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: KEGG:D02011 (FAD)
5,530 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Delta5-3beta-hydroxysteroid oxidoreductase was extracted in magnesium-containing Tris buffer from sonicated Streptomyces griseocarneus cells. The enzyme was partially purified (150 X) by ion exchange chromatography and gel filtration following (NH4)2SO4 fractionation. Upon gel filtration on Sephadex G-75 to G-200, the greatest part of the activity gave a peak in the fractionation range. The enzyme obtained from the gel yielded small enzyme molecules on repeated chromatography. A molecular weight of 32 to 36 000 was calculated for the activity appearing in the fractionation range of Sephadex G-75 to G-200. The enzyme is highly specific for the irreversible oxidation of the 3beta-hydroxyl group in steroids with a trans-anellated A : B ring system with either C5 or C6 double bond. Delta5-3-ketosteroids are converted into delta5-3-ketosteroids at a high rate, but the isomerase activity cannot be separated from the oxidoreductase activity either by chromatography or by selective heat inactivation. NAD, NADP, FMN or FAD did not influence the activity, but the enzyme is inactive in the absence of molecular oxygen.
...
PMID:Properties of delta5-3beta-hydroxysteroid oxidoreductase isolated from Streptomyces griseocarneus. 0 56

The assimilatory NADPH-nitrate reductase (NADPH:nitrate oxidoreductase, EC 1.6.6.3) from Neurospora crassa is competitively inhibited by 3-aminopyridine adenine dinucleotide (AAD) and 3-aminopyridine adenine dinucleotide phosphate (AADP) which are structural analogs of NAD and NADP, respectively. The amino group of the pyridine ring of AAD(P) can react with nitrous acid to yield the diazonium derivative which may covalently bind at the NAD(P) site. As a result of covalent attachment, diazotized AAD(P) causes time-dependent irreversible inactivation of nitrate reductase. However, only the NADPH-dependent activities of the nitrate reductase, i.e. the overall NADPH-nitrate reductase and the NADPH-cytochrome c reductase activities, are inactivated. The reduced methyl viologen- and reduced FAD-nitrate reductase activities which do not utilize NADPH are not inhibited. This inactivation by diazotized AADP is prevented by 1 mM NADP. The inclusion of 1 muM FAD can also prevent inactivation, but the FAD effect differs from the NADP protection in that even after removal of the exogenous FAD by extensive dialysis or Sephadex G-25 filtration chromatography, the enzyme is still protected against inactivation. The FAD-generated protected form of nitrate reductase could again be inactivated if the enzyme was treated with NADPH, dialyzed to remove the NADPH, and then exposed to diazotized AADP. When NADP was substituted for NADPH in this experiment, the enzyme remained in the FAD-protected state. Difference spectra of the inactivated nitrate reductase demonstrated the presence of bound AADP, and titration of the sulfhydryl groups of the inactivated enzyme revealed that a loss of accessible sulfhydryls had occurred. The hypothesis generated by these experiments is that diazotized AADP binds at the NADPH site on nitrate reductase and reacts with a functional sulfhydryl at the site. FAD protects the enzyme against inactivation by modifying the sulfhydryl. Since NADPH reverses this protection, it appears the modifications occurring are oxidation-reduction reactions. On the basis of these results, the physiological electron flow in the nitrate reductase is postulated to be from NADPH via sulfhydryls to FAD and then the remainder of the electron carriers as follows: NADPH leads to -SH leads to FAD leads to cytochrome b-557 leads to Mo leads to NO-3.
...
PMID:Reactions of the Neurospora crassa nitrate reductase with NAD(P) analogs. 1 30

Under anaerobic conditions, cells of Entamoeba histolytica grown with bacteria produce H2 and acetate while cells grown axenically produce neither. Aerobically, acetate is produced and O2 is consumed by amebae from either type of cells. Centrifuged extracts, 2.4 x 106 x g x min, from both types of cells contain pyruvate synthase (EC 1.2.7.1) and an acetate thiokinase which, together, form a system capable of converting pyruvate to acetate. Pyruvate synthase catalyzes the reaction: pyruvate + CoA leads to CO2 + acetyl-CoA + 2E. Electron acceptors which function with this enzyme are FAD, FMN, riboflavin, ferredoxin, and methyl viologen, but not NAD or NADP. The amebal acetate thiokinase catalyzes the reaction acetyl-CoA + ADP + Pi leads to acetate + ATP + CoA. For this apparently new enzyme we suggest the trivial name acetyl-CoA-synthetase (ADP-forming). Extracts from axenic amebae do not contain hydrogenase, but extracts from cells grown with bacteria do. It is postulated that in bacteria-grown amebae electrons generated at the pyruvate synthase step are utilized anaerobically to produce H2 via the hydrogenase and that the acetyl-CoA is converted to acetate in an energy-conserving step catalyzed by amebal acetyl-CoA synthetase. Aerobically, cells grown under either regimen may utilize the energy-conserving pyruvate-to-acetate pathway since O2 then serves as the ultimate electron acceptor.
...
PMID:An energy-conserving pyruvate-to-acetate pathway in Entamoeba histolytica. Pyruvate synthase and a new acetate thiokinase. 1 76

The three-dimensional structure of the dimeric flavoenzyme glutathione reductase from human erythrocytes has been elucidated by an X-ray diffraction analysis at 0.3 nm resolution. The polypeptide chain has been traced, and the binding positions of FAD, NADP and glutathione have been determined. A mechanism for the electron transfer is discussed.
...
PMID:The structure of the flavoenzyme glutathione reductase. 2 87

NAD prevents a DNA repair-type synthesis that is dependent on polymerase I in toluene-treated, X-irradiated Bacillus subtilis. In unirradiated preparations, NAD had little effect on an ATP-dependent, semiconservative synthesis but partially inhibited a repair-type synthesis. In a mutant lacking polymerase I (polA1-), the presence of NAD did not affect dTTP utilization in DNA synthesis. Nicotinamide mononucleotide (NMN) partially reverses the NAD inhibition of repair-type DNA synthesis. NADP and FAD were ineffective as substitutes for NAD. Since NAD is the cofactor for polynucleotide ligase in Bacillus subtilis and NMN is known to discharge AMP from the active AMP ligase complex, it is proposed that activation of DNA ligase reduces dTMP incorporation by reducing sites for, or limiting DNA polymerase I action.
...
PMID:Depression by NAD of x-ray-induced repair-type DNA synthesis in toluene-treated Bacillus subtilis. 16 15

Asparagusate dehydrogenases I and II and lipoyl dehydrogenase have been obtained in homogeneous state from asparagus mitochondria. They are flavin enzymes with 1 mol of FAD/mol of protein. Asparagusate dehydrogenases I and II and lipoyl dehydrogenase have s20,w of 6.22 S, 6.39 S, and 5.91 S, respectively, and molecular weights of 111,000, 110,000, and 95,000 (sedimentation equilibrium) or 112,000, 112,000, and 92,000 (gel filtration). They are slightly acidic proteins with isoelectric points of 6.75, 5.75, and 6.80. Both asparagusate dehydrogenases catalyzed the reaction Asg(SH)2 + NAD+ equilibrium AsgS2 + NADH + H+ and exhibit lipoyl dehydrogenase and diaphorase activities. Lipoyl dehydrogenase is specific for lipoate and has no asparagusate dehydrogenase activity. NADP cannot replace NAD in any case. Optimum pH for substrate reduction of the three enzymes are near 5.9. Asparagusate dehydrogenases I and II have Km values of 21.5 mM and 20.0 mM for asparagusate and 3.0 mM and 3.3 mM for lipoate, respectively. Lipoyl dehydrogenase activity of asparagusate dehydrogenases is enhanced by NAD and surfactants such as lecithin and Tween 80, but asparagusate dehydrogenase activity is not enhanced. Asparagusate dehydrogenases are strongly inhibited by mercuric ion, p-chloromercuribenzoic acid, and N-ethylmaleimide. Amino acid composition of the three enzymes is presented and discussed.
...
PMID:Asparagusate dehydrogenases and lipoyl dehydrogenase from asparagus mitochondria. Physical, chemical, and enzymatic properties. 18 3

Glutathione reductase from rat liver has been purified greater than 5000-fold in a yield of 20%. The molecular weights of the enzyme and its subunits were estimated to be 125,000 and 60,000, respectively, indicating that the native enzyme is a dimer. The enzyme molecular contains 2 FAD molecules, which are reducible by NADPH, GSH or dithioerythritol. The reduced flavin is instantaneously reoxidized by addition of GSSG. The steady state kinetic data are consistent with a branching reaction mechanism previously proposed for glutathione reductase from yeast (MANNERVIK, B. (1973) Biochem. Biophy. Res. Commun. 53, 1151-1158). This mechanism is also favored by the nonlinear inhibition pattern produced by NADP-+. However, at low GSSG concentrations the rate equation can be approximated by that of a simple ping pong mechanism. NADPH and the mixed disulfide of coenzyme A and GSH were about 10% as active as NADPH and GSSG, respectively, whereas some sulfenyl derivatives related to GSSG were less active as substrates. The pH activity profiles of these substrates differed from that of the NADPH-GSSG substrate pair.
...
PMID:Purification and characterization of the flavoenzyme glutathione reductase from rat liver. 23 22

NADPH-cytochrome P-450 reductase was isolated from liver microsomes of phenobarbital-induced rats. The enzyme exhibits an apparent minimal molecular weight of 76,000 as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and contains 1 molecule each of FMN and FAD. Trypsin treatment of the reductase yields an enzyme with an apparent minimal molecular weight of 69,000 which retains the ability to reduce cytochrome c but has no activity toward cytochrome P-450. Various spectrophotometric titrations were performed to examine the electron-accepting properties of the purified NADPH-cytochrome P-450 reductase and, in particular, to determine the oxidation state of the stable semiquinone form produced by air oxidation of NADPH-reduced enzyme. Titration of the air-stable semiquinone form of the reductase with ferricyanide indicated that 1 mol/2 mol of flavin was required for complete oxidation. Furthermore, a spectrum corresponding to that of the air-stable semiquinone form was produced by the addition of approximately 0.5 mol of reductant/2 mol of flavin when the oxidized enzyme was titrate with NADPH or dithionite under anaerobic conditions. The spectral changes which accompanied the overall reduction of oxidized enzyme to the reduced form with dithionite produced four sets of isosbestic points, and the spectrophotometric titration curve consisted of four approximately equal phases. In the titration with NADPH, no significant further reduction was observed after the addition of approximately 1.5 mol/2 mol of flavin. However, the enzyme was fully reduced by NADPH when an NAPH-generating system was used to prevent the accumulation of NADP. Our results establish that the air-stable semiquinone form is a 1-electron-reduced form, rather than a half-reduced (2-electron-reduced) form as maintained by others and are in agreement with earlier studies (Iyanagi, T., Makino, N., and Mason, H.S. (1974) Biochemistry 13, 1701-1710) with the purified trypsin-solubilized reductase. Accordingly, the air-stable species represents a form of the NADPH-cytochrome P-450 reductase in which one of the two flavins exists in the semiquinone state and the other in the oxidized state.
...
PMID:Purified liver microsomal NADPH-cytochrome P-450 reductase. Spectral characterization of oxidation-reduction states. 63 95

The kinetic properties and regulation of activity of GTP-cyclohydrolase, the enzyme of the first step of flavinogenesis in the Pichia guilliermondii yests, partially purified by gel-filtration were studied. It was found that the curve of the dependence of reaction rate on substrate concentration is non-hyperbolic. FAD inhibited the enzyme activity, while riboflavin and FMN had no such effect. In addition to FAD, 5'-AMP, 3',5'-AMP, ADP, ATP, NAD and NADP inhibited the enzyme activity. Under combined action of FAD and AMP on GTP-cyclohydrolase no synergetic or antagonistic effects of the inhibitors on the enzyme activity were observed. The enzyme appreciably lost its sensitivity to FAD and AMP after thermal treatment. The data obtained suggest that GTP-cyclohydrolase from P. guilliermondii is an allosteric enzyme, which is inhibited by the end product of flavinogenesis FAD, as well as by other 5'-AMP-containing nucleotides.
...
PMID:[Regulation of the activity of GTP-cyclohydrolase, the enzyme of the first step of flavinogenesis in yeasts]. 73 22

[14C]Mevalonate or (14C)isopentenyl pyrophosphate was found to be converted to transphytoene, trans-phytofluene, lycopene, and beta-carotene by a cell-free 270 000 X g supernatant fraction prepared from Halobacterium cutirubrum cells that were broken by manual grinding with glass beads. Incubations were done under N2 in the dark at 37 degrees C in 4 M NaCl in presence of FAD, NADP, and MgCl2; ATP was also added when mevalonate was the substrate. This system was also capable of converting trans-(14C)phytoene to beta-carotene via the intermediates trans-phytofluene, zeta-carotene, neurosporene, lycopene, and gamma-carotene. Each of these labelled intermediates on incubation separately with the same enzyme system was shown to be converted to the intermediates farther down the pathway. The results of this study show that the biosynthetic pathway for the formation of C40 carotenes in H. cutirubrum proceeds as follows: isopentenyl pyrophosphate leads to trans-phytoene leads to trans-phytofluene leads to zeta-carotene leads to neurosporene leads to lycopene leads to gamma-carotene leads to beta-carotene. This pathway differs from that in higher plants in that the cis isomers of phytoene and phytofluene are not on the main pathway of carotene biosynthesis, as they are in higher plants. Furthermore, trans-phytoene, which has not been reported to have any role in higher plants, appears to be the main intermediate in carotene biosynthesis in H. cutirubrum.
...
PMID:Enzymatic synthesis of C40 carotenes by cell-free preparation from Halobacterium cutirubrum. 97 65


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

---