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1.
Continuous removal of fruits from soybean plants (Glycine max [L.] Merr.) causes a redistribution of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco, EC 4.1.1.39) from the soluble to the insoluble phase of leaf extracts. The extent of this redistribution is genotype-dependent. We previously reported that insoluble Rubisco occurs in a high-molecular-mass complex together with a protein composed of 30-kDa subunits (S.J. Crafts-Brander et al., Planta, 183, 300–306). In the present study, the Rubisco Complex Protein (RCP), was isolated from the Rubisco-RCP complex by gel-filtration chromatography in 4 M urea. Under these conditions, RCP migrated with an apparent molecular mass of 120 kDa, indicating that the protein maintains a tetrameric structure even in 4 M urea. Once freed of urea, purified RCP was soluble, but formed insoluble complexes with Rubisco from soybean, tobacco and spinach when RCP and Rubisco were incubated in a ratio of 11 by weight. Purified Rubisco and RCP also associated into a high-molecular-mass complex when either component was in several-fold excess, but in this case the complex was soluble. Similarly, the amount of Rubisco sequestered as an insoluble Rubisco:RCP complex in leaf extracts of different soybean genotypes was related to the relative amounts of Rubisco and RCP present in the extracts. Thus, with both purified components and in leaf extracts, formation of an insoluble complex between Rubisco and RCP required a precise stoichiometry. Antibodies directed against purified RCP detected an accumulation of RCP in soybean leaves around the time of flowering. The RCP was also detected in petioles, stems, and pod walls of soybean, but not seeds. Fruit removal caused a marked increase in the amount of RCP in the leaves to levels as high as 15% of the total soluble protein. The accumulation of RCP in response to source:sink manipulations was similar to soybean vegetative storage proteins (VSPs). However, immunogold-localization showed that RCP was located in the cytosol of leaves, compartmentalized separate from both Rubisco and the VSPs. Thus, the physiological relevance of the specific association between RCP and Rubisco is obscure.Abbreviations Rubisco
ribulose-1,5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39)
- RCP
rubisco complex protein
- VSPs
vegetative storage proteins
Kentucky Agricultural Experiment Station Journal Article No. 93-3-162We wish to acknowledge L.F. Staples and J.C. Anderson for their expert technical assistance. Electron microscopy was performed by the Nano-Probe Laboratory, Lucille Parker Markey Cancer Center, University of Kentucky. We thank Dr. K.C. Vaughn, USDA-ARS, for providing guidance pertaining to immunogold-localization procedures. 相似文献
2.
Trypsin digestion reduces the sizes of both the large and small subunits of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco; EC 4.1.1.39) from the green alga Chlamydomonas reinhardtii. Incubation of either CO2/Mg2+ -activated or nonactivated enzyme with the transition-state analogue carboxyarabinitol bisphosphate protects a trypsin-sensitive site of the large subunit, but not of the small subunit. Incubation of the nonactivated enzyme with ribulosebisphosphate (RuBP) provided the same degree of protection. Thus, the very tight binding that is a characteristic of the transitionstate analogue is apparently not required for the protection of the trypsin-sensitive site of the large subunit. Mutant enzymes that have reduced CO2/O2 specificities failed to bind carboxyarabinitol bisphosphate tightly. However, their large-subunit trypsin-sensitive sites could still be protected. The K
m values for RuBP were not significantly changed for the mutant enzymes, but the V
max values for carboxylation were reduced substantially. These results indicate that the failure of the mutant enzymes to bind the transition-state analogue tightly is primarily the consequence of an impairment in the second irreversible binding step. Thus, in all of the mutant enzymes, defects appear to exist in stabilizing the transition state of the carboxylation step, which is precisely the step proposed to influence the CO2/O2 specificity of Rubisco.Abbreviations and Symbols CABP
2-carboxyarabinitol 1,5-bisphosphate
- enol-RuBP
2,3-enediolate of ribulose 1,5-bisphosphate
-
K
c
K
m for CO2
-
K
o
K
m for O2
- Rubisco
ribulose-1,5-bisphosphate carboxylase/oxygenase
- RuBP
ribulose 1,5-bisphosphate
-
V
c
V
max for carboxylation
-
V
o
V
max for oxygenation
Paper No. 9313, Journal Series, Nebraska Agricultural Research DivisionThis work was supported by National Science Foundation grant DMB-8703820. We thank Drs. Archie Portis and Raymond Chollet for their helpful comments, and also thank Dr. Chollet for graciously providing CABP and [14C]CABP. 相似文献
3.
Structural framework for catalysis and regulation in ribulose-1,5-bisphosphate carboxylase/oxygenase
Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is the enzyme assimilating CO2 in biology. Despite serious efforts, using many different methods, a detailed understanding of activity and regulation in Rubisco still eludes us. New results in X-ray crystallography may provide a structural framework on which to base experimental approaches for more detailed analyses of the function of Rubisco at the molecular level. This article gives a critical review of the field and summarizes recent results from structural studies of Rubisco. 相似文献
4.
5.
When photoheterotrophic Euglena gracilis Z Pringsheim was subjected to nitrogen (N)-deprivation, the abundant photosynthetic enzyme ribulose-1,5-bis-phosphate carboxylase/oxygenase (Rubisco; EC 4.1.1.39) was rapidly and selectively degraded. The breakdown began after a 4-h lag period and continued for a further 8 h at a steady rate. After 12 h of starvation, when the amount of Rubisco was reduced to 40%, the proteolysis of this enzyme slowed down while degradation of other proteins started at a similar pace. This resulted in a decline of culture growth, chloroplast disassembly — as witnessed by chlorophyll (Chl) loss — and cell bleaching. Experiments with spectinomycin, an inhibitor of chloroplastic translation, indicated that there was an absolute increase in the rate of Rubisco degradation in the N-deprived culture as compared with control conditions, where no significant carboxylase breakdown was detected. Oxidative aggregation of Rubisco (as detected by non-reductive electrophoresis) and association of the enzyme to membranes increased with time of N-starvation. Fluorescent labeling of oxidized cysteine (Cys) residues with monobromobimane indicated a progressive oxidation of Cys throughout the first hours of N-deprivation. It is concluded that Rubisco acts as an N store in Euglena, being first oxidized, and then degraded, during N-starvation. The mobilization of Rubisco allows sustained cell growth and division, at almost the same rate as the control (non-starved) culture, during 12 h of N-deprivation. Afterwards, breakdown is extended to other photosynthetic structures and the whole chloroplast is dismantled while cell growth is greatly reduced.Abbreviations Chl
chlorophyll
- Cys
cysteine
- Rubisco
ribulose-1,5-bisphosphate carboxylase/oxygenase
- RuBP
ribulose-1,5-bisphosphate
We thank Drs. Pablo Vera and Ismael Rodrigo (Univ. Politécnica, Valencia, Spain) for advice and facilities in raising and collecting the anti-Rubisco serum. This work was supported by grants PB87-0353 and PB92-0821 of DGICYT and by a fellowship of the Spanish Ministerio de Educación y Ciencia (awarded to C.G.-F.). 相似文献
6.
Spreitzer RJ 《Archives of biochemistry and biophysics》2003,414(2):141-149
Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) catalyzes the rate-limiting step of CO2 fixation in photosynthesis, but O2 competes with CO2 for substrate ribulose 1,5-bisphosphate, leading to the loss of fixed carbon. Interest in genetically engineering improvements in carboxylation catalytic efficiency and CO2/O2 specificity has focused on the chloroplast-encoded large subunit because it contains the active site. However, there is another type of subunit in the holoenzyme of plants, which, like the large subunit, is present in eight copies. The role of these nuclear-encoded small subunits in Rubisco structure and function is poorly understood. Small subunits may have originated during evolution to concentrate large-subunit active sites, but the extensive divergence of structures among prokaryotes, algae, and land plants seems to indicate that small subunits have more-specialized functions. Furthermore, plants and green algae contain families of differentially expressed small subunits, raising the possibility that these subunits may regulate the structure or function of Rubisco. Studies of interspecific hybrid enzymes have indicated that small subunits are required for maximal catalysis and, in several cases, contribute to CO2/O2 specificity. Although small-subunit genetic engineering remains difficult in land plants, directed mutagenesis of cyanobacterial and green-algal genes has identified specific structural regions that influence catalytic efficiency and CO2/O2 specificity. It is thus apparent that small subunits will need to be taken into account as strategies are developed for creating better Rubisco enzymes. 相似文献
7.
Effect of heat stress on the inhibition and recovery of the ribulose-1,5-bisphosphate carboxylase/oxygenase activation state 总被引:1,自引:0,他引:1
Experiments were conducted to determine the relative contributions of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco;
EC 4.1.1.39) activation state vis-à-vis Rubisco activase and metabolite levels to the inhibition of cotton (Gossypium hirsutum L.) photosynthesis by heat stress. Exposure of leaf tissue in the light to temperatures of 40 or 45 °C decreased the activation
state of Rubisco to levels that were 65 or 10%, respectively, of the 28 °C control. Ribulose-1,5-bisphosphate (RuBP) levels
increased in heat-stressed leaves, whereas the 3-phosphoglyceric acid pool was depleted. Heat stress did not affect Rubisco
per se, as full activity could be restored by incubation with CO2 and Mg2+. Inhibition and recovery of Rubisco activation state and carbon dioxide exchange rate (CER) were closely related under moderate
heat stress (up to 42.5 °C). Moderate heat stress had negligible effect on Fv/Fm, the maximal quantum yield of photosystem
II. In contrast, severe heat stress (45 °C) caused significant and irreversible damage to Rubisco activation, CER, and Fv/Fm.
The rate of Rubisco activation after alleviating moderate heat stress was comparable to that of controls, indicating rapid
reversibility of the process. However, moderate heat stress decreased both the rate and final extent of CER activation during
dark-to-light transition. Treatment of cotton leaves with methyl viologen or an oxygen-enriched atmosphere reduced the effect
of heat stress on Rubisco inactivation. Both treatments also reduced tissue RuBP levels, indicating that the amount of RuBP
present during heat stress may influence the degree of Rubisco inactivation. Under both photorespiratory and non-photorespiratory
conditions, the inhibition of the CER during heat stress could be completely reversed by increasing the internal partial pressure
of CO2 (Ci). However, the inhibition of the CER by nigericin, a K+ ionophore, was not reversible when the Ci was increased at ambient or high temperature. Our results indicate that inhibition
of photosynthesis by moderate heat stress is not caused by inhibition of the capacity for RuBP regeneration. We conclude that
heat stress inhibits Rubisco activation via a rapid and direct effect on Rubisco activase, possibly by perturbing Rubisco
activase subunit interactions with each other or with Rubisco.
Received: 25 February 2000 / Accepted: 13 May 2000 相似文献
8.
9.
The kinetic parameters of ribulose-1,5-bisphosphate (RuBP) carboxylase/oxygenase (EC 4.1.1.39) in wheat (Triticum aestivum L.) and rice (Oryza sativa L.) were determined by rapidly assaying the leaf extracts. The respective K
m and V
max values for carboxylase and oxygenase activities were significantly higher for wheat than for rice. In particular, the differences in the V
max values between the two species were greater. When the net activity of CO2 exchange was calculated at the physiological CO2-O2 concentration from these kinetic parameters, it was 22% greater in wheat than in rice. This difference in the in-vitro RuBP-carboxylase/oxygenase activity between the two species reflected a difference in the CO2-assimilation rate per unit of RuBP-carboxylase protein. However, there was no apparent difference in the CO2-assimilation rate for a given leaf-nitrogen content between the two species. When the RuBP-carboxylase/oxygenase activity was estimated at the intercellular CO2 pressure from the enzyme content and kinetic parameters, these estimated enzyme activities in wheat and rice were similar to each other for the same rate of CO2 assimilation. These results indicate that the difference in the kinetic parameters of RuBP carboxylase between the two species was offset by the differences in RuBP-carboxylase content and conductance for a given leaf-nitrogen content.Abbreviations DTT
dithiothreitol
- EDTA
ethylenediamine-tetraacetic
- PAR
photosynthetically active radiation
- RuBP
ribulose-1,5-bisphosphate 相似文献
10.
11.
Molecular evolution of the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) 总被引:6,自引:0,他引:6
J.M. Shively W. Devore L. Stratford L. Porter L. Medlin S.E. Stevens Jr. 《FEMS microbiology letters》1986,37(3):251-257
Abstract The evolutionary relationship of the RuBisCO large subunit gene(s) ( rbcL ) of several prokaryotes was examined using the technique of heterologous DNA hybridization. Restriction fragments of cloned rbcL from Anacystis nidulans 6301, Chlamydomonas reinhardtii, Rhodospirillum rubrum , and maize were nick-translated and used as probes. The C. reinhardtii and maize probes hybridized with restriction fragment(s) only from cyanobacteria: Agmenellum quadruplicatum, Fremyella diplosiphon , and Mastigocladus laminosus . In addition, the A. nidulans probe hybridized with restriction fragment(s) from Alcaligenes eutrophus, Chromatium vinosum, Nitrobacter hamburgensis, Paracoccus denitrificans, Pseudomonas oxalaticus, Rhodomicrobium vannielii, Rhodopseudomonas capsulata, Rhodopseudomonas palustris, Rhodopseudomonas sphaeroides, Thiobacillus intermedius, Thiobacillus neapolitanus , and Thiothrix nivea . The elucidated fragment of Rhodopseudomonas species is presumably for the Form I RuBisCO LSU of these organisms. The R. rubrum probe hybridized only to a restriction fragment(s) from R. capsulata, R. palustris, R. sphaeroides, T. neapolitanus , and T. nivea . The fragment(s) of Rhodopseudomonas species is the Form II rbcL of these organisms. The restriction fragments of T. neapolitanus and T. nivea were also different from those elucidated by the A. nidulans probe, suggesting the presence of a second (different) rbcL in these organisms. Positive hybridization was not obtained using any of the probes with DNA from Beggiatoa alba, Chlorobium vibrioforme or Chloroflexus aurantiacus . It appears that all rbcL have evolved from a common ancestor. Our data are consistent with and supportive of the evolutionary scheme for RuBisCO proposed by Akazawa, Takabe, and Kobayashi [1]. 相似文献
12.
The light-dependent modulation of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activity was studied in two species: Phaseolus vulgaris L., which has high levels of the inhibitor of Rubisco activity, carboxyarabinitol 1-phosphate (CA1P), in the dark, and Chenopodium album L., which has little CA1P. In both species, the ratio of initial to fully-activated Rubisco activity declined by 40–50% within 60 min of a reduction in light from high a photosynthetic photon flux density (PPFD; >700 mol · m–2 · s–1) to a low PPFD (65 ± 15 mol · m–2 · s–1) or to darkness, indicating that decarbamylation of Rubisco is substantially involved in the initial regulatory response of Rubisco to a reduction in PPFD, even in species with potentially extensive CA1P inhibition. Total Rubisco activity was unaffected by PPFD in C. album, and prolonged exposure (2–6 h) to low light or darkness was accompanied by a slow decline in the activity ratio of this species. This indicates that the carbamylation state of Rubisco from C. album gradually declines for hours after the large initial drop in the first 60 min following light reduction. In P. vulgaris, the total activity of Rubisco declined by 10–30% within 1 h after a reduction in PPFD to below 100 mol · m–2 · s–1, indicating CA1P-binding contributes significantly to the reduction of Rubisco capacity during this period, but to a lesser extent than decarbamylation. With continued exposure of P. vulgaris leaves to very low PPFDs (< 30 mol · m–2 · s–1), the total activity of Rubisco declined steadily so that after 6–6.5 h of exposure to very low light or darkness, it was only 10–20% of the high-light value. These results indicate that while decarbamylation is more prominent in the initial regulatory response of Rubisco to a reduction in PPFD in P. vulgaris, binding of CA1P increases over time and after a few hours dominates the regulation of Rubisco activity in darkness and at very low PPFDs.Abbreviations CA1P
2-carboxyarabinitol 1-phosphate
- CABP
2-carboxyarabinitol 1,5-bisphosphate
- kcat
substrate-saturated turnover rate of fully carbamylated enzyme
- PPFD
photosynthetically active photon flux density (400–700 nm)
- Rubisco
ribulose-1,5-bisphosphate carboxylase/oxygenase
- RuBP
ribulose-1,5-bisphosphate 相似文献
13.
The substrate specificity factor, V
cKo/VoKc, of spinach (Spinacia oleracea L.) ribulose 1,5-bisphosphate carboxylase/oxygenase was determined at ribulosebisphosphate concentrations between 0.63 and 200 M, at pH values between 7.4 and 8.9, and at temperatures in the range of 5° C to 40° C. The CO2/O2 specificity was the same at all ribulosebisphosphate concentrations and largely independent of pH. With increasing temperature, the specificity decreased from values of about 160 at 5° C to about 50 at 40° C. The primary effects of temperature were on K
c [Km(CO2)] and V
c [Vmax (CO2)], which increased by factors of about 10 and 20, respectively, over the temperature range examined. In contrast, K
o [Ki (O2)] was unchanged and V
o [Vmax (O2)] increased by a factor of 5 over these temperatures. The CO2 compensation concentrations () were calculated from specificity values obtained at temperatures between 5° C and 40° C, and were compared with literature values of . Quantitative agreement was found for the calculated and measured values. The observations reported here indicate that the temperature response of ribulose 1,5-bisphosphate carboxylase/oxygenase kinetic parameters accounts for two-thirds of the temperature dependence of the photorespiration/photosynthesis ratio in C3 plants, with the remaining one-third the consequence of differential temperature effects on the solubilities of CO2 and O2.Abbreviations RuBPC/O(ase)
ribulose 1,5-bisphosphate carboxylase/oxygenase
- RuBP
ribulose 1,5-bisphosphate
-
CO2 compensation concentration 相似文献
14.
The kinetics of ribulose-1,5-bisphosphate carboxylase/oxygenase in vivo inferred from measurements of photosynthesis in leaves of transgenic tobacco 总被引:20,自引:0,他引:20
Transgenic tobacco (Nicotiana tabacum L. cv. W38) with an antisense gene directed against the mRNA of the ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) small subunit was used to determine the kinetic properties of Rubisco in vivo. The leaves of these plants contained only 34% as much Rubisco as those of the wild type, but other photosynthetic components were not significantly affected. Consequently, the rate of CO2 assimilation by the antisense plants was limited by Rubisco activity over a wide range of CO2 partial pressures. Unlike in the wild-type leaves, where the rate of regeneration of ribulose bisphosphate limited CO2 assimilation at intercellular partial pressures above 400 ubar, photosynthesis in the leaves of the antisense plants responded hyperbolically to CO2, allowing the kinetic parameters of Rubisco in vivo to be inferred. We calculated a maximal catalytic turnover rate, kcat, of 3.5+0.2 mol CO2·(mol sites)–1·s–1 at 25° C in vivo. By comparison, we measured a value of 2.9 mol CO2·(mol sites)–1·–1 in vitro with leaf extracts. To estimate the Michaelis-Menten constants for CO2 and O2, the rate of CO2 assimilation was measured at 25° C at different intercellular partial pressures of CO2 and O2. These measurements were combined with carbon-isotope analysis (13C/12C) of CO2 in the air passing over the leaf to estimate the conductance for transfer of CO2 from the substomatal cavities to the sites of carboxylation (0.3 mol·m–2·s–1·bar–1) and thus the partial pressure of CO2 at the sites of carboxylation. The calculated Michaelis-Menten constants for CO2 and O2 were 259 ±57 bar (8.6±1.9M) and 179 mbar (226 M), respectively, and the effective Michaelis-Menten constant for CO2 in 200 mbar O2 was 549 bar (18.3 M). From measurements of the photocompensation point (* = 38.6 ubar) we estimated Rubisco's relative specificity for CO2, as opposed to O2 to be 97.5 in vivo. These values were dependent on the size of the estimated CO2-transfer conductance.Abbreviations and Symbols A
CO2-assimilation rate
- gw
conductance for CO2 transfer from the substomatal cavities to the sites of carboxylation
- Kc, Ko
Michaelis-Menten constants for carboxylation, oxygenation of Rubisco
- kcat
Vcmax/[active site]
- O
partial pressure of O2 at the site of carboxylation
- pc
partial pressure of CO2 at the site of carboxylation
- pi
intercellular CO2 partial pressure
- Rd
day respiration (non-photorespiratory CO2 evolution)
- Rubisco
ribulose 1,5-bisphosphate carboxylase/oxygenase
- RuBP
ribulose-1,5-bisphosphate
- Sc/o
relative specificity factor for Rubisco
- SSu
small subunit of Rubisco
- Vcmax, Vomax
maximum rates of Rubisco carboxylation, oxygenation
- *
partial pressure of CO2 in the chloroplast at which photorespiratory CO2 evolution equals the rate of carboxylation 相似文献
15.
In the unicellular green alga Chlorogonium elongatum, the synthesis of the plastid enzyme ribulose bisphosphate carboxylase/oxygenase (RuBPCase) and its mRNAs is under the control of light and acetate. Acetate is the sole metabolizable organic carbon source for this organism. Light greatly promotes the synthesis of RuBPCase and the increase in the concentration of the mRNAs of both subunits of the enzyme while acetate has a strong inhibitory effect on this process. There is a good agreement between RuBPCase synthesis and the amount of translateable RuBPCase mRNA present in cells which are cultured under different conditions (autotrophic, heterotrophic, mixotrophic). During the transition period after transfer of the cells from heterotrophic to autotrophic growth conditions the amounts of the large and small subunits of the enzyme increase well coordinated. In contrast to the protein subunits the two subunit-mRNAs accumulate with different kinetics.Abbreviations LSU
large subunit of RuBPCase
- poly(A)-
RNA
- poly(A)+RNA
non-, poly-adenylated RNA
- RuBPCase
ribulose-1,5-bisphosphate carboxylase/oxygenase EC 4.1.1.39
- SSU
small subunit of RuBPCase 相似文献
16.
H. V. Daday M. Lawrence R. I. Forrester M. I. Whitecross J. V. Possingham 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1987,73(6):856-862
Summary The response to selection for leaf proteins was studied during three selection cycles. Selection for high total nitrogen content showed 75% heritability, and the levels of both ribulose 1,5-bisphosphate carboxylase oxygenase (Rubisco) and cytoplasmic protein were strongly under nuclear DNA control. High and low protein content were correlated with chloroplast area. Although the amounts of nuclear DNA were similar, the ratio of Rubisco/DNA and chlorophyll/DNA changed during the selection process. It can be concluded that the levels of Rubisco achieved in mature plants of M. sativa are under nuclear DNA control. The possible involvement of small subunit (SSU) genes in controlling these levels is discussed. 相似文献
17.
The short-term, in-vivo response to elevated CO2 of ribulose-1,5-bisphosphate carboxylase (RuBPCase, EC 4.1.1.39) activity, and the pool sizes of ribulose 1,5-bisphosphate, 3-phosphoglyceric acid, triose phosphates, fructose 1,6-bisphosphate, glucose 6-phosphate and fructose 6-phosphate in bean were studied. Increasing CO2 from an ambient partial pressure of 360–1600 bar induced a substantial deactivation of RuBPCase at both saturating and subsaturating photon flux densities. Activation of RuBPCase declined for 30 min following the CO2 increase. However, the rate of photosynthesis re-equilibrated within 6 min of the switch to high CO2, indicating that RuBPCase activity did not limit photosynthesis at high CO2. Following a return to low CO2, RuBPCase activation increased to control levels within 10 min. The photosynthetic rate fell immediately after the return to low CO2, and then increased in parallel with the increase in RuBPCase activation to the initial rate observed prior to the CO2 increase. This indicated that RuBPCase activity limited photosynthesis while RuBPCase activation increased. Metabolite pools were temporarily affected during the first 10 min after either a CO2 increase or decrease. However, they returned to their original level as the change in the activation state of RuBPCase neared completion. This result indicates that one role for changes in the activation state of RuBPCase is to regulate the pool sizes of photosynthetic intermediates.Abbreviations and symbols
A
net CO2 assimilation rate
- Ca
ambient CO2 partial pressure
- Ci
intercellular CO2 partial pressure
- CABP
2-carboxyarabinitol 1,5-bisphosphate
- kcat
catalytic turnover rate per RuBPCase molecule
- PFD
photon flux density (400 to 700 nm on an area basis)
- PGA
3-phosphoglyceric acid
- Pi
orthophosphate
- RuBP
ribulose 1,5-bisphosphate
- RuBPCase
ribulose-1,5-bisphosphate carboxylase (EC 4.1.1.39) 相似文献
18.
The effect of divalent metal ions on the activity of Mg++ depleted ribulose-1,5-bisphosphate oxygenase 总被引:1,自引:0,他引:1
Ribulose-1,5-bisphosphate carboxylase-oxygenase is deactivated by removal of Mg++. The enzyme activities can be restored to a different extent by the addition of various divalent ions in the presence of CO2. Incubation with Mg++ and CO2 restores both enzyme activities, whereas, the treatment of the enzyme with the transition metal ions (Mn++, Co++, and Ni++) and CO2 fully reactivates the oxygenase: however, the carboxylase activity remains low. In experiments where CO2-free conditions were conscientiously maintained, no reactivation of RuBP oxygenase was observed, although Mn++ ions were present. Other divalent cations such as Ca++ and Zn++, restore neither the carboxylase nor the oxygenase reaction. Furthermore, the addition of Mn++ to the Mg++ and CO2 preactivated enzyme significantly inhibited carboxylase reactions, but increased the oxygenase reaction.Abbreviation RuBP
ribulose-1,5-bisphosphate. The enyme unit for RuBP carboxylase is defined as mol CO2 fixed·min-1 and for the RuBP oxygenase as mol O2 consumed · min-1 相似文献
19.
Benoit Ranty Dominique Roby Gérard Cavalié Marie-Thérèse Esquerré-Tugayé 《Planta》1987,170(3):386-391
Ribulose-1,5-bisphosphate carboxylase/oxygelase (RuBPCase) was studied in melon leaves infected by Colletotrichum lagenarium, a fungal pathogen of melons. Electrophoretic analysis of melon leaf proteins indicated a strong effect of infection on RuBPCase, the subunits of which gradually disappeared during the different stages of infection. Enzyme activity also declined 4 d after inoculation and its content, measured by immunoelectrophoresis, decreased to a similar extent. Synthesis of the large and small subunits of RuBPCase was followed by in-vivo pulse-labeling experiments. A drastic decrease in the rate of RuBPCase-subunit synthesis occurred 3 d after inoculation and preceded the appearance of disease symptoms. There was an apparent coordination of the synthesis of the two subunits under these conditions.Abbreviations LS (SS)
Large (small) subunit of RuBPCase
- RuBPCase
ribulose-1,5-bisphosphate carboxylase/oxygenase
- SDS-PAGE
sodium dodecyl sulfate-polyacrylamide gel electrophoresis
- TCA
trichloroacetic acid 相似文献
20.
The effect of low-, ambient- and high-temperature pretreatments (48 h at 4° C, 20° C or 36° C) of wheat seedlings (spring wheat Triticum aestivum L., cv. Kolibri) on the solubility properties of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCase; EC 4.1.1.39) was studied. The extractable protein moiety of heat-pretreated plants exhibited increased solubility in dilute buffer (50 mM k-phosphate, pH 6.8), compared with protein extracted from 4° C- or 20° C-plants. The salting-out characteristics for ammonium-sulfate precipitation confirmed this finding since a delayed precipitation of extractable protein from 36°C-plants was observed. Using polyacrylamide gel electrophoresis, the in-vivo temperature-induced differences in protein solubility could be traced back to a change in the solubility of RuBPCase. The RuBPCase was purified from wheat seedlings, and the purified enzyme also exhibited differential solubility. In order to evaluate this further, purified RuBPCase was subjected to probing for conformational properties. A decrease of fluorescence of the RuBPCase 1-anilino-8-naphtalene sulfonate complex revealed that the RuBPCase from 36° C-plants had a more hydrophilic protein surface. Titration of the sulfhydryl groups of native RuBP-Case with 5,5-dithiobis (2-nitrobenzoic acid) pointed to a reduced accessibility of the R-SH groups in the case of the 36° C-type of RuBPCase. The large subunit of RuBPCase from 4° C/20° C-plants tended to give rise to an artificial lower-molecular-weight polypeptide which could not be found in crude or purified RuBPCase from heat-pretreated wheat seedlings.Abbreviations ANS
1-anilino-8-naphtalene sulfonate
- DTNB
5,5-dithiobis(2-nitrobenzoic acid)
- PAGE
polyacrylamide gel electrophoresis
- RuBPCase
ribulose-1,5-bis-phosphate carboxylase/oxygenase
- RuBP
ribulose-1,5-bis-phosphate 相似文献