共查询到20条相似文献,搜索用时 15 毫秒
1.
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
2.
A Novel function of cytochrome C (555, Chlorobium thiosulfatophilum) in oxidation of thiosulfate 总被引:2,自引:0,他引:2
Thiosulfate-cytochrome c-551 reductase derived from has been highly purified. The enzyme reduces cytochrome in the presence of thiosulfate while cytochrome -555 of the organism is not reduced by the enzyme. Cytochrome -555 reacts with the enzyme at an appreciable rate only in the presence of cytochrome -551. However, the reduction rate of cytochrome -551 by the enzyme is greatly enhanced on addition of a catalytic amount of cytochrome -555. Therefore, cytochrome -555 seems to function as an effector on thiosulfate-cytochrome -551 reductase as well as it acts as the electron donor to the light-excited chlorobium chlorophylls. 相似文献
3.
K P Hsiung S S Kuan G G Guilbault 《Biochemical and biophysical research communications》1975,66(4):1225-1230
A mutant of that grows in mineral medium with acetanilide as the sole carbon and nitrogen source for growth was isolated and a great amount of inducible enzyme was extracted from the cell. The crude enzyme extract was found to be very active toward the substrate acetanilide and the hydrolyzed products were identified as aniline and acetic acid. The enzyme was therefore characterized as an aryl acylamidase (EC 3.5.1.13). The growth and induction of the micro-organism as well as the extraction of the enzyme are described briefly in this paper. 相似文献
4.
P P Hipps M R Eveland M H Laird W R Sherman 《Biochemical and biophysical research communications》1976,68(4):1133-1138
-Inositol:NAD(P)+ oxidoreductase (-inositol oxidoreductase) has been identified in bovine brain. This enzyme elutes from DEAE cellulose with 0.3 M KCl in 50 mM Tris buffer, pH 7.5. Using NADH as cofactor -inosose-2 is reduced selectively to -inositol. With NADPH the enzyme forms both -inositol and -inositol, however, at a lower rate. The enzyme was chromatographed on G-100 Sephadex and found to have an apparent molecular weight of 74,000. This enzyme differs in DEAE binding, molecular weight and cofactor specificity from the previously described -inositol oxidoreductase which utilizes NADPH exclusively to produce 3 fold more -inositol than -inositol. 相似文献
5.
Kathryn L. Desphande Jon R. Katze James F. Kane 《Biochemical and biophysical research communications》1980,95(1):55-60
Glutamate synthase, an important enzyme in the assimilation of ammonia, was measured in cultures of grown with different nitrogen sources. An attempt was made to correlate the specific activity to the intracellular levels of five metabolites of glutamate metabolism: aspartate, glutamate, glutamine, alanine and . An inverse relationship was found between the activity of glutamate synthase and the pool level of glutamine. We propose that the intracellular concentration of glutamine is an important element in controlling the level of glutamate synthase. 相似文献
6.
Charles D. Boyer Jack Preiss 《Biochemical and biophysical research communications》1978,80(1):169-175
Purification of starch branching enzymes from kernels of two nonlinked mutants of maize, and , showed the basis of the two mutations to be associated with branching enzymes I and IIb, respectively. Branching enzyme I from kernels purified as nonmutant branching enzyme I, but had an altered pattern of activity when amylose was used as a substrate. In addition to the typical fall in absorbance at high wavelengths (550–700 nm) of the amylose-iodine complex, branching of amylose by branching enzyme I caused an increase in absorbance at low wavelengths (400–550 nm). Branching enzyme IIb was undetected in extracts of kernels, while branching enzymes I and IIa appeared unaltered. Low umprimed starch synthase activity was also observed in DEAE-cellulose fractions of maize, but this activity was regenerated by the addition of any branching enzyme. 相似文献
7.
Y Gopalakrishna T K Narayanan G R Rao 《Biochemical and biophysical research communications》1976,69(2):417-422
produced β-phenethyl alcohol and β-phenyllactic acid when grown in a synthetic medium containing L-phenylalanine as sole source of nitrogen. The cell-free preparations from these cells showed the following enzymes: phenylalanine aminotransferase, phenylpyruvate decarboxylase, phenylpyruvate reductase and phenylacetaldehyde reductase. The cell-free preparations of grown in medium with ammonium sulfate, lacked these enzyme activities, indicating the inducible nature of these enzymes. The results indicate the role of β-phenylpyruvate as a key intermediate in the pathway of biosynthesis of β-phenethyl alcohol and β-phenyllactic acid from L-phenylalanine. 相似文献
8.
S G Bhat M Ramanarayanan C S Vaidyanathan 《Biochemical and biophysical research communications》1973,52(3):834-842
A soluble fraction of catalyzed the hydroxylation of mandelic acid to -hydroxymandelic acid. The enzyme had a pH optimum of 5.4 and showed an absolute requirement for Fe2+, tetrahydropteridine, NADPH. -Hydroxymandelate, the product of the enzyme reaction was identified by paper chromatography, thin layer chromatography, UV and IR-spectra. 相似文献
9.
Chemical modification of opiate receptors with ethoxyformic anhydride and photo-oxidation: evidence for essential histidyl residues 总被引:1,自引:0,他引:1
In the presence of -carnitine significant decarboxylation of 2-oxoglutarate occurs with γ-butyrobetaine hydroxylase (EC 1.14.11.1) both from sp AK 1 and from human kidney. No product was formed from carnitine when -carnitine was incubated with either enzyme but succinate was formed in 1:1 stoichiometry to decarboxylation using -carnitine and the human enzyme. -Carnitine is also an uncoupler for the human enzyme. There is no significant decarboxylation of 2-oxoglutarate in the absence of a substrate, but during normal catalysis in the presence of γ-butyrobetaine the formation of CO2 from 2-oxoglutarate exceeds carnitine formation with 20% for the human enzyme. 相似文献
10.
Anthony L. Tarentino Frank Maley 《Biochemical and biophysical research communications》1975,67(1):455-462
The substrate specificities of the endo-β-N-acetylglucosaminidases from and were compared and found to differ considerably. The enzyme from released Asn-GlcNAc-Fuc-containing glycopeptides from exoglycosidase-treated acidic IgM glycopeptides but was limited in its capacity to hydrolyze ovalbumin glycopeptides larger than Asn(GlcNAc)2(Man)5. In contrast, the enzyme from hydrolyzed this and larger neutral oligosaccharides but could not hydrolyze the above fucose-containing IgM glycopeptides. Removal of the fucose residue, however, converted the latter to an active substrate for the enzyme, thus broadening its substrate range to encompass most of those substrates hydrolyzed by the endoglycosidase. 相似文献
11.
The cytochrome oxidase (EC 1.9.3.1) of HB8 was isolated from the membrane fraction, and was highly purified. The oxidase contained heme and heme as the prosthetic groups. The purified preparation showed a single band in polyacrylamide gel electrophoresis, and three major polypeptides with apparent molecular weights of 52,000, 37,000 and 29,000 were observed in the presence of sodium dodecyl sulfate. The enzyme reacted rapidly with cytochrome c-552. The oxidation of cytochrome -555,549 by the enzyme was very slow, and was stimulated by the addition of cytochrome -552. The enzyme was highly stable to heat. 相似文献
12.
Optimal conditions for activation of adenylate cyclase in membrane particles were studied. Enzyme activation with serotonin (5-hydroxytryptamine), NaF, and guanosine (GTPγS) was time- and temperature-dependent. Mg2+ was required for enzyme activation. Adenylate cyclase that was activated by NaF or GTPγS was gradually inhibited by while enzyme activated with serotonin and GTP responded faster to inhibition by the same sulfhydryl reagent. The enzyme responded in a similar fashion to a spin-labeled analog 3-(maleimidomethyl)-2,2,5,5-tetramethyl-1-pyrolidinyloxyl (i.e., nitroxide). Binding of the spin label was enhanced following enzyme activation by serotonin, NaF, or GTPγS in the presence of Mg2+. Activation of the enzyme was accompanied by an increase in the strong immobilization peaks in the EPR spectra. Both effects, the increase in binding and in the strong immobilization peaks, can be induced by Mg2+ alone. The results indicate that a general conformational change induced by Mg2+ may be essential for adenylate cyclase activation. 相似文献
13.
Recent work (Hizi and Yagil [1974] Eur. J. Biochem. : 211–221, and Kelly [1975] Fed. Proc. : 881) suggests that the marked increase in rat liver glucose-6-phosphate dehydrogenase activity which is observed upon feeding an animal a high carbohydrate diet does not involve an increase in the total amount of enzyme present. In contrast, the data presented herein involving immunological titrations of rat liver glucose-6-phosphate dehydrogenase indicates that the increase in enzyme activity resulting from feeding a high carbohydrate diet does involve an increase in the total amount of enzyme present. 相似文献
14.
Wolfgang Feller Hartmut Follmann 《Biochemical and biophysical research communications》1976,70(3):752-758
A ribonucleoside diphosphate reductase is demonstrated in the algae, and . In synchronized cultures an activity maximum at the 12th hour of the cell cycle coincides with maximum DNA production. Induction of reductase activity is prevented by cycloheximide. The enzyme requires dithiols for reduction of CDP ; it is not significantly stimulated by iron or magnesium ions nor dependent upon deoxyadenosylcobalamin. ATP stimulates the reaction but dATP or dTTP act as inhibitors. The ribonucleotide reductase of green algae differs from the B12-requiring enzyme characterized in . 相似文献
15.
Cytoplasmic catechol-O-methyltransferase activity from rat liver was resolved by gel filtration into two enzymes: a major form having an estimated molecular weight of 23,000 and a minor one of 45,500. The relative abundance of these forms in liver is about 5:1, respectively. Microsomal catechol-O-methyltransferase constituted only 2% of the total liver activity. After solubilization by sonication most of the microsomal enzyme showed a molecular weight in excess of 100,000, but some 23,000 - enzyme was also released. The bound enzyme thus may represent an aggregate form of the soluble activity. The two cytoplasmic enzymes differ in several properties, including pH optima and thermal stability. The two forms also differ in the extent of methylation of the hydroxyl group, the larger enzyme having a : methylation ratio twice that obtained with the smaller form. 相似文献
16.
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
17.
T Yagi H Kagamiyama M Nozaki 《Biochemical and biophysical research communications》1979,90(2):447-452
Aspartate aminotransferases from pig heart cytosol and mitochondria, B and accepted L-cysteine sulfinate as a good substrate. The mitochondrial isoenzyme and the enzyme showed higher activity toward L-cysteine sulfinate than toward the natural substrates, L-glutamate and L-aspartate. The cytosolic isoenzyme catalyzed the L-cysteine sulfinate transamination at 50% the rate of L-glutamate transamination. The enzyme had the same reactivity toward the three substrates. Antisera against the two isoenzymes and the enzyme inactivated almost completely cysteine sulfinate transamination activity in the crude extracts of pig heart muscle and B, respectively. These results indicate that cysteine sulfinate transamination is catalyzed by aspartate aminotransferase in these cells. 相似文献
18.
-Octopamine was characterized as substrate for monoamine oxidase (MAO) in rat brain and liver mitochondria. The m and max values of the brain enzyme were 735 μM and 32.5 nmoles/mg protein/30 min, and those of the liver enzyme 351 μM and 125 nmoles/mg protein/30 min, respectively. The inhibition experiments with clorgyline and deprenyl showed that -octopamine was a common substrate for type A and type B MAO, though a major part of the activity was due to type A enzyme. 相似文献
19.
The mitochondrial phenotype of and other extra-nuclear mutants is known to predominate over that of wild type in heteroplasms. This phenomenon was investigated in heterokaryons using normally occurring strain differences in restriction enzyme patterns to distinguish wild-type and mitochondrial DNAs. Each of ten independent heterokaryons eventually showed the phenotype as judged by slow growth rate and deficiency of 19 S RNA. Six heterokaryons contained mitochondrial DNAs with restriction enzyme patterns of the parent whereas four contained DNAs which lacked restriction enzyme fragments characteristic of the parent. The latter may be recombinants of wild-type and mitochondrial DNA. 相似文献
20.
J Limón-Lason M Lara B Resendiz J Mora 《Biochemical and biophysical research communications》1977,78(4):1234-1240
The effect of the nitrogen and carbon sources in the regulation of gu tamine synthetase has been studied in fed-batch cultures of . The limitation of ammonium in an excess of the carbon source, leads to an accumulation of α-ketoglutarate and elevation of glutamine sy thetase. The limitation of sucrose in an excess of ammonium results in a decrease in glutamine synthetase activity. These results indicate that the carbon source exerts a positive control in the regulation of glutamine synthetase. 相似文献