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1.
Many brown algae, including the kelp Laminaria digitata (Huds.) Lamour., exhibit enhanced photosynthesis when they are given a small amount of blue‐light in addition to a background of saturating red light. This blue light effect is correlated with an increased uptake of carbon. In the present study, we tested the hypothesis that blue light acts by increasing the activity of a plasma membrane H + ‐ATPase, thereby promoting an active carbon uptake across the plasma membrane. Photosynthetic carbon uptake was studied in pH‐drift experiments under illumination with red and blue light and using different inhibitors. Vanadate, an inhibitor of plasma membrane H + ‐ATPases, had a minor inhibitory effect on carbon uptake rates under saturating red light conditions, but inhibited the blue‐light enhancement by approximately 60%. An inhibitor of external carbonic anhydrase, acetazolamide, decreased the carbon uptake in both red light and in red plus blue light by 48% and 68%, respectively. These results suggest that photosynthetic carbon uptake depends on an external carbonic anhydrase under both red and red plus blue light conditions, and that blue light induces an increased activity of a P‐type H + ‐ATPase in the plasma membrane. The proton buffer Tris, which has a buffering capacity similar to vanadate in seawater, had no inhibitory effect on carbon uptake rates neither in red light nor in red plus blue light, showing that the inhibitory effect of vanadate is not caused by its effect as a buffer. The blue‐light enhancement was also abolished by a protein kinase inhibitor (H‐7), suggesting that the transduction of the blue‐light signal involves a protein kinase, which activates the plasma membrane H + ‐ATPase by phosphorylation. 相似文献
2.
Iodine uptake in Laminariales involves extracellular, haloperoxidase-mediated oxidation of iodide 总被引:6,自引:0,他引:6
F. C. Küpper N. Schweigert E. Ar Gall J.-M. Legendre H. Vilter B. Kloareg 《Planta》1998,207(2):163-171
Sporophytes of Laminaria digitata (L.) Lamour. were assayed for their content of accumulated iodine, which ranged from 0.4% of dry weight in adult plants up
to 4.7% for young plantlets. Sporophyte tissue from Laminaria saccharina (L.) Lamour. and L. digitata took up iodide according to Michaelis-Menten kinetics. Hydrogen peroxide and various substances known to interfere with oxidative
metabolism were shown to either inhibit or enhance the uptake of iodide, confirming that apoplastic oxidations play a key
role in iodide uptake in Laminaria. Consistently, iodide uptake was triggered in L. saccharina protoplasts by incubation in the presence of hydrogen peroxide. Similarly, the uptake of iodide was enhanced in L. digitata gametophytes by addition of haloperoxidase, suggesting that this enzyme catalyses the oxidation of iodide by hydrogen peroxide
and plays a key role in iodine uptake. Oxidative stress resulted in a marked efflux of the intracellular iodine. In both influx
and efflux experiments, a marked proportion (10–30%) of the tracer was not accounted for, indicating volatilisation of iodine.
The mechanism and possible functions of the accumulation of iodine by kelps are discussed.
Received: 11 February 1998 / Accepted: 18 June 1998 相似文献
3.
Several representatives of marine brown macroalgae (Phaeophyceae) including Fucus serratus L., Fucus spiralis L. and Fucus vesiculosus L. as well as Laminaria digitata (Huds.) Lamour., Laminaria hyperborea (Gunn.) Foslie and Laminaria saccharina (L.) Lamour. were investigated with particular regard to features of biosynthesis of the storage product mannitol. The respective catalytic system involved in the last step of mannitol formation, mannitol-1-phosphate dehydrogenase, appears to be a cytoplasmic enzyme as may be judged from the degree of correlation with the chloroplast key enzyme ribulose-1,5-bisphosphate carboxylase in different tissues of Laminaria digitata and Laminaria saccharina. Activity of mannitol-1-phosphate dehydrogenase in vitro is not affected by mannitol-l-phosphate or free mannitol, suggesting that mannitol biosynthesis in vivo) is mainly controlled by the environment and/or developmental stage. Certain inorganic ions such as NO3- (including K+) exert a strong influence on the activity of mannitol1-phosphate dehydrogenase thus suggesting that the intracellular pools of stored NO3- and mannitol are confined to spatially separated cellular compartments. 相似文献
4.
Active, Irreversible Accumulation of Extreme Levels of H(2)SO(4) in the Brown Alga, Desmarestia 总被引:1,自引:0,他引:1
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The brown algae Desmarestia ligulata var. ligulata (Lightf.) Lamour., and D. viridis (Mull.) Lamour., accumulate H2SO4 until their average internal pH is 0.5 to 0.8. A related species, D. aculeata (L.) Lamour., does not accumulate acid. The H2SO4 accumulation is accompanied by a reduction in the K+ and Cl− content, presumedly to maintain osmotic balance. Measurements of the membrane potential and H+ and SO42− concentrations indicate that both ions are accumulated in the vacuole against their electrochemical potential gradients.
The internal pH remains constant in all three species over the growing season, despite striking changes in the algal morphology. The pH is not affected by periods of darkness of up to 34 hours. Sulfate accumulated in the vacuoles appears to be trapped there since incubation of D. ligulata for up to 10 days in sulfate-free medium resulted in little loss of either vacuolar sulfate or H+. Although the uptake of H2SO4 into the vacuole must require energy, the maintenance of the vacuolar H2SO4 may be due to the impermeability of the tonoplast, with little necessity for continued expenditure of energy.
相似文献5.
Fucus serratus L., Fucus spiralis L., and Fucus vesiculosus L. (Fucales, Phaeophyceae) as well as Laminaria digitata (Huds.) Lamour., Laminaria hyperborea (Gunn.) Fosl., and Laminaria saccharina (L.) Lamour. (Laminariales, Phaeophyceae) have been investigated for the distribution of enzymic CO2 fixation capacities via phosphoenolpyruvate carboxykinase (EC 4.1.1.32) (PEP-CK) and via ribulose-1,5-bisphosphate carboxylase (EC 4.1.1.39) (RubP-C) in different regions of the thalli. The maximum of PEP-CK activity is found to be confined to the growing regions of the algae, while the activity of RubP-C achieves its highest values in the entirely differentiated parts of the fronds. These findings are confirmed by the results of photosynthetic and light-independent (dark) carbon assimilation as determined by in vivo 14CO2 fixation. The physiological significance of these differential patterns of carboxylation patterns is discussed with respect to the ontogenetic stage and the chemical constitution of the different thallus parts. 相似文献
6.
The taxonomy and evolutionary relationships of species in the genus Laminaria are poorly understood. Previous studies have demonstrated significant plasticity of morphological characters used to describe taxa, and interfertility has been reported among putative species. We analyzed nuclear ribosomal DNA (rDNA) sequence variation in eight species of Laminaria (L. agardhii Kjell., L. digitata (Huds.) Lamour., L. groenlandica Rosenv. [sensu Druehl 1968], L. longicruris De la Pyl., L. longipes Bory, L. saccharina (L.) Lamour., L. setchellii Silva, and L. yezoensis Miyabe) to elucidate evolutionary relationships in this genus. Restriction maps were constructed using a small subunit rDNA probe from Costaria costata (Turn.) Saunders, an rDNA repeat from the nematode Caenorhabditis elegans, and 11 hexameric restriction endonucleases in an annealing analysis of genomic DNA. Laminaria rDNA restriction maps were compared to each other and to that of the outgroup taxon, C. costata. rDNA restriction maps of Laminaria species and C. costata were similar. Restriction fragment length polymorphisms mapped to both the coding regions and the nontranscribed spacer of rDNA. Laminaria species were distinguished with this method. The restriction maps of L. agardhii, L. saccharina, and L. longicruris were identical, supporting a previous hypothesis that these species are conspecific. Comparison of restriction maps of Laminaria species suggested that the generic subdivision of Sections Simplices and Digitatae may be invalid. 相似文献
7.
Microsomal vesicles from 24-hour-old radish (Raphanus sativus L.) seedlings accumulate Ca2+ upon addition of MgATP. MgATP-dependent Ca2+ uptake co-migrates with the plasma membrane H+-ATPase on a sucrose gradient. Ca2+ uptake is insensitive to oligomycin, inhibited by vanadate (IC50 40 micromolar) and erythrosin B (IC50 0.2 micromolar) and displays a pH optimum between pH 6.6 and 6.9. MgATP-dependent Ca2+ uptake is insensitive to protonophores. These results indicate that Ca2+ transport in these microsomal vesicles is catalyzed by a Mg2+-dependent ATPase localized on the plasma membrane. Ca2+ strongly reduces ΔpH generation by the plasma membrane H+-ATPase and increases MgATP-dependent membrane potential difference (Δψ) generation. These effects of Ca2+ on ΔpH and Δψ generation are drastically reduced by micromolar erythrosin B, indicating that they are primarily a consequence of Ca2+ uptake into plasma membrane vesicles. The Ca2+-induced increase of Δψ is collapsed by permeant anions, which do not affect Ca2+-induced decrease of ΔpH generation by the plasma membrane H+-ATPase. The rate of decay of MgATP-dependent ΔpH, upon inhibition of the plasma membrane H+-ATPase, is accelerated by MgATP-dependent Ca2+ uptake, indicating that the decrease of ΔpH generation induced by Ca2+ reflects the efflux of H+ coupled to Ca2+ uptake into plasma membrane vesicles. It is therefore proposed that Ca2+ transport at the plasma membrane is mediated by a Mg2+-dependent ATPase which catalyzes a nH+/Ca2+ exchange. 相似文献
8.
Y. G. Voronova N. I. Rekhina T. A. Nikolaeva N. A. Tiunova I. V. Zaikina N. Ya. Kobzeva O. Valiente 《Journal of applied phycology》1991,3(3):243-245
A study was made of the use of laminaran extracted from algaeLaminaria saccharina andL. digitata with mineral acid solutions if the mixture was heated. The extract was neutralized to pH 4.0. The glucose solution obtained was used to culture fodder yeastsCandida scotti andHansenula anomalia. The yield of yeast biomass amounted to 87–83% of the medium utilized. The yeast biomass grown in the media withLaminaria extracts contained 43–50% protein. 相似文献
9.
Miriam Ruiz-Nieto José A. Fernández F. Xavier Niell Raquel Carmona 《Photosynthesis research》2014,121(2-3):277-284
Marine macroalgae possess a range of mechanisms to increase the availability of CO2 for fixation by ribulose-1,5-bisphosphate carboxylase/oxygenase. Of these, possession of a periplasmic or external carbonic anhydrase and the ability to use bicarbonate ions is widely distributed. The mechanisms of carbon acquisition were studied in two estuarine red macroalgae Bostrychia scorpioides and Catenella caespitosa using a range of techniques. pH-drift and CO2-depletion experiments at constant pH suggested that CO2 is the main source of inorganic carbon in both species. Inhibitors indicated that internal and external carbonic anhydrase were present in both species. Inhibitors also suggested that uptake of bicarbonate is unlikely to be present (P < 0.05). 相似文献
10.
Klaus Lüning 《Journal of phycology》1980,16(1):1-15
Gametophytes of three Laminaria species occurring near Helgoland, North Sea, were cultivated 4 wk in a 12:12 LD regime at different temperatures in artificial light fields, and in the sea at different water depths. In the artificial light fields underwater spectral distribution was simulated according to Jerlov water Types 5, 7, 9. Blue light in the simulated light fields amounted to 17, 12 or 4% of total quanta. The rate of vegetative growth did not depend on spectral distribution, was light-saturated at 4–6 W · m?2, and increased with temperature up to 15 C. L. saccharina (L.) Lamour. exhibited the highest tolerance towards temperature, light and UV. Gametophytes survived 1 wk at 21 C ± 0.1, but not 22 C ± 0.1. Gametophytes of L. hyperborea (Gunn.) Fosl. and L. digitata (Huds.) Lamour. survived 1 wk at 20 C ± 0.1, but not at 21 C ± 0.1. In sunlight, and in the light field of a xenon lamp, 50% of L. saccharina gametophytes were killed by a quantum dose of 50 μEin · cm?2, and 100% of the plants by 90 μEin · cm?2. Approximately half of these quantum doses killed the corresponding percent of the other species gametophytes. Appreciably higher quantum doses were survived in visible light, with red being the most detrimental. Fertility depended on a critical quantum dose of blue light which decreased almost exponentially with decreasing temperature. The quantum dose (400–512 nm) required for induction of fertilization of 50% of the female gametophytes (males react similarly) was 90 μEin · cm?2 at 5 C, 110 μEin · cm?2 at 10 C, 230 (560 in L. digitata)μEin · cm?2 at 15 C, and 560 (L. hyperborea) or about 850 (other 2 species) μEin · cm?2 at 18 C. In the sea the gametophytes survived the dark winter months in the unicellular stage, with almost no vegetative growth of the primary cell, due to lack of light. In early spring the female gametophytes matured in the unicellular, and the males in a few-celled stage at the depth of 2 m, as did the laboratory cultures under conditions inducing maximal fertility. 相似文献
11.
Ca2+ uptake by membrane fractions from barley (Hordeum vulgare L. cv CM72) roots was characterized. Uptake of 45Ca2+ was measured in membrane vesicles obtained from continuous and discontinuous sucrose gradients. A single, large peak of Ca2+ uptake coincided with the peak of proton transport by the tonoplast H+-ATPase. Depending on the concentration of Ca2+ in the assay, Ca2+ uptake was inhibited 50 to 75% by those combinations of ionophores and solutes that eliminated the pH gradient and membrane potential. However, 25 to 50% of the Ca2+ uptake in the tonoplast-enriched fraction was not sensitive to ionophores but was inhibited by vanadate. The results suggest that 45Ca uptake was driven by the low affinity, high capacity tonoplast Ca2+/nH+ antiporter and also by a high affinity, lower capacity Ca2+-ATPase. The Ca2+-ATPase may be associated with tonoplast, Golgi or contaminating vesicles of unknown origin. No Ca2+ transport was specifically associated with the distinct peak of endoplasmic reticulum that was identified by NADH cytochrome c reductase, choline phosphotransferase, and dolichol-P-man-nosyl synthase activities. A small shoulder of Ca2+ uptake in the plasma membrane region of the gradient was inhibited by vanadate and erythrosin B and may represent the activity of a separate plasma membrane Ca2+-ATPase. Vesicle volumes were estimated using electron spin resonance techniques, and intravesicular Ca2+ concentrations were estimated to be as high as 5 millimolar. ATP-driven uptake of Ca2+ created 800- to 2000-fold concentration gradients within minutes. Problems in interpreting the effects of Ca2+ on ATP-generated pH gradients are discussed and the suggestion is made that Ca2+ dissipates pH gradients by a different mechanism than is responsible for Ca2+ uptake into tonoplast vesicles. 相似文献
12.
Anthony Bertucci éric Tambutté Sylvie Tambutté Denis Allemand Didier Zoccola 《Proceedings. Biological sciences / The Royal Society》2010,277(1678):87-95
We report the molecular cloning of a H+-ATPase in the symbiotic dinoflagellate, Symbiodinium sp. previously suggested by pharmacological studies to be involved in carbon-concentrating mechanism used by zooxanthellae when they are in symbiosis with corals. This gene encodes a protein of 975 amino acids with a calculated mass of about 105 kDa. The structure of the protein shows a typical P-type H+-ATPase structure (type IIIa plasma membrane H+-ATPases) and phylogenetic analyses show that this new proton pump groups with diatoms in the Chromoalveolates group. This Symbiodinium H+-ATPase is specifically expressed when zooxanthellae are engaged in a symbiotic relationship with the coral partner but not in free-living dinoflagellates. This proton pump, therefore, could be involved in the acidification of the perisymbiotic space leading to bicarbonate dehydration by carbonic anhydrase activity in order to supply inorganic carbon for photosynthesis as suggested by earlier studies. To our knowledge, this work provides the first example of a symbiosis-dependent gene in zooxanthellae and confirms the importance of H+-ATPase in coral–dinoflagellate symbiosis. 相似文献
13.
Rob van Hille Marijke Fagan Lucinda Bromfield Robert Pott 《Journal of applied phycology》2014,26(1):377-385
Threat of global warming due to carbon dioxide (CO2) emissions has stimulated research into carbon sequestration and emissions reduction technologies. Alkaline scrubbing allows CO2 to be captured as bicarbonate, which can be photochemically fixed by microalgae. The carbon concentrating mechanism (CCM), of which external carbonic anhydrase is a key component, allows organisms to utilise this bicarbonate. In order to select a suitable strain for this application, a screening tool is required. The current method for determining carbonic anhydrase activity, the Wilbur and Anderson assay, was found to be unsuitable as a screening tool as the associated error was unacceptably large and tests on whole cells were inconclusive. This paper presents the development of a new, whole cell assay to measure inorganic carbon uptake and external carbonic anhydrase activity, based on classical pH drift experiments. Spirulina platensis was successfully used to develop a correlation between the specific carbon uptake (C) and the specific pH change (dpH). The relationship is described by the following: C[mmol C (g dry algae)?1?h?1]?=?0.064?×?(dpH). Inhibitor and salt dissociation tests validated the activity and presence of external carbonic anhydrase and allowed correlation between the Wilbur and Anderson assay and the new whole cell assay. Screening tests were conducted on S. platensis, Scenedesmus sp., Chlorella vulgaris and Dunaliella salina that were found to have carbon uptake rates of 5.76, 5.86, 3.86 and 2.15 mmol C (g dry algae)?1?h?1, respectively. These results corresponded to the species' known bicarbonate utilisation abilities and validated the use of the assay as a screening tool. 相似文献
14.
Evidence That an Internal Carbonic Anhydrase Is Present in 5% CO(2)-Grown and Air-Grown Chlamydomonas 总被引:5,自引:5,他引:0
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Inorganic carbon (Ci) uptake was measured in wild-type cells of Chlamydomonas reinhardtii, and in cia-3, a mutant strain of C. reinhardtii that cannot grow with air levels of CO2. Both air-grown cells, that have a CO2 concentrating system, and 5% CO2-grown cells that do not have this system, were used. When the external pH was 5.1 or 7.3, air-grown, wild-type cells accumulated inorganic carbon (Ci) and this accumulation was enhanced when the permeant carbonic anhydrase inhibitor, ethoxyzolamide, was added. When the external pH was 5.1, 5% CO2-grown cells also accumulated some Ci, although not as much as air-grown cells and this accumulation was stimulated by the addition of ethoxyzolamide. At the same time, ethoxyzolamide inhibited CO2 fixation by high CO2-grown, wild-type cells at both pH 5.1 and 7.3. These observations imply that 5% CO2-grown, wild-type cells, have a physiologically important internal carbonic anhydrase, although the major carbonic anhydrase located in the periplasmic space is only present in air-grown cells. Inorganic carbon uptake by cia-3 cells supported this conclusion. This mutant strain, which is thought to lack an internal carbonic anhydrase, was unaffected by ethoxyzolamide at pH 5.1. Other physiological characteristics of cia-3 resemble those of wild-type cells that have been treated with ethoxyzolamide. It is concluded that an internal carbonic anhydrase is under different regulatory control than the periplasmic carbonic anhydrase. 相似文献
15.
The carbon dioxide hydration activity of brush-border carbonic anhydrase from the dog kidney 总被引:2,自引:0,他引:2
The steady-state kinetic parameters for the hydration of CO2 catalyzed by membrane-bound carbonic anhydrase from the renal brush-border of the dog are compared with the same parameters for water-soluble bovine erythrocyte carbonic anhydrase. For the membrane-bound enzyme, the turnover number kcat is 6.5 × 105 s?1 and the Michaelis constant is 7.5 mm for CO2 hydration at pH 7.4 and 25 °C. The corresponding constants for bovine carbonic anhydrase under these conditions are 6.3 × 105 s?1 and 15 mm (Y. Pocker and D.W. Bjorkquist (1977)Biochemistry16, 5698–5707). The rate constant for the transfer of a proton between carbonic anhydrase and buffer was determined from the dependence of the catalytic rate on the concentration of the buffers imidazole and N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid (Hepes); the value of 2 × 108m?1s?1 describes this constant for both forms of carbonic anhydrase at pH 7.4. Furthermore, the pH dependence of the initial velocity of hydration of CO2 in the range of pH 6.5 to 8.0 is identical for the membrane-bound and soluble enzyme at low buffer concentration (1–2 mm imidazole). We conclude that the membrane plays no detectable role in affecting the CO2 hydration activity and that the active site of the renal, membrane-bound carbonic anhydrase is exposed to the aqueous phase. 相似文献
16.
R. V. Lun'kov I. M. Andreev N. A. Myasoedov G. F. Khailova E. B. Kurkova Yu. V. Balnokin 《Russian Journal of Plant Physiology》2005,52(5):635-644
A membrane fraction enriched in plasma membrane (PM) vesicles was isolated from the root cells of a salt-accumulating halophyte Suaeda altissima (L.) Pall. by means of centrifugation in discontinuous sucrose density gradient. The PM vesicles were capable of generating ΔpH at their membrane and the transmembrane electric potential difference (Δψ). These quantities were measured with optical probes, acridine orange and oxonol VI, sensitive to ΔpH and Δψ, respectively. The ATP-dependent generation of ΔpH was sensitive to vanadate, an inhibitor of P-type ATPases. The results contain evidence for the functioning of H+-ATPase in the PM of the root cells of S. altissima. The addition of Na+ and Li+ ions to the outer medium resulted in dissipation of ΔpH preformed by the H+-ATPase, which indicates the presence in PM of the functionally active Na+/H+ antiporter. The results are discussed with regard to involvement of the Na+/H+ antiporter and the PM H+-ATPase in loading Na+ ions into the xylem of S. altissima roots. 相似文献
17.
Hua Zhang Zhenhui Wang Lei Wang Ren Mu Zhi Zou Kun Yuan Yuekun Wang Haiping Wu Juquan Jiang Lifu Yang 《Extremophiles : life under extreme conditions》2014,18(1):89-98
In this study, metagenomic DNA was screened for the Na+/H+ antiporter gene from the halophilic bacteria in Daban Salt Lake by selection in Escherichia coli KNabc lacking three major Na+/H+ antiporters. One gene designated as Hb_nhaD encoding a novel NhaD-type Na+/H+ antiporter was finally cloned. The presence of Hb_NhaD conferred tolerance of E. coli KNabc to up to 0.5 M NaCl and 0.2 M LiCl, and an alkaline pH. Hb_NhaD has the highest identity (70.6 %) with a putative NhaD-type Na+/H+ antiporter from an uncharacterized Clostridiaceae species, and also has lower identity with known NhaD-type Na+/H+ antiporters from Halomonas elongata (20.8 %), Alkalimonas amylolytica (19.0 %), Vibrio parahaemolyticus (18.9 %) and Vibrio cholerae (18.7 %). pH-dependent Na+(Li+)/H+ antiport activity was detected from everted membrane vesicles prepared from E. coli KNabc carrying Hb_nhaD. Hb_NhaD exhibited very high Na+(Li+)/H+ antiport activity over a wide pH range from 6.5 to 9.0 with the highest activity at pH 7.0 which is significantly different from those of the above known NhaD-type Na+/H+ antiporters. Also, the apparent K m values of Hb_NhaD for Na+ and Li+ at pH 7.0 were determined to be 1.31 and 2.16, respectively. Based on the above results, we proposed that Hb_NhaD should be categorized as a novel NhaD-type Na+/H+ antiporter. 相似文献
18.
It has been proposed that many marine macroalgae are able to utilize HCO
3
–
for photosynthesis and growth, and that energy-dependent ion pumping is involved in this process. We have therefore studied the light-dependent alkalization of the surrounding medium by two species of marine macroscopic brown algae,Fucus serratus L. andLaminaria saccharina (L.) Lamour. with the aim of investigating the role of extracellular carbonic anhydrase (EC 4.2.1.1.) in the assimilation of inorganic carbon from the seawater medium. In particular, the influence of membrane-impermeable or slowly permeable carbonic-anhydrase inhibitors on the rate of alkalization of the seawater has been investigated. Inhibition of the alkalization rate occurred in both species at an alkaline pH (pH 8.0) but no inhibition was observed at an acidic pH (pH 6.0). The alkalization was found to be light-dependent and inhibited by 3-(3,4-dichlorophenyl)-1, 1-dimethylurea and, thus, correlated with photosynthesis. Alkalization by macroalgae has previously been shown to be proportional to inorganiccarbon uptake. We suggest that alkalization of the medium at alkaline pH in both of the species examined is mainly the consequence of an extracellular reaction. The reaction is catalyzed by extracellular carbonic anhydrase which converts HCO
3
–
to OH– and CO2; CO2 is then taken up through the plasmalemma. However, we do not exclude the involvement of other mechanisms of inorganic-carbon uptake.Abbreviations AZ
acetazolamide
- CA
carbonic anhydrase
- CAext
extracellular carbonic anhydrase
- Ci
inorganic carbon
- DBS
dextran-bound sulfonamide
- DCMU
3-(3,4-dichloro-phenyl)-1,1-dimethylurea
- PPFD
photosynthetic photon flux density
This study was carried out with financial support by SAREC (Swedish Agency for Research Cooperation with Developing Countries), Carl Trygger's Fund for Scientific Research (Sweden), SJFR (Swedish Council for Forestry and Agricultural Research) and CICYT (Spain). Z. Ramazanov is an invited professor of Ministerio de Educación y Ciencia, Spain. 相似文献
19.
A. Kotyk 《The Journal of membrane biology》1994,138(1):29-35
Acidification of the external medium of the yeast Saccharomyces cerevisiae, mainly caused by proton extrusion by plasma membrane H+-ATPase, was inhibited to different degrees by D2O, diethylstilbestrol, suloctidil, vanadate, erythrosin B, cupric sulfate and dicyclohexylcarbodiimide. The same pattern of inhibition was found with the uptake of amino acids, adenine, uracil, and phosphate and sulfate anions. An increase of the acidification rate by dioctanoylglycerol also increased the rates of uptake of adenine and of glutamic acid. In contrast, a decrease of the membrane potential at pH 4.5 from a mean of -40 to -20 mV caused by 20 mm KC1 had no effect on the transport rates. The ATPase-deficient mutant S. cerevisiae pmal-105 showed a markedly lower uptake of all the above solutes as compared with the wild type, while its membrane potential and pH were unchanged.Other types of acidification (spontaneous upon suspension; K+ stimulated) did not affect the secondary uptake systems. 相似文献
20.
Role of Photosynthetic Reactions in the Activity of Carbonic Anhydrase in Synechococcus sp. (UTEX 2380) in the Light : Inhibitor Studies Using the O-Exchange in C/O-Labeled Bicarbonate
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The role of the photosystems in the exchange of 18O between species of inorganic carbon and water was studied in suspensions of the cyanobacterium Synechococcus sp. (UTEX 2380) using membrane-inlet mass spectrometry. This 18O exchange is caused by the hydration-dehydration cycle of CO2 and is catalyzed by carbonic anhydrase. We observed the complex 18O exchange kinetics including dark-light-dark transients in suspensions of whole cells and found these to be identical to the 18O exchange kinetics of physiologically fully active spheroplast preparations. There was no enhancement effect of inorganic nitrogen on inorganic carbon accumulation. Membrane preparations exhibited no uptake of inorganic carbon and very little carbonic anhydrase activity, although these membranes were photosynthetically fully competent. DCMU, the inhibitor of photosystem II, eliminated almost entirely the 18O exchange activity of whole cells in the light. But this effect of DCMU could be reversed by addition of the electron donor couple 3,6-diaminodurene/ascorbate, suggesting the involvement of photosystem I in the events leading to 18O exchange. Iodoacetamide, an inhibitor of CO2 fixation, enhanced the 18O exchange in whole cell suspensions and inhibited neither the uptake of inorganic carbon nor the dehydration of bicarbonate in the light. The proton carrier carbonylcyanide m-chlorophenylhydrazone and the inhibitors diethylstilbestrol and N,N′ -dicyclohexyl carbodiimide affecting the membrane potential, totally abolished 18O exchange in the light. From 18 O-labeled inorganic carbon experiments we conclude that one of the roles of photosystem I is to provide the active uptake of inorganic carbon into the cells, where carbonic anhydrase catalyzes the interconversion between CO2 and HCO3− resulting in the 18O exchange from inorganic carbon to water. 相似文献