Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:1.6.99.6 (NADPH oxidase)
10,295 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Hydroethidine (HE) and 2',7'-dichlorofluorescin (DCFH) were used for the flow cytometric measurement of reactive oxygen metabolites in leukocytes. Hydroethidine and DCFH were both rapidly oxidized in a cell-free cuvette assay to ethidium bromide (EB) and 2',7'-dichlorofluorescein (DCF) by H2O2 and peroxidase, but not by H2O2 alone, while only HE was oxidized by KO2, a source of O2-. Quiescent lymphocytes, monocytes, and neutrophils spontaneously oxidized HE to EB, while DCFH was only oxidized to a low degree. Neutrophils increased 6.9-fold in EB red fluorescence and 12.5-fold in DCF green fluorescence during the respiratory burst induced by phorbol 12-myristate 13-acetate or 6.1-fold and 4.7-fold, respectively, during the respiratory burst induced by Escherichia coli bacteria. The HE or DCFH oxidation during the respiratory burst, unlike the spontaneous HE oxidation, was not inhibitable by 10 mM NaNe indicating a non-mitochondrial source of cellular oxidants during the respiratory burst such as NADPH oxidase, which produces O2-. The oxidation of DCFH, but not of HE, was decreased in stimulated neutrophils, which were simultaneously loaded with HE and DCFH. Intracellular DCFH oxidation induced by incubation of resting neutrophils with extracellular H2O2 was not influenced by the presence of HE. This indicates that HE is oxidized at an earlier step in the reactive oxygen metabolism of neutrophils than DCFH, i.e., by early oxygen metabolites like O2-, while DCFH is oxidized in part by H2O2 and phagosomal peroxidases. The differential oxidation of HE and DCFH during simultaneous cellular staining permits the analysis of up to three functionally different neutrophil populations in septic patients. This is of interest for the determination of disease-related alterations of oxygen metabolism in quiescent and stimulated leukocytes.
...
PMID:Flow cytometric analysis of respiratory burst activity in phagocytes with hydroethidine and 2',7'-dichlorofluorescin. 215 14

The plasma membrane fraction from porcine thyroid is known to exhibit an NADPH-dependent production of hydrogen peroxide (H2O2), which is utilized for the oxidative biosynthesis of thyroid hormones catalyzed by thyroid peroxidase. The H2O2 formation is cyanide-insensitive, ATP-activatable, and Ca2+-dependent (Nakamura, Y., Ogihara, S., and Ohtaki, S. (1987) J. Biochem. (Tokyo) 102, 1121-1132). It remains unknown, however, whether H2O2 is produced directly from molecular oxygen (O2) or formed via dismutation of superoxide anion (O2-). We therefore attempted to analyze the mechanism of H2O2 formation by utilizing a new method for the simultaneous measurement of O2- and H2O2, in which diacetyldeuteroheme-substituted horseradish peroxidase was employed as the trapping agent for both oxygen metabolites. When NADPH was incubated with the membrane fraction in the presence of the heme-substituted peroxidase, a massive O2 consumption was observed together with the formation of compound III, and O2- adduct of the peroxidase. The amounts of compound III formed and O2 consumed were stoichiometric with each other, while formation of compound II, an indicative of H2O2, was not observed during the reaction. On the other hand, when an excess amount of superoxide dismutase was included in the reaction mixture, compound II was produced with complete suppression of the compound III formation. NADH minimally supported both O2 consumption and formation of compound III or II. These results indicate that the NADPH oxidase in the plasma membrane of thyroid produces O2- as the primary metabolite of O2 and hence that H2O2 required for the thyroid hormone synthesis provided through the dismutation of O2-.
...
PMID:Superoxide anion is the initial product in the hydrogen peroxide formation catalyzed by NADPH oxidase in porcine thyroid plasma membrane. 253 59

When suddenly exposed to air the growth of the obligate anaerobic bacterium of the bacteroidaceae type, strain B6, continues for a few hours before coming to a complete stop. When air is shut off soon after growth has ceased, the organism is able to reestablish anaerobic conditions due to an ability to reduce O2, and resumes normal growth after another few hours. The O2 reducing ability of the organism is due to the presence in the cells of a particle-bound NADH oxidase, a soluble NADPH oxidase and a soluble pyruvate oxidase. The two pyridine nucleotide oxidases reduce O2 to H2O2, the pyruvate oxidase reduces O2 to H2O. Catalase and peroxidase were not detected in anaerobically grown cells. Kinetic studies with cell-free extracts showed that the pyruvate oxidase had a considerably greater affinity (smaller Km) for O2 and capacity (higher Vmax) for O2 reduction than the two other oxidases. It is postulated that the pyruvate oxidase acts as a scavenger for O2, leading to the non-toxic reduction product H2O, and thus functions as a defense mechanism against oxygen toxicity when the organism is exposed to aerobic condition.
...
PMID:Oxygen activation and defence against oxygen toxicity in a psychrophilic Bacteroidaceae. 271 28

A sensitive luminol-dependent chemiluminescence assay for H2O2 was developed for the indirect determination of the transient changes in NADPH oxidase activity associated with the respiratory burst of human neutrophils. A relatively large, controlled amount of horseradish peroxidase was used in combination with added luminol to rapidly remove and simultaneously detect H2O2 as soon as it is formed, thus preventing its accumulation during burst activity and minimizing the effects of side reactions. Cell-derived myeloperoxidase and possibly catalase were inhibited with 90 microM sodium azide to maintain the total catalytic activity toward H2O2 at a constant level. Chemiluminescence measurements of the respiratory burst activity of human neutrophils stimulated with N-formyl-Met-Leu-Phe (fMLP) were in good agreement with measurements made using an established fluorometric assay based on similar principles (P. A. Hyslop and L. A. Sklar (1984) Anal. Biochem. 141, 280-286). In contrast to fluorometry, the chemiluminescence progress curves reflect the instantaneous rather than the integrated levels of H2O2 at any time and are thus a more direct measure of the activity of the NADPH oxidase. This advantage, as well as higher signal-to-noise ratios and greater inherent sensitivity, distinguishes chemiluminescence as a means of following burst activity. The onset of fMLP-stimulated H2O2 generation was detectable by chemiluminescence within 2 s of stimulation (as opposed to more than double this time by fluorometry), showing that high sensitivity is an important consideration in evaluating respiratory burst kinetics. In contrast to fMLP stimulation, longer and concentration-dependent onset times were observed when phorbol myristate acetate was used as a stimulus.
...
PMID:Chemiluminescence detection of H2O2 produced by human neutrophils during the respiratory burst. 342 6

In thyroid gland, iodination takes place on the apical plasma membrane and requires the presence of the thyroid peroxidase and H2O2 generating system. H2O2 generation and NBT (nitro blue tetrazolium) reductase activity (both of which are NADPH-dependent) as well as peroxidase activity were compared for their respective orientations in membrane vesicles. The possible role of NADPH-NBT reductase activity in H2O2 generation was also examined. Results favor the conclusion that thyroid peroxidase is oriented towards the luminal side of the vesicles, whereas the NADPH site of NADPH oxidase-dependent H2O2 generation is located on the external side of the same or of different vesicles. Furthermore, it is shown that different NADPH-NBT reductase activities are present on both the outer and inner surfaces of the membrane vesicles, and that none of these activities is able to produce either H2O2 or O-2. The idea that a multi-component complex is involved in H2O2 generation is discussed, and a model is proposed which takes into account the possible spatial separation of the thyroid peroxidase site from the NADPH site of this H2O2 generation system on the apical membrane of the thyrocyte.
...
PMID:Relation between thyroid peroxidase, H2O2 generating system and NADPH-dependent reductase activities in thyroid particulate fractions. 401 97

Phagocytosis by rabbit alveolar macrophages (AM) is accompanied by increases in O(2) consumption, glucose oxidation, and H(2)O(2) formation. Two aspects of the interrelations between these metabolic features of phagocytosis have been studied.First, the following evidence indicates that glutathione, glutathione reductase, and peroxidase serve as a cytoplasmic shuttle between H(2)O(2) and NADPH-dependent glucose oxidation: (a) AM contain 5.9 mmumoles of reduced glutathione per 10(6) cells and exhibit glutathione peroxidase and NADPH-specific glutathione reductase activity; (b) oxidized glutathione potentiates NADP stimulation of glucose oxidation; (c) an artificial H(2)O(2)-generating system stimulates glucose oxidation; (d) the cell penetrating thiol inhibitor, N-ethylmaleimide diminishes glucose oxidation. This effect largely depends on inhibition of the glutathione system rather than on inhibition of either H(2)O(2) formation or enzymes directly subserving glucose oxidation.Second, three potential H(2)O(2)-generating oxidases have been sought. No cyanide-insensitive NADH or NADPH oxidase activity could be detected. D-amino acid oxidase activity was 0.48 +/-0.07 U/10(6) cells with D-alanine as substrate.
...
PMID:Glutathione-dependent peroxidative metabolism in the alveolar macrophage. 439 62

This article gives a synopsis of the inflammatory reactions as well as its mediators under special consideration of the efferent part of the reaction. There is no doubt that histamine, complement, and the kinin system play an essential role; arachidonic acid (eicosatetraenic acid) and its metabolites, however, have gained comparable significance: prostaglandines, prostacyclines, and thromboxanes as metabolites of the cyclo-oxygenase, the leucotrienes SRS-A (slow reacting substances of anaphylaxis) and ECF (eosinophilic chemotactic factor) mediated via lipoxygenase. Moreover, oxygen and its metabolites hydrogen peroxide (H2O2), peroxide radicals (O-2), and hydroxyl radicals (.OH) as well as activated oxygen (singulett oxygen (1O2) play an important part with all aerobic living organisms. Inborn enzyme deficiency of the oxygen metabolism such as NADPH oxidase or cytochrome b-245 deficiency lead to chronic septic granulomatosis. The disease is characterized by reduced resistence against infections, decreased phagocytosis, insufficient killing of bacteria by leucocytes, and diminished oxygen burst. Thus the underlying enzyme deficiency leads to reduced formation of peroxide radicals frequently causing infections with septic complications. On the other hand, increased formation or reduced degradation of peroxide radicals may result in pathological reactions like chromosomal alterations, lipidperoxidation or oxidation of sulph-hydryl groups. The fact that increased peroxide radical formation may cause inflammation or chromosomal aberration is of importance with regard to the pathogenesis of several chronic inflammatory diseases of unknown etiology, such as systemic scleroderma or lupus erythematodes. The enzyme superoxide dismutase (SOD) converts peroxide radicals (O-2) into hydrogen peroxide (H2O2) which can be inactivated by catalase or peroxidase. Consequently, treatment with SOD may have an effective influence on chronic inflammatory dermatoses of unknown pathogenesis.
...
PMID:[Biochemical aspects of the inflammatory reaction - with special reference to oxygen]. 666 95

This laboratory has recently reported that, in a reconstituted enzyme system containing alcohol-induced isozyme 3a of liver microsomal cytochrome P-450, the sum of acetaldehyde generated by the monooxygenation of ethanol and of hydrogen peroxide produced by the NADPH oxidase activity is inadequate to account for the O2 and NADPH consumed. Studies on the stoichiometry have revealed the occurrence of an additional reaction involving an overall 4-electron transfer to molecular oxygen which is presumed to yield water: O2 + 2 NADPH + 2H+----2 H2O + 2 NADP+. The occurrence of a peroxidase reaction in which free H2O2 is reduced to water by NADPH was ruled out. When the 4-electron oxidase activity is taken into account, measurements of NADPH oxidation and O2 consumption are in accord with the amounts of products formed in the presence of various P-450 isozymes, either in the absence or presence of typical substrates, including those which undergo hydroxylation, N- or O-demethylation, or oxidation of hydroxymethyl to aldehyde groups. Of the substrates examined, some had no effect on the oxidase reaction yielding hydrogen peroxide or the 4-electron oxidase reaction, some were inhibitory, and some were stimulatory, but the same substrate did not necessarily have the same effect on the two reactions.
...
PMID:On the stoichiometry of the oxidase and monooxygenase reactions catalyzed by liver microsomal cytochrome P-450. Products of oxygen reduction. 672 72

The effects of Zn, Mg, Cr, Cu, and Mn aspartates, their commercial formulation Inzolen, and the individual commercial medicine Unizinc, on oxygen radical production by enzymes [xanthine oxidase, horseradish peroxidase, and reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase] and phagocytic cells (human blood leukocytes) have been studied. The formation of oxygen radicals was measured by luminol- and lucigenin-amplified chemiluminescence and by the reduction of cytochrome c. All these compounds (excluding Cr aspartate) turn out to be inhibitors of oxygen radical formation in the systems studied (excluding horseradish peroxidase). Their inhibitory activities were a consequence of both the scavenging of free radicals and the inhibition of xanthine oxidase and NADPH oxidase activities. As expected, the most active free-radical scavengers were transition metal Cu and Mn aspartates, which mimicked the activities of copper-zinc and manganese dismutases. However, surprisingly non-transition metal Zn and Mg aspartates were also able to scavenge oxygen radicals. It was suggested that the scavenging activities of Zn and Mg aspartates may be explained by affecting the rate of spontaneous dismutation of the superoxide ion. In addition, it was found that Zn aspartate is an efficient inhibitor of the formation of the most reactive hydroxyl radicals. These antioxidant properties of Zn aspartate make it important in medicine for the prevention and treatment of free radical pathologies.
...
PMID:Study of antioxidant properties of metal aspartates. 774 Dec 42

This retrospective reviews the methodology we have developed over several decades for detecting reactive oxygen species (ROS), using the activated polymorphonuclear leukocyte (PMN) as the paradigm of a cell which vigorously generates ROS through activation of NADPH oxidase. In the seventies, the sites of ROS generation by PMN were not clear from biochemical data, and we sought to develop new methods for the cytochemical localization of O2.-, H2O2, and the H2O2-myeloperoxidase (MPO)-halide system. The H2O2-MPO-halide system in phagocytosing cells was localized at the fine structural level by our development of 3,3'-diaminobenzidine (DAB) as a cytochemical probe for detecting peroxidase activities. Using DAB and exogenous H2O2, we confirmed that azurophil granules discharged MPO into the phagosome, and using particles coated with DAB and relying on endogenous H2O2 to yield oxidized DAB, H2O2 was localized to phagolysosomes. The subcellular sites of H2O2 generation were shown using cerium ions which react with H2O2 and precipitate electron opaque cerium perhydroxides (Ce(OH)2OOH and Ce(OH)3OOH). The results suggested that NADPH oxidase is associated with the plasma lemma, and that the enzyme enters the phagosome along with the invaginating plasmalemma, accounting for the presence of H2O2 in the phagosome. As O2.- is the major product of NADPH oxidase, its detection was of some importance. Based on the concept that O2.- oxidizes Mn2+ to Mn3+, and Mn3+ oxidizes DAB, a medium containing DAB-Mn2+ was used to localize sites of O2.- production in stimulated PMN. The localizations were, as expected, similar to those for H2O2. These techniques have been of considerable usefulness and in general provide the foundation for cytochemistry of ROS in other systems.
...
PMID:Robert Feulgen Lecture 1994. Cytochemistry and reactive oxygen species: a retrospective. 781 66


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---