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:1.6.3.1 (NADPH oxidase)
11,281 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The thyroid plasma membrane contains a Ca(2+)-regulated NADPH-dependent H2O2-generating system which provides H2O2 for the thyroid-peroxidase-catalyzed biosynthesis of thyroid hormones. The molecular nature of the membrane-associated electron transport chain that generates H2O2 in the thyroid is unknown, but recent observations indicate that a flavoprotein containing a FAD prosthetic group is involved. Solubilization was reinvestigated using 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (Chaps), Triton X-100, and high salt concentrations. Chaps eliminated about 30% of the proteins, which included a ferricyanide reductase, without affecting the H2O2-generating system. Similarly, Triton X-100 alone did not extract the NADPH oxidase. An NADPH-oxidase activity, which was measured in the presence of the artificial electron acceptor potassium ferricyanide, was solubilized by increasing the ionic strength to 2 M KCl. This NADPH-ferricyanide reductase activity was shown to belong to the H2O2-generating system, although it did not produce H2O2. It was still Ca2+ dependent and H2O2 production was restored by decreasing the ionic strength by overnight dialysis. No H2O2 production activity was detected after sucrose density gradient centrifugation of the dialyzed solubilized enzyme, but a well-defined peak of NADPH oxidation activity with a sedimentation coefficient of 3.71 S was found in the presence of K3Fe(CN)6. These results suggest that some unknown component(s) (phospholipid or protein) is removed during sucrose density gradient centrifugation. Finally, thyrotropin, which induces NADPH oxidase and regulates H2O2 production in porcine thyrocytes in primary culture, also induced the NADPH-K3Fe(CN)6 reductase activity associated with the H2O2-generating system. Thus, this enzyme seems to be another marker of thyroid differentiation.
...
PMID:Solubilization and characterization of a thyroid Ca(2+)-dependent and NADPH-dependent K3Fe(CN)6 reductase. Relationship with the NADPH-dependent H2O2-generating system. 885 87

Macrophage cholesterol accumulation and foam cell formation, the hallmark of early atherosclerosis, is the result of enhanced cellular uptake of plasma low density lipoprotein (LDL). Native LDL, has to undergo oxidative modifications in order to be taken up at an enhanced rate by macrophages, leading to foam cell formation. Macrophage uptake of oxidized LDL involves its binding to scavanger receptors (including cellular proteoglycans) and this is followed by an impaired cellular cholesterol metabolism. Cells of the arterial wall including macrophages can oxidize LDL in a process that involves activation of cellular oxygenases, such as NADPH oxidase and 15-lipoxygenase. This process, however, also depends on the macrophage antioxidant environment, where glutathione peroxidase and reduced glutathione play an important protective role against cell-mediated oxidation of LDL. Macrophage phospholipids peroxidation under oxidative stress can also contribute to macrophage-mediated oxidation of LDL. Evidence for the occurrence of oxidized LDL in vivo is as follows: 1) In the atherosclerotic lesion [in humans, as well as in the transgenic, apolipoprotein E-deficient mice], LDL is oxidized (and as a result, it is also aggregated), in comparison to plasma LDL which is normally not oxidized. 2) Plasma LDL from patients at high risk for atherosclerosis (such as hypercholesterolaemic, hypertensive, diabetic and renal failure patients), as well as from the apolipoprotein E-deficient mice, demonstrates increased susceptibility to oxidation in comparison to normal LDL. In some groups of these patients LDL is minimally oxidized already in plasma. 3) Supplementation of nutritional antioxidants, which are rich in polyphenols (red wine, licorice, olive oil), or of selenium to humans or to the apolipoprotein E-deficient mice, as well as therapy with beta-hydroxy-beta-methyl-glutaryl-CoA reductase inhibitors (so-called "statins") in hyperocholesterolaemic patients, were shown to reduce the susceptibility of LDL to oxidation. This effect could be associated with a reduction in the size of the atherosclerotic lesion and may thus contribute to attenuation of the atherosclerotic process.
...
PMID:Interaction of oxidized low density lipoprotein with macrophages in atherosclerosis, and the antiatherogenicity of antioxidants. 887 34

A plasma membrane iron reductase, required for cellular iron acquisition by Saccharomyces cerevisiae, and the human phagocytic NADPH oxidase, implicated in cellular defense, contain low potential plasma membrane b cytochromes that share elements of structure and function. Four critical histidine residues in the FRE1 protein of the iron reductase were identified by site-directed mutagenesis. Individual mutation of each histidine to alanine eliminated the entire heme spectrum without affecting expression of the apoprotein, documenting the specificity of the requirement for the histidine residues. These critical residues are predicted to coordinate a bis-heme structure between transmembrane domains of the FRE1 protein. The histidine residues are conserved in the related gp91(phox) protein of the NADPH oxidase of human granulocytes, predicting the sites of heme coordination in that protein complex. Similarly spaced histidine residues have also been implicated in heme binding by organelle b cytochromes with little overall sequence similarity to the plasma membrane b cytochromes. This bis-heme motif may play a role in transmembrane electron transport by distinct families of polytopic b cytochromes.
...
PMID:Intramembrane bis-heme motif for transmembrane electron transport conserved in a yeast iron reductase and the human NADPH oxidase. 894 93

Recent reports suggest that excess amounts of sugar alcohol are linked to leukocyte dysfunctions associated with diabetes. As the polyol pathway has not been firmly established in leukocytes, we have investigated NADPH-dependent reductases and sugar alcohol formation in dog leukocytes. NADPH-dependent reductase activity was observed with DL-glyceraldehyde as substrate in both mononuclear and polymorphonuclear leukocytes isolated from dog. By chromatofocusing, this activity corresponded primarily to aldehyde reductase rather than aldose reductase. The enzymatic conversion of glucose to the sugar alcohol sorbitol in leukocytes was confirmed in vitro by 19F nuclear magnetic resonance (NMR) spectroscopy using 3-deoxy-3-fluoro-D-glucose as substrate. The NMR spectrum obtained after incubation with 10 Mm 3-deoxy-3-fluoro-D-glucose at 37 degrees C for 24 h displayed newly formed 3-deoxy-3-fluoro-D-sorbitol and 3-deoxy-3-fluoro-D-fructose peaks with both mononuclear and polymorphonuclear leukocytes. Sugar alcohol production in leukocytes from galactose-fed dogs was also observed in vivo. Galactitol accumulation was consistently observed by gas chromatography to occur in mononuclear cells while only trace amounts of galactitol were observed in polymorphonuclear leukocytes. Activation of NADPH oxidase activity in neutrophils isolated from galactose-fed dogs by zymosan was also significantly reduced compared to that of nongalactosemic control dogs. These results indicate that glucose is converted to fructose through sorbitol in both mononuclear and polymorphonuclear leukocytes despite the observations that these cells primarily contain aldehyde reductase rather than aldose reductase. In vivo, sugar alcohol accumulation in mononuclear cells is greater than in polymorphonuclear leukocytes.
...
PMID:Polyol pathway and NADPH-dependent reductases in dog leukocytes. 897 81

The leukocyte iodonitrotetrazolium violet (INT) reductase activity of disrupted bovine polymorphonuclear neutrophils is closely associated with the activation of the O2(-)-generating NADPH oxidase in a cell-free system. It is dependent upon NADPH, cytosolic factors, and amphiphiles (such as arachidonate), the same factors required for O2- generation. Both O2- generation and INT reductase activity are inhibited by phenylarsine oxide, an inhibitor of the activation of the NADPH oxidase [Li, J., & Guillory, R. J. (1997) J. Biochem. Mol. Biol. Biophys. (in press)]. In this report, the INT diaphorase activity of disrupted bovine polymorphonuclear neutrophils is shown to be resolved by DEAE-Sepharose chromatography into two fractions: an NADPH-cytochrome c reductase-containing fraction and a cytochrome b558-associated fraction. The diaphorase activity in the NADPH-cytochrome c reductase-containing portion is not dependent upon the presence of an amphiphile or phospholipid and is not associated with O2- generation. Upon incorporation into liposomes, the cytochrome b558-containing fraction demonstrates high O2- and INT reductase activities in the presence of cytosolic factors. Both O2- generation and INT reductase activities are SDS and FAD dependent and further stimulated by GTPgammaS. Phenylarsine oxide inhibits both O2- generation and INT reductase activities when added prior to activation by SDS. With the cytochrome b-containing liposomes, the Km values (O2- formation) for NADPH and NADH are 27.2 microM and 810 microM, and for INT reductase the Km values are 27.5 microM and 1017 microM, respectively. Under anaerobic conditions and thus in the absence of O2- formation, the NADPH-dependent INT reductase activity does not change, indicating that the dye reduction is not due to its direct reduction by O2 anion but is an intrinsic property of the superoxide-generating NADPH oxidase. Cytochrome b558 is the essential component of the NADPH oxidase and contains all the redox centers necessary for electron flow between NADPH and oxygen. The correlation of the activation and inhibition patterns for O2- generation and INT reduction by cytochrome b558 incorporated into artificial liposomes strongly indicates that the two activities are associated with the same membrane protein, cytochrome b558.
...
PMID:Purified leukocyte cytochrome b558 incorporated into liposomes catalyzes a cytosolic factor dependent diaphorase activity. 915 36

The gene encoding a putative NADPH:flavin oxidoreductase of the protozoan parasite Entamoeba histolytica (Eh34) was recombinantly expressed in Escherichia coli. The purified recombinant protein (recEh34) has a molecular mass of about 35 kDa upon SDS/PAGE analysis, exhibits a flavoprotein-like absorption spectrum and contains 1 mol of non-covalently bound FMN per mol of protein. RecEh34 reveals two different enzymic activities. It catalyses the NADPH-dependent reduction of oxygen to hydrogen peroxide (H2O2), as well as of disulphides such as 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB) and cystine. The disulphide reductase but not the H2O2-forming NADPH oxidase activity is inhibitable by sulphydryl-active compounds, indicating that a thiol component is part of the active site for the disulphide reductase activity, whereas for the H2O2-forming NADPH oxidase activity only the flavin is required. Compared with the recombinant protein, similar activities are present in amoebic extracts. Native Eh34 is active in a monomeric as well as in a dimeric state. In contrast to recEh34, no flavin was associated with the native protein. However, both NADPH oxidase as well as DTNB reductase activity were found to be dependent on the addition of FAD or FMN.
...
PMID:Recombinant expression and biochemical characterization of an NADPH:flavin oxidoreductase from Entamoeba histolytica. 949 88

Thioredoxin reductase (TR, EC 1.6.4.5) was purified 5800-fold from the livers of adult male B6C3F1 mice. The estimated molecular mass of the purified protein was about 57 kDa. The activity of the purified enzyme was monitored by the NADPH-dependent reduction of 5, 5'-dithiobis(2-nitrobenzoic acid) (DTNB); this activity was fully inhibited by 1 microM aurothioglucose. Arsenicals and arsinothiols, complexes of As(III)-containing compounds with L-cysteine or glutathione, were tested as inhibitors of the DTNB reductase activity of the purified enzyme. Pentavalent arsenicals were much less potent inhibitors than trivalent arsenicals. Among all the arsenicals, CH(3)As(III) was the most potent inhibitor of TR. CH(3)As(III) was found to be a competitive inhibitor of the reduction of DTNB (K(i) approximately 100 nM) and a noncompetitive inhibitor of the oxidation of NADPH. The inhibition of TR by CH(3)As(III) was time-dependent and could not be reversed by the addition of a dithiol-containing molecule, 2,3-dimercaptosuccinic acid, to the reaction mixture. The inhibition of TR by CH(3)As(III) required the simultaneous presence of NADPH in the reaction mixture. However, unlike other pyridine nucleotide disulfide oxidoreductases, there was no evidence that mouse liver TR was inactivated by exposure to NADPH. Treatment with CH(3)As(III) did not increase the NADPH oxidase activity of the purified enzyme. Thus, CH(3)As(III), a putative intermediate in the pathway for the biomethylation of As, is a potent and irreversible inhibitor of an enzyme involved in the response of the cell to oxidative stress.
...
PMID:Methylarsenicals and arsinothiols are potent inhibitors of mouse liver thioredoxin reductase. 1052 67

A NAD(P)H oxidase has been isolated from the archaeon Sulfolobus solfataricus. The enzyme is a homodimer with M(r) 38,000 per subunit (SsNOX38) containing 1 FAD molecule/subunit. It oxidizes NADH and, less efficiently, NADPH with the formation of hydrogen peroxide. The enzyme was resistant against chemical and physical denaturating agents. The temperature for its half-denaturation was 93 and 75 degrees C in the absence or presence, respectively, of 8 M urea. The enzyme did not show any reductase activity. The SsNOX38 encoding gene was cloned and sequenced. It accounted for a product of 36.5 kDa. The translated amino acid sequence was made of 332 residues containing two putative betaalphabeta-fold regions, typical of NAD- and FAD-binding proteins. The primary structure of SsNOX38 did not show any homology with the N-terminal amino acid sequence of a NADH oxidase previously isolated from S. solfataricus (SsNOX35) (Masullo, M., Raimo, G., Dello Russo, A., Bocchini, V. and Bannister, J. V. (1996) Biotechnol. Appl. Biochem. 23, 47-54). Conversely, it showed 40% sequence identity with a putative thioredoxin reductase from Bacillus subtilis, but it did not contain cysteines, which are essential for the activity of the reductase.
...
PMID:A NAD(P)H oxidase isolated from the archaeon Sulfolobus solfataricus is not homologous with another NADH oxidase present in the same microorganism. Biochemical characterization of the enzyme and cloning of the encoding gene. 1062 24

Three 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (HCRIs), atorvastatin, pravastatin, and cerivastatin, inhibited phorbol ester-stimulated superoxide anion (O(2)(-)) formation in endothelium-intact segments of the rat aorta in a time- and concentration-dependent manner (maximum inhibition of 70% after 18 hours at 1 to 10 micromol/L). The HMG-CoA reductase product mevalonic acid (400 micromol/L) reversed the inhibitory effect of the HCRIs, which, conversely, was mimicked by inactivation of p21 Rac with Clostridium sordellii lethal toxin but not by inactivation of p21 Rho with Clostridium botulinum exoenzyme (C3). A mevalonate-sensitive inhibition of phorbol ester-stimulated O(2)(-) formation by atorvastatin was also observed in porcine cultured endothelial cells and in a murine macrophage cell line. In the rat aorta, no effect of the HCRIs on protein kinase C, NADPH oxidase, or superoxide dismutase (SOD) activity and expression was detected, whereas that of endothelial nitric oxide (NO) synthase was enhanced approximately 2-fold. Moreover, exposure of the segments to atorvastatin resulted in a significant improvement of endothelium-dependent NO-mediated relaxation, and this effect was abolished in the presence of SOD. Taken together, these findings suggest that in addition to augmenting endothelial NO synthesis, HCRIs inhibit endothelial O(2)(-) formation by preventing the isoprenylation of p21 Rac, which is critical for the assembly of NADPH oxidase after activation of protein kinase C. The resulting shift in the balance between NO and O(2)(-) in the endothelium improves endothelial function even in healthy blood vessels and therefore may provide a reasonable explanation for the beneficial effects of HCRIs in patients with coronary heart disease in addition to or as an alternative to the reduction in serum LDL cholesterol.
...
PMID:Improvement of nitric oxide-dependent vasodilatation by HMG-CoA reductase inhibitors through attenuation of endothelial superoxide anion formation. 1063 1

Almost all iron uptake by fungi involves reduction from Fe(III) to Fe(II) in order to facilitate ligand exchange. This leads to two mechanisms: uptake before reduction, or reduction before uptake. Many fungi secrete specific hydroxamate siderophores when short of iron. The mechanism with uptake before reduction is described in the context of siderophore synthesis and usage, since it applies to many (but not all) siderophores. The hydroxamate functional group is synthesized from ornithine by N5 hydroxylation and acylation. In most fungal siderophores, two or three modified ornithines are joined together by a non-ribosomal peptide synthetase. The transcription of these genes is regulated by an iron activated repressor. There is evidence that the iron-free siderophore may be stored in intracellular vesicles until secretion is required. After loading with iron, re-entry is likely to be via a proton symport. In some fungi, siderophores are used for iron storage. The iron is liberated by an NADPH-linked reductase. The second mechanism starts with Fe(III) reduction. In yeast, this is catalysed by an NADPH-linked transmembrane reductase, which has homology with the NADPH oxidase of neutrophils. There are two closely similar reductases with overlapping roles in Fe(III) and Cu(II) reduction, while the substrates for reduction include Fe(III)-siderophores. External reductants, which may be important in certain fungi, include 3-hydroxyanthranilic acid, melanin, cellobiose dehydrogenase and 2,5-dimethylhydroquinone. In yeast, a high-affinity iron uptake pathway involves reoxidation of Fe(II) to Fe(III), probably to confer specificity for iron. This is catalysed by a copper protein which has homology with ceruloplasmin, and is closely coupled to Fe(III) transport. The transcription of these genes is regulated by an iron-inhibited activator. Because of its copper requirement, the high-affinity pathway is blocked by disruption of genes for copper metabolism. A low-affinity uptake transports Fe(II) directly and is important in anoxic growth. In many fungi, mechanisms with internal or external reduction are both important. The external reduction is applicable to almost any Fe(III) complex, while internal reduction is more efficient at low iron but requires a siderophore permease through which toxins might enter. Both mechanisms require close coupling of Fe(III) reduction and Fe(II) utilization in order to minimize production of active oxygen.
...
PMID:Iron uptake by fungi: contrasted mechanisms with internal or external reduction. 1090 54


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

---