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:1.6.99.3 (diaphorase)
5,903 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Membrane vesicles can be prepared from murine lymphoid cells by nitrogen cavitation and fractionated by sedimentation through nonlinear sucrose density gradients. Two subpopulations of membrane vesicles, PMI and PMII, can be distinguished on the basis of sedimentation rate. The subcellular distribution of adenylate and guanylate cyclases in these membrane subpopulations have been compared with the distribution of a number of marker enzymes. Approximately 20-30% of the total adenylate and guanylate cyclase activity is located at the top of the sucrose gradient (soluble enzyme), the remainder of the activity being distributed in the PMI and PMII fractions (membrane-bound enzyme). More than 90% of the 5'-nucleotidase and NADH oxidase activities detected in lymphoid cell homogenates are located in PMI and PMII fractions, whereas succinate cytochrome c reductase activity is detected only in the PMII fractions. In addition, beta-galactosidase activity is distributed in the soluble and PMII fractions of the sucrose density gradients. On the basis of the fractionation patterns of these various enzyme activities, it appears that PMI fractions contain vesicles of plasma membrane and endoplasmic reticulum, whereas PMII fractions contain mitochondria, lysomes, and plasma membrane vesicles. Approximately 30-40% of the adenylate and guanylate cyclase activities in PMII can be converted to a PMI-like form following dialysis and resedimentation through a second nonlinear sucrose gradient. Adenylate and guanulate cyclases can be distinguished on the basis of sensitivity to nonionic detergents.
...
PMID:The subcellular distribution of adenylate and guanylate cyclases in murine lymphoid cells. 0 90

One allele at each of the five nit loci in Neurospora crassa together with the wild type strain have been compared on various nitrogen sources with regard to (i) their growth characteristics (ii) the level of nitrate reductase and its associated activities (reduced benzyl viologen nitrate reductase and cytochrome c reductase) (iii) the level of nitrate reductase and (iv) their ability to take up nitrite from the surrounding medium. Results are consistent with the hypothesis that nit-3 is the structural gene for nitrate reductase, nit-1 specifies in part of molybdenum containing moiety which is responsible for the nit-3 gene product dimerising to form nitrate reductase, nit-4 and nit-5 are regulator genes whose products are involved in the induction of both nitrate reductase and nitrite reductase and nit-2 codes for a generalised ammonium activated repressor protein. Studies on the induction of nitrate reductase (and its associated activities) and nitrite reductase in wild type, nit-1 and nit-3 in the presence of either nitrate or nitrite suggest that each enzyme may be regulated independently of the other and that nitrite could be true co-inducer of the assimilatory pathway. Nitrite uptake experiments with nit-2, nit-4 and nit-5 strains show that whereas nit-4 and nit-5 are freely permeable to this molecule, it is unable to enter the nit-2 mycelium.
...
PMID:Biochemical studies on the nit mutants of Neurospora crassa. 13 3

The cell membrane-associated respiratory electron transport chain of Neisseria gonorrhoeae was examined using electron paramagnetic spectroscopy (EPR) at liquid helium temperatures and optical spectroscopy at liquid nitrogen and room temperatures. EPR spectra of dithionite-reduced particles indicated the presence of centers N-1 and N-3 in the site I region of the respiratory chain, whereas reduction with succinate revealed the existence of center S-1 from the succinate cytochrome c reductase segment. Free radical(s) resembling that due to falvin semiquinone were observed with both reductants. Low temperature (77 K) optical difference spectra indicated the presence of cytochromes with alpha band maxima at 549, 557, and 562. Bands at 567, 535, and 417 nm, characteristic of the CO compound of cytochrome o, were also identified. Cytochromes a1 and a3 were not detected; however, a broad but weak absorbance with an alpha band maximun at 600 nm and a Soret shoulder at 440 nm was observed. Hence the respiratory chain of N. gonorrhoeae appears to contain several nonheme iron centers, cytochrome c, two b cytochromes, with cytochrome o which probably serves as the terminal oxidase.
...
PMID:Physiology and metabolism of pathogenic Neisseria: partial characterization of the respiratory chain of Neisseria gonorrhoeae. 16 81

Oxidation of exogenous NADH in mitochondria isolated from wild type and mi-1 mutant of Neurospora crassa decreases rapidly in vitro. In mi-1 mutant mitochondria the inactivation concerns the alternate pathway of oxidation whereas in the wild type it involves an unknown component of the respiratory chain. The activity of the primary NADH dehydrogenase is constant within the time of the experiments (2-4 h). NADH oxidase is not inactivated if oxygen is removed from the incubation medium by nitrogen bubbling. Succinate oxidase does not show any remarkable changes in activity within 2-3 h. In fresh mitochondria of the mi-1 mutant reduced ubiquinone is completely reoxidized by cytochrome oxidase but only 80% reoxidized by the alternate oxidase. In aged mitochondria of the mi-1 mutant in the presence of cyanide, ubiquinone is reduced to the level characteristic for fresh mitochondria in which respiration is completely inhibited by cyanide plus salicylhydroxamic acid. In these mitochondria the reoxidation of the reduced ubiquinone proceeds only via the cytochrome pathway. It is supposed that a labile component(s) of the respiratory chain present in the mi-1 mutant and the wild type mitochondria may, in mi-1 mutant, act as an alternate oxidase.
...
PMID:Disappearance of the cyanide-insensitive pathway of oxidation in mitochondria of MI-1 mutant of Neurospora crassa in vitro. 20 34

The present study proposes a technique, using Metrizamide, which permits the preparation of brown adipose tissue plasma membranes from the crude mitochondria as well as from the crude microsome fraction. These plasma membranes have high relative specific activities of their marker enzyme, 5'-nucleotidase (15 +/- 3 and 14 +/- 2 respectively) and, particularly those originating in the crude microsomes, are relatively free of mitochondria contamination. This study also shows the influence of the mode of cell disruption on microsome integrity. When cell disruption was achieved by grinding in liquid nitrogen the purified microsome NADPH cytochrome c reductase specific activity was found to be 3.5 times greater than that of microsomes obtained after homogenization of the tissue.
...
PMID:Subcellular fractionation of brown adipose tissue. 54 24

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.
...
PMID:Lipids of rabies virus and BHK-21 cell membranes. 55 73

Plasma membranes, microsomes, and mitochondria were isolated from mouse fibroblast (LM) suspension cells by modification of several established procedures. Choline analogues such as N,N'-dimethylethanolamine, N-monomethylethanolamine, or ethanolamine were incorporated in vivo into phospholipids of all three cell fractions studied, but to varying degrees depending on the type of analogue used. The in vivo incorporation of these bases into membrane phospholipids produced no significant effect on the activities of seven membrane-bound enzymes: (Na+, K+)-ATPase, 5'-nucleotidase (plasma membranes); TPNH-cytochrome c reductase, glucose-6-phosphatase, inosine diphosphatase (microsomes); and succinate cytochrome c reductase (mitochondria). The incorporation of base analogues into phospholipids was accompanied by several compensatory mechanisms. (a) The quantity of both phosphatidylcholine and phosphatidylethanolamine decreased up to 75% and 50% respectively in 3 days. (b) The molar ratio of desmosterol/phospholipid in the plasma membranes of LM cells grown in suspension culture in the presence of choline analogues decreased from 0.65 to 0.45. (c) The percentage of lysophosphatidylcholine increased over 2-fold in the phospholipid of all subcellular fractions studied. The quantity of lysophosphatidylcholine was directly proportional to the number of methyl groups on the nitrogen atom of the base analogue supplemented to the cells. This was a specific effect since the quantity of lysophosphatidylethanolamine, the other major lysophospholipid, remained unchanged. (d) The ratio of zwitterionic phospholipids to acidic phospholipids remained relatively constant in all isolated membrane fractions regardless of analogue supplementation. Neither increase in the degree of unsaturation nor shortening of fatty acid chain length was noted in response to analogue supplementation.
...
PMID:Isolation and characterization of subcellular membranes with altered phospholipid composition from cultured fibroblasts. 95 75

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.
...
PMID:Fast fixation of brain in situ by high intensity microwave irradiation: application to neurochemical studies. 104 75

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.
...
PMID:Hypoxia-selective antitumor agents. 5. Synthesis of water-soluble nitroaniline mustards with selective cytotoxicity for hypoxic mammalian cells. 150 7

Recent studies have shown that intrarectal administration of 2,4,6-trinitrobenzene sulfonic acid (TNBS) in ethanol or intramural injection of TNBS in saline produces an acute and possibly chronic colitis in rats. It has been assumed that interstitial TNBS initiates the inflammatory response via macrophage-mediated recognition and degradation of TNBS-modified mucosal cells and proteins. However, it is known that certain flavoproteins and/or reductants interact with compounds containing the nitro functional group to generate pro-inflammatory, nitrogen-centered free radicals and reactive oxygen metabolites. The objective of this study was to assess the ability of the rat colon, using either colon homogenates, isolated colonocytes, or intestinal interstitial fluid, to produce reactive oxygen species via enzymatic and/or nonenzymatic metabolism of TNBS. It was found that the addition of TNBS (1 mmol/L) to the 10,000 x g supernatant of rat colon homogenates increased the rate of superoxide production from normally undetectable levels to 2.6 +/- 0.23 nmol.min-1.mg protein-1. Addition of nicotinamide adenine dinucleotide, reduced form (NADH; 1 mmol/L) to colon homogenates containing TNBS significantly enhanced superoxide production to 10.4 +/- 0.9 nmol.min-1.mg-1. Similarly, addition of nicotinamide adenine dinucleotide phosphate, reduced form (NADPH; 1 mmol/L) to colon extracts containing TNBS produced an even further increase in the rate of superoxide formation to 25.2 +/- 1.1 nmol.min-1.mg-1. Addition of NADH or NADPH to the colon homogenate in the absence of TNBS produced no detectable superoxide formation, suggesting that TNBS was required for the enhanced oxidative metabolism. In a separate series of experiments, it was found that isolated colonocytes produced small but significant amounts of superoxide (3.15 +/- 0.6 nmol/2 x 10(6) cells) that were significantly increased in the presence of ethanol to 6.55 +/- 1.14 nmol/2 x 10(6) cells. Using purified preparations of two flavoproteins found in the rat colon, it was shown that the addition of TNBS (1 mmol/L) to purified NADH dehydrogenase or glutathione reductase increased the rate of superoxide formation by these enzymes from normally undetectable levels to 1.6 nmol/min and 1.2 nmol/min, respectively. In addition, it was found that intestinal interstitial fluid (lymph) initiated redox cycling of TNBS such that 28.1 +/- 1.6 nmol of oxygen was consumed per minute per milliliter of lymph. This increase in oxygen consumption was inhibited by the addition of superoxide dismutase and catalase. One possible metabolite involved in both mucosal and lymph-mediated metabolism of TNBS is ascorbic acid.(ABSTRACT TRUNCATED AT 400 WORDS)
...
PMID:Metabolism of trinitrobenzene sulfonic acid by the rat colon produces reactive oxygen species. 164 28


1 2 3 4 5 6 7 8 Next >>

---