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PubMed1972

The relationship of the peroxidative indoleacetic Acid oxidase system to in vivo ethylene synthesis in cotton.

Since peroxidase and manganese have been implicated in both auxin destruction and ethylene production, the effect of auxins and high tissue levels of manganese on the peroxidative indoleacetic acid oxidase system and the internal level of ethylene was determined in cotton (Gossypium hirsutum L. cv. Watson GL-7). The highest level of manganese tested produced manganese toxicity symptoms, including necrotic lesions, accompanied by an increase in internal ethylene levels at about 15 days after treatment initiation. Statistically significant increases in indoleacetic acid oxidase and peroxidase activity were first observed 2 days later and were paralleled by tissue manganese levels above 7.4 milligrams per gram dry weight and internal ethylene levels of 0.77 microliters per liter air. Eight hours after application of 2,4-dichlorophenoxyacetic acid or indoleacetic acid, the internal levels of ethylene were increased to above 6.6 microliters per liter air in cotton plants, and levels of this magnitude were maintained for a 72-hour period of observation. Modification of peroxidase and indoleacetic acid oxidase activity in auxintreated plants definitely occurred well after the elevation of internal ethylene levels. While ethylene levels and indoleacetic acid oxidase activity were increased by both experimental approaches, the earlier appearance of increased ethylene indicates that the peroxidative indoleacetic acid oxidase system in cotton is not involved in ethylene synthesis or that this enzyme is not the rate-limiting factor when ethylene synthesis is increased. Ethylene, as well as auxin destruction, may be involved in some of the long term plant responses to toxic levels of manganese. The findings also suggest that auxin-induced ethylene may play a role in the elevation of peroxidase and indoleacetic acid oxidase activity eventually seen in extracts of plants treated with auxins. The data support the assumption that the enzymatic portion of the indoleacetic acid oxidase system in cotton is a peroxidase.

Journal Article↗
PubMed1998

Improved operational stability of biosensors based on enzyme-polyelectrolyte complex adsorbed into a porous carbon electrode.

A novel porous active carbon is utilized in order to adsorb the diethylaminoethyl-dextran (DEAE-dextran)-enzyme stabilized complexes, for the construction of highly stable biosensors. The interaction of DEAE-dextran with the examined enzymes increases dramatically the operational stabilization of the sensors, without adverse effects on the enzyme activity. At the same time, the porous active carbon allows for high enzyme loading, good electrical contact and low resistance throughout the sensing element. Glucose oxidase and horseradish peroxidase are used as model enzymes in this study to construct biosensors, with very good reproducibility (less than 5% RSD). As a result, the glucose sensor exhibits very long operational stability (over a period of 5 months), while the hydrogen peroxide sensor retains its initial activity after several weeks.

Biosensing Techniques↗
PubMed1999

Recent advances in understanding the origin of the apoplastic oxidative burst in plant cells.

The origin of the oxidative burst during plant-pathogen interactions remains controversial. A number of possibilities have been identified, which involve the protoplast, plasmalemma or apoplast. The apoplastic production of H2O2 requires three components, an extracellular peroxidase, ion fluxes leading to extracellular alkalinisation and release of a substrate. Fatty acids are the major compounds that appear in the apoplast following elicitation, which can activate H2O2 production by peroxidases in vitro. However, the reaction with peroxidases appears to be novel and is uncharacterised at present. The apoplastic mechanism also cannot be readily distinguished from the operation of a plasma membrane NADPH oxidase system by the use of the inhibitors diphenylene iodonium and N,N diethyl-dithiocarbamate since it is also inhibited by these. These inhibitors have often in the past been used to define the involvement of the latter in the oxidative burst. In common with the NADPH oxidase system, the peroxidase responsible has been cloned but unlike the NADPH oxidase it has been shown to function in vitro to generate H2O2. In vivo studies of the oxidative burst have shown that the alkalinisation is essential and the underlying ion fluxes may be regulated by cAMP. Calcium fluxes are also essential. Although the oxidative activity of peroxidase requires calcium the fluxes have obvious other function. These may include activation of release of substrate and through the activation of a CDPK, regulation of enzymes involved in phytoalexin and cell wall phenolic production such as PAL.

Calcium↗
PubMed1985

Cytochemical localization of peroxidase and hydrogen-peroxide-producing NAD(P)H-oxidase in thyroid follicular cells of propylthiouracil-treated rats.

The distribution of endogenous peroxidase and hydrogen-peroxide-producing NAD(P)H-oxidase, which are essential enzymes for the iodination of thyroglobulin, was cytochemically determined in the thyroid follicular cells of propylthiouracil (PTU)-treated rats. Peroxidase activity was determined using the diaminobenzidine technique. The presence of NAD(P)H-oxidase was determined using H2O2 generated by the enzyme; the reaction requires NAD(P)H as a substrate and cerous ions for the formation of an electron-dense precipitate. Peroxidase activity was found in the developed rough endoplasmic reticulum (rER) and Golgi apparatus, but it was also associated with the apical plasma membrane; NAD(P)H-oxidase activity was localized on the apical plasma membrane. The presence of both enzymes on the apical plasma membrane implies that the iodination of thyroglobulin occurs at the apical surface of the follicular cell in the TSH-stimulated state which follows PTU treatment.

Animals↗
PubMed2000

A three-cascaded-enzymes biosensor to determine lactose concentration in raw milk.

The increasing demand for on-line measurement of milk composition directs science and industry to search for practical solutions, and biosensors may be a possibility. The specific objective of this work was to develop an electrochemical biosensor to determine lactose concentration in fresh raw milk. The sensor is based on serial reactions of three enzymes--beta-galactosidase, glucose oxidase, and horseradish peroxidase--immobilized on a glassy carbon electrode. The sequential enzymatic reactions increase the selectivity and sensitivity of the sensor. The sensor requires dilution of the raw milk and the addition of 5-aminosalicylic acid. Lactose concentrations in raw milk measured by the sensor were in good agreement with those measured by a reference laboratory using infrared technology. The results were obtained in milk samples that varied in fat and protein composition. From the results, we conclude that an electrochemical biosensor for determination of lactose concentration in fresh raw milk can be developed, and that the biosensor presented in this study maintained the qualities required for further development into an online sensor in the milking parlor.

Animals↗
PubMed1989

A colorimetric assay for the measurement of D-glucose consumption by cultured cells.

A colorimetric method is described for measuring glucose consumption by tissue culture cells. This procedure, which utilizes the coupled activities of glucose oxidase and horseradish peroxidase, is insensitive to the spectral interferences caused by the phenol red and sera present in most tissue culture media. The spectral properties (absorbance maxima and apparent absorption coefficients) and stability of a large number of chromogenic horseradish peroxidase substrates were surveyed for their ability to perform in an assay for glucose in the presence of phenol red and sera components. One of these chromophores, the product of an oxidative couple between 4-aminoantipyrine and N-ethyl-N-sulfopropyl-m-toluidine, was subsequently used to develop a fixed time assay for glucose in media samples. The assay required only 10 microliters of media in a 1-ml assay volume; reproducibility studies showed variabilities of less than 5% in the assay of a single sample, and values obtained in glucose analyses correlated well with those obtained using commercially available test kits. The assay was used to study the rate of glucose consumption in two different cell types, bovine corneal endothelial cells and human diploid fibroblasts.

Animals↗
PubMed1988

Replacements of lysine 32 in yeast cytochrome c. Effects on the binding and reactivity with physiological partners.

Lysine 32 has been previously implicated by chemical modification and modeling studies as a key component of the domain which controls recognition and binding of cytochrome c to its physiological partners, e.g. cytochrome b2, cytochrome c peroxidase, and cytochrome oxidase. In order to quantitate the importance of this residue, we have investigated the role of Lys-32 in the reactivity of cytochrome c in redox reactions in vitro and in vivo with protein partners by using a series of altered forms of iso-1-cytochrome c from the yeast Saccharomyces cerevisiae in which Lys-32 is replaced by Leu-32, Gln-32, Trp-32, and Tyr-32. Leu-32 and Gln-32 represent substitutions which change charge without seriously affecting the steric bulk of the side chain or the stability of the protein. For the Leu-32- and Gln-32-altered proteins, steady state kinetic studies with cytochrome c peroxidase, cytochrome b2, and cytochrome oxidase showed that neither of the steady state kinetic parameters, Km nor Vmax, were substantially modified by mutation. Studies of single turnover kinetics with a small molecule (ascorbate) or within bound complexes with either cytochrome b5 or cytochrome c peroxidase demonstrated that redox kinetics are only slightly affected by these substitutions. NMR experiments demonstrated that the Gln-32-altered protein can still bind strongly to a physiological partner, cytochrome c peroxidase. Growth in lactate medium demonstrated that the activity in vivo compared with the normal value was reduced to only 85% with the Gln-32- and Leu-32-altered proteins and to 65% with the Trp-32- and Tyr-32-altered proteins. These findings suggest that the evolutionary invariance of Lys-32 reflects only small quantitative changes in the binding and reactivity of cytochrome c.

Alleles↗
PubMed1998

Stimulated polymorphonuclear leukocytes in vaginal secretions from patients with preterm labor.

The purpose of this study was to examine evidence for the presence of activated vaginal leukocytes in women with preterm labor. Vaginal polymorphonuclear leukocytes from 7 patients in preterm labor (24-32 weeks of gestation) as well as from 7 control women with uncomplicated pregnancy were analyzed morphologically using transmission electron microscopy. Peroxidase and NADPH oxidase cytochemistry was also performed. Viable leukocytes were abundant in patients in preterm labor. Phagosomes, phagocytosis of bacteria, attachment of primary granules to the phagosomal membrane, and cell surface projections were observed in the vaginal leukocytes but not in the peripheral blood leukocytes. Peroxidase activity was visible on the cell surface, the phagosomal membrane, and the primary granules. NADPH oxidase activity was demonstrated on the cell surface of leukocytes. Morphological and cytochemical features indicated that vaginal polymorphonuclear leukocytes were stimulated in situ. Such stimulated leukocytes may play a role in the pathogenesis or pathophysiology of preterm labor.

Cell Survival↗
PubMed2001

Effect of temperature on enzymatic and physiological factors related to chilling injury in carambola fruit (Averrhoa carambola L.).

Three groups of carambola fruits (Averrhoa carambola L.) were stored at 2 and 10 degrees C (85-90% relative humidity). The major physicochemical, physiological, and enzymatic responses of fruit were measured in each group over a 30-day period: chilling injury index (CII), decay (%), intracuticular waxes, cuticle permeability, pulp firmness, weight loss, sucrose, fructose and glucose contents, ion electrolyte leakage in pulp (%), ethylene and carbon dioxide production rates, and the activities of peroxidase (POD), polyphenol oxidase (PPO), and phenylalanine ammonia-lyase (PAL) enzymes. CII values were statistically different at 2 and 10 degrees C, showing high significance with respect to sucrose content and weight loss (P < 0.05). Chilling injury included darkened ribs and skin desiccation. According to the CI symptom development, a possible relationship of POD and PPO activities was found at 2 degrees C. A significant sucrose content increase was observed at 10 degrees C. CI symptoms were associated with POD and PAL activities.

Carbon Dioxide↗
PubMed1988

Serotonin metabolism and other biochemical parameters in infantile autism. A controlled study of 22 autistic children.

The serotonin metabolism was extensively studied in 22 couples of autistic children and age- and sex-matched controls. Histamine, calcium, and uric acid were also measured in urine and whole blood or plasma. Autistics and controls did not differ in histamine, and only minor changes were noticed in calcium content. According to previous reports, serotonin levels were often, but not always, elevated in the blood of autistic children. Based on data including urinary serotonin and 5-hydroxyindoleacetic acid, platelet serotonin uptake and efflux, platelet monoamine oxidase and glutathione peroxidase activities, and uric acid and plasma tryptophan, the origin(s) of such hyperserotonemia in autism appear(s) to be of metabolic origin, i.e., a decreased catabolism and/or an increased biosynthesis of serotonin.

Adolescent↗
PubMed1990

[Comparison of presence of ascorbic acid and the appearance of ascorbate peroxidase activity in embryos of Avena sativa L].

Avena sativa L. grains are devoid of ascorbic acid (AA) and of oxidative enzymes (AA oxidase and AA peroxidase), while both reducing enzymes (AFR reductase and DHA reductase) are present. AA biosynthesis in the embryos starts after 12-14 hours of germination and at the same time AA peroxidase activity is detectable. During the following 14 hours the AA peroxidase activity rises up to 28 nmoles/AA oxidated/min/mg/prot. Incubation of Avena embryos with GL (the last precursor of AA according to the Isherwood biosynthetic pathway), results in both earlier AA biosynthesis and enhanced AA peroxidase activity. A 4 hour treatment is enough to induce AA synthesis and AA peroxidase elicitation. These data suggest that the development of AA peroxidase activity is controlled by AA, but they are not sufficient to clarify how that happens. Probably AA induces the synthesis of specific m-RNAs or activates enzymic precursors present in the embryos but still not working.

Ascorbate Peroxidases↗
PubMed1983

Ligand binding to heme proteins. An evaluation of distal effects.

The O2, CO, and alkyl isocyanide-binding properties of a variety of vertebrate and invertebrate heme proteins have been compared in detail to those of protoheme mono-3-(1-imidazoyl)-propylamide monomethyl ester in aqueous suspensions of soap micelles. The proteins examined include: cytochrome P-450cam from Pseudomonas putida, beef heart cytochrome c oxidase, yeast cytochrome c peroxidase, alpha and beta subunits of human hemoglobin, sheep hemoglobin, carp hemoglobin, sperm whale myoglobin, horse heart myoglobin, a monomeric hemoglobin from Glycera dibranchiata, erythrocruorin from Chironomusthummii, soybean leghemoglobin, and several hemoglobins that lack distal histidines. The smallest bimolecular rates were observed for cytochrome P-450 containing bound camphor, cytochrome c oxidase, and cytochrome c peroxidase. In the case of P-450, the extremely low isonitrile binding rates (approximately 1 M-1 S-1 at 20 degrees C) are due to steric exclusion by bound camphor molecules. For the oxidase and peroxidase, inhibition of CO and isonitrile binding appears to be due to the polar nature of the active sites. In the cases of animal hemoglobins and myoglobins, the sixth coordination positions appear to be designed to accommodate diatomic molecules with no steric hindrance by distal protein residues. Protein resistance to the diffusion of CO and O2 does not limit the observed association rate constants. In contrast, ligands containing three or more atoms are sterically hindered both in their final bound positions and during diffusion to the active site. The magnitude of this hindrance (greater than or equal to 2 kcal/mol) exhibits a complex dependence on ligand size and shape. The most important protein residue appears to be His E7. In addition to restricting the size of the sixth coordination position, the distal histidine is also capable of forming a hydrogen bond with bound oxygen molecules. The strength of this hydrogen bond was estimated to be -2 and -1 kcal/mol for mammalian myoglobins and hemoglobins, respectively, and accounts for the smaller CO/O2 partition constants (M values) observed for these proteins in comparison to the constants observed for pentacoordinate model heme compounds.

Animals↗
PubMed1998

Rapid alcohol determination in plasma and urine by column liquid chromatography with biosensor detection.

An enzyme based amperometric biosensor used as a selective and sensitive detection unit in column liquid chromatography for the determination of ethanol and methanol in biological fluids such as plasma and urine is described. The reagentless enzyme electrode is based on the co-immobilisation of alcohol oxidase and horseradish peroxidase in carbon paste. The selectivity of the biosensor was found to vary when four various alcohol oxidase enzyme preparations from Candida boidinii, Pichia pastoris, and Hansenula polymorpha were used in the biosensors described. High sensitivity could be obtained for a number of alcohols, organic acids, and aldehydes. Optimisation regarding the sensitivity and selectivity of the four alcohol oxidase co-immobilised biosensors are outlined. A fast and reliable liquid chromatographic separation system with a PLRP-S polymer based separation column used with a phosphate buffer as the mobile phase was optimised using the best biosensor which was based on alcohol oxidase from P. pastoris and which showed the highest turnover rate for alcohols, as the detector for the determination of ethanol and methanol in human urine and plasma samples. The selectivity and stability of the biosensor were retained by working at an applied potential of -50 mV versus Ag/AgCl, the optimal operational potential, and by the casting of a protective membrane on the electrode surface. High selectivity of the enzyme electrode was also found towards other easily oxidisable interfering species normally present in biological fluids. It was found that stable and reliable determinations of ethanol and methanol in plasma and urine could be performed with only a simple dilution and centrifugation step prior to injection into the liquid chromatographic system. An analysis time of 4 min was required for the assay, with a sample throughput of 13 samples h(-1).

Acids↗
PubMed1990

Nitrogen-deregulated mutants of Phanerochaete chrysosporium--a lignin-degrading basidiomycete.

Two nitrogen-deregulated mutants of Phanerochaete chrysosporium, der8-2 and der8-5, were isolated by subjecting wild type conidia to gamma irradiation, plating on Poly-R medium containing high levels of nitrogen, and identifying colonies that are able to decolorize Poly-R. The mutants showed high levels of ligninolytic activity (14C-synthetic lignin----14CO2), and lignin peroxidase, manganese peroxidase and glucose oxidase activities in both low nitrogen (2.4 mM) and high nitrogen (24 mM) media. The wild type on the other hand displayed these activities in low nitrogen medium but showed little or no activities in high nitrogen medium. Fast protein liquid chromatographic analyses showed that the wild type as well as the der mutants produce three major lignin peroxidase peaks (designated L1, L2 and L3) with lignin peroxidase activity in low nitrogen medium. Furthermore, in low nitrogen medium, mutant der8-5 produced up to fourfold greater lignin peroxidase activity than that produced by the wild type. In high nitrogen medium, the wild type produced no detectable lignin peroxidase peaks whereas the mutants produced peaks L1 and L2, but not L3, and a new lignin peroxidase protein peak designated LN. Mutants der8-2 and der8-5 also produced high levels of glucose oxidase, an enzyme known to be associated with secondary metabolism and an important source of H2O2 in ligninolytic cultures, both in low and high nitrogen media. In contrast, the wild type produced high levels of glucose oxidase in low nitrogen medium and only trace amounts of this enzyme in high nitrogen medium.(ABSTRACT TRUNCATED AT 250 WORDS)

Basidiomycota↗
PubMed1973

Specific inhibitors of ammonia oxidation in Nitrosomonas.

The following compounds or treatments have been shown to inhibit the oxidation of ammonia, but not the oxidation of hydroxylamine in cells of Nitrosomonas: (i) metal-binding agents such as allylthiourea or potassium cyanide; (ii) compounds such as SKF 525 which interact with cytochrome P-450 of mammalian microsomes; (iii) carbon monoxide; (iv) inhibitors of catalase, peroxidase, and amine oxidases such as thiosemicarbazide, ethylxanthate, and iproniazid, respectively; (v) uncouplers of oxidative phosphorylation such as m-chlorocarbonylcyanidephenylhydrazone; (vi) electron acceptors such as phenazine methosulfate; (vii) compounds such as methanol or N(2)O which react with free radicals; and (viii) illumination with 420 lux (5,000 foot candles) of light.

Alcohols↗
PubMed1989

Injurious effect of the eosinophil peroxide-hydrogen peroxide-halide system and major basic protein on human nasal epithelium in vitro.

Tissue injury is observed in allergic and nonallergic eosinophilic rhinitis, but the mechanism of this injury is unclear. Because eosinophils are prominent in biopsy specimens in these conditions, we hypothesized that they may participate in the injury process. Initially, we developed techniques to isolate and purify human nasal epithelial cells from turbinate biopsies to use as target cells for eosinophil granule products. Primary cultures from explants were characterized by electron microscopy and indirect immunofluorescence with a panel of primary monoclonal and polyclonal antibodies. These studies revealed the homogeneity of the cells and confirmed their epithelial nature. Cultured nasal epithelial cells were then exposed to either purified human eosinophil peroxidase, bromide, and glucose plus glucose oxidase, as a continuous source of hydrogen peroxide, or eosinophil major basic protein. Neither eosinophil peroxidase alone nor glucose plus glucose oxidase in the absence of eosinophil peroxidase were injurious, but the combined addition of eosinophil peroxidase, glucose/glucose oxidase, and bromide produced marked target cell lysis. This effect was time- and eosinophil peroxidase dose-dependent. Catalase and azide significantly inhibited the lysis of these cells, suggesting the eosinophil peroxidase-catalyzed products of halide oxidation mediated this form of injury. The addition of purified human eosinophil major basic protein also caused dose- and time-dependent lysis of the nasal epithelial cells but required longer incubation periods to effect injury. We hypothesize that the eosinophil peroxidase-hydrogen peroxide-halide system and major basic protein may injure the nasal epithelium in inflammatory conditions such as allergic and nonallergic eosinophilic rhinitis.

Blood Proteins↗