Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A high proportion of neurons in the cerebellum and in cholinergic brainstem nuclei stain positive for nicotinamide adenine dinucleotide phosphate-diaphorase (NADPHd), which is a nitric oxide synthase (NOS). Recent evidence suggests that schizophrenia may involve increased numbers of NADPHd-stained neurons in different areas of the subcortex. This led us to examine the actual concentration of NOS in postmortem brain specimens of cerebellum, and the relevant regions of brainstem tegmentum, to see if NOS concentrations were also increased in schizophrenia. Postmortem brain tissue was obtained at autopsy from schizophrenics and controls who did not have other brain disease. In patients with schizophrenia, NOS concentration was higher.
Mol Chem Neuropathol 1996 Apr
PMID:Nitric oxide synthase (NOS) in schizophrenia: increases in cerebellar vermis. 914 13

The 15alpha-hydroxylation of 13-ethyl-gon-4-ene-3,17-dione (GD) with different subcellular fractions of Penicillium raistrickii i 477 was investigated. Cytochrome P-450 was shown to be involved in this reaction. The steroid transformation was inhibited by carbon monoxide, metyrapone, p-CMB, iodoacetamide, N-methylmaleimide and several metal ions. The 15alpha-hydroxylase was observed to be dependent on nicotinamide-adenine dinucleotide phosphate (NADPH) replaceable by NaIO4, and the activity was enhanced by a NADPH-regenerating system, indicating the involvement of the NADPH-cytochrome c (P-450) reductase. This was further confirmed by the inhibition of the hydroxylase activity in the presence of cytochrome c. No effect was observed in the presence of azide and antimycin A. Solubilized microsomes gave an absorption maximum at 453 nm in carbon monoxide difference spectrum, and showed a Type-I GD-binding spectrum typically for cytochrome P-450 interaction with substrate. First results about the inducibility of the enzymes involved in the 15alpha-hydroxylation of GD are shown.
J Steroid Biochem Mol Biol 1997 Mar
PMID:Involvement of cytochrome P-450 in the 15alpha-hydroxylation of 13-ethyl-gon-4-ene-3,17-dione by Penicillium raistrickii. 921 26

Thioredoxin reductase is a homodimeric flavoenzyme containing a flavin adenine dinucleotide (FAD) and a redox-active disulfide in each subunit. Structural work on the enzyme from Escherichia coli suggests that thioredoxin reductase exists in two conformations, both of which are necessary for catalysis [Waksman, G., Krishna, T. S. R., Williams, C. H., Jr., & Kuriyan, J. (1994) J. Mol. Biol. 236, 800-816]. These factors make it likely that the mechanism of this enzyme is complex. The rapid reaction of enzyme with nicotinamide adenine dinucleotide phosphate, reduced form (NADPH) (the reductive half-reaction), proceeds in three phases. The first phase represents the formation of an NADPH-FAD charge transfer complex. The second phase involves FAD reduction, with loss of the NADPH-FAD charge transfer band. The third phase shows a slower decrease in absorbance at 456 nm and the formation of a reduced flavin-NADP+ charge transfer band. These and other results indicate that NADP+ and NADPH compete for the single binding site on oxidized and fully reduced enzyme and that NADP+ release does not limit the third phase of reduction. Experiments that include examination of the reductive half-reactions of active-site mutants, having the active-site disulfide removed by mutating one or both of the active-site cysteines, indicate that the third phase does not represent reduction by a second equivalent of NADPH. Comparison of the rate constants and temperature dependence of the reductive half-reaction with those of turnover show that the reductive half-reaction is not solely rate-limiting in catalysis. The results suggest that wild type and each altered enzyme exists in a unique equilibrium of conformers. It is proposed that the third phase of the reductive half-reaction represents a flavin reduction event largely limited by the conformational change proposed in the structural work.
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PMID:Reductive half-reaction of thioredoxin reductase from Escherichia coli. 923 91

Peroxynitrite and hydroxyl radical are reactive oxidants produced during myocardial reperfusion injury. In various cell types, including macrophages and smooth muscle cells, peroxynitrite and hydrogen peroxide cause DNA single strand breakage, which triggers the activation of the nuclear enzyme poly (ADP-ribose) synthetase (PARS), resulting in cytotoxicity. Using 3-aminobenzamide and nicotinamide, inhibitors of PARS, we investigated the role of PARS in the pathogenesis of myocardial oxidant injury in H9c2 cardiac myoblasts in vitro. Peroxynitrite (100-1000 microM), hydrogen peroxide (0.3-10 microM) and the NO donor compounds S-nitroso-N-accetyl-DL-penicillamine (SNAP) and diethyltriamine NONOate all caused a dose-dependent reduction of the mitochondrial respiration of the cells, as measured by the mitochondrial-dependent conversion of MTT to formazan. Peroxynitrite and hydrogen peroxide, but not the NO donors caused activation of cellular PARS activity. The suppression of mitochondrial respiration by peroxynitrite and hydrogen peroxide, but not by the NO donors, was ameliorated by pharmacological inhibition of PARS. The protection by the PARS inhibitors diminished at extremely high concentrations of the oxidants. Hypoxia (1 h) followed by reoxygenation (1-24 h) also resulted in a significant activation of PARS, and caused a suppression of mitochondrial respiration, which was prevented by inhibition of PARS. Similar to the results obtained with the pharmacological inhibitors of PARS, a fibroblast cell line which derives from the PARS knockout mouse was protected against the suppression of mitochondrial respiration in response to peroxynitrite and reoxygenation, but not to NO donors, when compared to the result of cells derived from wild-type animals. Based on our data, we suggest that activation of PARS plays a role in the myocardial oxidant injury.
J Mol Cell Cardiol 1997 Sep
PMID:Protection by inhibition of poly (ADP-ribose) synthetase against oxidant injury in cardiac myoblasts In vitro. 929 80

The mitochondrial DNA (mtDNA) codes for essential hydrophobic components of the system of oxidative phosphorylation. Diseases caused by mtDNA defects are manifested as variable clinical phenotypes and the symptoms represent the involvement of tissues with high energy demand. Various approaches have been taken to treat mitochondrial diseases by administration of redox compounds, enzyme activators, vitamins and coenzymes or dietary measures. The MELAS mutation at the base pair 3243 of mitochondrial DNA demolishes a transcription termination sequence located within the tRNA(Leu)[UUR] gene, resulting in synthesis of an abnormally large derivative of 16 S rRNA and defective translation. The activity of NADH:Q oxidoreductase (complex I) is often decreased and lactic acidosis is a typical clinical finding. We hypothesized that defective translation of the seven mitochondrially coded subunits (of the total 41) of complex I may alter its affinity to the NADH substrate in which case the activity decrease may be compensated for by increasing the NADH concentration. A MELAS patient was treated with oral nicotinamide for 5 months. The blood NAD content representing the NAD + NADH pool of erythrocytes rose 24 fold and the blood lactate + pyrovate concentration fell by 50%. All these metabolic alterations suggested an improvement of the function of complex I or the whole mitochondrial respiratory chain. However, the kinetic properties of the patient's complex I were similar to the reference values. A tempting explanation is that the free NADH concentration in mitochondria is normally at the level of K(m), so that the decreased activity of the respiratory chain can be compensated for by increased mitochondrial [NADH]. Another possibility would be that the substrate shuttles for transport of reducing power of cytosolic NADH into mitochondria (the malate aspartate or glycerol-3-phosphate shuttles) may be enhanced by increased total NAD + NADH. Because the malate-aspartate shuttle is actually a pump for reducing equivalents driven by the mitochondrial membrane energization, it is proposed that the exacerbations of the MELAS syndrome be partly due to a vicious circle initiated by a defect of complex I and affecting the active transport of the hydrogen from cytosolic NADH into the mitochondrion.
Mol Cell Biochem 1997 Sep
PMID:Metabolic interventions against complex I deficiency in MELAS syndrome. 930 2

o-phthalaldehyde inactivates homodimeric, NADP+ dependent, 6-phosphogluconate dehydrogenase from sheep liver, upon formation of a single isoindole derivative per enzyme subunit. This indicates that the thiol group of a cysteine residue or the epsilon-amino group of a lysine residue located within 3 A and crosslinked by the reagent is essential for catalysis. Fluorescence analyses of the modified enzyme suggest that the isoindole derivative forms at the binding site of the nicotinamide moiety of NADP+. The enzymes from Trypanosoma brucei and Lactococcus lactis are also inactivated suggesting a similar three-dimensional structure in this domain. The isoindole derivative does not form with two mutants of the T. brucei enzyme (Lys185His and Lys185Leu), this allowing to identify not only the lysine but also the cysteine involved in the cross-linking. The formation of the isoindole derivative inactivates not only the oxidative decarboxylation, but also two partial reactions catalysed by the enzyme.
Biochem Mol Biol Int 1997 Sep
PMID:The cross-linking by o-phthalaldehyde of two amino acid residues at the active site of 6-phosphogluconate dehydrogenase. 931 93

Manganese superoxide dismutase (MnSOD) is a mitochondrial enzyme that dismutates potentially toxic superoxide radical into hydrogen peroxide and dioxygen. This enzyme is critical for protection against cellular injury due to elevated partial pressures of oxygen. Thioredoxin (TRX) is a potent protein disulfide reductase found in most organisms that participates in many thiol-dependent cellular reductive processes and plays an important role in antioxidant defense, signal transduction, and regulation of cell growth and proliferation. Here we describe induction of manganese superoxide dismutase by thioredoxin. MnSOD mRNA and activity were increased dramatically by low concentrations of TRX (28 microM). Elevation of MnSOD mRNA by TRX was inhibited by actinomycin D, but not cycloheximide, occurring both in cell lines and primary human lung microvascular endothelial cells. mRNAs for other antioxidant enzymes including copper-zinc superoxide dismutase and catalase were not elevated, demonstrating specificity of induction of MnSOD by TRX. Thiol oxidation by diamide or alkylation by chlorodinitrobenzene inhibited MnSOD induction, further indicating a requirement for reduced TRX. Because both oxidized and reduced thioredoxin (28 microM) induced MnSOD mRNA, the intracellular redox status of externally added Escherichia coli oxidized TRX was determined. About 45% of internalized E. coli TRX was reduced, with 8% in fully reduced form and about 37% in partially reduced form. However, when TRX reductase and nicotinamide adenine dinucleotide (NADPH) were added to the extracellular medium with TRX, more than 80% of E. coli TRX was found to be in a fully reduced state in human adenocarcinoma (A549) cells. Although lower concentrations of oxidized TRX (7 microM) did not induce MnSOD mRNA, this concentration of TRX, when reduced by NADPH and TRX reductase, increased MnSOD mRNA six-fold. In additional studies, MCF-7 cells stably transfected with the human TRX gene had elevated expression of MnSOD mRNA relative to vector-transfected controls. Thus, both endogenously produced and exogenously added TRX elevate MnSOD gene expression. These findings suggest a novel mechanism involving reduced TRX in regulation of MnSOD.
Am J Respir Cell Mol Biol 1997 Dec
PMID:Elevation of manganese superoxide dismutase gene expression by thioredoxin. 940 58

In this work, the tertiary butylhydroperoxide- (t-BuOOH) treated mouse was used as a model to study the oxidative stress that is associated with various neurodegenerative diseases. DNA was found to be an early target of t-BuOOH attack. Necrosis was associated with extensive DNA fragmentation that occurred in almost all regions of the brain within 20 min following intracerebroventricular (icv) injection of 109.7 mg/kg t-BuOOH. Apoptosis was associated with high levels of DNA fragmentation that was observed at 48 h after icv administration of 21.9 mg/kg t-BuOOH. Susceptibility to DNA damage was found to be age-dependent, since 24-mo-old mice exhibited consistently higher and more pervasive DNA damage than 8 mo-old-mice. Extensive DNA damage was seen in various brain regions in patients with Alzheimer disease (AD) and with both Alzheimer and Parkinson disease (AD-PD). These results directly implicate DNA damage in neurodegeneration. The DNA fragmentation ob-served can lead to both apoptosis and necrosis, as suggested by gel electrophoresis. Nicotinamide, a precursor of NAD in the brain, was able to prevent DNA fragmentation induced by low-dose t-BuOOH, when coadministered with the toxin.
Mol Chem Neuropathol
PMID:The effects of aging and neurodegeneration on apoptosis-associated DNA fragmentation and the benefits of nicotinamide. 943 58

We have presently determined the effect of inhibition of the DNA repair enzyme poly(ADP-ribose) polymerase (PARP) on the occurrence of apoptosis in insulin-producing cells. The ADP-ribosylation activities of intact cells were decreased by incubation of RINm5F cells for 16 h with the PARP inhibitors nicotinamide (NA) (20-50 mM) or 3-aminobenzamide (3-ABA) (10 mM). Exposure to 20-50 mM NA or 10 mM 3-ABA both resulted in massive apoptosis in RINm5F cells. A 24 h exposure to 50 mM nicotinamide induced apoptosis in fetal but not adult rat islet cells. In addition, exposure of RINm5F cells to 50 mM NA for 12-24 h induced the appearance of the 85 kDa proteolytic PARP fragment, indicating activation of the ICE-like protease caspase-3. Incubation with 20-50 mM NA did not induce any consistent effects upon transcription factor NF-kappaB activity, demonstrating that this pathway is not involved in induction of apoptosis by NA. It is concluded that in insulin-producing cells with a high mitotic rate, inhibition of ADP-ribosylation--and consequently of auto-modification and release of PARP bound to DNA strand breaks--leads to activation of programmed cell death.
Mol Cell Endocrinol 1998 Apr 30
PMID:Nicotinamide-induced apoptosis in insulin producing cells is associated with cleavage of poly(ADP-ribose) polymerase. 970 78

An experimental set-up for time-gated fluorescence spectroscopy and microscopy is described, and some recent applications in cellular and molecular biology are summarized. Selective detection of intrinsic fluorophores, in particular nicotinamide adenine dinucleotide (NADH) and flavins was demonstrated in living cells. Non-radiative energy transfer from reduced NADH to the mitochondrial marker rhodamine 123 was evaluated for probing mitochondrial malfunction in living cells. An increase of "energy transfer efficacy" up to a factor 4 was detected after inhibition of enzyme complexes of the respiratory chain. Two different fluorescence lifetimes of calcium orange were evaluated, whose relative intensities depended on calcium concentration. Therefore, fluorescence measured within two different time gates appeared to be suitable for ratio fluorometry of calcium. Time-gated fluorescence spectra of the membrane marker laurdan showed more pronounced changes than steady state spectra when temperature was increased from 24 degrees C to 38 degrees C. This may improve measurements of intracellular temperature. Time-gated detection of small amounts of porphyrins and their discrimination from a large fluorescent background caused by chlorophyll in transgenic tobacco plants again proved the advantages of time-gated fluorescence spectroscopy.
Cell Mol Biol (Noisy-le-grand) 1998 Jul
PMID:Time-gated fluorescence microscopy in cellular and molecular biology. 976 48


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