共查询到20条相似文献,搜索用时 62 毫秒
1.
Prabhakara V. Choudary G.Ramananda Rao 《Biochemical and biophysical research communications》1982,108(3):1293-1299
The requirement of a suitable energy source during the induced synthesis of nitrate reductase in was investigated. The levels of nitrate reductase induced were shown to be energy-dependent, and to vary in response to the type of carbon source provided. Glycerol, fructose, ethanol, glucose, and sucrose served as efficient energy sources. Growth rate of the yeast and the induced level of nitrate reductase were dependent on the ratio of carbon to nitrogen in the induction medium, and ratio of 2 being optimal. Induction of nitrate reductase was inhibited by uncouplers, 2,4-dinitrophenol (DNP), dicumarol and carbonyl cyanide -trifluoromethoxy phenyl hydrazone (CCCP), and by cyanide and azide, indicating an absolute energy-dependency. The facilitation of induction of a high level of nitrate reductase by exogenously added ATP as sole source of energy confirmed the obligate requirement of ATP for the synthesis of nitrate reductase in . 相似文献
2.
J M Maldonado J Herrera A Paneque M Losada 《Biochemical and biophysical research communications》1973,51(1):27-33
The active form of nitrate reductase can be reversibly converted into its inactive form by reduction with NADH in the presence of ADP. Under the experimental conditions used, no inactivation occurs when nitrate is simultaneously present or when the nucleotides act isolately, the inactivating effect being maximal at a concentration of ADP (0.3 mM) equimolecular with that of NADH. The inactive enzyme thus attained can be completely reactivated by reoxidation with ferricyanide. The redox state of the pyridine nucleotide and the phosphorylation degree of the adenine nucleotide are critical for the inactivation process to ensue, since neither NAD+ nor AMP or ATP do exert any effect. ADP is also a powerful, although rather unspecific, protector against thermal inactivation of the NADH-diaphorase moiety of the NADH-nitrate reductase complex. 相似文献
3.
Franco Renosto Norman D. Schmidt Irwin H. Segel 《Biochemical and biophysical research communications》1982,107(1):12-18
The steady-state kinetics of the NADPH + FAD-dependent reduction of nitrate by nitrate reductase from was studied at pH 6.18. At this sub-optimum pH, Vmax was about 83 units × mg protein?1 compared with 225 units × mg protein?1 at pH 7.20. All initial velocity reciprocal plot patterns at pH 6.18 as well as the NADP+/nitrate product inhibition pattern were intersecting. In contrast, the NADP(H)/nitrate plots at pH 7.20 were parallel (Renosto, F. J. Biol. Chem. , 8616, 1981). A major effect of lowering the assay pH was to change the Km for FAD from 0.17 μM at pH 7.20 to 4 μM at pH 6.18. The results suggest that nitrate reductase has a steady-state random kinetic mechanism in which kcat in the forward direction at pH 7.20 (ca. 375 sec?1) is greater that koff for the dissociation of one or more substrates. Several observations suggest that koff for FAD is extremely small at pH 7.20. 相似文献
4.
R Vila J A Bárcena A Llobell A Paneque 《Biochemical and biophysical research communications》1977,75(3):682-688
Nitrate reductase from the aerobic bacterium is a soluble enzyme with the characteristic features of Pichinoty's type B nitrate reductase. When cell suspensions of are repeatedly subcultured in liquid medium with nitrate as the nitrogen source, most of the nitrate-reducing activity is incorporated into the cytoplasmic membrane. The properties of the particulate nitrate reductase closely resemble Pichinoty's type A enzyme. 相似文献
5.
M. Dubourdieu E. Andrade J. Puig 《Biochemical and biophysical research communications》1976,70(3):766-773
Radioactive molybdenum is used to detect the existence of molybdo compounds in K12. Three membrane bound Mo-proteins are found, using sodium dodecyl sulfate. One of them is the nitrate reductase. The nature of the other two is discussed. The soluble fraction of the cellular extract contains a small Mo binding molecule which could be peptidic in nature (MW is about 1,500). Different chlorate resistant mutants are analyzed on the basis of these molybdo-compounds. None of the mutants is found to contain radioactivity bound to nitrate reductase protein. Defects in the biosynthesis of a molybdenum coenzyme is deduced for chlorate resistant pleiotropic mutants. 相似文献
6.
The role of molybdenum in formation of the NADPH-nitrate reductase by Aspergillus nidulans 总被引:1,自引:0,他引:1
R J Downey 《Biochemical and biophysical research communications》1973,50(3):920-925
Non-nitrate reducing mutants of have been noted to produce either a nitrate inducible or constitutive NADPH-cytochrome reductase which resides in either a 4.5s or a 7.8s protein. The latter closely resembles the nitrate inducible, FAD dependent NADPH-nitrate reductase from the wild type. Measurement of flavin adenine dinucleotide (FAD) and molybdenum (Mo) in these two proteins revealed significant differences particularly in Mo. The concepts that a nitrate inducible gene product constitutes the major flavin bearing component of the enzyme and that a constitutively produced gene product is implicated in formation of the larger Mo bearing multimer are further supported. 相似文献
7.
Hybrids were constructed between K12 ? mutants defective in nitrate respiration and an F′ plasmid carrying nitrogen fixation genes from . Examination of these hybrids showed that expression of Kp+ genes does not require a functional nitrate respiratory system, but that nitrate reductase and nitrogenase do share some Mo-processing functions. For nitrate repression of nitrogenase activity, reduction of nitrate to nitrite is not necessary, but the Mo-X cofactor encoded by genes is essential. Nitrate probably inhibits nitrogen fixation by affecting the membrane relationship of the nitrate and fumarate reduction systems such that the membrane cannot be energized for nitrogenase activity. 相似文献
8.
B L Currie J Warberg K Folkers 《Biochemical and biophysical research communications》1977,79(4):1207-1211
The hypocholesterolemic drug clofibrate (ethyl-α--chlorophenoxyisobutyrate) was found to strongly suppress 3-hydroxy-3-methylglutaryl coenzyme A reductase (EC 1.1.1.34) activity in cultured mouse L cells at concentrations of 20 – 50 μg/ml. The half-life () of the reductase (approximately 120 min) was strongly reduced when L cells were incubated with cycloheximide plus a maximal inhibitory concentration of clofibrate (50 μg/ml), resulting in a value of 10 min. Preliminary kinetic analysis of the inhibition suggested that clofibrate increased the rate of inactivation (or degradation) of the reductase without affecting the rate of enzyme synthesis. 相似文献
9.
Structural changes in the purified accompanying detergent inactivation were investigated by monitoring changes in light scattering, intrinsic protein fluorescence, and tryptophan to β-parinaric acid fluorescence resonance energy transfer. Two phases of inactivation were observed using the non-ionic detergents, digitonin, Lubrol WX and Triton X-100. The rapid phase involves detergent monomer insertion but little change in protein structure or little displacement of closely associated lipids as judged by intrinsic protein fluorescence and fluorescence resonance energy transfer. Lubrol WX and Triton X-100 also caused membrane fragmentation during the rapid phase. The slower phase of inactivation results in a completely inactive enzyme in a particle of 400 000 daltons with 20 mol/mol of associated phospholipid. Fluorescence changes during the course of the slow phase indicate some dissociation of protein-associated lipids and an accompanying protein conformational change. It is concluded that non-parallel inhibition of and activity by digitonin (which occurs during the rapid phase of inactivation) is unlikely to require a change in the oligomeric state of the enzyme. It is also concluded that at least 20 mol/mol of tightly associated lipid are necessary for either or activity and that the rate-limiting step in the slow inactivation phase involves dissociation of an essential lipid. 相似文献
10.
P Forget 《Biochemical and biophysical research communications》1979,89(2):659-663
The chlorate resistant mutants of synthetize, in variable quantities, proteins which give immunocomplex with specific nitrate reductase antiserum. The biosynthesis of these cross reacting materials presents the same type of regulation as nitrate reductase of the wild type. C.R.M. biosynthesis is repressed by oxygen and even in the presence of nitrate, the oxygen inhibition is not reversed with chlorate mutants and wild type. With anaerobically grown cells, nitrate acts as an inducer and increases the amount of antibody-precipitable material, three times in mutants and even four times with Chl-E. 相似文献
11.
In vitro formation of assimilatory nitrate reductase: presence of the constitutive component in bacteria 总被引:9,自引:0,他引:9
Cell-free extracts of a selected group of bacteria which are capable of metabolyzing dinitrogen and/or nitrate contain a soluble form of the constitutive component which is active in the formation of NADPH-nitrate reductase when mixed with extracts of . The constitutive component in these extracts is dialyzable and is insensitive to trypsin and protease. The constitutive component which substitutes for the absence of the formation of NADPH-nitrate reductase is postulated to be a low molecular weight cofactor or polypeptide and is shown to be present in a number of unrelated bacteria. 相似文献
12.
Dorothy A. Schafer Donald E. Hultquist 《Biochemical and biophysical research communications》1980,95(1):381-387
Microsomal NADH-cytochrome reductase has been purified from bovine liver by an improved procedure which employs affinity chromatography on ADP-agarose in combination with anion exchange chromatography. The reductase was extracted from a 105,000 × microsomal pellet with Triton X-100. The overall purification from isolated microsomes was 98-fold and the yield was 10%. The preparation was nearly homogeneous on SDS-PAGE. This procedure requires less time and effort than previously described procedures. Partially purified cytochrome is also obtained. 相似文献
13.
Carbodiimide-dependent inactivation of dihydrofolate reductase 总被引:1,自引:0,他引:1
Dihydrofolate reductase from amethopterin-resistant was inactivated by a water soluble carbodiimide, 1-ethyl-3-(3-dimethyl-aminopropyl)-carbodiimide HCl. The rapid inactivation observed at pH 5.0–6.0, coupled with lack of recovery of activity from inactivated samples incubated with NH2OH was consistent with modification of enzymic carboxyl groups. Significant protection against inactivation was provided by 7,8-dihydrofolate and NADPH. Analysis of the reaction order suggests that the carbodiimide-dependent inactivation may result from modification of a single essential carboxyl group. 相似文献
14.
Peter R. Alefounder Stuart J. Ferguson 《Biochemical and biophysical research communications》1982,104(3):1149-1155
The nitrous oxide reductase activity of can be conveniently measured using an electrochemical method for determining N2O. Introduction of this procedure has shown that (i) N2O reductase activity is reversibly inhibited by oxygen; (ii) antimycin strongly inhibits electron flow to N2O and that the inhibition is bypassed by tetramethyl-p-phenylenediamine; (iii) ascorbate plus tetramethyl-p-phenylenediamine, presumably by donating electrons to cytochrome c, is an effective reductant for nitrous oxide reductase; (iv) in the presence of the nitrous oxide reductase inhibitor, acetylene, N2O is promptly produced from nitrite, consistent with the product of nitrite reductase being N2O. 相似文献
15.
Claude Terrière Gérard Giordano Bruce Haddock Edgard Azoulay 《Biochemical and biophysical research communications》1983,111(3):830-839
A membrane-bound pathway for the biosynthesis of ubiquinone 8 (UQ8) in has been identified from the analysis of the precursors accumulated by mutants blocked in the pathway. Ubiquinone 8 (UQ8) deficient mutant which accumulate 2 octaprenylphenol (2-OPP) allowed to show that two components are involved in the hydroxylating system of this compound: one membranous, is cytochrome and the second cytoplasmic, is an NADPH cytochrome reductase. 相似文献
16.
J.A. Pérez-González A. Jiménez 《Biochemical and biophysical research communications》1984,125(3):895-901
The paromomycin producing organism is resistant to this antibiotic and contains a phosphotransferase which inactivates paromomycin. The gene encoding this enzyme has been inserted in the vector pIJ702 and then cloned in , selecting for paromomycin-resistance. Three plasmids have been isolated and one of them, pMJ1, contains a 2.2 kb insert with a single HindIII restriction site. Insertion of foreign DNA in this site blocks the expression of the phosphotransferase enzyme indicating that it is within the cloned gene. These findings provide a new dominant selective marker for cloning vectors with the versatility of insertional inactivation. 相似文献
17.
Ken F. Jarrell Andrew M. Kropinski 《Biochemical and biophysical research communications》1981,99(4):1185-1190
Lipopolysaccharides (LPS) isolated from various rough derivatives of strains were found to neutralize coliphage T7. Concentrations of 0.4 – 17 μg LPS/ml were sufficient for 50% inactivation of T7 within 1 hour. From the LPS analyses of the mutants, it is believed that T7 may be binding to the heptose region of LPS, suggesting a similarity in structure between the heptose regions of and LPS. 相似文献
18.
Bernard L. Trumpower 《Biochemical and biophysical research communications》1978,83(2):528-535
Mitochondrial ubiquinol-cytochrome reductase complex contains small amounts of succinate dehydrogenase. Estimates from electrophoresis indicate there is one dehydrogenase per eight complexes. This dehydrogenase transfers electrons to the - complex poorly, as judged by low succinate-ubiquinone and succinate-cytochrome reductase activities. Electron transfer to the - complex is restored by reconstitution of the complex with phospholipid. This phospholipid dependent restoration of electron transfer indicates that either reconstitutive activity of the dehydrogenase is preserved under conditions where electron transfer is absent, or that addition of phospholipid allows one dehydrogenase to transfer electrons to multiple - complexes. 相似文献
19.
Rat liver microsomal NADH-cytochrome reductase activity is stimulated by 20 μM thyroxine . Thyroxine does not influence microsomal NADH-dichlorophenolindophenol reductase, NADPH-cytochrome reductase, or NADPH-dichlorophenolindophenol reductase activity. Stimulation of NADH-cytochrome reductase activity is not mediated by super-oxide and is likely due to enhanced reduction or oxidation of cytochrome 5. 相似文献
20.
NADPH-cytochrome reductase (NADPH-cytochrome reductase, EC 1.6.2.4), the flavoprotein which is responsible for the NADPH-dependent reduction of cytochromes P-450 in hepatic microsomes, has been localized immunohistochemically at the light microscopic level in rat liver. Localization was achieved through the use of sheep antiserum to rat hepatic microsomal NADPH-cytochrome reductase in an unlabeled antibody peroxidase-antiperoxidase technique. Parenchymal cells throughout the liver lobule were found to be stained positively for NADPH-cytochrome reductase, although the intensity of immunostaining was slightly greater in the centrilobular regions. Immunostaining for NADPH-cytochrome reductase was not detected in Kupffer cells, connective tissue cells, or in cells of the hepatic vasculature. 相似文献