共查询到20条相似文献,搜索用时 29 毫秒
1.
The metabolism of translocated photosynthate by soybean ( Glycine max L. Merr.) nodules was investigated by 14CO 2-labeling studies and analysis of nodule enzymes. Plants were exposed to 14CO 2 for 30 minutes, followed by 12CO 2 for up to 5 hours. The largest amount of radioactivity in nodules was recovered in neutral sugars at all sampling times. The organic acid fraction of the cytosol was labeled rapidly. Although cyclitols and malonate were found in high concentrations in the nodules, they accumulated less than 10% of the radioactivity in the neutral and acidic fractions, respectively. Phosphate esters were found to contain very low levels of total label, which prohibited analysis of the radioactivity in individual compounds. The whole nodule-labeling patterns suggested the utilization of photosynthate for the generation of organic acids (principally malate) and amino acids (principally glutamate). The radioactivity in bacteroids as a percentage of total nodule label increased slightly with time, while the percentage in the cytosol fraction declined. The labeling patterns for the cytosol were essentially the same as whole nodule-labeling patterns, and they suggest a degradation of carbohydrates for the production of organic acids and amino acids. When it was found that most of the radioactivity in bacteroids was in sugars, the enzymes of glucose metabolism were surveyed. Bacteroids from nodules formed by Rhizobium japonicum strain 110 or strain 138 lacked activity for phosphofructokinase and NADP-dependent 6-phosphogluconate dehydrogenase, key enzymes of glycolysis and the oxidative pentose-phosphate pathways. Enzymes of the glycolytic and pentose phosphate pathways were found in the cytosol fraction. In three experiments, bacteroids contained about 10 to 30% of the total radioactivity in nodules 2 to 5 hours after pulse-labeling of plants, and 60 to 65% of the radioactivity in bacteroids was in the neutral sugar fraction at all sampling times. This strongly suggests some absorption and metabolism of sugars by bacteroids in spite of the lack of key enzymes. Bacteroids did possess enzymes for the formation of hexose phosphates from glucose or fructose. Radioactivity in α,α-trehalose in bacteroids increased until, after 5 hours, trehalose was a major labeled compound in bacteroids. Thus, trehalose synthesis may be a major fate of sugars entering bacteroids. 相似文献
2.
The aim of the work reported here was to ascertain that the patterns of labeling seen in isolated bacteroids also occurred in bacteroids in intact nodules and to observe early metabolic events following exposure of intact nodules to 14CO 2. Intact nodules of soybean ( Glycine max L. Merr. cv Ripley) inoculated with Bradyrhizobium japonicum USDA 110 and pea ( Pisum sativum L. cv Progress 9) inoculated with Rhizobium leguminosarum bv viciae isolate 128C53 were detached and immediately fed 14CO 2 for 1 to 6 min. Bacteroids were purified from these nodules in 5 to 7 min after the feeding period. In the cytosol from both soybean and pea nodules, malate had the highest radioactivity, followed by citrate and aspartate. In peas, asparagine labeling equaled that of aspartate. In B. japonicum bacteroids, malate was the most rapidly labeled compound, and the rate of glutamate labeling was 67% of the rate of malate labeling. Aspartate and alanine were the next most rapidly labeled compounds. R. leguminosarum bacteroids had very low amounts of 14C and, after a 1-min feeding, malate contained 90% of the radioactivity in the organic acid fraction. Only a trace of activity was found in aspartate, whereas the rate of glutamate and alanine labeling approached that of malate after 6 min of feeding. Under the conditions studied, malate was the major form of labeled carbon supplied to both types of bacteroids. These results with intact nodules confirm our earlier results with isolated bacteroids, which showed that a significant proportion of provided labeled substrate, such as malate, is diverted to glutamate. This supports the conclusion that microaerobic conditions in nodules influence carbon metabolism in bacteroids. 相似文献
3.
More ethanol soluble material (carbohydrate and amino nitrogen) was found in both host cell and bacteroid components of Phaseolus vulgaris nodules from plants grown at 28 W/m 2 than from plants grown at 7 W/m 2. The range of compounds identified was similar at the two irradiances. On feeding 14CO 2 to the plant tops at either irradiance the labelling patterns of carbohydrates and organic acids in the nodule host cells and bacteroids suggested that any or all of the following substances could be donated by the host to the bacteroids for general metabolism: sucrose, fructose, glucose, an unidentified carbohydrate, malic acid and an organic acid co-chromatographing with 6-phosphogluconate. Distribution and labelling patterns of nodule amino compounds were consistent with the hypothesis that ammonia is the primary product of nitrogen fixation within bacteroids, and that this ammonia is transported to host cells for assimilation, initially into glutamine and glutamate. 相似文献
4.
The yeast Kluyveromyces marxianus has been pointed out as a promising microorganism for a variety of industrial bioprocesses. Although genetic tools have been developed for this yeast and different potential applications have been investigated, quantitative physiological studies have rarely been reported. Here, we report and discuss the growth, substrate consumption, metabolite formation, and respiratory parameters of K. marxianus CBS 6556 during aerobic batch bioreactor cultivations, using a defined medium with different sugars as sole carbon and energy source, at 30 and 37 °C. Cultivations were carried out both on single sugars and on binary sugar mixtures. Carbon balances closed within 95 to 101 % in all experiments. Biomass and CO 2 were the main products of cell metabolism, whereas by-products were always present in very low proportion (<3 % of the carbon consumed), as long as full aerobiosis was guaranteed. On all sugars tested as sole carbon and energy source (glucose, fructose, sucrose, lactose, and galactose), the maximum specific growth rate remained between 0.39 and 0.49 h ?1, except for galactose at 37 °C, which only supported growth at 0.31 h ?1. Different growth behaviors were observed on the binary sugar mixtures investigated (glucose and lactose, glucose and galactose, lactose and galactose, glucose and fructose, galactose and fructose, fructose and lactose), and the observations were in agreement with previously published data on the sugar transport systems in K. marxianus. We conclude that K. marxianus CBS 6556 does not present any special nutritional requirements; grows well in the range of 30 to 37 °C on different sugars; is capable of growing on sugar mixtures in a shorter period of time than Saccharomyces cerevisiae, which is interesting from an industrial point of view; and deviates tiny amounts of carbon towards metabolite formation, as long as full aerobiosis is maintained. 相似文献
5.
[ 14C]Methylamine (MA; an analog of ammonia) was used to investigate ammonia transport across the bacteroid and peribacteroid membranes (PBM) from soybean ( Glycine max) root nodules. Free-living Bradyrhizobium japonicum USDA110 grown under nitrogen-limited conditions showed rapid MA uptake with saturation kinetics at neutral pH, indicative of a carrier. Exchange of accumulated MA for added ammonia occurred, showing that the carrier recognized both NH 4+ and CH 3NH 3+. MA uptake by isolated bacteroids, on the other hand, was very slow at low concentrations of MA and increased linearly with increasing MA concentration up to 1 millimolar. Ammonia did not inhibit MA by isolated bacteroids and did not cause efflux of accumulated MA. PBM-enclosed bacteroids (peribacteroid units [PBUs]) were qualitatively similar to free bacteroids with respect to MA transport. The rates of uptake and efflux of MA by PBUs were linearly dependent on the imposed concentration gradient and unaffected by NH 4Cl. MA uptake by PBUs increased exponentially with increasing pH, confirming that the rate increased linearly with increasing CH 3NH 2 concentration. The results are consistent with other evidence that transfer of ammonia from the nitrogen-fixing bacteroid to the host cytosol in soybean root nodules occurs solely by simple diffusion of NH 3 across both the bacteroid and peribacteroid membranes. 相似文献
6.
Assimilation of carbohydrates by carrot ( Daucus carota L. cv Danvers) cells in liquid culture was studied to delineate the major metabolic pathways used in transformation of external carbohydrates to UDP-glucose. The cells grown on either sucrose or glucose for several years proved equally capable of utilizing each of these sugars. Sucrose was rapidly hydrolyzed extracellularly to glucose and fructose, and glucose was preferentially taken up. Uptake of fructose was slower and delayed until glucose was nearly depleted from the medium. Concentrations of cellular sugars, mainly glucose and sucrose, increased during late logarithmic phase of growth and decreased during the plateau phase. Continuous labeling of the cells with d-[ 14C]glucose resulted in rapid accumulation of radioactivity in glucose-6-phosphate and UDP-glucose. Because there was virtually no uptake of sucrose, UDP-glucose was likely derived from glucose-1-phosphate in a reaction catalyzed by UDP-glucose pyrophosphorylase and not directly from sucrose. Concentrations of major nucleotides and nucleotide sugars were maximal during the early logarithmic phase of growth and decreased several-fold in the stationary phase. A modified `energy charge' for adenylates calculated with the omission of AMP decreased steadily from 0.9 to 0.8 during the course of culture cycle. An analogous uracil nucleotide ratio was considerably lower (0.85) during early culture, decreased to about 0.7 for the entire logarithmic phase, and returned to initial values as cells entered stationary phase. The uracil nucleotide ratio may provide a useful index to assess the coupling between the energy available in phosphoanhydride bond in adenine nucleotides and the demand for sugar for polysaccharide synthesis through uridine diphosphate-sugar pools. 相似文献
7.
The effects of kinetin on starch and sugar levels and on 14CO 2 and 32P-orthophosphate labeling patterns of floated Chinese cabbage ( Brassica pekinensis) leaf discs were investigated. Kinetin caused gross starch degradation. Neutral sugars were depressed by 30 to 40% in leaf tissue treated with kinetin for 24 hours. 14CO 2 labeling of leaf discs pretreated with kinetin for 24 hours showed increased radioactivity in chloroform-soluble material and most sugar phosphates, and a 35 to 40% decrease in radioactivity in the neutral sugars, glucose, sucrose, and fructose. Incorporation into ATP was increased by 40% by kinetin. 32P-Orthophosphate uptake was inhibited 30% by kinetin. When corrected for uptake, kinetin stimulated incorporation into chloroform-soluble material but had little effect on other cell fractions. These results indicate that kinetin mobilizes starch reserves and increases the flow of sugars required for the synthesis of lipids and structural materials in floated discs. 相似文献
8.
Abstract— - 1 The metabolism of two 14C-labelled hexoses and one hexose analogue, viz. mannose, fructose and glucosamine, has been compared with that of glucose for slices of rat cerebral cortex incubated in vitro.
- 2 The metabolism of [U-14C]mannose was essentially identical to that of glucose; oxygen consumption and CO3 production were similar and maximal at a substrate concentration of 2·75 mM. Incorporation of label into lactate, aspartate, glutamate and GABA was similar for the two substrates at 5·5 mM substrate concentration.
- 3 With [U-14C]fructose, maximal oxygen consumption and CO3 production were obtained at a substrate concentration of 11 mM. At 5·5 mM, incorporation into lactate was 5 per cent, into glutamate and GABA 30 per cent, into alanine 63 per cent and into aspartate 152 per cent of that from glucose. Increasing substrate concentration to 27·5 mm was without effect on incorporation into amino acids from glucose and raised incorporation from fructose into glutamate, GABA and alanine to a level similar to that found with glucose; at the higher substrate concentration aspartate incorporation from fructose was 200 per cent and lactate 42 per cent of that with glucose. Unlabelled fructose was without effect on incorporation of radioactivity from [3-14C]pyruvate into CO2 or amino acids; it increased incorporation into lactate by 36 per cent. Unlabelled glucose diminished incorporation into CO2 from [U-14C]fructose to 35 per cent; incorporation into lactate was stimulated 178 per cent at 5·5 mM fructose; at 27·5 mM it was diminished to 75 per cent.
- 4 By comparison with [1-14C]glucose, incorporation of radioactivity from [1-14C]-glucosamine into lactate, CO2, alanine, GABA and glutamine was very low; incorporation into aspartate was similar to glucose. Thus the metabolism of glucosamine resembled that of fructose. Glucosamine-1-phosphate, glucosamine-6-phosphate, and an unidentified metabolite, all accumulated.
相似文献
9.
Rates of respiratory CO 2 loss and nitrogenase activities of H 2 uptake-negative mutant strains and H 2 uptake-positive revertant strains of Rhizobium japonicum have been investigated. Two-dimensional gel protein patterns of bacteroids formed by inoculation of soybeans ( Glycine max L.) with these two strains show that they are closely related and revealed only one obvious difference between them. On the basis of molecular weight standards, it was concluded that the missing protein spot in the H 2 uptake-negative mutant strain could be caused by a failure of the mutant to synthesize hydrogenase. Nodules formed by the H 2 uptake-negative mutant strain evolved respiratory CO 2 at a rate of about 10% higher than that of nodules formed by the H 2 uptake-positive revertant strain. During short-term experiments employed, rates of both C 2H 2 reduction and 15N 2 fixation varied considerably among replicate samples and no statistically significant differences between mutant and revertant strains were observed. It was observed that increasing the partial pressure of O 2 over nodules significantly decreased the proportion of nitrogenase electrons allocated to H +. 相似文献
10.
The site of anaerobic respiration in the latex is the serum. The main respiratory substrate is fructose. The CO 2 formation in serum is increased by additional fructose on the average about 2.5–3 times. Glucose does not influence CO 2 evolution by serum but slightly increases O 2 consumption. With respect to sugars, latex serum contains essentially only sucrose and a low amount of raffinose. During the incubation of serum sucrose is hydrolysed, the fructose component is immediately utilized in respiration and glucose accumulates. The rate of CO 2 formation in latex as influenced by fructose is negatively related to the rubber content of the latex. Latex with a high rubber content reacts only slightly or not at all on additional fructose. The main limiting factors of latex respiration and sugar utilization are the following: - The deficiency of substrate, due to low activity of β-fructofuranosidase.
- The rate of glucose phosphorylation (D'Auzac, Jacob 1967).
- Presumably the low activity of phosphoglucoisomerase.
- The rubber content of the latex.
- The concentration of CO2 in latex; this factor may be important in vivo, in the laticiferous system.
相似文献
11.
The H 2-oxidizing complex in Rhizobium japonicum 122 DES bacteroids failed to catalyze, at a measurable rate, 2H 1H exchange from a mixture of 2H 2 and 1H 2 in presence of 2H 2O and 1H 2O, providing no evidence for reversibility of the hydrogenase reaction in vivo. In the H 2 oxidation reaction, there was no significant discrimination between 2H 2 and 1H 2, indicating that the initial H 2-activation step in the over-all H 2 oxidation reaction is not rate-limiting. By use of improved methods, an apparent Km for H 2 of 0.05 micromolar was determined. The H 2 oxidation reaction in bacteroids was strongly inhibited by cyanide (88% at 0.05 millimolar), theonyltrifluoroacetone, and other metal-complexing agents. Carbonyl cyanide m-chlorophenylhydrazone at 0.005 millimolar and 2,4-dinitrophenol at 0.5 millimolar inhibited H 2 oxidation and stimulated O 2 uptake. This and other evidence suggest the involvement of cytochromes and nonheme iron proteins in the pathway of electron transport from H 2 to O 2. Partial pressures of H 2 at 0.03 atmosphere and below had a pronounced inhibitory effect on endogenous respiration by bacteroid suspensions. The inhibition of CO 2 evolution by low partial pressures of H 2 suggests that H 2 utilization may result in conservation of oxidizable substrates and benefits the symbiosis under physiological conditions. Succinate, acetate, and formate at concentrations of 50 millimolar inhibited rates of H 2 uptake by 8, 29, and 25%, respectively. The inhibition by succinate was noncompetitive and that by acetate and formate was uncompetitive. A concentration of 11.6 millimolar CO 2 (initial concentration) in solution inhibited H 2 uptake by bacteroid suspensions by 18%. Further research is necessary to establish the significance of the inhibition of H 2 uptake by succinate, acetate, formate, and CO 2 in the metabolism of the H 2-uptake-positive strains of Rhizobium. 相似文献
12.
The flagellate Cyanophora paradoxa contains blue-greenish, organelle-like inclusions termed cyanelles which perform photosynthetic CO 2-fixation in place of chloroplasts. By the use of the HPLC-technique, Cyanophora was shown to form glucose, sucrose, maltose, mannitol, ribose, glycerol and trehalose. Extracts from the whole organism and from the eucaryotic host, but not from the cyanelles, convert 14C-labelled UDP-glucose to polyglucan. Synthesis of sucrose from UDP-glucose and fructose-6-P or fructose could not be demonstrated in any extract from Cyanophora. The transfer of metabolites into cyanelles was monitored by the silicone oil filtering technique. The solute spaces for 14C-labelled sorbitol and 3H 2O were the same indicating that sorbitol freely penetrated the plasma membrane of cyanelles in contrast to the situation found in chloroplasts. The measurements of the solute spaces for the different compounds showed that maltose and sucrose were not accumulated by isolated cyanelles. Other compounds like fructose, fucose, glutamine or glycine had intermediate sizes of their solute spaces. Cyanelles apparently possess a rapidly transporting glucose carrier and not a malate/oxaloacetate shuttle and also not an ATP/ADP translocator. The carrier composition at the plasma membrane of cyanelles and at the inner envelope membrane of chloroplasts seems to be totally different. 相似文献
13.
Aerobic and anaerobic chloroplastic respiration was monitored by measuring 14CO 2 evolution from [ 14C]glucose in the darkened spinach ( Spinacia oleracea) chloroplast and by estimating the conversion of fructose 1,6-bisphosphate to glycerate 3-phosphate in the darkened spinach chloroplast in air with O 2 or in N 2 with nitrite or oxaloacetate as electron acceptors. The pathway of 14CO 2 evolution from labeled glucose in the absence and presence of the inhibitors iodoacetamide and glycolate 2-phosphate under air or N 2 were those expected from the oxidative pentose phosphate cycle and glycolysis. Of the electron acceptors, O 2 was the best (2.4 nanomoles CO 2 per milligram chlorophyll per hour), followed by nitrite and oxaloacetate. With respect to glycerate 3-phosphate formation from fructose 1,6-bisphosphate, methylene blue increased the aerobic rate from 3.7 to 5.4 micromoles per milligram chlorophyll per hour. A rate of 4.8 micromoles per milligram chlorophyll per hour was observed under N 2 with nitrite and oxaloacetate. 相似文献
14.
Oxyleghemoglobin was used to supply low concentrations of O 2 to H 2-oxidizing bacteroids from Rhizobium japonicum USDA 122 DES. The H 2 oxidation system of these bacteroids was capable of effectively utilizing O 2 at the low concentrations of O 2 expected to be found in soybean nodules. Apparent Km values of approximately 10 nanomolar O 2 have been calculated for the oxyhydrogen reaction. These values include the Km values for both H 2 oxidation and endogenous substrate oxidation. Even in the presence of oxyleghemoglobin, H 2 additions stimulated C 2H 2 reduction, reduced the rate of endogenous respiration and maintained the ATP contents of bacteroids. In our reconstituted oxyleghemoglobin and bacteriod system, we estimate that the H 2 oxidation system is capable of recycling all of the H 2 evolved during the N 2 fixation process. 相似文献
15.
Rhizodeposition, i.e. the release of carbon into the soil by growing roots, is an important part of the terrestrial carbon
cycle. However the in situ nature and dynamics of root-derived carbon in the soil are still poorly understood. Here we made an investigation of the
latter in laboratory experiments using 13CO 2 pulse chase labelling of wheat ( Triticum aestivum L.). We analyzed the kinetics of 13C-labelled carbon and more specially 13C carbohydrates in the rhizosphere. Wheat seedlings-soil mesocosms were exposed to 13CO 2 for 5 hours in controlled chambers and sampled repeatedly during two weeks for 13C/C analysis of organic carbon. After a two-step separation of the soil from the roots, the amount of total organic 13C was determined by isotope ratio mass spectrometry as well as the amounts of 13C in arabinose, fructose, fucose, glucose, galactose, mannose, rhamnose and xylose. The amount and isotopic ratio of monosaccharides
were obtained by capillary gas chromatography coupled with isotope ratio mass spectrometry (GC/C/IRMS) after trimethyl-silyl
derivatization. Two fractions were analyzed : total (hydrolysable) and soluble monomeric (water extractable) soil sugars.
The amount of organic 13C found in the soil, expressed as a percentage of the total photosynthetically fixed 13C at the end of the labelling period, reached 16% in the day following labelling and stabilised at 9% after one week. We concluded
that glucose under the form of polymers was the dominant moietie of rhizodeposits. Soluble glucose and fructose were also
present. But after 2 days, these soluble sugars had disappeared. Forty percent of the root-derived carbon was in the form
of neutral sugars, and exhibited a time-increasing signature of microbial sugars. The composition of rhizospheric sugars rapidly
tended towards that of bulk soil organic matter. 相似文献
16.
Hydrolysis of plant biomass generates a mixture of simple sugars that is particularly rich in glucose and xylose. Fermentation of the released sugars emits CO 2 as byproduct due to metabolic inefficiencies. Therefore, the ability of a microbe to simultaneously convert biomass sugars and photosynthetically fix CO 2 into target products is very desirable. In this work, the cyanobacterium, Synechocystis 6803, was engineered to grow on xylose in addition to glucose. Both the xylA (xylose isomerase) and xylB (xylulokinase) genes from Escherichia coli were required to confer xylose utilization, but a xylose-specific transporter was not required. Introduction of xylAB into an ethylene-producing strain increased the rate of ethylene production in the presence of xylose. Additionally, introduction of xylAB into a glycogen-synthesis mutant enhanced production of keto acids. Isotopic tracer studies found that nearly half of the carbon in the excreted keto acids was derived from the engineered xylose metabolism, while the remainder was derived from CO 2 fixation. 相似文献
17.
Summary The ability of bacteroids, isolated from Lupinus luteus L. nodules at the stage of active nitrogen fixation, to assimilate (1- 14C)-glucose and (2- 14C)-glucose was being studied. The label is incorporated into all the Krebs cycle metabolites, amino acids and sugars after 5 min of glucose insertion into cell suspension. High activity of glucose phosphorylation was found in bacteroids in vitro, the reaction rate being the highest at a glucose concentration of over 100 m M.In lupine nodules sugars can be essential carbon substrate delivered to the bacteroids from host-plant cells. This point of view is discussed. 相似文献
18.
Photoassimilation of 14CO 2 by intact chloroplasts from the Crassulacean acid metabolism plant Sedum praealtum was investigated. The main water-soluble, photosynthetic products were dihydroxyacetone phosphate (DHAP), glycerate 3-phosphate (PGA), and a neutral saccharide fraction. Only a minor amount of glycolate was produced. A portion of neutral saccharide synthesis was shown to result from extrachloroplastic contamination, and the nature of this contamination was investigated with light and electron microscopy. The amount of photoassimilated carbon partitioned into starch increased at both very low and high concentrations of orthophosphate. High concentrations of exogenous PGA also stimulated starch synthesis. DHAP and PGA were the preferred forms of carbon exported to the medium, although indirect evidence suported hexose monophosphate export. The export of PGA and DHAP to the medium was stimulated by high exogenous orthophosphate, but depletion of chloroplastic reductive pentose phosphate intermediates did not occur. As a result only a relatively small inhibition in the rate of CO2 assimilation occurred. The rate of photoassimilation was stimulated by exogenous PGA, ribose 5-phosphate, fructose 1,6-bisphosphate, fructose 6-phosphate, and glucose 6-phosphate. Inhibition occurred with phosphoenolpyruvate and high concentrations of PGA and ribose 5-phosphate. PGA inhibition did not result from depletion of chloroplastic orthophosphate or from inhibition of ribulose 1,5-bisphosphate carboxylase. Exogenous PGA and phosphoenolpyruvate were shown to interact with the orthophosphate translocator. 相似文献
19.
After NTG treatment of the very effective wild type strain P121 of Rhizobium leguminosarum biovar phaseoli, mutants defective in the utilization of sugars or organic acids were obtained. All the mutants nodulated the cultivar Goldie
of Phaseolus vulgaris. The arabinose, fructose, glucose and pyruvate utilization mutants formed nodules similar in shape and size to the nodules
formed by the wild type strain. These mutants exhibited an acetylene reduction activity significantly lower than the activity
observed with the wild type strain. All the C 4-dicarboxylic acid utilization mutatns, formed ineffective nodules that did not show a significant acetylene reduction activity.
The C 4-dicarboxylic acids uptake system is apparently inducible in the free-living bacteria of strain P121. When P121 cells were
grown on glucose in the presence of 2.5 m M malate, the rate of glucose-dependent O 2 consumption significantly decreased suggesting the presence of a catabolite repression-like phenomenon. Isolated bacteroids
of strain P121, under the experimental conditions used, were able to oxidize succinate, fumarate or malate but did not oxidize
pyruvate, glucose, fructose or sucrose. 相似文献
20.
H 2-uptake positive strains (122 DES and SR) and H 2-uptake negative strains SR2 and SR3 of Rhizobium japonicum were examined for ribulosebisphosphate (RuBP) carboxylase and H 2-uptake activities during growth conditions which induced formation of the hydrogenase system. The rate of 14CO 2 uptake by hydrogenase-derepressed cells was about 6-times greater in the presence than in the absence of H 2. RuBP carboxylase activity was observed in free-living R. japonicum strains 122 DES or SR only when the cells were derepressed for their hydrogenase system. Hydrogenase and RuBP carboxylase activities were coordinately induced by H 2 and both were repressed by added succinate. Hydrogenase-negative mutant strains SR2 and SR3 derived from R. japonicum SR showed no detecyable RuBP carboxylase activities under hydrogenase derepression conditions. No detectable RuBP carboxylase was observed in bacteroids formed by H 2-uptake positive strains R. japonicum 122 DES or SR. Propionyl CoA carboxylase activity was consistently observed in extracts of cells from free-living cultures of R. japonicum but activity was not appreciably influenced by the addition of H 2. Neither phosphoenolpyruvate carboxylase nor phosphoenolpyruvate carboxykinase activity was detected in extracts of R. japonicum.Abbreviations RuBP
Ribulose 1,5-bisphosphate
- (Na 2EDTA)
(Ethylenedinitrilo)-tetraacetic acid, disodium salt
- (propionyl CoA)
Propionyl coenzyme A
- (PEP)
Phosphoenolpyruvate
- (GSH)
Reduced glutathione
- (Tricine)
N-tris(hydroxymethyl)-methylglycine 相似文献
|