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

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Query: EC:1.6.5.2 (NQO1)
6,196 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A rapid, precise, and accurate photometric method for determining free and esterified fecal 3 alpha-hydroxy bile acids is described. Feces are homogenized and (a) extracted with boiling absolute ethanol, or (b) lyophilized and extracted with chloroform:methanol 2:1 (v/v). Hydrolyzed and nonhydrolyzed crude extracts are prepared and aliquots treated with a reagent containing nitro blue tetrazolium (NBT), 3 alpha-hydroxysteroid oxidoreductase, beta-nicotinamide adenine dinucleotide (beta-NAD) and diaphorase. The reagent first oxidizes bile acid 3 alpha-hydroxyls to 3-oxo groups and 3 beta-hydrogen is transferred to beta-NAD yielding beta-NADH. beta-NADH in turn reduces NBT (yellow) to its diformazan (blue). Absorbance is measured at 540 nm and is proportional to the 3 alpha-hydroxy bile acid titer of fecal extract aliquots. Fecal pigments present in crude extracts do not interfere with the assay since they absorb minimally at 540 nm.
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PMID:Rapid photometric determination of free and esterified 3 alpha-hydroxy fecal bile acids. 666 19

The role of various enzymes and biological molecules on the activation and deactivation of the metabolites of phenol was investigated in vitro. Phenol, the major metabolite of benzene, is metabolized to hydroquinone and catechol. Activation of these metabolites and deactivation of their oxidized forms was assessed by the amount of covalent binding to microsomal protein. [14C]Phenol and NADPH were incubated with hepatic microsomes isolated from phenobarbital-pretreated guinea pigs, and 2.33 nmoles of hydroquinone and 0.12 nmole of catechol were formed per minute per milligram of microsomal protein. Covalent binding of the metabolites to microsomal protein incubated with microsomes isolated from guinea pigs pretreated with phenobarbital was 252 pmoles bound/min/mg; with microsomes from untreated guinea pigs, covalent binding was 146 pmoles bound/min/mg. Covalent binding was inhibited greater than 90% with the addition of N-octylamine, ascorbate, or GSH. The addition of superoxide dismutase inhibited covalent binding with microsomes isolated from phenobarbital-pretreated guinea pigs 35% but did not inhibit it with microsomes isolated from untreated animals. Partially purified guinea pig hepatic DT-diaphorase [NAD(P)H (quinone acceptor) oxidoreductase, EC 1.6.99.2] inhibited covalent binding 70%. This effect was reversed in the presence of dicumarol, a specific inhibitor of DT-diaphorase. DT-diaphorase present in the 10(5) X g supernatant fraction was also active in inhibiting covalent binding but only after the removal of endogenous reduced glutathione. This effect could also be reversed by dicumarol. The addition of diaphorase (NADH:lipoamide oxidoreductase, EC 1.6.4.3) partially purified from Clostridium kluyveri inhibited covalent binding 86%. The addition of hydrogen peroxide and horseradish peroxidase (peroxidase, EC 1.11.17) or myeloperoxidase(s) increased covalent binding 30-fold and 6-fold, respectively. Ascorbate decreased this binding greater than 95%. These results indicate that hydroquinone, catechol, and phenol as well as their oxidized forms can be activated or deactivated by several of the above model systems. These systems may play a role in the myelotoxicity of benzene by modulating covalent binding.
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PMID:DT-diaphorase and peroxidase influence the covalent binding of the metabolites of phenol, the major metabolite of benzene. 674 27

In this simple and direct method for determining total bile acids in serum, the serum was mixed with sodium pyruvate, a lactate dehydrogenase blocker, and bile acids were then measured spectrophotometrically after the following enzyme reaction. Bile acids are converted to 3-oxo bile acids with 3 alpha-hydroxysteroid dehydrogenase (EC 1.1.1.50) with concomitant reduction of NAD+ to NADH. The hydrogen in the NADH generated is transferred by diaphorase (EC 1.6.4.3) to nitrotetrazolium blue to yield diformazan 540 nm). Analytical recovery of the various bile acids in serum averaged 96.2%. The CV for the day-to-day variation was 4.3%. Normal values are less than 7 mumol/L. Total serum bile acids were estimated by this method in 118 fasting patients with various liver diseases. This determination is clearly shown to be useful as a liver-function test.
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PMID:Direct spectrophotometry of total bile acids in serum. 689 53

A new enzymatic fluorimetric assay for the determination of total serum bile acids is described. The enzyme 3 alpha-idroxysteroid NAD oxireductase by oxydising the free OH in position 3 alpha of bile acid molecule, reduce NAD previously added. Afterwards the hydrogen of the generated NADH is transferred by a diaphorase to resazurin to yield the fluorophore resorufin proportionally to the amount of bile acids in the sample. The assay is simple, accurate, without bilirubin's influence and useful for a routine use because the analysis time is not different from the more common laboratory tests.
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PMID:[Spectrophotofluorimetric enzymatic determination of total serum bile acids]. 692 10

Phenanthrenequinone (PQ), which occurs widely as a pollutant and as a major metabolite of phenanthrene in a number of species, has been demonstrated to undergo futile redox cycling leading to oxidative stress. In the presence of cytosolic fractions of selected channel catfish tissues, PQ undergoes enzymatic reduction which is mediated by either NADH or NADPH and is composed of dicoumarol-sensitive and -insensitive components. Most notably, gastric cytosol catalyzed a disproportionately high level of NADPH-dependent, dicoumarol-sensitive PQ reduction as compared to gill, liver, and kidney cytosols. In the presence of stomach cytosol and NADPH, PQ facilitated production of superoxide anion at rates several fold higher than those mediated by menadione. The dicoumarol-sensitive PQ-reducing agent, which we have termed NADPH: phenanthrenequinone oxidoreductase (PQR), was purified by affinity chromatography and was demonstrated to be separable from DT diaphorase activity in gastric cytosol. Under aerobic conditions, purified PQR facilitates redox cycling of PQ as indicated by continued NADPH oxidation and hydrogen peroxide production. Under anaerobic conditions, NADPH oxidation is limited to a quantity indicative of PQ reduction to the hydroquinone. Substrate specificities, pH profiles, and kinetic characteristics combine to indicate that PQR represents a novel quinone reductase in this species.
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PMID:Dicoumarol-sensitive NADPH: phenanthrenequinone oxidoreductase in channel catfish (Ictalurus punctatus). 751 48

In the present study, nicotinamide adenine dinucleotide hydrogen phosphate-diaphorase (NADPH-d) histochemistry has been used as a marker for nitric oxide synthase. NADPH-d positive neuronal cell bodies and fibres have been localized in the pancreas of the mouse, rat, chick, kitten and monkey. In all these species, most of the NADPH-d labelled neuronal cell bodies in the ganglia were found in the interlobular and interacinar connective tissue while some were intimately associated with pancreatic ducts and blood vessels. There was, however, a gradation of innervation amongst the species. Only in the pancreatic islets of the mouse and monkey were NADPH-d positive neuronal cell bodies and nerve fibres detected in the formation of neuro-insular complexes. Besides labelling of neuronal cell bodies, nerve fibres and endothelial cells, the islet cells of the mouse, kitten and chick pancreas also gave a light positive reaction for NADPH-d activity. The nerve fibre and the outer core of the connective tissue of the Pacinian corpuscles in the kitten pancreas were also labelled for NADPH-d activity. It is concluded that nitric oxide may play an important role in the neural regulation of both exocrine and endocrine secretion and in controlling the activity of the blood vessels and ducts of the pancreas.
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PMID:Localization of NADPH-diaphorase positive neurons in the pancreas of the mouse, rat, chick, kitten and monkey. 753 10

In the present study, nicotinamide adenine dinucleotide hydrogen phosphate-diaphorase (NADPH-d) histochemistry has been used as a marker for nitric oxide synthase (NOS). The colored reaction product, formazan, was localized in neuronal cell bodies, nerve fibers, and vascular endothelium in the thyroid of chick and mouse. In these two animal species, most of the NADPH-d-labeled neuronal cell bodies were found in the thyroid capsule and interfollicular connective tissue while some were associated with blood vessels. Most nerve fibers travelled with blood vessels supplying the thyroid gland, while a few of them were intimately associated with the thyroid follicular cells. Control sections not incubated with beta-NADPH failed to show labeling of the above structures. It is concluded that nitric oxide may play an important role in endocrine secretion by controlling the regional blood flow in the thyroid gland and by directly acting on the thyroid follicular cells.
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PMID:Localization of NADPH-diaphorase reactivity in the chick and mouse thyroid gland. 753 60

Trypanothione reductase is a member of the structurally and functionally well-characterized family of flavoprotein reductases, which catalyze the reduced pyridine nucleotide dependent reduction of their disulfide, peroxide, or metal ion substrates. Trypanothione reductase is found in a wide variety of Trypanosoma species, where the enzyme serves physiologically to protect the organism from oxidative stress and assists in maintaining low intracellular levels of hydrogen peroxide. The redox potential of the flavin and the hydride ion transfer reaction of the pro-S hydrogen of NADPH to N5 of FAD have been proposed to be influenced by the presence of a conserved Lys-Glu (K60-E201) ion pair at the bottom of the nicotinamide binding pocket. We have evaluated this hypothesis by making modest substitutions for both the Lys and Glu residues using site-directed mutagenesis. Replacement of the K60 residue with an arginine led to a poorly expressed, and completely inactive, enzyme. Replacement of the Glu201 residue with either a glutamine (E201Q) or an aspartate (E201D) residue led to expressed enzymes which could be readily purified in > 20 mg amounts using protocols developed for the WT enzyme, and which had significant residual trypanothione-reducing activity. These enzymes have now been characterized to determine their redox potentials, catalytic activities, and nucleotide specificities. Relative to the WT enzyme, both E201D and E201Q exhibit ca. 5% of WT trypanothione-reducing activity using NADPH as reductant, but significantly enhanced quinone reductase activity. The oxidase activity of both mutants is enhanced by over 50-fold compared to that of the WT. The redox potential of the WT enzyme has been determined to be -273 mV, while both the E201D and E201Q exhibit more positive redox potentials (-259 and -251 mV, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Catalytic and potentiometric characterization of E201D and E201Q mutants of Trypanosoma congolense trypanothione reductase. 754 22

NAD(P)H:quinone oxidoreductase1 (DT-diaphorase or NQO1) is a flavoprotein that promotes obligatory two-electron reduction of quinones, preventing their participation in redox cycling, oxidative stress, and neoplasia. NQO1 is ubiquitously expressed. However, a large amount of variation in NQO1 gene expression was noticed among various human tissues. NQO1 gene is upregulated in livers of hepatocarcinoma patients, and its expression is induced in response to a variety of compounds, including planar aromatic hydrocarbons, phenolic antioxidants/chemoprotectors, tumor promoters, and hydrogen peroxide. Deletion mutagenesis in the NQO1 gene promoter identified several cis-elements including antioxidant response element (ARE), xenobiotic response element, and AP2 element, which regulate the expression and induction of the NQO1 gene. Among these DNA elements, ARE is the most important cis-element required for high basal expression of the NQO1 gene in tumor tissues, as compared to the normal tissues of the same origin, and for its induction in response to xenobiotics and antioxidants. Nucleotide sequence analysis of the ARE indicated presence of three AP1/AP1-like elements and a GCA box. Mutational analysis indicated a requirement of two AP1/AP1-like elements arranged as inverse repeats at the interval of three base pairs for the ARE activity. The GCA box in the ARE was required for optimum basal and induced expression. ARE is a novel cis-element because a single AP1/AP1-like element did not stimulate gene expression in response to xenobiotics and antioxidants. Band shift and supershift assays identified Jun, Fos, and novel proteins in the hARE-nuclear protein complexes that mediate regulation of the NQO1 gene expression.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:NAD(P)H:quinone oxidoreductase1 (DT-diaphorase): expression, regulation, and role in cancer. 762 Feb 21

The inhibitory non-adrenergic non-cholinergic (i-NANC) innervation of the guinea pig airways was suggested to be mediated, at least partially, by nitric oxide (NO). The enzyme catalyzing the generation of NO and citrulline from L-arginine, nitric oxide synthase (NOS), was found to be identical with neuronal nicotinamide-adenine dinucleotide hydrogen phosphate (NADPH)-diaphorase. In the present study, we report the distribution of NOS in guinea pig lower airways and in vagal sensory and sympathetic ganglia as revealed by NOS immunohistochemistry and NADPH-diaphorase histochemistry. The distribution of NOS was identical using either technique and displayed a similar distribution pattern in all parts of the lower airways. Yet, the number of NOS-containing fibres was increasing from cervical trachea towards principal bronchi and decreasing to complete absence in bronchioli. Innervation with NOS-containing nerve fibres was densest in the smooth muscle layer and in the lamina propria of the mucosa. Single fibres were found in the respiratory epithelium. Labelling was absent from nerve fibres innervating the submucosal glands. Perivascular fibre networks enmeshed tracheal arteries, pulmonary arteries and veins. A substantial number of NOS-immunoreactive and NADPH-diaphorase-positive neurons was observed in vagal sensory ganglia, whereas such neurons were rather sparse in sympathetic ganglia. Tracheal and peribronchial ganglia of the airways were devoid of labelling. These findings suggest that extrinsic rather than intrinsic (tracheal and peribronchial) neurons are the source of NO release from guinea pig airway nerve fibres after electrical field stimulation. These extrinsic nerve fibres may originate from both sympathetic and vagal sensory ganglia.
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PMID:Nitric oxide synthase in guinea pig lower airway innervation. 768 79


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