Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.6.99.6 (NADPH oxidase)
 10,295 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Pig blood neutrophils were briefly activated by various fatty acids and then fractionated into membrane vesicles with different NADPH oxidase activities. Treatment of these membranes with a detergent, octyl glucoside, resulted in a high yield of solubilized oxidase, which was subjected to isoelectric focusing on gels (pI 4.0-8.0). 1) A distinct band staining with NADPH-nitroblue tetrazolium focused at pI 5.0. The enzyme (pI 5.0) showed high specificity for NADPH and similar characteristics to the oxidase involved in the respiratory burst. 2) The enzyme was extracted from gel slices and analyzed. When measured promptly after its extraction, its NADPH oxidase activity was high, but there was apparent superoxide dismutase-insensitive cytochrome c reduction, probably due to direct electron transfer to the heme protein. However, it could produce superoxide anion (O2-) under some micelle conditions. 3) Therefore, the formation of the enzyme-substrate complex of yeast cytochrome c peroxidase was employed for the detection of H2O2. A fresh extract of stimulated cells catalyzed equimolar NADPH oxidation and H2O2 production of 306 and 300 nmol min-1 (mg protein)-1, respectively. The Km value of the enzyme for NADPH was 30 +/- 13 (S.D.) microM. The recovery of the extract (pI 5.0) was 19% of the total activity. 4) The enzyme extract contained 1.1-1.9 nmol of FAD/mg of protein, giving a turnover number of 300-600 min-1 in terms of O2- generation/FAD. No heme protein was found in the enzyme. The enzyme was mainly of 67-kDa molecular mass.
 ...
PMID:The respiratory burst oxidase of neutrophils. Separation of an FAD enzyme and its characterization. 362 61

As previously reported, the membrane fraction of liquid paraffin-induced, guinea pig peritoneal macrophages exhibits an NADPH-dependent hemolytic activity toward sheep erythrocytes. This activity was inhibited with N-ethylmaleimide, superoxide dismutase, cytochrome c, catalase, desferrioxamine, mannitol, and benzoate. These inhibition profiles indicate that O2- generation by the NADPH oxidase, peroxidation of the membranous lipids with H2O2 or .OH secondarily formed from O2-, and hemolysis of sheep erythrocytes with the peroxides occur in this order in the hemolytic reaction. In fact, the lipid peroxides were found to be formed in the membrane fraction in the presence of Fe3+, subsequent to the O2- generation, and to act as a final hemolytic agent.
 ...
PMID:The NADPH oxidase-dependent hemolysis of sheep erythrocytes with the membrane fraction of guinea pig peritoneal macrophages. 366 51

Solubilization of the thyroid particulate-associated NADPH-dependent H2O2 generating system has been tested with different detergents; (3-(3-cholamidopropyl)-dimethylammonio)1-propane sulfonate (CHAPS) was found to be the best of the six detergents tested. The ratio of H2O2 generation to NADPH oxidation was similar for CHAPS extract and native particulate material. CHAPS was also the only detergent able to preserve the Ca++-sensitivity of the NADPH oxidase. Solubilization of this enzyme allowed the determination of some of its characteristics: specificity for divalent cations, apparent Km for NADPH, optimum pH and sensitivity to SH- reagents.
 ...
PMID:Solubilization and characteristics of the thyroid NADPH-dependent H2O2 generating system. 380 Oct 31

Granulocyte functions, viz. endocytosis, NADPH oxidase activity and iodination by leukocytes, were studied in granulocytes isolated from 17 chronic myeloid leukemia (CML) patients at initial diagnosis (stage I), from 10 patients in relapse (stage II), and 10 patients in acute blastic crisis (stage III). The mean phagocytic index of granulocytes from CML patients was similar to the normal value. NADPH activity decreased as the disease progressed. Thus, the amount of formazan produced was lower in granulocytes from patients in stage II (P less than 0.05) and stage III (P less than 0.01) than that produced by normal granulocytes. H2O2-Myeloperoxidase-dependent iodination was found to be significantly reduced in granulocytes from all stages of the disease compared to that of normal, stage I (P less than 0.01), stage II (P less than 0.05) and stage III (P less than 0.01). It thus seems that granulocyte function becomes less efficient as the disease progresses towards acute blastic crisis. Immature cells from the same patients carried out these functions at a more reduced level than did their mature counterparts.
 ...
PMID:Studies on granulocyte functions in patients with chronic myeloid leukemia. 386 54

Cetiedil, alpha-cyclohexyl-3-thiopheneacetic acid 2-(hexahydro-lH-azepin-l-yl)-ethyl ester, was found to specifically suppress oxygen uptake by polymorphonuclear leucocytes (PMN) that were exposed to myristate or heat-killed E. coli. The chemical had no effect on the basal respiration rate of PMN in the resting state. Inhibition of oxygen uptake by cetiedil was proportionate to the degree of inhibition of the generation of O-2 and H2O2. It was also found that cetiedil suppressed the rate of the phagocytosis by PMN of opsonized oil droplets. Cetiedil had no effect on subcellular NADPH oxidase, an enzyme responsible for the respiratory burst that is activated by the perturbation of PMN plasma membrane with phagocytable particles or stimulators such as myristate. These results suggest that cetiedil affects the trigger mechanism of the plasma membrane to inhibit the activation of NADPH oxidase.
 ...
PMID:Effects of cetiedil on the oxidative metabolism of activated polymorphonuclear leucocytes. 401 89

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

The paper deals with 1) the features of the respiratory burst (increase of the respiration with production of O2 metabolites, O2-, H2O2, OH) of the inflammatory cells; 2) the factors responsible for its activation; 3) the methods for its measurement; 4) the molecular events which take place at the level of the plasma membrane following the interaction between the stimuli and the cell surface (the Ca++ changes, the modification of membrane potential, the activation of phospholipid turnover) and the hypothesis of the activation of the protein kinase C; 5) the nature of the NADPH oxidase whose activation is responsible for the respiratory burst and the production of O2 metabolites; 6) the defensive, toxic, proinflammatory and modulatory effects due to the reactivity of the oxygen metabolites.
 ...
PMID:Mechanism of production of toxic oxygen radicals by granulocytes and macrophages and their function in the inflammatory process. 405 21

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.
 ...
PMID:The influence of vitamin E on human polymorphonuclear cell metabolism and function. 629 63

The bactericidal activity of the human neutrophil is dependent on a coordinated series of events by which the bacteria become confined to a vacuole. Fusion of the azurophil and specific granules with the phagocytic vacuole results in secretion of BPI, the primary oxygen independent bactericidal protein, and of myeloperoxidase into the phagolysosome. Simultaneously, an electron transport chain, the NADPH oxidase, is activated in the membrane of the phagolysosome, resulting in generation of H2O2, which together with myeloperoxidase and Cl- forms a highly bactericidal agent. Digestion of the killed bacteria is subsequently effectuated by proteases and lipases of the neutrophil granules. The neutrophil thus has several highly efficient bactericidal systems that overlap to a certain degree, thereby giving the neutrophil an overcapacity to kill. This is appreciated in the defence against microorganisms, but is increasingly being recognized as a cause of perturbation of serum protease anti-protease homeostasis that may cause major tissue destruction. The recent achievements in the understanding of neutrophil function will hopefully permit better control to be exerted over this potent cell.
 ...
PMID:Bactericidal mechanisms of the human neutrophil. An integrated biochemical and morphological model. 632 83

Control of the intraphagosomal pH in neutrophils may be of importance in creating a microbicidal environment by regulating the activity of the O2-.-generating NADPH oxidase and the lysosomal enzymes discharged into this compartment. In this study, we examined the proton stoichiometry associated with the primary enzymatic reaction underlying the respiratory burst. A preparation of the neutrophil-derived, membrane oxidase consumed NADPH and generated O2-. with a stoichiometry of 1 NADPH:2 O2-. When the enzymatically produced O2-. was prevented from undergoing dismutation, net protons were released in an approximate 1:2 stoichiometry with O2-. generated. In contrast, when O2-. was allowed to dismutate to H2O2, net protons were consumed in a 1:1 stoichiometry with the accumulated H2O2. Thus, the delta pH associated with the NADPH oxidase-dependent production of O2-. was dictated by the fate of the generated radical. The consumption of the oxidase-generated H2O2 by the lysosomal enzyme myeloperoxidase resulted in the formation of HOCl which was trapped in the presence of taurine as the N-chloro derivative. The ratio of chlorinated product formed to H+ consumed was 1:1. The implications of these results are discussed in terms of the known intraphagosomal pH changes that occur following neutrophil stimulation. We conclude that the O2-.-generating oxidase plays a dual role in the phagosome by simultaneously creating an oxidizing environment that optimizes pH-dependent microbicidal processes.
 ...
PMID:Proton stoichiometry associated with human neutrophil respiratory-burst reactions. 649 Jun 51


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