的特异性指标.     

Hydrogen Peroxide Modification of Human Oxyhemoglobin

The effect of H₂O₂ on the primary structure of OxyHb was studied. Upon treatment of Oxy Hb with H₂O₂ ([Heme]/[H₂O₂] =I), tryptophan and methionine residues of the /-chain were modified. Treatment of ApoHb with H₂O₂ resulted in the modification of histidine and methionine residues in both globin chains. Tryptophan residues were unaffected. Modification of methionine residues in both the β-chain of OxyHb and ApoHb probably results from the direct oxidation of mcthionine by H₂O₂. The modification of histidine residues in ApoHb may be mediated by a metal-catalyzed oxidation system comprised of H₂O₂ and histidine-bound iron. The H₂O₂-mediated modification of tryptophan in the OxyHb β-chain. however, requires the heme moiety.     

Hydrogen Peroxide Modification of Human Oxyhemoglobin

The effect of H₂O₂ on the primary structure of OxyHb was studied. Upon treatment of Oxy Hb with H₂O₂ ([Heme]/[H₂O₂] =I), tryptophan and methionine residues of the /-chain were modified. Treatment of ApoHb with H₂O₂ resulted in the modification of histidine and methionine residues in both globin chains. Tryptophan residues were unaffected. Modification of methionine residues in both the β-chain of OxyHb and ApoHb probably results from the direct oxidation of mcthionine by H₂O₂. The modification of histidine residues in ApoHb may be mediated by a metal-catalyzed oxidation system comprised of H₂O₂ and histidine-bound iron. The H₂O₂-mediated modification of tryptophan in the OxyHb β-chain. however, requires the heme moiety.     

Hydrogen Peroxide Metabolism in Yeasts

A catalase-negative mutant of the yeast Hansenula polymorpha consumed methanol in the presence of glucose when the organism was grown in carbon-limited chemostat cultures. The organism was apparently able to decompose the H₂O₂ generated in the oxidation of methanol by alcohol oxidase. Not only H₂O₂ generated intracellularly but also H₂O₂ added extracellularly was effectively destroyed by the catalase-negative mutant. From the rate of H₂O₂ consumption during growth in chemostat cultures on mixtures of glucose and H₂O₂, it appeared that the mutant was capable of decomposing H₂O₂ at a rate as high as 8 mmol · g of cells⁻¹ · h⁻¹. Glutathione peroxidase (EC 1.11.1.9) was absent under all growth conditions. However, cytochrome c peroxidase (CCP; EC 1.11.1.5) increased to very high levels in cells which decomposed H₂O₂. When wild-type H. polymorpha was grown on mixtures of glucose and methanol, the CCP level was independent of the rate of methanol utilization, whereas the level of catalase increased with increasing amounts of methanol in the substrate feed. Also, the wild type decomposed H₂O₂ at a high rate when cells were grown on mixtures of glucose and H₂O₂. In this case, an increase of both CCP and catalase was observed. When Saccharomyces cerevisiae was grown on mixtures of glucose and H₂O₂, the level of catalase remained low, but CCP increased with increasing rates of H₂O₂ utilization. From these observations and an analysis of cell yields under the various conditions, two conclusions can be drawn. (i) CCP is a key enzyme of H₂O₂ detoxification in yeasts. (ii) Catalase can effectively compete with mitochondrial CCP for hydrogen peroxide only if hydrogen peroxide is generated at the site where catalase is located, namely in the peroxisomes.     

Hydrogen Peroxide in Human Blood

Blood and plasma of humans and rats were analyzed for hydrogen peroxide. The samples were analyzed after deproteinization with trichloroacetic acid, immediately after they were withdrawn from human volunteers or rats. A radio-isotopic technique based on peroxide-dependent decarboxylation of 1-¹⁴C-alpha-ketoacids and consequent liberation of ¹⁴CO₂ was used. The results demonstrate the presence ofmicromolar levels of H₂O₂, both, in the plasma as well as in the whole blood. The values in the whole blood were substantially greater than the plasma. This was true for rats as well as humans. The presence of such significant quantities of H₂O₂ in the blood have been demonstrated for the first time. The investigation, therefore, opens a newer avenue of research on diseases purported to be related to the generation of oxygen radicals in vivo.     

Response of Plant-Colonizing Pseudomonads to Hydrogen Peroxide

Colonization of plant root surfaces by Pseudomonas putida may require mechanisms that protect this bacterium against superoxide anion and hydrogen peroxide produced by the root. Catalase and superoxide dismutase may be important in this bacterial defense system. Stationary-phase cells of P. putida were not killed by hydrogen peroxide (H₂O₂) at concentrations up to 10 mM, and extracts from these cells possessed three isozymic bands (A, B, and C) of catalase activity in native polyacrylamide gel electrophoresis. Logarithmic-phase cells exposed directly to hydrogen peroxide concentrations above 1 mM were killed. Extracts of logarithmic-phase cells displayed only band A catalase activity. Protection against 5 mM H₂O₂ was apparent after previous exposure of the logarithmic-phase cells to nonlethal concentrations (30 to 300 μM) of H₂O₂. Extracts of these protected cells possessed enhanced catalase activity of band A and small amounts of bands B and C. A single form of superoxide dismutase and isoforms of catalase were apparent in extracts from a foliar intercellular pathogen, Pseudomonas syringae pv. phaseolicola. The mobilities of these P. syringae enzymes were distinct from those of enzymes in P. putida extracts.     

Hemolysin and Peroxide Activity of Mycoplasma Species

Various methods for the detection of hemolysin production by Mycoplasma species were compared. Inoculation of blood-agar by the push-block method and by use of concentrated mycoplasma cell suspensions was compared with the agar-overlay technique. The preferred method was direct surface inoculation of concentrated suspensions onto the blood-agar. Among the conditions tested, refrigeration of 48-hr cultures gave the best results. A wide variety of mycoplasma species were tested for hemolytic activity towards rabbit, sheep, guinea pig, duck, and chicken bloods. Guinea pig erythrocytes were found to be the most susceptible to lysis by mycoplasma, and rabbit erythrocytes were found to be the least susceptible. A sensitive technique for the detection of peroxide production by mycoplasma strains, employing agar containing benzidine and sheep blood, was used. With this method, peroxide production could be correlated with hemolysis on blood-agar. Peroxidase and catalase inhibited both the benzidine reaction and hemolysis. It was concluded that the major hemolysin of the Mycoplasma species examined is a peroxide.     

Oxidation of d-Limonene with Selenium Dioxide-hydrogen Peroxide

Oxidation of d-Iimonene with selenium dioxide-hydrogen peroxide affords (+)-l-hydroxyneodihydrocarveol as the major product formed via cis- and trans-limonene epoxide. Hydrolysis of the former epoxide is much faster than that of the latter, which can therefore be obtained in almost quantitative yield on acid hydrolysis of a mixture of cis- and trans-limonene epoxide (1:1) under mild condition.

Minor significance of oxygenation in an allylic position to a trisubstituted double bond and the difference of accessibility of an allylic position to di- and trisubstituted double bond toward the oxidant were also observed.     

双氧水介导制备对硝基苯甲酸乙酯的初步研究（英文）

目的：探讨双氧水催化合成对硝基苯甲酸乙酯的可行性,并考察了反应物的摩尔比、催化剂用量、反应温度及反应时间对产物收率的影响。方法：分别采用单因素设计实验与正交设计实验,分析比较这两种方法的最佳反应条件。采用数字熔点仪测定样品的熔点;用GC112A型气相色谱仪测定了产物的纯度;用傅里叶变换红外光谱仪测定产物的结构。结果：双氧水可以作为合成对硝基苯甲酸乙酯的催化剂。综合分析可知：当无水乙醇和对硝基苯甲酸的摩尔比为4：1,催化剂含量为10%,反应温度为80℃,反应时间为2.5-3h时酯化产率可达到最高值。结论：双氧水催化对硝基苯甲酸、无水乙醇合成对硝基苯甲酸乙酯的效率较高,产品纯度高,环境污染小,不失为一种新的合成方法。     

Resistance of Serratia marcescens to Hydrogen Peroxide

Irradiation with ultraviolet (u.v.) light (71 J/m²) reduced the viable count of suspenrsions of Serratia marcescens , grown in a glycerol-salts defined medium, to five in 10⁴ cells. Subsequent incubation of irradiated cells in hydrogen peroxide failed to decrease the survivors, but u.v. irradiation in the presence of hydrogen peroxide reduced the viable count to fewer than two in 10⁶ cells. Cells grown in defined medium with added iron had more measurable catalase activity and were more resistant to hydrogen peroxide alone and to simultaneous treatment with u.v. irradiation and hydrogen peroxide. Cells grown in a non-defined medium contained little iron and measurable catalase activity but were more resistant to hydrogen peroxide. Treatment with toluene, heat killing or sonication increased the catalase activity detected in all cell suspensions and showed that resistance to hydrogen peroxide and to u.v. irradiation in hydrogen peroxide was related to the total catalase activity within cells.     

Nitration of Tyrosine by Hydrogen Peroxide and Nitrite

Peroxynitrite anion is a powerful oxidant which can initiate nitration and hydroxylation of aromatic rings. Peroxynitrite can be formed in several ways, e.g. from the reaction of nitric oxide with superoxide or from hydrogen peroxide and nitrite at acidic pH. We investigated pH dependent nitration and hydroxylation resulting from the reaction of hydrogen peroxide and nitrite to determine if this reaction proceeds at pH values which are known to occur in vivo. Nitration and hydroxylation products of tyrosine and salicylic acid were separated with an HPLC column and measured using ultraviolet and electrochemical detectors. These studies revealed that this reaction favored hydroxylation between pH 2 and pH4, while nitration was predominant between pH 5 and pH 6. Peroxynitrite is presumed to be an intermediate in this reaction as the hydroxylation and nitration profiles of authentic peroxynitrite showed similar pH dependence. These findings indicate that hydrogen peroxide and nitrite interact at hydrogen ion concentrations present under some physiologic conditions. This interaction can initiate nitration and hydroxylation of aromatic molecules such as tyrosine residues and may thereby contribute to the biochemical and toxic effects of the molecules.     

Nitration of Tyrosine by Hydrogen Peroxide and Nitrite

Peroxynitrite anion is a powerful oxidant which can initiate nitration and hydroxylation of aromatic rings. Peroxynitrite can be formed in several ways, e.g. from the reaction of nitric oxide with superoxide or from hydrogen peroxide and nitrite at acidic pH. We investigated pH dependent nitration and hydroxylation resulting from the reaction of hydrogen peroxide and nitrite to determine if this reaction proceeds at pH values which are known to occur in vivo. Nitration and hydroxylation products of tyrosine and salicylic acid were separated with an HPLC column and measured using ultraviolet and electrochemical detectors. These studies revealed that this reaction favored hydroxylation between pH 2 and pH4, while nitration was predominant between pH 5 and pH 6. Peroxynitrite is presumed to be an intermediate in this reaction as the hydroxylation and nitration profiles of authentic peroxynitrite showed similar pH dependence. These findings indicate that hydrogen peroxide and nitrite interact at hydrogen ion concentrations present under some physiologic conditions. This interaction can initiate nitration and hydroxylation of aromatic molecules such as tyrosine residues and may thereby contribute to the biochemical and toxic effects of the molecules.