Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.6.3.1 (NADPH oxidase)
 11,281 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The oxidative metabolism of rabbit alveolar macrophages (A-MO) was compared with that of rabbit polymorphonuclear leukocytes (PMN) with respect to H2O2 generation by intact cells or subcellular fractions. Rabbit PMN exhibited an increase in the oxygen uptake and a marked release of H2O2 upon addition of heat-killed E. coli in the presence and absence of opsonin. However, rabbit A-MO exhibited an increase in the oxygen uptake upon addition of E. coli only in the presence of anti-E. coli serum as an opsonin, whereas a very small amount of H2O2 release was observed during ingestion of the opsonized E. coli. The generation of O2- and H2O2 by a granule-rich fraction isolated from phagocytosing PMN was larger than that by a similar fraction isolated from resting PMN. However, there was no significant difference in O2- and H2O2 generation by the granule fractions between phagocytosing and resting A-MO in the presence of either NADH or NADPH. In contrast to the granule fraction of rabbit PMN, the O2- and H2O2 generating activities in the A-MO granule fraction were higher in the presence of NADH than in the presence of NADPH. The rates of NADH and NADPH oxidation by both A-MO and PMN granule fractions were measured with and without addition of Mn2+ to the assay medium. The effect of Mn2+ on the NAD(P)H oxidase was found to differ between rabbit A-MO and PMN.
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PMID:Comparative studies on alveolar macrophages and polymorphonuclear leukocytes. I. H2O2 and O2- generation by rabbit alveolar macrophages. 624 9

Phorbol myristate acetate activated in normal human neutrophils a single enzymatic entity that was dormant in unstimulated cells, optimally active at pH 7.0, and capable of oxidizing either NADH or NADPH, producing NAD(P)+ and superoxide (O27). Comparative fluorometric and spectrophotometric measurements supported the stoichiometry NAD(P)H + 20(2) leads to NAD(P)+ + 20(27) + H+. the seemingly considerable NAD(P)+ production at pH 5.5 and 6.0 was due largely to nonenzymatic oxidation of NAD(P)H by chain reactions initiated by HO27 (perhydroxyl radical), the conjugate acid of O27. This artifact, responsible for earlier erroneous assignments of an acid pH optimum for NAD(P)H oxidase, was prevented by including superoxide dismutase in fluorometric assays. NAD(P)H oxidase was more active towards NADPH (Km = 0.15 +/- 0.03 mM) than NADH (Km = 0.68 +/- 0.2 mM). No suggestion that oxidase activity was allosterically regulated by NAD(P)H was seen. Phorbol myristate acetate-induced O27 production was noted to be modulated by pH in intact neutrophils, suggesting that NAD(P)H oxidase is localized in the plasma membrane where its activity may be subject to (auto) regulation by local H+ concentrations.
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PMID:NAD(P)H oxidase activity in human neutrophils stimulated by phorbol myristate acetate. 625 12

These studies on the effect of administration of 1,600 units of vitamin E to humans indicated the following responses to the PMNs (TABLE 6). Functional alterations occur with an increased ability to ingest particles but a mild decrease in bactericidal potency of the PMN. Although the respiratory burst is slightly enhanced as is superoxide anion release, H2O2 release from the PMN is markedly impaired. The hexose monophosphate shunt activity, which is dependent on intracellular H2O2 is decreased during phagocytosis. Membrane responses such as changes in order parameter during phagocytosis as reported by the stearic acid analogue probe 5DS are similar to those of normal PMNs. The release of arachidonic acid from membranes of vitamin E PMNs during phagocytosis of opsonized zymosan is slightly enhanced, indicating normal phospholipase A2 activation. NADH oxidase-derived H2O2 is not impaired within phagocytic generated by NADPH oxidase in phagocytic vesicles, accounting for impairment in HMPS activity and bactericidal activity in these cells.
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PMID:The influence of vitamin E on human polymorphonuclear cell metabolism and function. 629 63

The subcellular distribution of the superoxide-forming enzyme in horse polymorphonuclear leukocytes was investigated. After activation of the cells with sodium oleate, a relatively stable and NAD(P)H-dependent oxygen consumption and superoxide production was found in association with the plasma membranes. The pH dependence displayed an optimum near neutrality. The apparent Km values were 38 x 10(-6) mol/l for NADPH and 1,560 x 10(-6) mol/l for NADH, suggesting that NADPH is the physiological donor. The rates of oxygen uptake, O2- production, and NADP consumption were consistent with the stoichiometry: 2 O2 + NADPH leads to 2 O2- + NADP. The failure to demonstrate an increase of NAD(P)H-dependent oxidative activity in the cellular fractions that the investigated NADPH oxidase is identical with the enzyme responsible for the respiratory burst in phagocytizing leukocytes.
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PMID:Subcellular localization and properties of the NAD(P)H oxidase from equine polymorphonuclear leukocytes. 630 78

Superoxide (O-2) production by partially purified NADPH oxidase from guinea pig neutrophils was markedly increased when the cells were activated by exposure to phorbol-myristate acetate. On the contrary, NADPH-dependent cytochrome c and 2,6-dichlorophenolindophenol (DCIP) reductase activities in preparations from resting and activated neutrophils were similar. The apparent Km values for NADH and NADPH of the reductase activities were different from those of the O-2 producing enzyme. The electron acceptors did not inhibit the oxygen consumption by NADPH oxidase in the presence of superoxide dismutase. Even in anaerobiosis the oxidase failed to reduce cytochrome c and DCIP. These results suggest that NAD(P)H-dependent dye reductase activities are not involved in the electron transport system responsible for the O-2 production by neutrophils.
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PMID:NADPH oxidase of neutrophils forms superoxide anion but does not reduce cytochrome c and dichlorophenolindophenol. 632 73

Generation of H2O2, an essential component in thyroid hormone synthesis, was studied by biochemical and cytochemical methods. Both parts of the study were performed on isolated open pig thyroid follicles in which the cells have preserved polarity and both the apical and basal cell surfaces are exposed to the incubation medium. The biochemical studies, performed with the scopoletin fluorescence assay, showed that H2O2 was released from the follicles into the medium at a rate of 0.5-1.0 nmol min-1 mg-1 DNA under basal conditions. The H2O2 release rate was promptly increased about 10 times by addition of the ionophore A23187 to Ca2+-containing medium. TSH caused an acute but weaker stimulation of H2O2 release, whereas (Bu)2cAMP was without effect, indicating that the TSH action was linked to Ca2+. Both basal and stimulated H2O2 release were strongly inhibited by p-chloromercuribenzene sulfonate. The cytochemical study, performed with the cerium technique, confirmed our previous observations on rat thyroid follicles. Reaction product was found on the apical cell surface but never on the basal cell surface or intracellularly. The apical reaction was enhanced by NADH and NADPH as well as by A23187 in Ca2+-containing medium. The apical reaction was strongly inhibited by p-chloromercuribenzene sulfonate. The observations indicate that the H2O2 released from the open follicles is generated on the apical plasma membrane of the follicle cells, possibly by NAD(P)H oxidase in this membrane. Furthermore, Ca2+ seems to be an important factor in the regulation of this H2O2 generation and, through that, in the regulation of iodination.
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PMID:Generation of H2O2 in isolated porcine thyroid follicles. 632 61

Chemoattractant-receptor coupling triggers several biologic responses in phagocytic cells including activation of the respiratory burst. Prior evidence in intact cells implied that stimulation of the respiratory burst by chemoattractants was by a mechanism different from other soluble agents suggesting the possibility that different oxidative enzymes were responsible. We now show that the chemoattractants N-formyl-methionyl-leucyl-phenylalanine and a split fragment of the fifth component of complement (C5a) stimulate an NADPH oxidase activity, measured in the 50,000-g particulate fraction from human polymorphonuclear leukocytes (PMN). Levels of oxidase activity stimulated by the chemoattractants were both time and dose dependent and required the presence of cytochalasin B during stimulation. In contrast, activation by two nonchemotactic stimuli, the ionophore A23187 and phorbol myristate acetate (PMA), did not require cytochalasin B. Temporal patterns of oxidase activation suggested that different stimuli follow different transductional pathways. Chemoattractant-mediated activation was immediate (no lag); peaked by 45 s and declined rapidly to approximately 50% of maximal by 2 min. In contrast, activation by A23187 or PMA had a 15-30-s lag and increased more slowly. Stimulation by A23187 peaked at 5 min, then declined. Stimulation by PMA plateaued at 20 min and did not decline by 90 min. Comparison of Km values for NADPH and NADH obtained by Lineweaver-Burk analysis of the oxidase activity stimulated by N-formyl-methionyl-leucyl-phenylalanine, A23187, and PMA suggested that the same enzyme was activated by all stimuli. Thus, chemoattractants and other soluble stimuli appear to activate the same respiratory burst enzyme in PMN but they utilize different transductional mechanisms and are regulated differently.
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PMID:Activation of the respiratory burst enzyme in human polymorphonuclear leukocytes by chemoattractants and other soluble stimuli. Evidence that the same oxidase is activated by different transductional mechanisms. 640 28

The superoxide (O2.-)-forming enzyme NADPH oxidase from pig neutrophils was solubilized and partially purified by gel-filtration chromatography. The purification procedure allowed the separation of NADPH oxidase activity from NADH-dependent cytochrome c reductase and 2,6-dichlorophenol-indophenol reductase activities. O2.-forming activity was co-purified with cytochrome b-245 and was associated with phospholipids. However, active fractions endowed with cytochrome b were devoid of ubiquinone and contained only little FAD. The cytochrome b/FAD ratio was 1.13:1 in the crude solubilized extract and increased to 18.95:1 in the partially purified preparations. Most of FAD was associated with fractions containing NADH-dependent oxidoreductases. These results are consistent with the postulated role of cytochrome b in O2.-formation by neutrophil NADPH oxidase, but raise doubts about the participation of flavoproteins in this enzyme activity.
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PMID:Composition of partially purified NADPH oxidase from pig neutrophils. 643 85

Lactate and acetate at 5 mM were found to be antagonistic to the killing action of metronidazole on Trichomonas vaginalis under aerobic but not anaerobic conditions. These compounds had no effect on the growth of the parasite, or the rate of metronidazole reduction by, and the activities of NADH oxidase and NADPH oxidase in, parasite homogenates. The phenomenon reported could be one reason why metronidazole is not always effective in the treatment of trichomoniasis.
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PMID:The antagonistic effects of acetate and lactate upon the trichomonacidal activity of metronidazole. 660 56

Human neutrophils were fractionated by nitrogen cavitation and Percoll density centrifugation, and the subcellular localization of FAD-flavoprotein, b-cytochrome, NADH-cytochrome b5 reductase, and NADPH-dependent cytochrome c reductase were determined in normal cells, cells from two patients with chronic granulomatous disease (CGD), and normal cells that had been stimulated with phorbol myristate acetate. In normal cells, a FAD-flavoprotein is found in a 1:2 molar ratio, with cytochrome b in the fractions containing the specific granules. Triton X-114 phase distribution indicates that the b-cytochrome but not the b-cytochrome-associated flavoprotein is an integral membrane protein. 80% of this flavoprotein, as well as all the b-cytochrome, was absent in these fractions from 2 CGD patients, although these patients had normal quantities of FAD in the fractions containing plasma membranes and cytosol. During stimulation the b-cytochrome-associated flavoprotein of the granules translocates with the b-cytochrome to the plasma membrane where NADPH oxidase is localized. Definition of the role of these NADPH oxidase constituents may provide a molecular description of the normal neutrophil respiratory burst and the molecular defect(s) in CGD.
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PMID:Subcellular localization of the human neutrophil NADPH oxidase. b-Cytochrome and associated flavoprotein. 670 48


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