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)

The lipid composition of highly purified Flury strain of rabies virus (HEP) propagated in BHK-21 cells in a chemically defined medium was observed to be 6.7% neutral lipids, 15.8% phospholipids, and 1.5% glycolipids. In the virion, phosphatidylethanolamine, phosphatidylcholine, and sphingomyelin were the most abundant phospholipids, accounting for 90% of the total, and the molar ratio of cholesterol to phospholipid was 0.48. Uninfected BHK-21 cell membranes were obtained by nitrogen cavitation techniques and separated by density gradient centrifugation, and the membranes were assayed for purity using 5'-nucleotidase, cytochrome oxidase, and reduced nicotinamide adenine dinucleotide phosphate diaphorase activities. Lipids of the plasma membrane were enriched in cholesterol, phosphatidylcholine, and phosphatidylethanolamine. In contrast, membranes of the endoplasmic reticulum were enriched in phosphatidylcholine, but contained smaller amounts of phosphatidylethanolamine and sphingomyelin. Comparison of the fatty acyl chains of virus and membranes from uninfected cells revealed the virion to have the lowest ratio of C18:1 to C18:0 (1.771), compared with values of about 3.0 for the plasma membrane and endoplasmic reticulum. Total polyenoic fatty acids were enriched in the plasma membrane, whereas the virus contained higher amounts of total saturates than either of the two membrane preparations. Analysis of the polar and neutral lipid fractions as well as the acyl chain analysis suggests the virion has a lipid composition that is intermiediate to that of the plasma membrane and endoplasmic reticulum and is consistent with the view that numerous viral particles are synthesized de novo by not utilizing a preexisting membrane template. From the ratio of cholesterol to phospholipid of 0.48, we calculated that 1.92 X 10(5) molecules of lipid would cover 4.14 X 10(4) nm2 in the form of a bilayer. Considerations of the molecular dimensions of the rabies envelope (total surface area, 5 X 10(4) nm2) as a bilayer suggest that some penetration of lipids by envelope proteins (M and G) is necessary.
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PMID:Lipids of rabies virus and BHK-21 cell membranes. 55 73

The levels of acetylcholine and choline were measured in various brain regions of the rat after fixation by microwave irradiation of the head and after decapitation and subsequent freezing in liquid nitrogen. Levels of acetylcholine were increased by approximately 50% after microwave irradiation, while choline levels were reduced. These biochemical findings were correlated with virtually complex loss of acetylcholinesterase and NADH-diaphorase activity after 1 s exposure to microwave irradiation at a level of 5 kW.
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PMID:Fast fixation of brain in situ by high intensity microwave irradiation: application to neurochemical studies. 104 75

DT-diaphorase (DTD) mediated reduction of a series of 2,5-bis-substituted-3,6-diaziridinyl-1,4-benzoquinones was found to increase the level of DNA interstrand cross-linking (ISC) formed at neutral pH with an enhancement observed as the pH was decreased to 5.8. The analogues used were symmetrically alkyl-substituted carbamoyl ester analogues of AZQ (D1-D7), 3,6-diaziridinyl-1,4-benzoquinone (DZQ), the 2,5-dimethyl derivative (MeDZQ), and a 2,5-bis[(2-hydroxyethyl)amino] analogue (BZQ). At pH 5.8, the level of DNA ISC induced by enzymatic reduction was as follows: DZQ greater than MeDZQ much greater than D1 (methyl) greater than D3 (n-propyl) greater than D2 (AZQ; ethyl) greater than D5 (n-butyl) greater than D7 (sec-butyl) greater than D4 (isopropyl) D6 greater than (isobutyl). A similar trend was observed at pH 7.2. The level of DNA ISC induced by BZQ, which is not a substrate for DTD, was not increased by enzymatic reduction. Dicumarol, a known inhibitor of DTD, was capable of inhibiting the DNA ISC induced by these quinones upon enzymatic reduction. MeDZQ and DZQ reacted with guanines, as measured by Maxam and Gilbert sequencing, with a sequence selectivity similar to that of the nitrogen mustard class of antitumor agents. Enzymatic reduction of DZQ and MeDZQ by DTD was found to alter their sequence-selective alkylation. Reduced DZQ showed enhanced guanine alkylation in 5'-GC-3' sequences and new sites of adenine alkylation in 5'-(A/T)AA-3' sequences. Reduced MeDZQ only showed new sites of adenine alkylation at 5'-(A/T)AA-3' sequences but no enhancement of guanine alkylation. The new sites of adenine alkylation were found to be inhibited in the presence of magnesium and rapidly converted into apurinic sites.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Alteration in DNA cross-linking and sequence selectivity of a series of aziridinylbenzoquinones after enzymatic reduction by DT-diaphorase. 137 18

Nitroaniline mustards have potential as hypoxia-selective cytotoxic agents, with reductive metabolism activating the nitrogen mustard by converting the electron-withdrawing nitro group to an electron-donating hydroxylamine or amine. However, the parent compounds have poor aqueous solubility, and their potencies are limited by low reduction potentials (E1/2 ca. -600 mV versus the normal hydrogen electrode) and corresponding slow rates of nitro reduction. To address these limitations, a series of 4-nitroaniline mustards bearing hydrophilic side chains attached via an electron-withdrawing carboxamide group was prepared and evaluated for hypoxia-selective cytotoxicity against Chinese hamster cell lines. The N-[(N,N-dimethylamino)ethyl]carboxamide derivatives proved to have excellent aqueous solubility and improved cytotoxic potency, but their reduction potentials, while higher than the non-carboxamide compounds, were still low and little selectivity for hypoxic cells were observed. A series of carboxamides of 2,4-dinitroaniline mustard was also prepared. These compounds had reduction potentials in the desired range (E1/2 ca. -450 mV by cyclic voltammetry) and were more toxic to hypoxic than aerobic UV4 cells. The most selective compounds were 5-[N,N-bis(2-chloroethyl)amino]-2,4-dinitrobenzamide (20, SN 23862) and its water-soluble N-[(N,N-dimethylamino)ethyl]carboxamide analogue. These showed selectivities of 60- to 70-fold for hypoxic UV4 cells. The selectivity of 20 was much superior to that of its aziridine analogue (23, CB 1954), which was only 3.6-fold more toxic to hypoxic than oxic cells in the same system. Compound 20 is a much less efficient substrate than CB 1954 for the major aerobic nitroreductase from rat Walker tumor cells, NAD(P)H:quinone oxidoreductase (DT diaphorase). Lack of aerobic bioactivation of 20 by DT diaphorases may be responsible for its higher hypoxic selectivity than that of 23.
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PMID:Hypoxia-selective antitumor agents. 5. Synthesis of water-soluble nitroaniline mustards with selective cytotoxicity for hypoxic mammalian cells. 150 7

Heart lipoamide dehydrogenase (LADH) catalyzed redox-cycling and O2-. production by (5-nitro-2-furfurylidene)amino derivatives using NADH as electron donor. NADH was a much more effective electron donor than NADPH for the nitroreductase activity. O2-. production was demonstrated by cytochrome c reduction, adrenochrome formation and the effect of superoxide dismutase. Under optimum conditions, nitroreductase activity was about 1% of LADH activity. One electron oxygen reduction and NADH oxidation correlated in 2:1 stoichiometry. The nitroreductase kinetics was in accordance with an ordered bi-bi mechanism. Nitrofuran derivatives bearing unsaturated five- or six-membered nitrogen heterocycles were more effective substrates than those bearing other groups, namely nifurtimox, nitrofurazone, nitrofurantoin and 5-nitro-2-furoic acid. Other nitro compounds (chloramphenicol, benznidazole, 2-nitroimidazole and 5-nitroindole) were ineffective. With the triazole, traizine and imidazole nitrofuran derivatives, the nitroreductase pH curve showed a maximum at pH 8.8, different from the pH optimum for the lipoamide reductase and diaphorase activities. Spectroscopic observations demonstrated pH-dependent structural changes in the triazole(I) and triazine derivatives which would affect their behavior as nitroreductase substrates. The nitroreductase activity was inhibited by p-chloromercuribenzoate and enhanced by cadmium and arsenite, whereas the NADH-induced LADH inactivation failed to affect the nitroreductase activity. In the absence of oxygen. LADH catalyzed nitrofuran reduction to products more reduced than the nitroanion, which were not reoxidized by oxygen. The anaerobic nitrofuran reduction was inhibited by cadmium and arsenite. The assayed nitrofuran compounds did not inhibit LADH lipoamide reductase activity, at variance with their action on glutathione reductase (Grinblat et al., Biochem Pharmacol 38: 767-772, 1989).
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PMID:Catalysis of nitrofuran redox-cycling and superoxide anion production by heart lipoamide dehydrogenase. 217 92

NADH-cytochrome b5 reductase is the predominant NADH-diaphorase found in the human neutrophil (Blood 62:152, 1983). Although this reductase segregates with the light membranes of nitrogen-cavitated neutrophils separated on Percoll gradients (which include the plasma membrane markers alkaline phosphatase and NADPH-oxidase), it is approximately 95% excluded from plasma membrane-enriched phagocytic vacuoles. The reductase constitutes approximately 5% of the light membrane fraction FAD-flavoprotein (14.8 +/- 5.5 pmol/mg protein) and was found in equimolar concentration with a high potential b cytochrome also present in this light membrane fraction and tentatively identified as cytochrome b5. Isolation of the reductase from human neutrophils was accomplished by Triton X-114 solubilization of the light Percoll gradient membranes, followed by temperature-dependent phase separation and then affinity chromatography on AMP-Sepharose. The active preparation contained 1.3 mol FAD/mol protein, migrated on sodium dodecyl sulfate-polyacrylamide gels as a single band corresponding to an apparent mol wt of 45,000 daltons, exhibited a pl of 5.7 on chromatofocusing and was obtained in greater than 70% yield, with an overall purification of almost 900-fold. The purified enzyme was characterized by a high specificity for NADH as electron donor (Km = 6.4 mumol/L v Km greater than 1.6 mmol/L for NADPH) and exhibited a maximal turnover of ca. 30,000 min-1 at 22 degrees C with either ferricyanide or cytochrome b5 (Km = 10 nmol/L) as electron acceptor. Although the physical characterization and biochemical properties described here demonstrate that this neutrophil NADH b5 reductase is similar to the corresponding liver and erythrocyte enzymes, its unique function in the neutrophil has yet to be determined.
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PMID:Purification and characterization of the human neutrophil NADH-cytochrome b5 reductase. 299 39

The involvement of the cytoplasmic membrane in electron transport to nitrogenase has been studied. Evidence shows that nitrogenase activity in Azotobacter vinelandii is coupled to the flux of electrons through the respiratory chain. To obtain information about proteins involved, the changes occurring in A. vinelandii cells transferred to nitrogen-free medium after growth on NH4Cl (depression of nitrogenase activity) were studied. Synthesis of the nitrogenase polypeptides was detectable 5 min after transfer to nitrogen-free medium. No nitrogenase activity could be detected until t = 20 min, whereupon a linear increase of nitrogenase activity with time was observed. Synthesis of nitrogenase was accompanied by synthesis of flavodoxin II and two membrane-bound polypeptides of Mr 29,000 and 30,000. Analysis with respect to changes in membrane-bound NAD(P)H dehydrogenase activities revealed the induction of an NADPH dehydrogenase activity, which was not detectable in membranes isolated from cells grown in the presence of NH4OAc. This induced activity was associated with the appearance of a polypeptide of Mr 29,000 in the NADPH dehydrogenase complex.
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PMID:Studies on the mechanism of electron transport to nitrogenase in Azotobacter vinelandii. 345 4

The effects of dietary administration of equimolar doses (5 mmol/kg body wt per day) of trimethylene oxide, trimethylene sulfide, coumaran, benzofuran, indole, and indole-3-carbinol on the activities of microsomal epoxide hydrolase and several other xenobiotic metabolizing enzymes were measured in the liver of female CD-1 mouse. Every compound, with the exception of indole, caused a significant increase (P less than 0.01) of the styrene oxide epoxide hydrolase activity over controls in hepatic microsomes. These results indicate that the enzyme activity is elevated in vivo by several heterocyclic compounds with strained bond angles to a nucleophilic hetero-atom. In addition, the ability of sulfur-containing trimethylene sulfide and nitrogen-containing indole-3-carbinol to elevate the enzyme activity indicates that the heterocyclic oxygen atom is not an absolute requirement for this effect. Data from the other xenobiotic metabolizing enzymes indicate that trimethylene oxide and trimethylene sulfide enhance the epoxide hydrolase activity rather specifically, while not affecting the activities of the other enzymes measured. While the oxygen-containing coumaran and benzofuran both increased the NADH: quinone reductase activity in hepatic cytosol, the nitrogen-containing indole and indole-3-carbinol did not. This indicated a specific requirement for the oxygen atom in elevating the quinone reductase activity, which was not the case for the elevation of microsomal epoxide hydrolase activity.
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PMID:Enhancement of epoxide hydrolase activity in hepatic microsomes of mice given heterocyclic compounds. 376 53

To study the cryopreservation of osteoarticular allografts, a lateral femoral condyle of the rabbit was transplanted fresh, after uncontrolled freezing to -80 degrees C with 4 weeks preservation, and after freezing 1 degree C per min to -100 degrees C in 10 per cent dimethylsulphoxide medium with 4-week storage in liquid nitrogen. Autografts were used as controls. After 3 months, the incorporation of the grafted bone was good in all technically successful cases. The NADH2 diaphorase activity and 35S sulphate uptake indicated well-functioning chondrocytes in all autografts. In the allografts, areas lacking enzyme activity and lacking 35S uptake were observed in cartilages with otherwise normally functioning chondrocytes. No differences were found between the three allograft groups. We conclude that freezing permits reasonably good short-term bank preservation of cartilage. We found no difference between conventional freezing and controlled slow freezing with preservative.
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PMID:Cryopreservation of osteo-chondral grafts in rabbits. 389 7

The reduction of resorufin (7-hydroxyphenoxazone) fluorescence was catalyzed by enzymes present in the hepatic cytosol of rats and hamsters. This reaction was mediated by either NADH or NADPH, was completely inhibited by 10 microM dicumarol, and was not affected by anaerobic conditions (purging the reaction cuvette with nitrogen). The enzyme-mediated decrease in resorufin fluorescence was also associated with the loss of the primary absorbance maximum at 570 nm as well as the shoulders at 530 and 600 nm. Similar spectral changes were observed after resorufin was nonenzymatically reduced by sodium dithionite. The enzymatic activity was induced 20- to 40-fold by animal pretreatment with Aroclor-1254 or methylcholanthrene, but only minimally by phenobarbital. A 2.5-fold increase in the rate of the reaction was noted when the pH of the reaction mixture was lowered from pH 7.5 to 6.0. This pH optimum was not a result of slower rates of reoxidation of the reduced resorufin at lower pH, but was due to increased rates of reduction of the compound. Several of the characteristics of the reaction were congruent with the involvement of DT-diaphorase (quinone oxidoreductase, EC 1.6.99.2), and this newly developed fluorimetric assay would appear to be a rapid, sensitive, and direct method for measurement of DT-diaphorase activity.
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PMID:Cytosol-mediated reduction of resorufin: a method for measuring quinone oxidoreductase. 642 57


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