Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: KEGG:D02011 (FAD)
 5,530 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The system involved in the reduction of 2-[4'-di(2''-bromopropyl) aminophenylazolbenzoic acid (CB10-252), an agent designed for treating primary liver cell cancer, has been demonstrated to be localised mainly in the 108 000 X g supernatant fraction of rat liver homogenate. It is also present in other organs particularly in the spleen. DAB-azoreductase as shown previously is present almost entirely in the microsomal fraction and is found in high concentration only in liver. The pH maximum for CB10-252-azoreductase implying the importance of the 2'-carboxyl group in determining substrate specificity. The use of enzyme inhibitors and other additives showed that CB10-252 WAS NOT AXANTHINE OXIDASE OR DIHYDROFOLATE REDUCTASE. Its activity was not affected by carbon monoxide, phenobarbitone (PB), or 3-methylcholanthrene (MC) pretreatment. Enhancement of the activity by ferrous ions and FAD indicated that at least part of the reduction system could involve a flavoprotein with FAD as the prosthetic group. The activity of CB10-252-azoreductase and methylred-azoreductase was reduced by menadione (vitamin K3), cyanide and propylgallate. A diaphorase preparation from pig heart reduced both CB10-252 and methylred with both NADPH- and NADH-generating systems.
 ...
PMID:Some characteristics of two azoreductase systems in rat liver. Relevance to the activity of 2-[4'-di(2"-bromopropyl)-aminophenylazo]benzoic acid (CB10-252), a compound possessing latent cytotoxic activity. 0 Jan 49

1. Glutathione reductase (NAD(P)H:oxidized-glutathione oxidoreductase, EC. 1.6.4.2) from human erythrocytes was purified 49 000-fold with an overall yield of 15% and a 280/460 nm absorbance ratio of 6.03. The procedure used was the method of Worthington and Rosemeyer modified by addition of heating and recrystallization. 2. It was concluded from the results of purification, electrofocusing and inhibition studies that glutathione reductase is a single enzyme which used both NADPH and NADH as hydrogen donors. 3. Apoenzyme cross-reacts with the antibody to the holoenzyme but has a slightly reduced affinity to the antibody. Apoenzyme can be removed from the hemolysate by heating and centrifugation without loss of holoenzyme. 4. Indirect immunological assay of the specific activity of the erythrocyte glutathione reductase is possible in the enzyme saturated with FAD.
 ...
PMID:Human erythrocyte glutathione reductase. I. Purification and properties. 0 43

The purified respiratory chain NADH dehydrogenase of Escherichia coli oxidizes NADH with either dichlorophenolindophenol (DCIP). ferricyanide, or menadione as electron acceptors, with values for NADH are similar with the three electron acceptors (approximately 50 muM). The purified enzyme contains no flavin and has an absolute requirement for FAD, with Km values around 4 muM. The pH optimum of the enzyme appears to be between 6.5 and 7; the optimum is difficult to establish because of nonenzymatic reduction of DCIP at the lower pH values. Potassium cyanide stimulates the DCIP reductase activity about 2-fold, but has no effect on ferricyanide reductase. The enzyme exhibits hyperbolic kinetics with respect to NADH concentration in both the ferricyanide and DCIP reductase assays, but cooperatively is seen in the menadione reductase reaction. NAD+ is an effective competitive inhibitor of the reaction (Ki congruent to 20 muM); in the presence of NAD+, the NADH saturation curve becomes cooperative, even in the DCIP reductase assay. Many adenine containing nucleotides are competitive inhibitors of the enzyme. The apparent Ki values for these nucleotides as inhibitors of the purified enzyme, the membrane-bound NADH dehydrogenase, and the NADH oxidase are equivalent. An examination of inhibitory effects of a series of adenine nucleotides suggests that the inhibitors act as analogues of NAD+, which is the true physiological inhibitor. The results suggest that the enzyme in situ is always partially inhibited by the levels of NAD- in the E coli cell, and thus behaves in a cooperative fashion to changes in the NAD+/NADH ratio. An antibody has been elicited against the purified NADH dehydrogenase. Immunodiffusion and crossed immunoelectrophoresis show that the antibody is directed principally against the NADH dehydrogenase, with some activity against minor contaminants in the purified preparation. The antibody inhibits NADH dehydrogenase activity 50% at saturating levels. When this antibody preparation is used to examine solubilized membrane preparations, two major immunoprecipitates are found. A parallel inhibition of the membrane-bound NADH dehydrogenase and NADH oxidase activities is seen, supporting the hypothesis that the purified enzyme is indeed a component of the respiratory chain-dependent NADH oxidase pathway.
 ...
PMID:The NADH dehydrogenase of the respiratory chain of Escherichia coli. II. Kinetics of the purified enzyme and the effects of antibodies elicited against it on membrane-bound and free enzyme. 0 8

The presence of NADH-cytochrome b5 reductase [EC 1.6.2.2] in microsomes from anaerobically grown yeast was confirmed by its isolation and purification. The purified preparation of the reductase showed an apparent molecular weight of 27,000 daltons. The reductase appeared to contain loosely-bound FAD as a prosthetic group. The reductase required NADH as a specific electron donor, and could reduce some redox dyes as well as cytochrom b5. The reductase, however, could not reduce cytochrome c. Michaelis constants of the reductase for NADH and calf liver cytochrome b5 were 6.3 and 1.5 micron M, respectively, and optimal pH for cytochrome b5 reduction was 5.6. Although some differences exist between the properties of NADH-cytochrome b5 reductase from yeast and from mammalia, the results indicate a functional similarity of the present enzyme to mammalian NADH-cytochrome b5 reductase in the microsomal electron-transport system.
 ...
PMID:Studies on the microsomal electron-transport system of anaerobically grown yeast. IV. Purification and characterization of NADH-cytochrome b5 reductase. 1 30

Chromatography on DEAE-cellulose and gel filtration on Sephadex revealed that pyrazon dioxygenase from pyrazon-degrading bacteria consists of three different enzyme components. No component alone oxidizes the phenyl moiety of pyrazon, only when the three components are combined can oxidation be detected. Following electron paramagnetic resonance and ultraviolet measurements the protein nature of the three components was determined: component A1 (molecular weight about 180000,red-brown in colour) is an iron-sulphur protein. The existence of approximately two moles of iron and two moles of inorganic sulphur per mole of protein was demonstrated. This enzyme component was purified to homogeneity in disc electrophoresis. Component A2 is a yellow protein of a molecular weight of about 67000. FAD was shown to be the prosthetic group of this protein. Component B (molecular weight about 12000, brown in colour) is a protein of the ferredoxin type, which was purified to homogeneity, as demonstrated by disc electrophoresis. A hypothetical scheme for the cooperation of the three components is proposed: component A2 accepts as cosubstrate NADH and functions as a ferredoxin reductase. The ferredoxin, component B, has the function of an electron carrier. The conversion of the substrates is effected by component A1, the terminal dioxygenase.
 ...
PMID:Purification and properties of pyrazon dioxygenase from pyrazon-degrading bacteria. 1 33

Hepatic NADH-cytochrome b5 reductase was reduced by 1 mol of dithionite or NADH per mol of enzyme-bound FAD, without forming a stable semiquinone or intermediate during the titrations. However, the addition of NAD+ to the partially reduced enzyme or illumination in the presence of both NAD+ and EDTA yielded a new intermediate. The intermediate had an absorption band at 375 nm and the optical spectrum resembled anionic semiquinones seen on reduction of other flavin enzymes. Electron paramagnetic resonance measurements confirmed the free-radical nature of the species. To explain the results, a disproportionation reaction between the oxidized and reduced NAD+ complexes (E-FAD-NAD+ + E-FADH2-NAD+ in equilibrium 2E-FADH.-NAD+) is assumed. Potentiometric titration of NADH-cytochrome b5 reductase at pH 7.0 with dithionite gave a midpoint potential of -258 mV; titration with NADH gave -160 mV. This difference may be due to a difference in the relative affinity of NAD+ for the reduced and oxidized forms of the enzyme. The effects of pH on the midpoint potential of the NAD+-free enzyme were very similar to those which have been measured with free FAD. At pH 7.0, midpoint potentials of trypsin-solubilized and detergent-solubilized cytochrome b5 were 13 and 0 mV, respectively.
 ...
PMID:Redox properties of microsomal reduced nicotinamide adenine dinucleotide-cytochrome b5 reductase and cytochrome b5. 1 38

The effect of adrenalectomy on the activities of monoamine oxidase (MAO), NADH cytochrome c reductase (NCR), succinate dehydrogenase, malate dehydrogenase, fumarase, NAD+ nucleosidase and acid phosphatase in homogenates of rat hearts was examined. Besides MAO only the NCR activity increased. However, both the total and the rotenone-insensitive NCR activities increased, with that of the rotenone-insensitive being about half of the total, which indicated that the effect of adrenalectomy was exerted on components of this enzyme localized on both the inner and outer membranes of the mitochondrion. The lack of effect on the other enzymes suggests that adrenalectomy has a relatively selective action on MAO and NCR, and does not work by a generalized increase in protein synthesis or by an effect on the FAD cofactor. The MAO increase was seen with a variety of substrates, and was due to a rise in Vmax without change in Km. The response to adrenalectomy in the summer differed from that seen in the winter. The possible reasons for these effects of adrenalectomy are discussed.
 ...
PMID:The influence of adrenalectomy on monoamine oxidase and NADH cytochrome c reductase in the rat heart. 2 98

Highly purified NADH and NADPH:FMN oxidoreductases from Beneckea harveyi have been characterized with regard to kinetic parameters, association with luciferase, activity with artificial electron acceptors, and the effects of inhibitors. The NADH:FMN oxidoreductase exhibits single displacement kinetics while the NADPH:FMN oxidoreductase exhibits double displacement or ping-pong kinetics. This is consistent with the formation of a reduced enzyme as an intermediate in the reaction of catalyzed by the NADPH:FMN oxidoreductase. Coupling of either of the oxidoreductases to the luciferase reaction decreases the apparent Kms for NADH, NADPH, and FMN, supporting the suggestion of a complex between the oxidoreductases and luciferase. The soluble oxidoreductases are more efficient in producing light with luciferase than is a NADH dehydrogenase preparation obtained from the membranes of these bacteria. The soluble enzymes use either FMN or FAD as substrates for the oxidation of reduced pyridine nucleotides while the membrane NADH dehydrogenase is much more active with artificial electron acceptors such as ferricyanide and methylene blue. FMN and FAD are very poor acceptors. The evidence indicates that neither of the soluble oxidoreductases is derived from the membranes. Both enzymes are constitutive and do not depend on the synthesis of luciferase.
 ...
PMID:Studies of the control of luminescence in Beneckea harveyi: properties of the NADH and NADPH:FMN oxidoreductases. 2 27

Glutathione reductase (NAD(P)H: oxidized-glutathione oxidoreductase, EC 1.6.4.2) was purified to homogeneity from porcine erythrocytes by use of affinity chromatography on 2',5'-ADP-Sepharose 4-B. Analytical ultracentrifugation experiments were analysed to give the following physical parameters for the enzyme: s20,w = 5.7 S, D20,w = 50 microgram2/s, and Mw = 103 000 (protein concentration, 0.5 mg/ml). The frictional ratio was 1.37 and the Stokes radius was 4.3 nm. The enzyme molecule is a dimer composed of subunits of equal size each containing a FAD molecule. The amino acid compositions and circular dichroism spectra of the porcine and human enzymes indicated extensive structural similarities. The isoelectric point was at pH 6.85 (at 4 degrees C). The absorption spectrum of the oxidized enzyme had maxima at 377 and 462 nm. In vivo the enzyme appears to be partially reduced. At a physiological concentration of reduced glutathione the apparent Michaelis constants for glutathione disulfide and NADPH were higher than in the absence of reduced glutathione. At 0.15 M ionic strength the catalytic activity obtained with NADPH as reductant was optimal at pH 7 and more than 200 times higher than that obtained with NADH. S-sulfoglutathione and some mixed disulfides of glutathione were poor substrates with the exception of the mixed disulfide of coenzyme A and reduced glutathione. The purified enzyme displayed low transhydrogenase activity with oxidized pyridine nucleotide analogs and diaphorase activity with 2,6-dichlorophenolindophenol as acceptor substrates; both NADPH and NADH served as donors.
 ...
PMID:Characterization of glutathione reductase from porcine erythrocytes. 3 12

A strain of the obligate anaerobe, Eubacterium lentum, isolated from human feces, catalyzes the 21-dehydroxylation of 11-deoxycorticosterone to progesterone. A quantitative radiochromatographic assay was developed to measure 21-dehydroxylase activity in cell extracts. Maximum enzyme activity in cell extracts required both a reduced pyridine nucleotide and an oxidized flavin coenzyme. However, photochemically reduced flavin (FMNH2) could replace the requirement for NAD(P)H plus oxidized flavin. NAD(P)H : flavin (either FMN or FAD) oxidoreductase activity was detected spectrophotometrically in cell extracts assayed under anaerobic conditions. 21-Dehydroxylase was active from pH 5.4 to 8.5 with an apparent optimum between 6.4 and 6.8 using mixtures of NADH plus FMN as coenzymes. The substrate concentration at half-maximal reaction velocity was 8.0 microM and a specific acitivity of 5.8 nmol [3H]progesterone formed . h-1 . mg-1 protein was determined using [3th]deoxycorticosterone as substrate. Atabrine, rotenone, acriflavin, and 2,4-dinitrophenol (all at 1 mM) inhibited 21-dehydroxylase activity in cell extracts by 25, 24, 35 and 84%, respectively. These results suggest that 21-dehydrogenase may be coupled to a NAD(P)H : flavin oxidoreductase system in E. lentum.
 ...
PMID:Characterization of a C21 neutral steroid hormone transforming enzyme, 21-dehydroxylase, in crude cell extracts of Eubacterium lentum. 3 50


1 2 3 4 5 6 7 8 9 10 Next >>