Selective oxidation and reduction of methionine residues in peptides and proteins by oxygen exchange between sulfoxide and sulfide

Treatment of amino acids, peptides, and proteins with aqueous solution of dimethyl sulfoxide (Me2SO) and hydrochloric acid (HCl) resulted in the oxidation of methionine to methionine sulfoxide. In addition to methionine, SH groups are also oxidized, but this reaction proceeds after a lag period of 2 h. Other amino acids are not modified by aqueous Me2SO/HCl. The reaction is strongly pH-dependent. Optimal conditions are 1.0 M HCl, 0.1 M Me2SO, at 22 degrees C. The reaction exhibits pseudo-first order kinetics with Kobs = 0.23 +/- 0.015 M-1 min-1 at 22 degrees C. Incubation of methionine sulfoxide with dimethyl sulfide and HCl resulted in the conversion of methionine sulfoxide to methionine. This reaction is fast (t1/2 = 4 min at room temperature) and quantitative at relatively anhydrous condition (i.e. at H2O:concentrated HCl:dimethyl sulfide ratio of 2:20:1). Quantitative conversions of methionine sulfoxide back to methionine are obtained in peptides and proteins as well, with no observable other side reactions in amino acids and proteins. The wide applications of this selective oxidation and reduction of methionine residues are demonstrated and discussed.     

Contributions of physical and chemical properties of mild irritants to gastric cytoprotection in rats

The present study demonstrated the cytoprotective abilities of low concentrations of ethanol, NaCl and HCl, against the gastric mucosal damage caused by 100% ethanol, and the contributions of the physical and chemical properties of these mild irritants to their protective actions. The results have shown the differential protective effects of ethanol (10–40%), NaCl (2.5–12.5%) and HCl (0.15–0.45M), with the optimal cytoprotective concentrations being 20% ethanol, 5% NaCl and 0.3M HCl, respectively. Solutions of KCl and NaCl with similar osmolarity, and H₂SO₄ and HCl of similar acidity and osmolarity, all showed similar protective potentials as compared to the osmotic agent mannitol, which possessed a concentration- and tonicity-dependent protective action against 100% ethanol-induced mucosal damage. Same concentration of methanol, propan-2-ol and ethanol, having similar osmolarity with deionized water, exerted indifferent protective effects. It is therefore concluded that adaptive cytoprotection induced by low concentrations of NaCl and HCl could depend on their physical properties, while that of ethanol could act through its unique chemical property.     

Ethanol production from dilute acid hydrolysate of rice hulls using genetically engineered Escherichia coli

Approximately 30% of rice hulls, which represent an abundant residue with little commercial value, was solubilized with 0.4 M H2SO4 acid to produce a syrup containing over 100 g monomer sugar/l. Toxins generated during hydrolysis were mitigated with Ca(OH)2. Treated hydrolysate plus additional nutrients was fermented with Escherichia coli KO11 to produce over 46 g ethanol/L in 72 h (92% of theoretical yield). © Rapid Science Ltd. 1998     

HCl causes less intracellular acidification in Necturus gastric mucosa surface epithelial cells than other acids

Luminal acid causes intracellular acidification in the gastric epithelium, but the mechanism by which H(+) enters surface cells remains obscure. This study addressed the problem by assessing how different acids affect intracellular pH in gastric surface cells. Isolated Necturus maculosus antral mucosa was exposed to HCl, HNO(3), H(2)SO(4), and H(3)PO(4) at pH 2.30. Intracellular pH was measured with microelectrodes. The physicochemical interaction of a synthetic model of gastric phospholipids with the different acids was studied using Langmuir film balance. Exposure to luminal HNO(3), H(2)SO(4), or H(3)PO(4) caused significantly larger intracellular acidification than exposure to HCl. The degree of acidification was not dependent on the valence or nature of the anionic counterion of the acid but significantly correlated with the amount of molecular acid. By Langmuir film balance, subphases acidified with HNO(3), H(2)SO(4), or H(3)PO(4) caused more close packing of phospholipid molecules than those acidified with HCl, possibly allowing hydrogen bonding between head groups to facilitate H(+) movement across the phospholipid membrane. HCl causes significantly less intracellular acidification in gastric epithelium than HNO(3), H(2)SO(4), or H(3)PO(4). This may be caused by the lower amount of molecular HCl in solution and possible hydrogen bonding between the head groups of phospholipid molecules and the other acids.     

Monte Carlo calculation of the primary radical and molecular yields of liquid water radiolysis in the linear energy transfer range 0.3-6.5 keV/micrometer: application to 137Cs gamma rays

Monte Carlo simulations of the radiolysis of neutral liquid water and 0.4 M H(2)SO(4) aqueous solutions at ambient temperature are used to calculate the variations of the primary radical and molecular yields (at 10(-6)s) as a function of linear energy transfer (LET) in the range approximately 0.3 to 6.5 keV/micrometer. The early energy deposition is approximated by considering short (approximately 20-100 micrometer) high-energy (approximately 300-6.6 MeV) proton track segments, over which the LET remains essentially constant. The subsequent nonhomogeneous chemical evolution of the reactive species formed in these tracks is simulated by using the independent reaction times approximation, which has previously been used successfully to model the radiolysis of water under various conditions. The results obtained are in good general agreement with available experimental data over the whole LET range studied. After normalization of our computed yields relative to the standard radical and molecular yields for (60)Co gamma radiation (average LET approximately 0.3 keV/micrometer), we obtain empirical relationships of the primary radiolytic yields as a function of LET over the LET range studied. Such relationships are of practical interest since they allow us to predict a priori values of the radical and molecular yields for any radiation from the knowledge of the average LET of this radiation only. As an application, we determine the corresponding yields for the case of (137)Cs gamma radiation. For this purpose, we use the value of approximately 0.91 keV/micrometer for the average LET of (137)Cs gamma rays, chosen so that our calculated yield G(Fe(3+)) for ferrous-ion oxidation in air-saturated 0.4 M sulfuric acid reproduces the value of 15.3 molecules/100 eV for this radiation recommended by the International Commission on Radiation Units and Measurements. The uncertainty range on those primary radical and molecular yields are also determined knowing the experimental error (approximately 2%) for the measured G(Fe(3+)) value. The following values (expressed in molecules/100 eV) are obtained: (1) for neutral water: G(e(-)(aq)) = 2.50 +/- 0.16, G(H(.)) = 0.621 +/- 0.019, G(H(2)) = 0.474 +/- 0.025, G((.)OH) = 2.67 +/- 0.14, G(H(2)O(2)) = 0.713 +/- 0.031, and G(-H(2)O) = 4.08 +/- 0.22; and (2) for 0.4 M H(2)SO(4) aqueous solutions: G(H(.)) = 3.61 +/- 0.09, G(H(2)) = 0.420 +/- 0.019, G((.)OH) = 2.78 +/- 0.12, G(H(2)O(2)) = 0.839 +/- 0.037, and G(-H(2)O) = 4.46 +/- 0.16. These computed values are found to differ from the standard yields for (60)Co gamma rays by up to approximately 6%.     

Intake of Farmed Atlantic Salmon Fed Soybean Oil Increases Insulin Resistance and Hepatic Lipid Accumulation in Mice

Background

To ensure sustainable aquaculture, fish derived raw materials are replaced by vegetable ingredients. Fatty acid composition and contaminant status of farmed Atlantic salmon (Salmo salar L.) are affected by the use of plant ingredients and a spillover effect on consumers is thus expected. Here we aimed to compare the effects of intake of Atlantic salmon fed fish oil (FO) with intake of Atlantic salmon fed a high proportion of vegetable oils (VOs) on development of insulin resistance and obesity in mice.

Methodology/principal findings

Atlantic salmon were fed diets where FO was partly (80%) replaced with three different VOs; rapeseed oil (RO), olive oil (OO) or soy bean oil (SO). Fillets from Atlantic salmon were subsequently used to prepare Western diets (WD) for a mouse feeding trial. Partial replacement of FO with VOs reduced the levels of polychlorinated biphenyls (PCB) and dichloro-diphenyl-tricloroethanes (DDT) with more than 50% in salmon fillets, in WDs containing the fillets, and in white adipose tissue from mice consuming the WDs. Replacement with VOs, SO in particular, lowered the n−3 polyunsaturated fatty acid (PUFA) content and increased n−6 PUFA levels in the salmon fillets, in the prepared WDs, and in red blood cells collected from mice consuming the WDs. Replacing FO with VO did not influence obesity development in the mice, but replacement of FO with RO improved glucose tolerance. Compared with WD-FO fed mice, feeding mice WD-SO containing lower PCB and DDT levels but high levels of linoleic acid (LA), exaggerated insulin resistance and increased accumulation of fat in the liver.

Conclusion/Significance

Replacement of FO with VOs in aqua feed for farmed salmon had markedly different spillover effects on metabolism in mice. Our results suggest that the content of LA in VOs may be a matter of concern that warrants further investigation.     

酸提高绿茶提取物对脂肪酸合酶的抑制活性

脂肪酸合酶和肥胖、癌症等人类重大疾病相关.获取高活性脂肪酸合酶抑制剂有重要应用价值.50％乙醇的绿茶提取物具有抑制脂肪酸合酶和经口服降低大、小鼠体重的功能.该提取物在酸的作用下可明显地提高其抑制脂肪酸合酶的能力.采用1 mol/L硫酸或盐酸在100℃下处理绿茶提取物,发现该提取物对脂肪酸合酶的抑制活性随时间逐步提高.在25℃至120℃温度下,提高处理温度使抑制活性提高的速度加快和程度加大. 用1 mol/L盐酸120℃处理35 min或3 mol/L盐酸100℃处理30 min可使绿茶提取物抑制脂肪酸合酶的半抑制浓度下降20倍左右,达到1 μg/ml以下.用pKa值4.76至1.27的1 mol/L浓度的4种有机酸在100℃作用150 min使绿茶提取物抑制活性分别提高到1.48至5.84倍.提高酸的浓度也使被作用的提取物的抑制活性提高的更多.表现抑制活性提高的速度及程度和氢离子浓度正相关.判断绿茶提取物在酸作用下抑制活性的提高来源于其中所含儿茶素在氢离子作用下发生了化学变化.初步实验表明其变化过程比较复杂,确定其分子机制还需进一步的研究工作.     

Allenic derivatives of nucleic acid components and their transformation products: a new class of biologically active nucleoside analogues

Reaction of adenine (1a) or cytosine (1b) with excess 1,4-dichloro-2-butyne catalyzed by K2CO3 in (CH3)2SO gave the 4-chloro-2-butynyl derivatives 2a and 2b. The latter were converted to the 4-hydroxy-2-butynyl compounds 3a and 3b by refluxing in 0.1 M HCl. Isomerization of 3a in 0.1 M NaOH at 100 degrees C for 1 h gave an equilibrium mixture of 3a and allene 4a. Pure 4a was obtained by column chromatography. Similarly, compound 3b was transformed/0.1 M NaOH, 20% aq. dioxane, 9 h, 100 degrees C/ to a mixture of 3b and 4b from which pure 4b was obtained by chromatography and crystallization. By contrast, reflux of 3a or 3b in 1 M NaOH in 50% aq. dioxane for 1 h afforded cyclized products - dihydrofuryl derivatives 5a and 5b. Hydrogenation of 4a and 5a gave 9-(4-hydroxybutyl)adenine (6a) and 9-(tetrahydro-2-furyl)adenine (7a), respectively. Scope and limitations of allenic isomerization in nucleic acid base series, spectroscopy and biological activity of the obtained products will be discussed.     

Different mechanism for in vitro formation of nucleosome core particles

The interaction of different histone oligomers with nucleosomes has been investigated by using nondenaturing gel electrophoresis. In the presence of 0.2 M NaCl, the addition of the pairs H2A,H2B or H3,H4 or the four core histones to nucleosome core particles produces a decrease in the intensity of the core particle band and the appearance of aggregated material at the top of the gel, indicating that all these histone oligomers are able to associate with nucleosomes. Equivalent results were obtained by using oligonucleosome core particles. Additional electrophoretic results, together with second-dimension analysis of histone composition and fluorescence and solubility studies, indicate that H2A,H2B, H3,H4, and the four core histones can migrate spontaneously from the aggregated nucleosomes containing excess histones to free core DNA. In all cases the estimated yield of histone transfer is very high. Furthermore, the results obtained from electron microscopy, solubility, and supercoiling assays demonstrate the transfer of excess histones from oligonucleosomes to free circular DNA. However, the extent of solubilization obtained in this case is lower than that observed with core DNA as histone acceptor. Our results demonstrate that nucleosome core particles can be formed in 0.2 M NaCl by the following mechanisms: (1) transfer of excess core histones from oligonucleosomes of free DNA, (2) transfer to excess H2A,H2B and H3,H4 associated separately with oligonucleosomes to free DNA, (3) transfer to excess H2A,H2B initially associated with oligonucleosomes to DNA, followed by the reaction of the resulting DNA-(H2A,H2B) complex with oligonucleosomes containing excess H3,H4, and (4) a two-step transfer reaction similar to that indicated in (3), in which excess histones H3,H4 are transferred to DNA before the reaction with oligonucleosomes containing excess H2A,H2B. The possible biological implications of these spontaneous reactions are discussed in the context of the present knowledge of the nucleosome function.     

The role of the DMPO-hydrated electron spin adduct in DMPO-*OH spin trapping

Time-resolved in situ radiolysis ESR (electron spin resonance, equivalently EPR, electron paramagnetic resonance) studies have shown that the scavenging of radiolytically produced hydroxyl radical in nitrous oxide-saturated aqueous solutions containing 2 mM DMPO is essentially quantitative (94% of the theoretical yield) at 100 micros after the electron pulse [1]. This result appeared to conflict with earlier results using continuous cobalt-60 gamma radiolysis and hydrogen peroxide photolysis, where factors of 35 and 33% were obtained, respectively [2,3]. To investigate this discrepancy, nitrogen-saturated aqueous solutions containing 15 mM DMPO were cobalt-60 gamma irradiated (dose rate = 223 Gy/min) for periods of 0.25-6 min, and ESR absorption spectra were observed approximately 30 s after irradiation. A rapid, pseudo-first-order termination reaction of the protonated DMPO-hydrated electron adduct (DMPO-H) with DMPO-OH was observed for the first time. The rate constant for the reaction of DMPO-H with DMPO-OH is 2.44 x 10(2) (+/- 2.2 x 10(1)) M(-1) s(-1). In low-dose radiolysis experiments, this reaction lowers the observed yield of DMPO-OH to 44% of the radiation-chemical OH radical yield (G = 2.8), in good agreement with the earlier results [2,3]. In the absence of the DMPO-H radical, the DMPO-OH exhibits second-order radical termination kinetics, 2k(T) = 22 (+/- 2) M(-1) s(-1) at initial DMPO-OH concentrations > or = 13 microM, with first-order termination kinetics observed at lower concentrations, in agreement with earlier literature reports [4].     

Effect of different physico-chemical conditions on malolactic fermentation of fourLactobacillus plantarum wild strains isolated from wines of northwestern Spain

Summary Four strains ofLactobacillus plantarum, were tested for malolactic fermentation under conditions of variations in temperature, pH and SO2, L-malate and ethanol levels. When the pH value was below 3.5, malolactic fermentation was lower and was more sensitive to temperature changes. Malolactic fermentation decreased when the SO2 and ethanol levels were increased. The effects of L-malate levels were not significant.     

Effect of potassium salts and distillery effluent on carbon mineralization in soil

Distillery effluent, a rich source of potassium, is used for irrigation at many places in the world. A laboratory experiment was conducted to study the influence of potassium salts present in post-methanation distillery effluent (PME) along with two other salts, KCl and K2SO4, on mineralization of carbon in soil. PME oxidized with H2O2, raw PME, KCl and K2SO4 solutions containing K equivalent to 10%, 20%, 40% and 100% of K present in PME were added to the soil separately, maintaining four replications for each treatment and control. Addition of salts up to a certain concentration stimulated C mineralization but a decline was noticed at higher concentrations. All the levels of salts caused higher CO2 evolution than the control suggesting that the presence of K salts enhanced the microbial activity resulting in increased CO2 evolution. The influence of K2SO4 was significantly higher than KCl in stimulating C mineralization in soil. Oxidized effluent had a higher stimulating effect than inorganic salts, showing the influence of other salts accompanying K in the PME. Raw PME, which contained excess organic C, increased CO2 evolution even at the highest salt level (100% PME) signifying the effect of added C on alleviating the salt stress on microbial activity.     

pH dependency of kinetic parameters and reaction mechanism of beef liver catalase.

The pH-dependence of the kinetic parameters in H2O2 decomposition by beef liver catalase was investigated. At pH 7.0, the ternary complex (ESS) decomposition rate was about 100 times faster than ESS formation (42 microM H2O2), and the value of the Michaelis constant was 0.025 M. From ethanol competition experiments, two different proton dissociation constants of the enzyme (pKe1 = 5.0, pKes2 = 5.9) were obtained for the binding of first and second H2O2 molecules. Another pKa value (pKes1) of 4.2 was obtained from the pH dependence of overall rate constant (ko). The reaction mechanism of catalase was discussed in relation to these ionizable groups.     

Studies of the reactivity of HO2/O2- with unsaturated hydroperoxides in ethanolic solutions

A study of the reactivity of HO2/O2- with unsaturated hydroperoxides/peroxides was carried out in a stopped-flow spectrophotometer equipped with an O2--generating plasma lamp. The results show that, in 80% aqueous ethanol solution containing either 0.05 M H2SO4 (for HO2 studies) or 0.005 M KOH (for O2- studies), these oxy-radicals do not react with oleic acid hydroperoxide, linoleic acid hydroperoxide, 1-hydroperoxy-2-cyclooctene, and tert-butyl allyl peroxide. These findings are discussed in the light of conflicting evidence concerning the reaction of HO2/O2- with organic hydroperoxides/peroxides.     

3 beta-Hydroxy-5 beta-steroid dehydrogenase activity of human liver alcohol dehydrogenase is specific to gamma-subunits

Human liver alcohol dehydrogenase [alcohol:NAD+ oxidoreductase, EC 1.1.1.1 (ADH)] catalyzes the stereospecific oxidation of different 3 beta-hydroxy-5 beta-steroids with ranges of Km from 46 to 320 microM and values of kcat from 7.0 to 72 min-1, pH 8.5. Only the class I isozymes containing gamma-subunits, gamma 1 gamma 1, alpha gamma 1, beta 1 gamma 1, gamma 2 gamma 2, and beta 1 gamma 2, catalyze oxidation of these steroids with kcat/Km ratios 4-10-fold greater than those for ethanol. In marked contrast, class I alpha alpha, alpha beta 1, and beta 1 beta 1, class II, and class III isozymes do not oxidize 3 beta-hydroxy-5 beta-steroids though they readily oxidize ethanol. 1,10-Phenanthroline and 4-methylpyrazole competitively inhibit both alcohol dehydrogenase catalyzed ethanol and 3 beta-hydroxy-5 beta-steroid oxidation demonstrating that the catalysis of both types of substrates occurs at the same active site. The gamma-subunit-catalyzed oxidation of 3 beta-hydroxy-5 beta-steroids is the most specific catalytic function described thus far for any human liver alcohol dehydrogenase isozyme: there is no other isozyme that catalyzes this reaction. Testosterone, an allosteric inhibitor of ethanol oxidation specific for gamma-subunit-containing human liver ADH isozymes [M?rdh, G., Falchuk, K. H., Auld, D. S., & Vallee, B. L. (1986) Proc. Natl. Acad. Sci. U.S.A. 83, 2836-2840], also noncompetitively inhibits gamma-subunit-catalyzed sterol oxidation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Novolak PF resins prepared from phenol liquefied Cryptomeria japonica and used in manufacturing moldings

The wood of Japanese cedar (Cryptomeria japonica) was liquefied in phenol with H2SO4 and HCl as catalysts. The liquefied wood was reacted with formalin to prepare the novolak PF resin. The results showed that the reaction of liquefied Japanese cedar with formalin was an exothermic reaction, and formed a solid-like resin without extra heating. Two novolak PF resins were prepared from the liquefied wood which were identified as SF and CF that using the liquefied wood with H2SO4 and HCl as catalyst respectively. The novolak PF powder displayed thermo-melting characteristic. The resins of SF and CF had weight average molecular weight of 3638 and 3941 respectively and melting temperature of 149.4 degrees C and 127.5 degrees C respectively. Both of the novolak resins could be used to make moldings with good performance by mixing the novolak resin with wood powder, hardener and zinc stearate at the weight ratio of 60:30:10:1 and hot-pressed under 200 degrees C for 10min.     

A comparison of chemical pretreatment methods for improving saccharification of cotton stalks

The effectiveness of sulfuric acid (H(2)SO(4)), sodium hydroxide (NaOH), hydrogen peroxide (H(2)O(2)), and ozone pretreatments for conversion of cotton stalks to ethanol was investigated. Ground cotton stalks at a solid loading of 10% (w/v) were pretreated with H(2)SO(4), NaOH, and H(2)O(2) at concentrations of 0.5%, 1%, and 2% (w/v). Treatment temperatures of 90 degrees C and 121 degrees C at 15 psi were investigated for residence times of 30, 60, and 90 min. Ozone pretreatment was performed at 4 degrees C with constant sparging of stalks in water. Solids from H(2)SO(4), NaOH, and H(2)O(2) pretreatments (at 2%, 60 min, 121 degrees C/15 psi) showed significant lignin degradation and/or high sugar availability and hence were hydrolyzed by Celluclast 1.5L and Novozym 188 at 50 degrees C. Sulfuric acid pretreatment resulted in the highest xylan reduction (95.23% for 2% acid, 90 min, 121 degrees C/15 psi) but the lowest cellulose to glucose conversion during hydrolysis (23.85%). Sodium hydroxide pretreatment resulted in the highest level of delignification (65.63% for 2% NaOH, 90 min, 121 degrees C/15 psi) and cellulose conversion (60.8%). Hydrogen peroxide pretreatment resulted in significantly lower (p相似文献   

Biosorptive removal of cadmium from contaminated groundwater and industrial effluents

The cadmium removing capacity of a biosorbent Calotropis procera, a perennial wild plant, is reported here. The biomass was found to possess high uptake capacity of Cd(II). Adsorption was pH dependent and the maximum removal was obtained at two different pH i.e. pH 5.0 and 8.0. Maximum biosorption capacity in batch and column mode was found to be 40 and 50.5 mg/g. The adsorption equilibrium (> or =90% removal) was attained within 5 min irrespective of the cadmium ion concentration. Interfering ions viz. Zn(II), As(III), Fe(II), Ni(II) interfered only when their concentration was higher than the equimolar ratio. The Freundlich isotherm best explained the adsorption, yet the monolayer adsorption was also noted at lower concentrations of Cd(II). The FTIR analysis indicates the involvement of hydroxyl (-OH), alkanes (-CH), nitrite (-NO(2)), and carboxyl group (-COO) chelates in metal binding. The complete desorption of the cadmium was achieved by 0.1M H(2)SO(4) and 0.1M HCl. The C. procera based Cd(II) removal technology appears feasible.     

Steady-state kinetics of the catalase reaction in the presence of cyanide

Under carefully controlled experimental conditions, the Michaelis constant for H2O2 was measured to be 1.39 and 1.29 M in the reactions of beef erythrocyte and liver catalases, respectively. These values remained unchanged at temperatures between 1 and 26 degrees C. The turnover number of the Michaelis complex was about 2.25 X 10(7) s-1 for either enzyme at 26 degrees C. The cyanide inhibition in the catalase reaction has been reported to be noncompetitive in spite of the fact that cyanide and H2O2 compete for the same site on the catalase molecule. At high concentrations of H2O2, however, the inhibition became clearly competitive. The existence of the Michaelis complex and the anomalous features of cyanide inhibition were clearly accounted for on the basis of simple kinetic models. At H2O2 concentrations below 100 mM, the catalase reaction obeyed first order kinetics with respect to H2O2 and its apparent second order rate constant was measured to be 7.6 X 10(6) and 7.9 X 10(6) M-1 . S-1 for erythrocyte and liver catalases, respectively.     

Regulation of oxygen radical release from murine peritoneal macrophages by pharmacologic doses of PGE2

The ability of pharmacologic doses of PGE2 to alter the release of superoxide (O2-) and hydrogen peroxide (H2O2) from elicited peritoneal macrophages (M theta) was studied. Twice-daily administration of 200 or 100 micrograms of PGE2 to mice during accumulation of peritoneal M theta resulted in a significant reduction in M theta recovery and in the triggered release of H2O2, but not O2-. Cultivation of elicited M theta from normal mice with concentrations of PGE2 in excess of 10(-7) M for 24-48 h resulted in a significant reduction in the triggered release of H2O2, but not O2-. Cultivation for shorter periods of time or with lower concentrations of PGE2 failed to alter H2O2 release. This effect of PGE2 was reproduced by the phosphodiesterase inhibitor theophylline. The ability of PGE2 to inhibit H2O2 release in the presence of normal production of O2- was not prevented by the addition of superoxide dismutase. Cultivation of peritoneal M theta with 10(-5) M PGE2 for 48 h failed to increase intracellular catalase, although increased H2O2 scavenger activity was demonstrated. The inhibition of extracellular release of H2O2, but not O2-, by pharmacologic doses of PGE2 may be one mechanism for the anti-inflammatory action of this compound.