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1.
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
2.
Te May Ching 《Life sciences》1976,18(10):1071-1076
Nonphosphorylating condition under anaerobiosis stopped nitrogenase activity in nodules of soybean ( var. Chippewa) in less than three minutes and aeration quickly activated the enzyme. This stop-and-go treatment can be repeatedly applied on excised nodules, and a concomitant low-and-high ATP and energy charge (EC) was observed. After 2 minutes under anaerobiosis, nodule ATP and EC were decreased, respectively, to 20 and 40% of the control. These decreases were not as great with longer anaerobic treatments, and there was no change in the content of total adenosine phosphates. Oxygen enrichment (40%) stimulated the activity of nitrogenase by 2.5 fold in four minutes with a concomitant increase of ATP and EC by 40% and 14%, respectively, and an exhaustion of AMP. Longer treatments of oxygen enrichment lessened the initial effects. These findings indicate that ATP and energy charge probably regulate the activity of nitrogenase and an active adenylate kinase must be operating in the nodules to maintain an energy supply for the basal metabolism and for the nitrogenase under temporary stressed conditions. 相似文献
3.
Effect of carbamyl phosphate on the regulation of nitrogenase in Clostridium pasteurianum 总被引:5,自引:0,他引:5
One mM carbamyl phosphate inhibited the acetylene reduction activity of nitrogenase 30% whereas at high concentrations a maximum inhibition of 50% was observed. When 1 mM carbamyl phosphate was added to a culture growing of N2 1) nitrogenase synthesis was completely repressed and 2) after a period of 2.5 hrs in the absence of growth, the specific activity decreased to less than 50% of its activity just before the addition of the inhibitor. 相似文献
4.
Lawrence C. Davis Sotaro Kotake 《Biochemical and biophysical research communications》1980,93(3):934-940
Nitrogenase functions at or near its maximum capacity , despite a reported energy charge in the cell that should severely inhibit the enzyme. Deenergizing cellular membranes, which is postulated to release magnesium in mitochondria, has been reported to produce rapid inhibition of nitrogenase activity while giving only small changes in energy charge and ratio. It is proposed that the level of magnesium available for complexation by the potent inhibitor ADP is the rate controlling variable for nitrogenase activity. 相似文献
5.
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
6.
W R Scowcroft A H Gibson J D Pagan 《Biochemical and biophysical research communications》1976,73(2):516-523
Nitrogenase activity in agar cultures of cowpea rhizobia, strain 32H1, was rapidly inhibited by but this was relieved by increased O2 tension. Inhibition was more rapid than that caused by inhibitors of protein synthesis and was not relieved by methionine sulfoximine or methionine sulfone. Under conditions were nitrogenase activity was inhibited by , glutamine synthetase and glutamate synthase were substantially unaffected. Glutamate dehydrogenase was undetected in either nitrogenase active or inhibited cultures. These results indicate that inhibition of nitrogenase activity in strain 32H1 is not effected through glutamine synthetase regulation of nitrogenase synthesis. 相似文献
7.
Pyruvate and nitrogenase activity in cell-free extracts of the blue-green alga Anabaena cylindrica 总被引:1,自引:0,他引:1
G A Codd P Rowell W D Stewart 《Biochemical and biophysical research communications》1974,61(2):424-431
When extracts of are prepared in the absence of dithionite, they catalyze pyruvate-dependent acetylene reduction, a reaction not observable in assays containing dithionite. Ferredoxin and coenzyme-A, but not NADP and ferredoxin-NADP reductase, are required for maximal pyruvate-dependent activity. These acetylene-reducing extracts do not exhibit NADP-pyruvate dehydrogenase activity. However, pyruvate:ferredoxin oxidoreductase is present at levels of activity sufficient to support the rate of pyruvate-supported acetylene reduction. These data support earlier evidence that pyruvate:ferredoxin oxidoreductase transfers electrons from pyruvate to nitrogenase in . 相似文献
8.
J F Grillo P J Bottomley C Van Baalen F R Tabita 《Biochemical and biophysical research communications》1979,89(2):685-693
Studies on the O2 protection mechanism for nitrogenase in a mutant (PM10) of sp. CA indicated that the ability to protect nitrogenase from O2 was functionally impaired. Growth rates of PM10 were substantially improved when cells were cultured under microaerobic conditions. Nitrogenase activity was totally inhibited by exposure to O2 for 30 min; partial restoration of activity was attained when cell suspensions were subsequently made microaerobic. Experiments in which induction of nitrogenase activity was followed indicated that the synthesis of the O2 protection mechanism was temporally separated from synthesis of heterocysts and nitrogenase. 相似文献
9.
Derepression of nitrogenase in Azotobacter 总被引:1,自引:0,他引:1
When nitrogenase in 12837 is repressed by ammonia, the derepression is accelerated by endotoxin or cyclic AMP. The phenomenon appears neither to be a consequence of accelerated ammonia utilization nor altered activity of preformed enzyme. This is a unique example of an effect of endotoxin on a procaryotic system. 相似文献
10.
Purification of azotophore membranes containing the nitrogenase from Azotobacter vinelandii 总被引:1,自引:0,他引:1
Azotophore membranes containing nitrogenase have been purified in high yield from by differential and sucrose density gradient sedimentation. The purified preparations appeared as uniform vesicular membranes of 40–75 nm diameter containing the majority of the nitrogenase activity from these cells and were readily separated from the intracytoplasmic membranes containing the cytochromes of the respiratory electron transfer system. The yield and specific activity of azotophores from cells broken by mechanical or osmotic treatment were similar. 相似文献
11.
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
12.
Isolated heterocysts of the N2-fixing blue-green alga Anabaena cylindrica contain the Photosystem I components P-700, bound and soluble ferredoxins and ferredoxin-NADP reductase. They also show Photosystem I activity being able to photoreduce both methylviologen and NADP when ascorbate+dichlorophenol-indophenol acts as reductant. They photophosphorylate (64 μmol ATP produced/mg chlorophyll ) and carry out oxidative phosphorylation (8.7 μmol ATP produced/mg chlorophyll ). Ninety per cent of the total cell-free extract nitrogenase activity is located in the heterocyst fraction of aerobic cultures. 相似文献
13.
Nitrogenase activity of ‘membrane-free’ extracts, produced from nitrogenstarved Rhodospirillum rubrum to which 4 mM NH+4 had been added is only about 10% of the activity in the control. The activity could be restored to 80% by including the membrane component, earlier found to activate R. rubrum nitrogenase, in the reaction mixture. The relation between this ‘switch-off/switch-on’ effect and the function of the membrane component is discussed.Hydrogen production catalyzed by R. rubrum nitrogenase is also dependent on activation by the membrane component. Hydrogen production is inhibited by acetylene but the degree of inhibition is dependent on the nitrogenase component ratio. The strongest inhibition is achieved at low MoFe protein/Fe protein ratios. The values are 4–5 at the component ratios giving the highest activity and increase at high MoFe protein/Fe protein ratios. CO inhibits acetylene reduction but has no effect on the hydrogen production. 相似文献
14.
Effect of oxygen tension on nitrogenase and on glutamine synthetases I and II in Rhizobium jaonicum 61A76. 总被引:2,自引:0,他引:2
V R Rao R A Darrow D L Keister 《Biochemical and biophysical research communications》1978,81(1):224-231
When grown under aerobic conditions, 61A76 contains two forms of glutamine synthetase, GSI and GSII, as previously described. In contrast, cells grown under the low O2 tensions required for nitrogenase synthesis contain only GSI. GSII activity disappears completely at O2 levels below 0.4%. GSI activity decreases by only 50%, but the enzyme appears to become highly adenylylated under the low O2 tensions required for nitrogenase synthesis. 相似文献
15.
Adenylate-pool composition, energy charge, and nitrogenase activity were examined in isolated heterocysts from Anabaena variabilis (ATCC 29413). ATP formation was detected as a light- or oxygen-induced increase in ATP concentration. No cofactors or substrates had to be added for photophosphorylation to occur, whereas oxidative phosphorylation was dependent on hydrogen and oxygen (Knallgas reaction). The increase in ATP concentration was reflected by a decrease in AMP concentration, accompanied by small changes in ADP levels. Thus, a regulation of the adenylate pool by a myokinase (adenylate kinase) has to be assumed. Upon dark-light transitions, the energy charge in heterocysts increased from values below 0.4 to values approaching 0.8. High energy-charge values, reached in the light only, allowed for high rates of acetylene reduction in the presence of hydrogen. The increase in the energy charge in the dark to approx. 0.64 by addition of oxygen (5% () in the presence of hydrogen) resulted in low nitrogenase activities, generally not exceeding 1–3% of the light-induced rates. In the dark, oxygen concentrations above 10% were inhibitory to both ATP formation and acetylene reduction. Increasing light intensities led to a steep increase in energy charge followed by an increase in nitrogenase activity. Plotting enzyme activity versus energy charge, a nonlinear, asymptotic relationship was observed. 相似文献
16.
Alternate exposure of the nitrogen-fixing blue-green alga L-31 to acetylene in air and ambient atmosphere resulted in substantial enhancement in the rate of acetylene reduction activity. The stimulation occurred even when protein synthesis was inhibited in the dark or in the presence of rifampicin and chloramphenicol. Residual nitrogenase of ammonium chloride treated cultures also showed the stimulation effect. The results indicate that the stimulation is due to a substrate (acetylene) mediated alteration of the enzyme molecule and not due to fresh synthesis. 相似文献
17.
T Ruiz-Argüeso D W Emerich H J Evans 《Biochemical and biophysical research communications》1979,86(2):259-264
Some strains of rhizobia possess a hydrogenase system which catalyzes the oxidation of the H2 that is evolved from nitrogenase during N2 fixation. Oxidation of H2 by a hydrogen uptake positive strain of provides energy for support of the N2 fixation reactions and protects nitrogenase from O2 damage 相似文献
18.
19.
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
20.
Ronald M. Hamelik Mead M. McCabe 《Biochemical and biophysical research communications》1982,106(3):875-880
An inhibitor of , endodextranase was detected in proteins prepared from batch cultures of , strains representing serotypes through . Affinity chromatography of strain 6715-49 proteins, which apparently were free of endodextranase activity, yielded an active endodextranase and, in a separate peak, the endodextranase inhibitor. The presence of the inhibitor in culture fluids accounts for the absence of endodextranase activity in batch-grown cultures of , known to produce this enzyme. 相似文献