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1.
Rhizobium japonicum CJ1 was capable of growing using formate as the sole source of carbon and energy. During aerobic growth on formate a cytoplasmic NAD +-dependent formate dehydrogenase and ribulose bisphosphate carboxylase activity was demonstrated in cell-free extracts, but hydrogenase enzyme activity could not be detected. Under microaerobic growth conditions either formate or hydrogen metabolism could separately or together support ribulose bisphosphate carboxylase-dependent CO 2 fixation. A number of R. japonicum strains defective in hydrogen uptake activity were shown to metabolise formate and induce ribulose bisphosphate carboxylase activity. The induction and regulation of ribulose bisphosphate carboxylase is discussed.Abbreviations hup
hydrogen uptake
- MOPS
3-(N-morpholino)-propanesulphonate
- TSA
tryptone soya agar
- RuBP
ribulose 1,5-bisphosphate
- FDH
formate dehydrogenase 相似文献
2.
Wheat ( Triticum aestivum L. cv Albis) was grown in open-top chambers in the field and fumigated daily with charcoal-filtered air (0.015 microliters per liter O 3), nonfiltered air (0.03 microliters per liter O 3), and air enriched with either 0.07 or 0.10 microliters per liter ozone (seasonal 8 hour/day [9 am-5 pm] mean ozone concentration from June 1 until July 10, 1987). Photosynthetic 14CO 2 uptake was measured in situ. Net photosynthesis, dark respiration, and CO 2 compensation concentration at 2 and 21% O 2 were measured in the laboratory. Leaf segments were freeze-clamped in situ for the determination of the steady state levels of ribulose 1,5-bisphosphate, 3-phosphoglycerate, triose-phosphate, ATP, ADP, AMP, and activity of ribulose, 1,5-bisphosphate carboxylase/oxygenase. Photosynthesis of flag leaves was highest in filtered air and decreased in response to increasing mean ozone concentration. CO 2 compensation concentration and the ratio of dark respiration to net photosynthesis increased with ozone concentration. The decrease in photosynthesis was associated with a decrease in chlorophyll, soluble protein, ribulose bisphosphate carboxylase/oxygenase activity, ribulose bisphosphate, and adenylates. No decrease was found for triose-phosphate and 3-phosphoglycerate. The ratio of ATP to ADP and of triosephosphate to 3-phosphoglycerate were increased suggesting that photosynthesis was limited by pentose phosphate reductive cycle activity. No limitation occurred due to decreased access of CO 2 to photosynthetic cells since the decrease in stomatal conductance with increasing ozone concentration did not account for the decrease in photosynthesis. Ozonestressed leaves showed an increased degree of activation of ribulose bisphosphate carboxylase/oxygenase and a decreased ratio of ribulose bisphosphate to initial activity of ribulose bisphosphate carboxylase/oxygenase. Nevertheless, it is suggested that photosynthesis in ozone stressed leaves is limited by ribulose bisphosphate carboxylation possibly due to an effect of ozone on the catalysis by ribulose bisphosphate carboxylase/oxygenase. 相似文献
3.
Ribulose 1,5-bisphosphate in the chloroplast has been suggested to regulate the activity of the ribulose bisphosphate carboxylase/oxygenase. To generate high levels of ribulose bisphosphate, isolated and intact spinach chloroplasts were illuminated in the absence of CO 2. Under these conditions, chloroplasts generate internally up to 300 nanomoles ribulose 1,5-bisphosphate per milligram chlorophyll if O 2 is also absent. This is equivalent to 12 millimolar ribulose bisphosphate, while the enzyme, ribulose bisphosphate carboxylase, offers up to 3.0 millimolar binding sites for the bisphosphate in the chloroplast stroma. During illumination, the ribulose bisphosphate carboxylase is deactivated, due mostly to the absence of CO 2 required for activation. The rate of deactivation of the ribulose bisphosphate carboxylase was not affected by the chloroplast ribulose bisphosphate levels. Upon addition of CO 2, the carboxylase in the chloroplast was completely reactivated. Of interest, addition of 3-phosphoglycerate stopped deactivation of the carboxylase in the chloroplast while ribulose bisphosphate accumulated. With intact chloroplasts in light, no correlation between deactivation of the carboxylase and ribulose bisphosphate levels could be shown. 相似文献
4.
Leaf photosynthesis and ribulose bisphosphate carboxylase activation level were inhibited in several mutants of the C 3 crucifer Arabidopsis thaliana which possess lesions in the photorespiratory pathway. This inhibition occurred when leaves were illuminated under a photorespiratory atmosphere (50% O 2, 350 microliters per liter CO 2, balance N 2), but not in nonphotorespiratory conditions (2% O 2, 350 microliters per liter CO 2, balance N 2). Inhibition of carboxylase activation level was observed in strains with deficient glycine decarboxylase, serine transhydroxymethylase, serine-glyoxylate aminotransferase, glutamate synthase, and chloroplast dicarboxylate transport activities, but inhibition did not occur in a glycolate-P phosphatase-deficient strain. Also, the photorespiration inhibitor aminoacetonitrile produced a decline in leaf and protoplast ribulose bisphosphate carboxylase activation level, but was without effect on intact chloroplasts. Fructose bisphosphatase, a light-activated enzyme which is strongly dependent on stromal pH and Mg 2+ for regulation, was unaffected by conditions which caused inhibition of ribulose bisphosphate carboxylase. Thus, the mechanism of inhibition does not appear to involve changes in stromal Mg 2+ and pH but rather is associated with metabolite flux through the photorespiratory pathway. 相似文献
5.
Among the several strains of halobacteria grown heterotrophically, ribulose bisphosphate carboxylase activity was detected in those which accumulate poly (-hydroxybutyrate), viz. Haloferax mediterranei, Haloferax volcanii and Halobacterium marismortui. In H. mediterranei, the activity was present in cell extracts prepared after growth on a variety of carbohydrates. The ribulose bisphosphate carboxylase activity in H. mediterranei was inhibited by carboxyarabinitol bisphosphate, and the enzyme cross-reacted with antibodies raised against the spinach enzyme. CO 2 fixation by cell extract was stimulated by the addition of ATP and NADH. Preliminary data suggested that hydrogen could be a possible reductant.Abbreviations RuBP
ribulose bisphosphate
- Ru5P
ribulose 5-phosphate
- R5P
ribose 5-phosphate
- CABP
carboxyarabinitol bisphosphate
- PHB
poly (-hydroxybutyrate)
- DTT
dithiothreitol 相似文献
6.
Because glyoxylate inhibits CO 2 fixation by intact chloroplasts and purified ribulose bisphosphate carboxylase/oxygenase, glyoxylate might be expected to exert some regulatory effect on photosynthesis. However, ribulose bisphosphate carboxylase activity and activation in intact chloroplasts from Spinacia oleracea L. leaves were not substantially inhibited by 10 millimolar glyoxylate. In the light, the ribulose bisphosphate pool decreased to half when 10 millimolar glyoxylate was present, whereas this pool doubled in the control. When 10 millimolar glyoxylate or formate was present during photosynthesis, the fructose bisphosphate pool in the chloroplasts doubled. Thus, glyoxylate appeared to inhibit the regeneration of ribulose bisphosphate, but not its utilization. The fixation of CO2 by intact chloroplasts was inhibited by salts of several weak acids, and the inhibition was more severe at pH 6.0 than at pH 8.0. At pH 6.0, glyoxylate inhibited CO2 fixation by 50% at 50 micromolar, and glycolate caused 50% inhibition at 150 micromolar. This inhibition of CO2 fixation seems to be a general effect of salts of weak acids. Radioactive glyoxylate was reduced to glycolate by chloroplasts more rapidly in the light than in the dark. Glyoxylate reductase (NADP+) from intact chloroplast preparations had an apparent Km (glyoxylate) of 140 micromolar and a Vmax of 3 micromoles per minute per milligram chlorophyll. 相似文献
7.
Isolated wheat chloroplasts were pre-incubated in the dark inthe presence of various concentrations of inorganic phosphatewith or without carbon dioxide, oxaloacetate, glycerate, and3-phosphoglycerate. The effect of subsequent illumination onphotosynthetic oxygen evolution, ribulose bisphosphate carboxylaseactivity, ATP content, and ribulose bisphosphate content wasinvestigated. Inorganic phosphate had little effect on ribulosebisphosphate carboxylase activity in darkness or during theinitial phase of illumination, but it prevented the declinein activity that occurred during later stages of illumination,when photoreduction of CO 2 was decreasing in rate. Additionof inorganic phosphate to chloroplasts illuminated without phosphaterestored the ribulose bisphosphate carboxylase activity, increasedthe ATP, and decreased the ribulose bisphosphate in the organelles.The responses to CO 2, oxaloacetate, glycerate, and 3-phosphoglyceratesuggest that the decreased activity of ribulose bisphosphatecarboxylase during photosynthesis results from ATP consumption. Purified ribulose bisphosphate carboxylase was activated byinorganic phosphate, but this activation did not occur in thepresence of ATP. ATP inhibited ribulose bisphosphate carboxylasewhen it was present in combination with various photosyntheticmetabolites. Inactivation of ribulose bisphosphate carboxylase in chloroplasts,illuminated in the absence of inorganic phosphate, is not dueto lack of activation by inorganic phosphate or ATP. It mayresult from decreased stromal pH. Key words: Ribulose bisphosphate carboxylase, Chloroplasts, Wheat, Phosphate, ATP 相似文献
8.
The activities of carbon metabolism enzymes were determined in cellular extracts of the moderately thermophilic, chemolithotrophic,
acidophilic bacterium Sulfobacillus thermosulfidooxidans subsp. asporogenes, strain 41, grown either at an atmospheric content of CO 2 in the gas phase (autotrophically, heterotrophically, or mixotrophically) or autotrophically at a CO 2 content increased to 5–10%. Regardless of the growth conditions, all TCA cycle enzymes (except for 2-oxoglutarate dehydrogenase),
one glyoxylate bypass enzyme (malate synthase), and some carboxylases (ribulose bisphosphate carboxylase, pyruvate carboxylase,
and phosphoenolpyruvate carboxylase) were detected in the cell-free extracts of strain 411. During autotrophic cultivation
of strains 41 and 1269, the increase in the CO2 content of the supplied air to 5–10% resulted in the activation of growth
and iron oxidation, a 20–30% increase in the cellular content of protein, enhanced activity of the key TCA enzymes (citrate
synthase and aconitase), and, in strain 41, a decrease in the activity of carboxylases. 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.
Twenty species and strains of aerobic CO-oxidizing bacteria were screened for the occurrence of plasmids. Six of them harbored plasmids between 45 and 558kb. Megaplasmids of 428 and 558 kb were resolved in Alcaligenes carboxydus. Restriction digest patterns of plasmids from different carboxydotrophic bacteria were dissimilar. However, the patterns obtained with the plasmids from the strains OM5, OM4 and OM2 of Pseudomonas carboxydovorans were very much the same. The nine cured mutants of P. carboxydovorans OM5, as well as the deletion mutant OM5-29, could not grow chemolithotrophically with CO or H 2 plus CO 2, as they were devoid of CO dehydrogenase, hydrogenase and ribulose bisphosphate carboxylase. The deletion mutant OM5-24 retained the ability to grow with CO. It could not grow with H 2 plus CO 2 and was devoid of H 2ase. The data suggest the residence of structural and/or regulatory genes of CODH, H 2ase and RuBPCx on plasmid pHCG3 of P. carboxydovorans.Abbreviations CODH
carbon monoxide dehydrogenase
- CRM
cross reacting material
- EMS
ethyl methane sulfonate
- H 2ase
hydrogenase
- kb
kilobase
- NTG
N-methyl-N-nitro-N-nitrosoguanidine
- RuBPCx
ribulose bisphosphate carboxylase
- SDS
sodium dodecylsulfate 相似文献
11.
Suspensions of freshly lysed spinach chloroplasts, in which ribulose bisphosphate carboxylase displays an in vivo Km [CO], exhibited a ribulose bisphosphate-dependent uptake of oxygen. The kinetic properties of this oxygenase activity were examined at air levels of CO 2 (10 μm) and O 2 (240 μm). The pH optimum was 8.6–8.8 and the KM [ribulose bisphosphate] was 45 μm. At 240 μm O 2, the oxygenase activity is inhibited one-half by 25 μm CO 2. The apparent Km(O 2) is large, somewhere between 1 and 2 atm. The phosphoglycolate phosphatase activity of the chloroplasts was in great excess, suggesting that phosphoglycolate formed by the oxygenase would be quickly hydrolyzed to glycolate for possible metabolism by photorespiration.A comparison of the pH dependence of both the carboxylase and oxygenase activities at air levels of CO 2 and O 2 suggests that the pH of the chloroplast stroma could regulate their relative activities and that the oxygenase activity is sufficient to account for glycolate production during photosynthesis. It is predicted that at pH 7.8, about 40% of the carbon assimilated by the Calvin cycle would go through glycolate. 相似文献
12.
Seven day old wheat and maize seedlings were exposed to 1300 or 2000 microeinsteins per square meter per second photosynthetically active radiation in CO 2-free air for 3 hours with either 1% O 2 in N 2 or N 2-only and then returned to normal air of 340 microliters per liter CO 2, 21% O 2 in N 2. Activity of the ribulose bisphosphate carboxylase and amount of the substrate, ribulose 1,5-bisphosphate, were measured during and following the CO 2-free treatments as was photosynthetic CO 2 fixation. Photoinhibition of photosynthesis was observed only with wheat seedlings following the N 2 only treatment. During the CO 2-free treatments, the levels of RuBP rose during all experiments except when wheat was photoinhibited. The activity of the ribulose bisphophate carboxylase, measured directly upon grinding the leaves, declined during the CO 2-free conditions. The carboxylase total activity increased in minutes in the leaf during and following the CO 2-free treatments. The specific activities of the wheat carboxylase went from 0.16 to 1.06 micromoles CO 2 fixed per milligram protein per minute while the maize carboxylase varied from 0.05 to 0.36 micromole CO 2 fixed per millogram protein per minute. This suggests that in these seedlings considerable inactive carboxylase must be stored in a form not activatable in extracts by CO 2 and Mg 2+. Possible mechanisms of regulation of photosynthesis by the ribulose bisphosphate carboxylase must consider not only the amount of active enzyme, but the amount of enzyme which the plant can make activatable upon demand. 相似文献
13.
Chlorate-resistant Nicotiana plumbaginifolia (cv Viviani) mutants were found to be deficient in the nitrate reductase apoprotein (NR −nia). Because they could not grow with nitrate as sole nitrogen source, they were cultivated as graftings on wild-type Nicotiana tabacum plants. The grafts of mutant plants were chlorotic compared to the grafts of wild type. Mutant leaves did not accumulate nitrogen and nitrate but contained less malate and more glutamine than wild leaves. They exhibited a slight increase of the proportion of the light-harvesting chlorophyll a/ b protein complexes and a lowering of the efficiency of energy transfer between these complexes and the active centers. After a 3 second 14CO 2 pulse, the total 14C incorporation of the mutant leaves was approximately 20% of that of the control. The 14C was essentially recovered in ribulose bisphosphate in these plants. It was consistent with a decline of ribulose bisphosphate carboxylase activity observed in the mutant. After a 3 second 14CO 2 pulse followed by a 60 second chase with normal CO 2, 14C was mainly accumulated in starch which was labeled more in the mutant than in the wild type. These results confirm the observation that in the nitrate reductase deficient leaves, chloroplasts were loaded with large starch inclusions preceding disorganization of the photosynthetic apparatus. 相似文献
14.
Phosphorus-deficient spinach plants were grown by transferring them to nutrient solutions without PO 4. Photosynthetic rates were measured at a range of intercellular CO 2 partial pressures from 50–500 bar and then the leaves were freeze-clamped in situ to measure ribulose bisphosphate carboxylase (Rubisco) activity and metabolite concentrations. Compared with control leaves, deficient leaves had significantly lower photosynthetic rates, percentage activation of Rubisco, and amounts of ribulose bisphosphate and 3-phosphoglycerate at all CO 2 partial pressures. After feeding 10 mM PO 4 to the petioles of detached deficient leaves, all these measurements increased within 2 hours. At atmospheric CO 2 partial pressure the photosynthetic rate was stimulated in 19 mbar O 2 compared with 200 mbar. At higher CO 2 partial pressures this stimulation was less but the percentage stimulation in deficient leaves was no different from controls in either CO 2 partial pressure. It was concluded that phosphorus deficiency affects both Rubisco activity and the capacity for ribulose bisphosphate regeneration, and possible causes are discussed.Abbreviations A
CO 2 assimilation rate
- C i
intercellular CO 2 partial pressure
- PGA
3-phosphoglycerate
- RuP 2
ribulose 1,5-bisphosphate
- Rubisco
RuP 2 carboxylase/oxygenase 相似文献
15.
Photosynthetic carbon assimilation in plants is regulated by activity of the ribulose 1,5-bisphosphate (RuBP) carboxylase/oxygenase. Although the carboxylase requires CO 2 to activate the enzyme, changes in CO 2 between 100 and 1,400 microliters per liter did not cause changes in activation of the leaf carboxylase in light. With these CO 2 levels and 21% O 2 or 1% or less O 2, the levels of ribulose bisphosphate were high and not limiting for CO 2 fixation. With high leaf ribulose bisphosphate, the Kact(CO 2) of the carboxylase must be lower than in dark, where RuBP is quite low in leaves. When leaves were illuminated in the absence of CO 2 and O 2, activation of the carboxylase dropped to zero while RuBP levels approached the binding site concentration of the carboxylase, probably by forming the inactive enzyme-RuBP complex. The mechanism for changing activation of the RuBP carboxylase in the light involves not only Mg2+ and pH changes in the chloroplast stroma, but also the effects of binding RuBP to the enzyme. In light when RuBP is greater than the binding site concentration of the carboxylase, Mg2+ and pH most likely determine the ratio of inactive enzyme-RuBP to active enzyme-CO2-Mg2+-RuBP forms. Higher irradiances favor more optimal Mg2+ and pH, with greater activation of the carboxylase and increased photosynthesis. 相似文献
16.
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
17.
Leaves of Peperomia camptotricha contain three distinct upper tissue layers and a one-cell thick lower epidermis. Light and dark CO 2 fixation rates and the activity of ribulose bisphosphate carboxylase/oxygenase and several C 4 enzymes were determined in the three distinct tissue layers. The majority of the C 4 enzyme activity and dark CO 2 fixation was associated with the spongy mesophyll, including the lower epidermis; and the least activity was found in the median palisade mesophyll. In contrast, the majority of the C 3 activity, that is ribulose bisphosphate carboxylase/oxygenase and light CO 2 fixation, was located in the palisade mesophyll. In addition, the diurnal flux in titratable acidity was greatest in the spongy mesophyll and lowest in the palisade mesophyll. The spatial separation of the C 3 and C 4 phases of carbon fixation in P. camptotricha suggests that this Crassulacean acid metabolism plant may have low photorespiratory rates when it exhibits daytime gas exchange (that is, when it is well watered). The results also indicate that this plant may be on an evolutionary path between a true Crassulacean acid metabolism plant and a true C 4 plant. 相似文献
18.
When the amount of activation of ribulose 1,5-bisphosphate carboxylase has been measured, two forms of the enzyme, not one, are actually determined experimentally. Only the enzyme-activator CO 2-Mg 2+ form can bind ribulose bisphosphate for reaction with substrate CO 2 or O 2. A method is presented which measures only this catalytically active form by stabilizing it with ribulose bisphosphate just before dilution and assay in Mg 2+-free reaction medium. 相似文献
19.
Ribulose 1,5-biphosphate carboxylase has been purified to homogeneity from extracts of Cylindrotheca sp. (strain N-1), a marine, pennate diatom. The carboxylase has a molecular weight and structural composition similar to the enzyme from higher plants. When assayed in the presence of 1 mM NaHCO 3 the enzyme was stimulated nearly 40% by 1 mM aspartate and over 20% by 1 mM malate, and was inhibited to over 60% by 1 mM phosphoenolpyruvate. Similar experiments, using spinach carboxylase, failed to show activation by these metabolites. When assayed in the presence of 20 mM NaHCO 3, 6-phosphogluconate (1 mM) inhibited activity of ribulose bisphosphate carboxylase from Cylindrotheca by 60%, and higher concentrations of maiate (10 mM) inhibited activity by 25% Carbon isotope fractionation by ribulose bisphosphate carboxylase was -32.6% (ppt) when measured under N2 using homogeneous enzyme, whereas maximum carbon isotope fractionation by the whole alga grown in 1% -C02-in air averaged - 16.8%. Carbon isotope fractionation by the whole alga varied with the density of the culture and was maximum at a low cell density (1.7 ± 106 cellslml). At higher densities, the fractionation decreased by 4.0%. Carbon isotope fractionation has been used previously to determine the pathway of carbon metabolism in other organisms; the results of this investigation seem to indicate that this strain uses both the reductive pentose phosphate pathway and the C4 carbon pathway for primary CO2 fixation. 相似文献
20.
The ac-20 mutant strain of the unicellular green alga, Chlamydomonas reinhardii, lacks both chloroplast ribosomes and ribulose bisphosphate carboxylase activity when grown on organic medium. Under these conditions, the cells do not posses pools of either the large or small subunit of this enzyme. When transferred to inorganic medium, the carboxylase activity recovers. During this recovery, de novo synthesis of both subunits occurs. Synthesis of both subunits is inhibited by chloramphenicol even when possible free subunit pools rather than just the subunits incorporated into whole enzyme are examined.Abbreviations RubP
ribulose bisphosphate
- CAP
D-threochloramphenicol
- CHI
cycloheximide
- PPO
2,5-diphenyloxazole
- POPOP
1,4-bis[2(5-phenyloxazolyl)]-benzene
- SDS
sodium dodecyl sulfate 相似文献
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