共查询到20条相似文献,搜索用时 15 毫秒
1.
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
2.
Giovanna Grimaldi John Guardiola 《Biochemical and biophysical research communications》1981,101(4):1233-1240
The mutation (obtained by phage mediated mutagenesis) affects the sensitivity to valine inhibition of the acetohydroxy acid synthase III isoenzyme of K-12, as shown by constructing multiple mutants containing the mutation and only one of the genes for the expression of the three acetohydroxy acid synthase isoenzymes, at once. The mutation is dominant. This suggests that the phenotype of mutation is not caused by inactivation of a gene concerned with the expression of the AHASIII enzyme, consequent to prophage insertion into that locus. 相似文献
3.
Both the cytosolic and mitochondrial isoenzyme of aspartate aminotransferase from pig heart were inactivated during transamination with chloropyruvate. Inactivation occurred with L-alanine as the amino group donor in the presence of potassium formate. When L-glutamate or L-aspartate was employed as the amino group donor in the transamination reaction with chloropyruvate, no inactivation occurred. This is in contrast to the case of inactivation by bromopyruvate (Okamoto, M. &; Morino, Y. (1973) J. Biol. Chem. , 82–90) where these natural dicarboxylic amino acid substrates were effective in the transamination reaction leading to syncatalytic inactivation (Birchmeier, W. &; Christen, P. (1974) J. Biol. Chem. , 6311–6315). The Cys390 in the cytosolic isoenzyme which was modified in the syncatalytic inactivation was not modified under the present condition for inactivation with either chloropyruvate or bromopyruvate. 相似文献
4.
J M Schneller C Schneider A J Stahl 《Biochemical and biophysical research communications》1978,85(4):1392-1399
Total methionine-tRNA synthetases from wild type can be fractionated on hydroxylapatite into two peaks: Peak I is the mitochondrial, peak II the cytoplasmic isoenzyme. The specificity towards various tRNAs and the antigenic determinants are not identical. A mutant strain, known for its altered cytoplasmic enzyme, contains a mitochondrial species with the same properties as the wild type mitochondrial enzyme, as well as a cytoplasmic isoenzyme with a KM for methionine about 300 times higher than the corresponding wild type enzyme. Another strain, obtained by back-crossing the mutant with a wild type strain, retains the enzyme pattern found in the mutant. The results are in favor of two distinct nuclear genes for yeast mitochondrial and cytoplasmic methionyl-tRNA synthetases. 相似文献
5.
H. Gehring P. Christen G. Eichele M. Glor J.N. Jansonius A.-S. Reimer J.D.G. Smit C. Thaller 《Journal of molecular biology》1977,115(1):97-101
The mitochondrial isoenzyme of aspartate aminotransferase (E.C. 2.6.1.1) has been isolated from chicken heart in an electrophoretically and immunologically homogeneous form. Large, well-diffracting single crystals of this enzyme, a dimeric molecule with a molecular weight of 90,000, have been grown by vapour phase diffusion against polyethylene glycol solutions. The crystals belong to space group P1. The unit cell, with the dimensions , α = 85.3 °, β = 109.2 °, γ = 115.6 °, contains a single dimer. The diffraction pattern extends to at least 2.1 Å resolution. 相似文献
6.
Tito Ureta Jasna Radojković Nelson Díaz Juan C. Slebe Carlos Lozano 《Archives of biochemistry and biophysics》1978,186(2):235-247
Glucose phosphorylating activities were measured in liver extracts from two urodeles and twenty-six anurans. Fractionation on diethylaminoethyl-cellulose columns of liver extracts from these amphibians permitted the recognition of four hexokinases which are called A, B, C, and D. However, any given amphibian displays only three liver hexokinases and the profiles so far observed are either of the type A-B-D or C-B-D. The distribution of the amphibians in either type of pattern does not show any simple taxonomic relationship. A wide generic and specific, but not individual, variation of the relative proportion of each isoenzyme was observed. Hexokinases A and B were shown to be low Km glucose isoenzymes (0.06 and 0.15 mm glucose, respectively) with normal hyperbolic kinetics. Hexokinase C, also a low Km isoenzyme (0.05 mm) was found to be inhibited by excess substrate at physiological levels of glucose. Hexokinases A, B, and C were able to phosphorylate fructose, mannose, and 2-deoxyglucose at equal or higher rates than glucose when assayed at saturating sugar levels. Hexokinase D was found to be a high Km isoenzyme () with sigmoidal saturation curves for glucose (Hill coefficient ? 1.6). Fructose and mannose were also phosphorylated by this isoenzyme at about 70% of the glucose rate when studied at saturating sugar concentrations. The properties of the amphibian hexokinases are thus similar, although not identical, to those of mammalian hexokinases. 相似文献
7.
The acetohydroxy acid synthase III isoenzyme of Escherichia coli K-12: regulation of synthesis by leucine. 总被引:9,自引:0,他引:9
Acetohydroxy acid synthase III (AHAS III) is one of the three isoenzymes which catalyze the condensation reaction for the biosynthesis of the branched chain amino acids in K-12. The synthesis of this enzyme is repressed by leucine. As a consequence of this regulatory feature, strain PS1035, in which AHAS III is the only AHAS isoenzyme expressed, does not grow in minimal medium containing leucine. The other two branched chain amino acids, isoleucine and valine, do not have regulatory effects on AHAS III synthesis. 相似文献
8.
Heinz Gehring Philipp Christen 《Biochemical and biophysical research communications》1975,63(2):441-447
One sulfhydryl group of the mitochondrial isoenzyme of aspartate aminotransferase from both chicken and pig heart exhibits syncatalytic reactivity changes similar to those found previously in the cytosolic isoenzyme from pig heart (Birchmeier, W., Wilson, K.J., and Christen, P. (1973) J. Biol. Chem. , 1751–1759). The reactivity of the only titratable sulfhydryl group toward 5,5′-dithiobis-(2-nitrobenzoate) is at a minimum in the free pyridoxal and pyridoxamine form of the enzyme and is increased by approximately one order of magnitude when covalent enzyme-substrate intermediates are formed. The modification of the sulfhydryl group does not affect enzymatic activity. This finding supports the earlier conclusion that the syncatalytic reactivity changes are not due to a direct participation of this group in the active site but rather to conformational adaptations of the enzyme-coenzyme-substrate compound occurring in the catalytic mechanism of aspartate aminotransferases. 相似文献
9.
The replication defective transducing phage λp3 carries a portion of the operon in the 2 region of the lambda phage. This operon segment contains the promoter, the operator, and the β-galactosidase gene, but does not contain the repressor gene. The gene can be expressed from both the inserted promoter and the phage promoter. When strain 594 (?, +) or JC6256 (Δ) is infected by λp3 in the absence of additional cyclic AMP, β-galactosidase synthesis is shown to be expressed from the phage promoter. When 594 (λ+) or JC6256 (λ+) is infected by λp3 in the presence of additional cyclic AMP and IPTG, β-galactosidase synthesis is shown to be expressed from the inserted promoter.The ability to separate the phage promoter from the inserted promoter for β-galactosidase expression will simplify the interpretation whenever λp5 is used. 相似文献
10.
C T Hadden 《Biochemical and biophysical research communications》1973,51(3):501-506
The effect of a deficiency in DNA polymerase on recombination in has been studied. It is concluded that the major DNA polymerase of is not required for recombination, and that the recombination deficiency of a previously described DNA polymerase-deficient mutant is actually due to a mutation. Genetic crosses imply that this recombination deficiency is not or . 相似文献
11.
D M Haverstick D Dickemper A H Gold 《Biochemical and biophysical research communications》1979,87(1):177-183
Cycloheximide given to insulin-treated alloxan diabetic rats results in the inhibition of insulin-induced liver glycogen synthase conversion without affecting the level of synthase . The effect of cycloheximide, believed to elevate cAMP in liver of normal rats, is independent of cAMP levels of the insulin-treated diabetic rat. The inhibition of insulin-mediated synthase to conversion by cycloheximide does not appear to be the result of a cycloheximide-induced cAMP-dependent phosphorylation of synthase to and suggests that insulin control of synthase and interconversions is dependent upon cycloheximide-sensitive protein synthesis. 相似文献
12.
The detection of a bound ferredoxin in the photosynthetic lamellae of blue-green algae and other oxygen evolving photosynthetic organisms 总被引:3,自引:0,他引:3
M C Evans S G Reeves A Telfer 《Biochemical and biophysical research communications》1973,51(3):593-596
The presence of an electron transport component with an EPR spectrum similar to that of a ferredoxin has been demonstrated in the blue-green alga , the green alga , and in chloroplasts from sorghum () and beans (). The component is photoreduced at 77°K and is very similar to that previously reported in spinach. It seems likely that this component is a primary electron acceptor in photosynthesis in all of these organisms. 相似文献
13.
The accumulation of glycinamide ribotide by ade3 and ade8 mutants of Saccharomyces cerevisiae 总被引:4,自引:0,他引:4
The purine intermediate GAR is present in cell free extracts of and mutants of yeast. It is also detectable following acid hydrolysis of extracts of and which accumulate FGAR and FGAM respectively. GAR accumulation is repressed by growing cells in high levels of adenine. Neither nor accumulate GAR and both prevent accumulation of GAR in and and FGAR in . Since is known to be defective in folate metabolism these results indicate that is blocked in the conversion of GAR→FGAR. 相似文献
14.
C H Letendre P C MacDonnell G Guroff 《Biochemical and biophysical research communications》1976,76(2):615-617
Determination of the complete amino acid sequence of the rubredoxin isolated from the sulfate reducing bacterium showed that the molecule consists of a single polypeptide chain of 52 residues. The sequence of the first 42 residues was determined using an automatic Protein Sequencer. Peptides derived from tryptic hydrolysis and from specific cleavage at tryptophan residue were used to construct the total sequence. Compared with the sequence of rubredoxin, 37 positions are identical, and with the sequences of , , and rubredoxins, 20 matching residues occur. A crystallographic study of the rubredoxin is in progress. 相似文献
15.
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
16.
The addition of formate to oxidized cytochrome oxidase (ferrocytochrome : oxygen oxidoreductase, EC 1.9.3.1) causes the appearance of a high spin heme signal at g = 6 and a splitting of g = 3 signal to g = 2.98 and 3.07. When formate-cytochrome oxidase is reduced, the g = 2.98 signal decreases significantly. The spectrophotometric studies showed that formate is a specific ligand to cytochrome 3. Data suggest that binding of formate to oxidized cytochrome oxidase produces a ligand-3 interaction leading to the splitting of g = 3 signal hitherto considered as due to cytochrome . Thus both cytochrome and 3 contribute to the resonance of g = 3 signal of cytochrome oxidase. 相似文献
17.
H.R. Bosshard M. Zürrer H. Schägger G. von Jagow 《Biochemical and biophysical research communications》1979,89(1):250-258
Cytochrome 1, the electron donor for cytochrome , is a subunit of the mitochondrial cytochrome 1 complex (complex III, cytochrome reductase). To test if cytochrome 1 is the cytochrome -binding subunit of the 1 complex, binding of cytochrome to the complex and to isolated cytochrome 1 was compared by a gel-filtration method under non-equilibrium conditions (a 1 complex lacking the Rieske ironsulfur protein was used; von Jagow et al. (1977) Biochim. Biophys. Acta , 549–558). The approximate stoichiometries and binding affinities were found to be very similar. Binding of cytochrome to isolated cytochrome which is another subunit of the reductase was not detectable by the gel-filtration method. Further, the same lysine residues of cytochrome were shielded towards chemical acetylation in the complexes 1 and 1. From this we conclude that the same surface area of cytochrome is in direct contact with cytochrome 1 and with cytochrome 1 in the respective complexes and that therefore cytochrome is most probably the structural ligand for cytochrome in mitochondrial cytochrome reductase. 相似文献
18.
R B Frydman J Awruch M L Tomaro B Frydman 《Biochemical and biophysical research communications》1979,87(3):928-935
Hemin XIII , hemin III , and iron were enzymatically oxidized by a microsomal heme oxygenase preparation from rat liver. These are all better substrates of the oxygenase than the natural substrate, hemin IX . The enzymatic oxidation was selective for the α-methine bridge and in every case only the α-biliverdins were obtained. The latter were readily reduced by biliverdin reductase to the corresponding α-bilirubins. The absence of isomers in addition to the α-bilirubins was established by preparing the derived azopigments and by using [α-14C] and [α-14C] as substrates. The chemical oxidation of , , and gave the expected mixture of biliverdins. It is concluded that heme oxygenase is not specific for hemin IX. On the other hand, the enzyme is highly selective for the α-methine bridge, defined as the methine opposed to that flanked by the 6,7-propionic acid residues. 相似文献
19.
The site of action of the crinkled (cr) locus was determined by combining dermis and epidermis from the tail of 15-day and mice and by growing the recombined skins in the testes of histocompatible mice. Since mice have bald tails, the presence or absence of hair in the graft was the feature used to determine gene action. Grafts of the combinations dermis and dermis grew hair, whereas grafts of the combinations dermis and dermis produced no hair. It was concluded that the cr locus, at least for tail skin, is active in the epidermis. 相似文献
20.
The cleavage of the kDNA minicircles of by the restriction endonucleases I, II, I, I and II revealed that this kDNA is homogeneous in base sequence. This is in contrast with the kDNA of minicircles of the other species of trypanosomes so far studied. The 10 cleavage sites, obtained with these endonucleases, were ordered and a restriction cleavage map of the minicircles was thus drawn. 相似文献