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)

We have tested an ethanol reagent strip developed at the Addiction Research Foundation of Ontario. Alcohol dehydrogenase and nicotinamide adenine dinucleotide, in the presence of pyrazole, react with ethanol to yield acetaldehyde plus reduced nicotinamide adenine dinucleotide. The latter reduces iodonitrotetrazolium chloride in the presence of diaphorase, generating an intense red color. The rate of color development is proportional to the concentration of ethanol. Color is compared at a specific time against a calibrated color scale ranging from green (negative) to red, representing alcohol concentrations of 0, 25, 50, 100, 200, and 400 mg/dl (0-0.4%; 0-87 mmol/liter). We were able to interpolate the color observed between the calibrated blocks. When tested on urine, serum/plasma, and saliva, ethanol concentration determined by the reagent strip correlates well with ethanol concentration as determined by gas chromatography or by automated enzymatic analysis (r = 0.92-0.98, p less than 0.001; slope 0.83-1.16). The reagent strip was shown to be used appropriately by nonexperienced individuals following a 1-min explanation (reagent strip values, r = 0.92; p less than 0.001, slope = 0.97, versus gas chromatography). The reagent strip does not react with methanol (wood alcohol), isopropanol (rubbing alcohol), and ethylene glycol (antifreeze) often found in accidental poisonings. In 379 clinical samples obtained without exclusion criteria from 12 hospital emergency rooms and a liver clinic, the sensitivity of the reagent strip in detecting ethanol was 98%. Specificity was 99%. The reagent strip was found to have virtually unlimited stability under refrigeration (4 degrees C) and to be stable for 3 to 4 months at room temperature (22-23 degrees C).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Characteristics of a new urine, serum, and saliva alcohol reagent strip. 159 May 43

The glucuronide conjugates of oroxylin A and two other flavones, baicalein, and wogonin, were isolated from the methanol extract of the herb scutellariae radix (Huang Qin) and were found to be inhibitors of rat liver NAD(P)H:quinone acceptor oxidoreductase (EC 1.6.99.2). Baicalin (baicalein 7-O-glucuronide) and oroxylin-A 7-O-glucuronide are approximately 50-fold more potent than wogonin 7-O-glucuronide. The enzyme kinetic analysis revealed that oroxylin-A 7-O-glucuronide is a competitive inhibitor with respect to NADH (the electron donor), with a Ki value of 63 nM. Considering the similarities of their structures and inhibition kinetics to those of dicoumarol, it is thought that oroxylin-A 7-O-glucuronide and the other two flavonoids bind to an identical site and inhibit this quinone reductase in the same fashion as dicoumarol. The results also suggest that the inhibition of NAD(P)H:quinone acceptor oxidoreductase or another vitamin K reductase by oroxylin-A 7-O-glucuronide and the related flavonoids may be one of the steps associated with the anticoagulation action of the herb. These compounds are potentially useful anticoagulant drugs.
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PMID:Inhibition of rat liver NAD(P)H:quinone acceptor oxidoreductase (DT-diaphorase) by flavonoids isolated from the Chinese herb scutellariae radix (Huang Qin). 169 61

An enzymatic assay method for the determination of urinary formic acid is described. Formic acid in urine was cleaved to carbon dioxide and water by formic acid dehydrogenase, whereby NAD+ was converted to NADH, which reacted with INT (p-iodonitrotetrazolium violet) in the presence of NAD-diaphorase. The color thus produced was determined at 500 nm. In addition, a simple gas chromatographic method of urinary formic acid is described, in which head space gas of formic acid methylester was applied into the wide bore column. The urinary formic acid concentrations by the enzymatic method agreed well with that by the gas chromatographic method. A simple gas chromatographic method for urinary methanol assay is also described. Acetonitrile was added to an equal volume of urine containing methanol. After centrifugation, the supernatant was injected into gas chromatography (GC). The peaks of urinary methanol and ethanol were separated by GC. Formic acid and methanol in urine of unexposed healthy subjects and workers exposed to methanol were analyzed by the colorimetric and gas chromatographic methods. Geometric mean concentrations of urinary formic acid and methanol in the healthy subjects were 7.82 mg/g creatinine and 1.34 mg/l, respectively. The concentration ratio of formic acid to methanol in the urine of the workers exposed to methanol was calculated to be 3.67 +/- 2.10, which agreed with the ratio under a controlled exposure experiment. A slower excretion of formic acid than that of methanol in the urine of a volunteer was also observed.
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PMID:Enzymatic assay of formic acid and gas chromatography of methanol for urinary biological monitoring of exposure to methanol. 234 46

Measurement of the bioequivalence of formulations of chenodiol, a bile acid which is used for gallstone dissolution, is difficult because its high first-pass clearance results in low plasma levels after ingestion of usual dosages. To solve this problem, a new method was developed to determine the bioequivalence of several chenodiol formulations. The method included the following steps: isolation of all bile acids from serum by absorption to a hydrophobic resin, elution of bile acids from the resin by methanol, separation of the unconjugated bile acid fraction by an ion-exchange procedure, and bioluminescence measurement of the unconjugated 7 alpha-hydroxy bile acids using Sepharose beads containing co-immobilized 7 alpha-hydroxysteroid dehydrogenase, diaphorase, and luciferase. The isolation method gave complete recovery, and the bioluminescence procedure was simple, rapid, and sensitive. The peak level of systemic chenodiol occurred 1 to 2 h following oral ingestion and ranged from 4 to 8 microM. This method appears superior to previously reported methods for determining the bioequivalence of chenodiol preparations. In principle, the method is suitable for measurement of the bioequivalence of other bile acids provided the appropriate hydroxysteroid dehydrogenase is available.
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PMID:Determination of chenodiol bioequivalence using an immobilized multi-enzyme bioluminescence technique. 370 13

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

An assay for glycine and taurine conjugates of cholic, chenodeoxycholic and deoxycholic acid in serum by a high pressure liquid chromatographic-enzymatic system is presented. The bile acids are extracted from serum by a reverse-phase liquid chromatographic process with an octadecylsilane column. The bile acid conjugates are separated on a muBondapak C18 column with methanol/KH2PO4 buffer, 20 mmol/l, pH 5.3 as a mobile phase in less than 30 min at a flow rate of 1.4 ml/min. The bile acid fractions are measured by enzymatic fluorometry using a 3 alpha-hydroxysteroid dehydrogenase-diaphorase system. Recoveries ranged from 82 to 96%, coefficients of variation were from 5 to 15%, and detection limits were from 0.03 to 0.08 mumol/l. Mean serum concentrations ranged from 0.10 to 0.39 mumol/l in the fasting state and from 0.29 to 1.55 mumol/l postprandially in subjects with normal liver function.
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PMID:A high-pressure liquid chromatographic-enzymatic assay for glycine and taurine conjugates of cholic, chenodeoxycholic and deoxycholic acid in serum. 715 57

Succinate:quinone reductases (SQRs) and quinol:fumarate reductases (QFRs) each contain a bi-, a tri- and a tetra-nuclear iron-sulfur cluster. The C-terminal half of the iron-sulfur protein subunit of these enzymes shows two fully conserved motifs of cysteine residues, stereotypical for ligands of [3Fe-4S] and [4Fe-4S] clusters. To analyze the functional role of the trinuclear cluster S3 in Bacillus subtilis SQR, a fourth cysteine residue was introduced into the putative ligation motif to that cluster. A corresponding mutation in Escherichia coli QFR results in a tri- to tetranuclear conversion (Manodori et al. (1992) Biochemistry 31, 2703-2731). We have found that presence of the extra cysteine in B. subtilis SQR does not result in cluster conversion. It does, however, affect the EPR properties of the cluster S3, whereas those of the other two clusters remain normal. The results strongly support the view that residues in the most C-terminal cysteine motif in the iron-sulfur protein subunit of SQRs and QFRs ligate the trinuclear cluster. Compared to wild-type SQR, S3 in the B. subtilis mutant enzyme is not sensitive to methanol and the midpoint redox potential is close to normal. The quinone reductase activity of the mutant enzyme is only 35% of normal. Thus, the architecture around cluster S3 plays a role in electron transfer to quinone or in the binding of quinone to the enzyme.
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PMID:The trinuclear iron-sulfur cluster S3 in Bacillus subtilis succinate:menaquinone reductase; effects of a mutation in the putative cluster ligation motif on enzyme activity and EPR properties. 774 86

Since the toxicity of diesel exhaust particles (DEP) after intratracheal injection, was suppressed by pretreatment with superoxide dismutase (SOD) modified with polyethylene glycol (Sagai et al. Free Rad. Biol. Med. 14: 37-47; 1993), the possibility that superoxide could be enzymatically and continuously generated from diesel exhaust particles (DEP), was examined. Nicotinamide-adenine dinucleotide phosphate, reduced (NADPH) oxidation was stimulated during interaction of a methanol extract of DEP with the Triton N-101 treated microsomal preparation of mouse lung whereas the cytosolic fraction was less active, suggesting that DEP contains substrates for NADPH-cytochrome P450 reductase (EC 1.6.2.4, P450 reductase) rather than DT-diaphorase. When purified P450 reductase was used as the enzyme source, the turnover value was enhanced approximately 260-fold. Quinones appeared to be served as substrate for P450 reductase because reaction was inhibited by addition of glutathione (GSH) to form those GSH adduct or pretreatment with NaBH4 to reduce those to the hydroxy compounds although a possibility of nitroarenes as the alternative substrates cannot be excluded. A methanol extract of DEP (37.5 micrograms) caused a significant formation of superoxide (3240 nmol/min/mg protein) in the presence of P450 reductase. Electron spin resonance (ESR) experiments revealed that hydroxyl radical was formed as well. The reactive species generated by DEP in the presence of P450 reductase caused DNA scission which was reduced in the presence of superoxide dismutase (SOD), catalase, or hydroxyl radical scavenging agents. Taken together, these results indicate that DEP components, probably quinoid or nitroaromatic structures, that appear to promote DNA damage through the redox cycling based generation of superoxide.
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PMID:Generation of reactive oxygen species during interaction of diesel exhaust particle components with NADPH-cytochrome P450 reductase and involvement of the bioactivation in the DNA damage. 898 Oct 40

The effect of extracts of scutellariae radix (Scutellaria baicalensis Georgi) and its flavonoids, baicalin, baicalein and wogonin, on induction of quinone reductase (QR) in the Hepa 1c1c7 murine hepatoma cell line was examined. A significant and dose-dependent induction of QR activity was observed in the methanol extract of scutellariae radix and baicalin. HPCL analysis showed that baicalin was contained as a main component in the methanol extract of scutellariae radix, indicating that baicalin may be the major active principle of QR induction mediated by scutellariae radix extract. To elucidate the mechanism of baicalin-mediated induction of QR enzyme activity, the effect on QR mRNA levels in Hepa 1c1c7 cell cultures was investigated. Using reverse transcriptase-polymerase chain reaction techniques, time- and dose-dependent induction of QR mRNA levels by baicalin were demonstrated in Hepa 1c1c7 cells. On the basis of these results, the scutellariae radix extract or baicalin can be regarded as a readily available, promising, novel cancer chemopreventive agent.
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PMID:Induction of quinone reductase by a methanol extract of Scutellaria baicalensis and its flavonoids in murine Hepa 1c1c7 cells. 992 95

Polyphenolic antioxidants are being identified as cancer preventive agents. Recent studies in our laboratory have identified and defined the cancer preventive and anticarcinogenic potential of a polyphenolic flavonoid antioxidant, silymarin (isolated from milk thistle). More recent studies by us found that these effects of silymarin are due to the major active constituent, silibinin, present therein. Here, studies are done in mice to determine the distribution and conjugate formation of systemically administered silibinin in liver, lung, stomach, skin, prostate and pancreas. Additional studies were then performed to assess the effect of orally administered silibinin on phase II enzyme activity in liver, lung, stomach, skin and small bowel. For tissue distribution studies, SENCAR mice were starved for 24 h, orally fed with silibinin (50 mg/kg dose) and killed after 0.5, 1, 2, 3, 4 and 8 h. The desired tissues were collected, homogenized and parts of the homogenates were extracted with butanol:methanol followed by HPLC analysis. The column eluates were detected by UV followed by electrochemical detection. The remaining homogenates were digested with sulfatase and beta-glucuronidase followed by analysis and quantification. Peak levels of free silibinin were observed at 0.5 h after administration in liver, lung, stomach and pancreas, accounting for 8.8 +/- 1.6, 4. 3 +/- 0.8, 123 +/- 21 and 5.8 +/- 1.1 (mean +/- SD) microg silibinin/g tissue, respectively. In the case of skin and prostate, the peak levels of silibinin were 1.4 +/- 0.5 and 2.5 +/- 0.4, respectively, and were achieved 1 h after administration. With regard to sulfate and beta-glucuronidate conjugates of silibinin, other than lung and stomach showing peak levels at 0.5 h, all other tissues showed peak levels at 1 h after silibinin administration. The levels of both free and conjugated silibinin declined after 0.5 or 1 h in an exponential fashion with an elimination half-life (t((1/2))) of 57-127 min for free and 45-94 min for conjugated silibinin in different tissues. In the studies examining the effect of silibinin on phase II enzymes, oral feeding of silibinin at doses of 100 and 200 mg/kg/day showed a moderate to highly significant (P < 0.1-0.001, Student's t-test) increase in both glutathione S-transferase and quinone reductase activities in liver, lung, stomach, skin and small bowel in a dose- and time-dependent manner. Taken together, the results of the present study clearly demonstrate the bioavailability of and phase II enzyme induction by systemically administered silibinin in different tissues, including skin, where silymarin has been shown to be a strong cancer chemopreventive agent, and suggest further studies to assess the cancer preventive and anticarcinogenic effects of silibinin in different cancer models.
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PMID:Tissue distribution of silibinin, the major active constituent of silymarin, in mice and its association with enhancement of phase II enzymes: implications in cancer chemoprevention. 1054 12


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