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1.
Inhibitors of glutamine synthetase cause derepression of nitrogenase biosynthesis in the presence of in the photosynthetic bacterium Rhodopseudomonas capsulata. A new derepressor of nitrogenase biosynthesis, β-N-oxalyl-L-α,β-diaminopropionic acid (ODAP), is here compared with the widely used L-methionine-DL-sulfoximine (MSX). With both compounds, a quantitative correlation has been observed between inhibition of glutamine synthetase and derepression of nitrogenase biosynthesis. We also find that both MSX and ODAP inhibit nitrogenase activity in vivo in R. capsulata. The latter effect seems to be indirect and related to the previously reported reversible inhibition of nitrogenase activity in vivo by . As a control it was observed that neither nor MSX nor ODAP inhibit nitrogenase activity in vivo in Clostridium pasteurianum. 相似文献
2.
J K Ladha P Rowell W D Stewart 《Biochemical and biophysical research communications》1978,83(2):688-696
5-hydroxylysine, an analogue of glutamate and lysine, causes production by N2-fixing A. cylindrica; it also reversibly inhibits GS activity in vitro but has no effect on alanine dehydrogenase or GOGAT. On adding 5-hydroxylysine intracellular pools of glutamine, glutamate and aspartate decrease; those of alanine and serine increase. 5-hydroxylysine alleviates the inhibitory effect of on heterocyst production and C2H2 reduction and in cultures results in heterocyst synthesis and in C2H2 reduction. The data suggest that the GS-GOGAT pathway is the sole route of importance in primary assimilation in A. cylindrica, that alone does not inhibit nitrogenase and heterocyst production, and that GS and/or a product is involved in regulating the production of both. 相似文献
3.
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
4.
In the glycolytic system derived from rat brain acetone powder, ammonium ion has been found to stimulate three different reactions: (a) the transphosphorylase reaction from phosphoenolpyruvate, (b) the phosphohexokinase reaction, and (c) the hexokinase reaction. The transphosphorylases are affected differently depending upon whether adenosine diphosphate or adenylic acid is the phosphate acceptor; in the case of the latter, the dependency upon is particularly marked. A highly active myokinase is present in these extracts and its activity influences the transphosphorylase reaction to a considerable extent. The phosphohexokinase reaction is stimulated to a greater extent by than is the hexokinase reaction. In contrast to these reactions which require the participation of the adenylic system, triose phosphate oxidase activity is uninfluenced by the presence of . 相似文献
5.
Delocalized chemiosmotic coupling of oxidative phosphorylation requires that a single-value correlation exists between the extent of and the kinetic parameters of respiration and ATP synthesis. This expectation was tested experimentally in nigericin-treated plant mitochondria in single combined experiments, in which simultaneously respiration (in State 3 and in State 4) was measured polarographically, FΔψ (which under these conditions was equivalent to ) was evaluated potentiometrically from the uptake of tetraphenylphosphonium+ and the rate of phosphorylation was estimated from the transient depolarization of mitochondria during State 4-State 3-State 4 transitions. The steady-state rates of the different biochemical reactions were progressively inhibited by specific inhibitors active with different modalities on various steps of the energy-transducing process: succinate respiration was inhibited competitively with malonate or noncompetitively with antimycin A, or by limiting the rate of transport into the mitochondria of the respiratory substrate with phenylsuccinate; was dissipated by uncoupling with increasing concentrations of valinomycin; ADP phosphorylation was limited with oligomycin. The results indicate generally that when the rate of respiratory electron flow is decreased, a parallel inhibition of the rate of phosphorylation is also observed, while very limited effects can be detected on the extent of . This behavior is in marked contrast to the effect of uncoupling where the decreased rate of ATP synthesis is clearly due to energy limitation. Extending previous observations in bacterial photosynthesis and in respiration by animal mitochondria and submitochondrial particles the results indicate, therefore, that respiration tightly controls the rate of ATP synthesis, with a mechanism largely independent of . These data cannot be reconciled with a delocalized chemiosmotic coupling model. 相似文献
6.
ColE1 hybrid plasmids containing Escherichia coli genes involved in the biosynthesis of glutamate and glutamine 总被引:11,自引:0,他引:11
The Clarke-Carbon bank of Escherichia coli strains carrying ColE1 hybrid plasmids was screened for complementation of gdh, gltB, and glnA mutations affecting nitrogen metabolism in E. coli. Plasmids which complemented each one of these mutations were isolated. In every case, the plasmids conferred to otherwise mutant cells the capacity to synthesize the corresponding wild-type enzymes: glutamate dehydrogenase, glutamate synthase, and glutamine synthetase (GS), respectively. For three representative plasmids, endonuclease restriction maps were constructed. One of the plasmids, pACR1, which complemented glnA mutations, including the glnA21::Tn5 insertion, was deemed to carry the glnA+ allele. GS synthesis by pACR1 heterozygous merodiploids was subjected to repression by growth on 15 mm NH4+ and had a twofold high derepressed level than wild-type (glnA+) haploid cells when grown on 0.5 mm NH4+ or on glutamate as only nitrogen sources. The presence of glutamine as sole nitrogen source promoted repressed GS synthesis in the merodiploids. By contrast, glutamine allowed almost fully derepressed synthesis of GS in glnA+ haploid cells. 相似文献
7.
Interaction of lymphocytes and macrophage cell line cells (M1 cells). I. Functional maturation and appearance of Fc receptors im M1 cells 总被引:2,自引:0,他引:2
M1 cells, which are cell line cells established from myeloid leukemia cells of the SL strain mouse, can differentiate from blast cells () to mature macrophages () within 48 hr, when they are cultured with conditioned medium (CM) obtained from murine embryonic fibroblasts. While cells have no phagocytic activity nor Fc receptor (FcR), cells possess both characteristics. The appearance of FcR is temperature-dependent and inhibited by a metabolic inhibitor, cycloheximide. FcR on cells is resistant to trypsin and pronase. cells improve the viability of macrophage-depleted SL splenic lymphocytes and restore the in vitro secondary plaque forming cell response of macrophage-depleted spleen cells to particulate and soluble antigens. cells lack this macrophage-substituting capacity. Mm1 cells, mutant cells from M1 cells, having FcR and higher phagocytic activity than cells, are also devoid of this capacity. 相似文献
8.
Quercetin inhibited a dog kidney ( preparation without affecting for ATP or for cation activators, attributable to the slowly-reversible nature of its inhibition. Dimethyl sulfoxide, a selector of E2 enzyme conformations, blocked this inhibition, while the K+-phosphatase activity was at least as sensitive to quercetin as the ( activity, all consistent with quercetin favoring E1 conformations of the enzyme. Oligomycin, a rapidly-reversible inhibitor, decreased the for ATP and the for cation activators, and its inhibition was also diminished by dimethyl sulfoxide. Although oligomycin did not inhibit the K+-phosphatase activity under standard assay conditions, a reaction presumably catalyzed by E2 conformations, its effects are nevertheless accommodated by a quantitative model for that reaction depicting oligomycin as favoring E1 conformations. The model also accounts quantitatively for effects of both dimethyl sulfoxide and oligomycin on , for substrate, and for K+, as well as for stimulation of phosphatase activity by both these reagents at low K+ but high Na+ concentrations. 相似文献
9.
Oxygen-limited continuous cultures of the cowpea sp. strain CB756, had high levels of nitrogenase activity, which were not significantly affected by excess ammonium ions or glutamine. When the growth-restricting O2-limitation was partially relieved, nitrogenase was repressed and this was accompanied by increased adenylylation of glutamine synthetase. It is suggested that the restricted supply of ATP interferes with adenylylation of glutamine synthetase during O2-limited growth, thus preventing repression of nitrogenase in the presence of excess ammonium ions. 相似文献
10.
Ole Scharff 《生物化学与生物物理学报:生物膜》1978,512(2):309-317
The additional activation by monovalent cations of the ATPase (ATP phosphohydrolase, EC 3.6.1.3) in human erythrocyte membranes was studied.The Ca2+-ATPase occurs in two different states. In the A-state the enzyme is virtually free of protein activator and the kinetics of Ca2+ activation is characterized by low apparent Ca2+ affinity and low maximum activity. In the B-state the enzyme is associated with activator and the kinetics is characterized by high Ca2+ affinity and high maximum activity.At optimum concentrations of Ca2+ the additional activation of the B-state by K+, NH4+, Na+ and Rb+ exceeded the corresponding activations of the A-state, and half-maximum activations by K+, NH4+, and Na+ were achieved at lower concentrations in the B-state than in the A-state. Li+ and Cs+ activated the two states almost equally but maximum activation was obtained at lower cation concentrations in the B-state than in the A-state.The activation of the B-state by the various cations decreased in the order . The A-state was activated almost equally by K+, Na+, NH4+, and Rb+ and to a smaller extent by Li+ and Cs+.At sub-optimum concentrations of Ca2+ high concentrations of monovalent cations (100 mM) activated the Ca2+-ATPase equally in the A-state and the B-state. In the absence of Ca2+ the monovalent cations inhibited the Mg2+-dependent ATPase in both types of membranes. This dependence on Ca2+ indicates that the monovalent cations interact with the Ca2+ sites in the B-state.The results suggest that K+ or Na+, or both, contribute to the regulation of the Ca2+ pump in erythrocytes. 相似文献
11.
Chloroplasts which were rapidly isolated from illuminated leaves showed activity of ATP hydrolysis at a level much higher than that of the dark control. Under the high-intensity illumination or under repetitive flash excitation, the activated chloroplasts synthesized more ATP than those with a low ATP hydrolysis activity. formed under repetitive flashes was smaller in the activated chloroplasts than in the inactive chloroplasts. The inhibition of ATP yield per flash by valinomycin or nigericin in the presence of K+ was stronger in the inactive chloroplasts than in the activated chloroplast. ATP synthesis in the activated chloroplasts seems to have a lower threshold. 相似文献
12.
ADP and Pi-loaded membrane vesicles from l-malate-grown Bacillus alcalophilus synthesized ATP upon energization with . ATP synthesis occurred over a range of external pH from 6.0 to 11.0, under conditions in which the total protonmotive force was as low as ?30 mV. The phosphate potentials (ΔGp) were calculated to be 11 and 12 kcal/mol at pH 10.5 and 9.0, respectively, whereas the values in vesicles at these two pH values were quite different (?40 ± 20 mV at pH 10.5 and ?125 ± 20 mV at pH 9.0). ATP synthesis was inhibited by KCN, gramicidin, and by N,N′-dicyclohexylcarbodiimide. Inward translocation of protons, concomitant with ATP synthesis, was demonstrated using direct pH monitoring and fluorescence methods. No dependence upon the presence of Na+ or K+ was found. Thus, ATP synthesis in B. alcalophilus appears to involve a proton-translocating ATPase which functions at low . 相似文献
13.
G.E. Breitwieser 《生物化学与生物物理学报:生物膜》1982,689(3):457-463
(1) A membrane fraction enriched in (EC 3.6.1.3) was obtained from optic ganglia of the squid (Loligo pealei) by density gradient fractionation of membranes followed by treatment with either SDS or Brij-58. The resulting membrane had an specific activity of approx. 2 units/mg and was ouabain-sensitive. (2) The had a for ATP of and a pH optimum of 7.0. It was inhibited by ouabain with a of . (3) Optimum monovalent cation concentrations were: 240 mM NaCl, 60 mM KCl, tested with . (4) The Mg2+ dependence of hydrolysis varied with the absolute ATP concentration. At 3 mM ATP, the for Mg2+ was , and at 6 mM ATP, the was . High levels of Mg2+ caused inhibition of hydrolysis. (5) The interactions of Na+ and K+ were examined over a range of conditions. K+ levels caused modulations in the Na+ dependence in the range of 1–150 mM. (6) The prepared from squid optic ganglion displays properties similar to those of the sodium pump in injected nerves. 相似文献
14.
Calcium uptake by adipocyte endoplasmic reticulum was studied in a rapidly obtained microsomal fraction. The kinetics and ionic requirements of Ca2+ transport in this preparation were characterized and compared to those of (Ca2+ + Mg2+)-ATPase activity. The time course of Ca2+ uptake in the presence of 5 mM oxalate was nonlinear, approaching a steady-state level of 10.8–11.5 nmol Ca2+/mg protein after 3–4 min of incubation. The rate of Ca2+ transport was increased by higher oxalate concentrations with a near linear rate of uptake at 20 mM oxalate. The calculated initial rate of calcium uptake was 18.5 nmol Ca2+/mg protein per min. The double reciprocal plot of ATP concentration against transport rate was nonlinear, with apparent values of 100 μM and 7 μM for ATP concentration ranges above and below 50 μM, respectively. The apparent values for Mg2+ and Ca2+ were 132 μM and 0.36–0.67 μM, respectively. The energy of activation was 23.4 kcal/mol. These kinetic properties were strikingly similar to those of the microsomal ()-ATPase. The presence of potassium was required for maximum Ca2+ transport activity. The order of effectiveness of monovalent cations in stimulating both Ca2+ transport and ( activity was transport and ( activity were both inhibited 10–20% by 6 mM procaine and less than 10% by 10 mM sodium azide. Both processes were completely inhibited by 3 mM dibucaine or 50 μM sulfonate. The results indicate that Ca2+ transport in adipocyte endoplasmic reticulum is mediated by a and suggest an important role for endoplasmic reticulum in control of intracellular Ca2+ distribution. 相似文献
15.
Diethelm Kleiner 《生物化学与生物物理学报:生物膜》1982,688(3):702-708
Klebsiella pneumoniae can accumulate methylammonium up to 80-fold by means of a transport system as indicated by the energy requirement, saturation kinetics and a narrow pH profile around pH 6.8. Methylammonium transport (apparent , per g dry weight at 15°C) is competitively inhibited by ammonium (apparent ). The low value and the finding that methylammonium cannot serve as a nitrogen source indicate that ammonium rather than methylammonium is the natural substrate. Uphill transport is driven by a component of the protonmotive force, probably the membrane potential. The transport system is under genetic control; it is partially repressed by amino acids and completely by ammonium. Analysis of mutants suggest that the synthesis of the ammonium transport system is subject to the same ‘nitrogen control’ as nitrogenase and glutamine synthetase. 相似文献
16.
Inhibition of fructose 1,6-bisphosphatase by excess substrate and its reversal by monovalent cations
V.N. Singh John S. MacGregor S. Pontremoli B.L. Horecker 《Biochemical and biophysical research communications》1980,94(4):1140-1144
Purified rabbit liver fructose 1,6-bisphosphatase is maximally active with 2 μM fructose 1,6-bisphosphate. Above this concentration the substrate becomes inhibotory. Inhibition is reversed by or by physiological concentrations of K+. Substrate inhibition and its modification by monovalent cations may play a role in the regulation of gluconeogenesis at the step catalyzed by fructose 1,6-bisphosphatase. 相似文献
17.
18.
Fraser J. Bergersen Graham L. Turner 《Biochimica et Biophysica Acta (BBA)/General Subjects》1978,538(3):406-416
In samples from nitrogen-fixing continuous cultures of strain CB756 of the cowpea type rhizobia (Rhizobium sp.), newly fixed NH4+ is in equilibrium with the medium, from where it is assimilated by the glutamine synthetase/glutamate synthase pathway. In samples from steady state cultures with different degrees of oxygen-limitation, nitrogenase activity was positively correlated with the biosynthetic activity of glutamine synthetase in cell free extracts. Also, activities in biosynthetic assays were positively correlated with activities in γ-glutamyl transferase assays containing 60 mM Mg2+. Relative adenylylation of glutamine synthetase was conveniently measured in cell free extracts as the ratio of γ-glutamyl transferase activities without and with addition of 60 mM Mg2+.Automatic control of oxygen supply was used to facilitate the study of transitions between steady-state continuous cultures with high and low nitrogenase activities. Adenylylation of glutamine synthetase and repression of nitrogenase activity in the presence of excess NH4+, were masked when oxygen strongly limited culture yield. Partial relief of the limitation in cultures supplied with 10 mM NH4+ produced early decline in nitrogenase activity and increase in relative adenylylation of glutamine synthetase. Decreased oxygen supply produced a rapid decline in relative adenylylation, followed by increased nitrogenase activity, supporting the concept that control of nitrogenase synthesis is modulated by glutamine synthetase adenylylation in these bacteria. 相似文献
19.
J.J. Schrijen A. Omachi W.A.H.M. Van Groningen-Luyben J.J.H.H.M. De Pont S.L. Bonting 《生物化学与生物物理学报:生物膜》1981,649(1):1-12
(1) The total phospholipid content of a gradient purified ()-ATPase preparation from pig gastric mucosa is 105 μmol per 100 mg protein, and consists of 29% sphingomyelin, 29% phosphatidylcholine, 28% phosphatidylethanolamine, 10% phosphatidylserine and 4% phosphatidylinositol. The cholesterol content corresponds to 50 μmol per 100 mg protein. (2) Treatment with phospholipase C (from Clostridium welchii and Bacillus cereus) results in an immediate decrease of the phosphate content. Up to 50% of the phospholipids are hydrolyzed by each phospholipase C preparation alone, without further hydrolysis by increased phospholipase concentration or prolonged incubation time. Combined treatment with the two phospholipase C preparations, sequentially or simultaneously, hydrolyzes up to 65% of the phospholipids. (3) The ()-ATPase and K+ stimulated activities are decreased proportionally with the total phospholipid content, indicating that these enzyme activities are dependent on phospholipids. (4) Phospholipase C treatment does not change optimal pH, value for ATP and temperature dependence of the gastric ()-ATPase, but slightly decreases the value for K+. (5) Phospholipase C treatment lowers the binding and phosphorylation capacities, suggesting that inactivation occurs primarily on the substrate binding level. (6) Most of the results can be understood by assuming that hydrolysis of the phospholipids by phospholipase C leads to aggregation of the membrane protein molecules and complete inactivation of the aggregated ATPase molecules. 相似文献
20.
The permeability of the lysosomal membrane to small anions and cations was studied at 37°C and pH 7.0 in a lysosomal-mitochondrial fraction isolated from the liver of untreated rats. The extent of osmotic lysis following ion influx was used as a measure of ion permeancy. In order to preserve electroneutrality, anion influx was coupled to an influx of K+ in the presence of valinomycin, and cation influx was coupled to an efflux of H+ using the protonophore . Lysosomal lysis was monitored by observing the loss of latency of two lysosomal hydrolases.The order of permeability of the lysosomal membrane to anions was found to be and that to cations . These orders are largely in agreement with the lyotropic series of anions and cations.The implications of these findings for the mechanism by means of which a low intralysosomal pH is produced and maintained are discussed. 相似文献