共查询到20条相似文献,搜索用时 31 毫秒
1.
- Using the Chlorella cells which had been uniformly labeled with32P, the distribution of phosphorus in various fractions ofcell material was investigated. Uniformly 32P-labeled Chlorellawas further grown in a P-free medium or in a standard "cold"medium, and the change of distribution of 32P (as well as theuptake of exogenous P) in various cell fractions was followed.
- Analysis of the 32P-labeled algal cells showed that the highestin P-content was the fraction of RNA followed by those of polyphosphates,lipid, nucleotidic labile phosphate compounds, DNA and protein(in decreasing order). ATP and ADP were found to be only minorfractions of the total labile phosphates.
- On incubating the3P-labeled alga in a P-free medium, the P.contentsin the fractionsof DNA, protein, lipid and ATP increased, thosein polyphosphatesand ADP decreased, and that in RNA remainedalmost unchanged.When the 32P-labeled alga was further grownin the normal "cold"medium, DNA and protein increased withthe expenditure of endogenous32P, but with practically no incorporationof external P. Inthe meantime the P in polyphosphates decreasedconsiderably,and the RNA fraction incorporated a large amountof externalP but only a little of endogenous32P.
- It was inferred that,under the experimental conditions of thepresent study, thephosphorus used in the syntheses of DNA andprotein was primarilytaken from polyphosphates, while thatused in the synthesesof RNA, phospholipid and polyphosphateswas, for the most part,taken from the extracellular P-source.
2.
长角血蜱唾液腺中腺苷三磷酸双磷酸酶的纯化及其酶切机制 总被引:2,自引:0,他引:2
利用染料亲和层析(Cibacorn Blue柱)和离子交换层析(Macrosphere WCX柱)对长角血蜱Haemaphysalis longicornis唾液腺的腺苷三磷酸双磷酸酶进行纯化,经SDS-PAGE证实其分子量为66 kD。腺苷三磷酸双磷酸酶可以水解ATP和ADP,但对AMP无水解作用,水解ATP和ADP的Km值均为0.2 μmol/L,Vmax值分别为12.5和15.6 μmol/(min·mg)。腺苷三磷酸双磷酸酶水解ATP的中间产物是ADP,最终产物是AMP和正磷酸。表明腺苷三磷酸双磷酸酶水解ATP的位点是5'-核苷酸的γ-磷酸键,水解ADP的位点是5'-核苷酸的β-磷酸键。 相似文献
3.
Pools of ATP, ADP and AMP in algae were compared after extractionwith Trisbuffer, ethanol, chloroform, sulfuric acid, trichloroaceticacid and perchloric acid. Experimental organisms were Anacystisnidulans, Euglena gracilis, Chlorella kessleri and Scenedesmusobtusiusculus. Adenine nucleotides were determined by fireflyluciferase assay. Extraction of illuminated algae in situ with the different methodsresulted in great variations in the proportions between ATP,ADP and AMP. The sum of adenine nucleotides varied less. Extractionwith trichloroacetic acid or perchloric acid generally yieldedthe highest energy charge and ATP/ADP ratio. Experiments withilluminated Anacystis and Scenedesmus showed that extractionwith perchloric acid in situ gave higher yields of ATP in theextracts than if samples were withdrawn for extraction (timefor sample withdrawal {small tilde}1 sec). For Anacystis, itwas demonstrated that the extraction methods giving the highestproportions of ATP were suitable for studies on fluctuationsof the adenine nucleotide pools at transitions from dark tolight.
1 Permanent address: National Defence Research Institute, Department4, S-172 04 Sundbyberg, Sweden. (Received September 4, 1978; ) 相似文献
4.
Yazaki Yoshiaki; Asukagawa Norio; Ishikawa Yutaka; Ohta Eiji; Sakata Makoto 《Plant & cell physiology》1988,29(6):919-924
The cytoplasmic [MgATP]/[ATP]free ratios, free Mg2+ concentrations,and phosphorylation potentials in mung bean [Vigna mungo (L.)Hepper] root tip cells were investigated by 31P nuclear magneticresonance spectroscopy. 31P NMR spectra show well defined peaksdue to G6P, cytoplasmic Pi, vacuolar Pi, ATP, UDP-glucose andnicotinamide adenine nucleotides. The concentrations of phosphorusmetabolites were determined from quantitative 31P NMR spectra.The [MgATP]/[ATP]free ratio was 9.45. Accordingly, about 90%of the cytoplasmic ATP was complexed to Mg2+. Utilizing thedissociation constant (Kd) determined for MgATP, the cytoplasmicfree Mg2+ concentration was estimated to be 0.4mM. The NMR-derivedphosphorylation potential, [ATP]/([ADP][Pi]), was 960 M-1. Thesodium azide treatment decreased the [ATP]/[ADP] ratio and thephosphorylation potential, and increased the [Mg2+]free. Metabolicinhibition may have been enhanced by an increase in [Mg2+freeand a decrease in the free energy change for ATP hydrolysis,which resulted due to a decrease in the ATP level.
1Present address: National Food Research Institute, TsukubaCity, Ibaraki 305, Japan. (Received February 8, 1988; Accepted June 1, 1988) 相似文献
5.
- In the presence of NADP+ and Mg++, the bundle sheath strandsisolated from corn (Zea mays) leaves by cellulase treatmentsdecarboxylated malate in the light at an initial rate (200 µmoles/mgchl.hr), which was sufficient to account for photosyntheticCO2 fixation in intact leaves. This rate gradually slowed downand then stopped. The final level of the malate decarboxylatedwas approximately equal to the amount of NADP+ added.
- Rapidand continued decarboxylation of malate was observed whenNADP+,3-phosphoglyceric acid and ATP (and Mg++) were addedtogether.The addition of ADP instead of ATP showed a similareffect.Light did not show any effect on the malate decarboxylationin the presence of ATP or ADP.
- When malate was added to thebundle sheath strands in the presenceof exogenous NADP+ NADP+was rapidly reduced. The reductionstopped after 2 min when,73% of the added NADP+ was reduced.The further addition of3-phosphoglyceric acid and ATP broughtabout a decrease in theNADPH-level, which rose again to attaina new steady level.
- The transfer of radioactivity from (1-14C-3-phosphoglycericacid to dihydroxyacetone phosphate in the bundle sheath strandsin the presence of ATP and NADP+ was greatly enhanced by theaddition of malate.
- In the presence of ribose 5-phosphateand ATP, the rate of 14C-transferfrom (4-14C)-malate to theintermediates of the reductive pentosephosphate cycle was equalto that of 14CO2 fixation in the light.
6.
Nucleotide regulation of the voltage-dependent nonselective cation conductance in murine colonic myocytes 总被引:1,自引:0,他引:1
Monaghan KP Koh SD Ro S Yeom J Horowitz B Sanders KM 《American journal of physiology. Cell physiology》2006,291(5):C985-C994
ATP is proposed to be a major inhibitory neurotransmitter in the gastrointestinal (GI) tract, causing hyperpolarization and smooth muscle relaxation. ATP activates small-conductance Ca2+-activated K+ channels that are involved in setting the resting membrane potential and causing inhibitory junction potentials. No reports are available examining the effects of ATP on voltage-dependent inward currents in GI smooth muscle cells. We previously reported two types of voltage-dependent inward currents in murine proximal colonic myocytes: a low-threshold voltage-activated, nonselective cation current (IVNSCC) and a relatively high-threshold voltage-activated (L-type) Ca2+ current (IL). Here we have investigated the effects of ATP on these currents. External application of ATP (1 mM) did not affect IVNSCC or IL in dialyzed cells. ATP (1 mM) increased IVNSCC and decreased IL in the perforated whole-cell configuration. UTP and UDP (1 mM) were more potent than ATP on IVNSCC. ADP decreased IL but had no effect on IVNSCC. The order of effectiveness was UTP = UDP > ATP > ADP. These effects were not blocked by pyridoxal phosphate-6-azo(benzene-2,4-disulfonic acid) (PPADS), but the phospholipase C inhibitor U-73122 reversed the effects of ATP on IVNSCC. ATP stimulation of IVNSCC was also reversed by protein kinase C (PKC) inhibitors chelerythrine chloride or bisindolylmaleimide I. Phorbol 12,13-dibutyrate mimicked the effects of ATP. RT-PCR showed that P2Y4 is expressed by murine colonic myocytes, and this receptor is relatively insensitive to PPADS. Our data suggest that ATP activates IVNSCC and depresses IL via binding of P2Y4 receptors and stimulation of the phospholipase C/PKC pathway. inhibitory junction potentials; smooth muscle; enteric nervous system 相似文献
7.
Michailova A Lorentz W McCulloch A 《American journal of physiology. Cell physiology》2007,293(2):C542-C557
To investigate the mechanisms regulating excitation-metabolic coupling in rabbit epicardial, midmyocardial, and endocardial ventricular myocytes we extended the LabHEART model (Puglisi JL and Bers DM. Am J Physiol Cell Physiol 281: C2049–C2060, 2001). We incorporated equations for Ca2+ and Mg2+ buffering by ATP and ADP, equations for nucleotide regulation of ATP-sensitive K+ channel and L-type Ca2+ channel, Na+-K+-ATPase, and sarcolemmal and sarcoplasmic Ca2+-ATPases, and equations describing the basic pathways (creatine and adenylate kinase reactions) known to communicate the flux changes generated by intracellular ATPases. Under normal conditions and during 20 min of ischemia, the three regions were characterized by different INa, Ito, IKr, IKs, and IKp channel properties. The results indicate that the ATP-sensitive K+ channel is activated by the smallest reduction in ATP in epicardial cells and largest in endocardial cells when cytosolic ADP, AMP, PCr, Cr, Pi, total Mg2+, Na+, K+, Ca2+, and pH diastolic levels are normal. The model predicts that only KATP ionophore (Kir6.2 subunit) and not the regulatory subunit (SUR2A) might differ from endocardium to epicardium. The analysis suggests that during ischemia, the inhomogeneous accumulation of the metabolites in the tissue sublayers may alter in a very irregular manner the KATP channel opening through metabolic interactions with the endogenous PI cascade (PIP2, PIP) that in turn may cause differential action potential shortening among the ventricular myocyte subtypes. The model predictions are in qualitative agreement with experimental data measured under normal and ischemic conditions in rabbit ventricular myocytes. ATP-sensitive K+ channel; creatine and adenylate kinase reactions; phosphatidylinositol phosphates; heart; mathematical model 相似文献
8.
Cells of Nitella axilliformis were made tonoplast-free by intracellularperfusion of media containing ethyleneglycol-bis-(ß-aminoethylether)N,N'-tetraaceticacid (EGTA). When the perfusion medium contained ADP as wellas ATP, the membrane hyperpolarized in darkness in a mannersimilar to light-induced hyperpolarization. This light-independenthyperpolarization seems to be due to activation of the electrogenicion pump in the plasma membrane because the hyperpolarized valueof the membrane potential was more negative than the equilibriumpotential for K$, the most negative ion equilibrium potentialin Nitella. The hyperpolarization was inhibited by the respiratory chaininhibitors NaCN (1 mM), antimycin A (10 µM) and rotenone(10 µM). NaCN slightly decreased the ATP concentrationin the cell perfused with medium containing 1 mM ATP and 1 mMADP; but, even after treatment with NaCN, the cell had about80% of the ATP value for the control.
* This study is dedicated to the late Professor J. Ashida. (Received June 24, 1982; Accepted October 15, 1982) 相似文献
9.
Data from 31P-nuclear magnetic resonance spectroscopy of human forearm flexor muscle were analyzed based on a previously developed model of mitochondrial oxidative phosphorylation (PLoS Comp Bio 1: e36, 2005) to test the hypothesis that substrate level (concentrations of ADP and inorganic phosphate) represents the primary signal governing the rate of mitochondrial ATP synthesis and maintaining the cellular ATP hydrolysis potential in skeletal muscle. Model-based predictions of cytoplasmic concentrations of phosphate metabolites (ATP, ADP, and Pi) matched data obtained from 20 healthy volunteers and indicated that as work rate is varied from rest to submaximal exercise commensurate increases in the rate of mitochondrial ATP synthesis are effected by changes in concentrations of available ADP and Pi. Additional data from patients with a defect of complex I of the respiratory chain and a patient with a deficiency in the mitochondrial adenine nucleotide translocase were also predicted the by the model by making the appropriate adjustments to the activities of the affected proteins associates with the defects, providing both further validation of the biophysical model of the control of oxidative phosphorylation and insight into the impact of these diseases on the ability of the cell to maintain its energetic state. computational model; mitochondria; cellular energetics; oxidative phosphorylation; 31P-NMR spectroscopy 相似文献
10.
Spinach chloroplasts catalyzed ATP formation from acetyl phosphateand ADP when exposed to light. No ATP formation was detectablein the dark. In the absence of ADP, chloroplasts did not hydrolyzeacetyl phosphate in the light or dark. Neither high-energy phosphatessuch as creatine phosphate and phosphoenol pyruvate nor inhibitorsof photophosphorylation competitive with Pi, such as ß-naphthylmonophosphate, phenyl phosphate and pyridoxal 5-phosphate, couldsubstitute for acetyl phosphate as a Pi donor. The apparentKm values for acetyl phosphate and Pi were 0.81 mM and 0.25mM, respectively. The maximal rate of ATP formation with acetylphosphate and Pi were 331 and 521 µmol ATP formed mg chl1hr1, respectively. The optimum pH value for acetyl phosphate-dependentATP formation was about 8.0. NH4Cl, dicyclohexylcarbodiimideand triphenyltin chloride inhibited the acetyl phosphate-dependentATP formation. Acid-base transition also could induce subsequentATP formation from acetyl phosphate and ADP. These results suggestthat the acetyl phosphate-dependent ATP formation requires theformation and the utilization of a proton-motive force as ordinaryphotophosphorylation does.
1 This work was supported in part by Grants-in-Aid for ScientificResearch from the Ministry of Education, Science and Culture,Japan to H. S. Part of this work was reported at the 1981 AnnualMeeting of the Japanese Society of Plant Physiologists (Sapporo,May 8, 1981). (Received August 25, 1981; Accepted November 1, 1981) 相似文献
11.
The activity of plasma membrane H+-ATPase was measured withmembrane fragments of guard-cell protoplasts isolated from Viciafaba L. ATP hydrolytic activity was slightly inhibited by oligomycinand ammonium molybdate, and markedly inhibited by NO3and vanadate. In the presence of oligomycin, ammonium molybdateand NO3, the ATP-hydrolyzing activity was strongly inhibitedby vanadate. It was also inhibited by diethylstilbestrol (DES),p-chloromercuribenzoic acid (PCMB) and Ca2+, but slightly stimulatedby carbonyl cyanide m-chlorophenylhydrazone (CCCP). The acitivityhad higher specificity for ATP as a substrate than other phosphoricesters such as ADP, AMP, GTP and p-nitrophenylphosphate; theKm was 0.5 mM for ATP. The activity required Mg2+ but was notaffected by K+, and it was maximal around pH 6.8. When guard-cellprotoplasts were used instead of membrane fragments, the ATPaseactivity reached up to 800µmol Pi.(mg Chl)1.h1in the presence of lysolecithin. These results indicate thatthe guard cell has a high plasma membrane H+-ATPase activity. (Received December 23, 1986; Accepted April 28, 1987) 相似文献
12.
The light-induced H+ efflux observed at acidic pH in Cyanidiumcells was shown to be an active H+ transport depending on theintracellular ATP produced by cyclic photo-phosphorylation.Triton X-100 was found to act as an effective uncoupler in intactCyanidium cells without collapsing the pH gradient across theplasma membrane. Triton X-100 at 0.015% significantly reducedthe intracellular ATP levels, stimulated the p-BQ, Hill reactionand completely inhibited the light-induced H+ efflux. Inhibitionof the H+ efflux by Triton X-100 correlated well with the depressionof the apparent rale of light-induced ATP synthesis as wellas the decrease in the intracellular ATP level in light. The light-induced H+ efflux was completely inhibited by diethylstilbestrol,a specific inhibitor of plasma membrane ATPase, without anychanges in the intracellular ATP level, thereby suggesting theparticipation of the plasma membrane ATPase in the light-inducedH+ efflux.
1The data in this paper are included in the Ph. D. dissertationsubmitted by M. Kura-Hotta to Tokyo Metropolitan University. (Received February 3, 1984; Accepted June 14, 1984) 相似文献
13.
The luciferin-luciferase method was used to determine ATP extractedfrom darkmaintained and light-exposed samples of the green algaChlorella pyrenoidosa and of the blue-green alga Anacystis nidulans.A few measurements on Synechococcus lividus (a bluegreen thermophile,clone 65?C) are also reported.
- The light-minus-dark ATP levels (ATP) from aerobic cells ofChlorella and Anacystis were negative; however, ATP from Synechococcuswas positive. Large positive ATP was obtained in regularly grown(RG: moderate light) Chlorella treated with oligomycin; darklevels were reduced, light levels remained essentially unaffected.In high-light exposed (HLE) Chlorella, oligomycin reduced bothlight and dark ATP levels, but positive ATP was still obtained.However, in Anacystis, which has a different organization ofthylakoid membrane, oligomycin severely reduced both the lightand the dark ATP levels and the ATP remained negative.
- Theoligomycin (12 µM) treated Chlorella and the untreatedAnacystis and Synechococcus show the presence of cyclic photophosphorylationunder conditions in which the non-cyclic electron flow fromphotosystem II to photosystem I is blocked by 10 µM 3-(3,4-dichlorophenyl)-l,l-dimethylurea(DCMU), or not allowed to operate by the absence of CO2. Cyclicphotophosphorylation ranged from 1030% of the maximumATP in RG, to 4050% in HLE Chlorella. In RG Chlorella,cyclic and non-cyclic (in the absence of DCMU) photophosphorylation(ATP) saturate at about 103 ergs cm2 sec1 and104 ergs cm2 sec1 and 104 ergs cm2 sec1red (>640 nm) light, respectively; a lag was observed inthe light curve.
- In Chlorella, the addition of the photosystemI electron acceptormethyl viologen (MV; 1 mM) increased ATPby twofold. Furtheraddition of DCMU (25 µm) reduced thisto the level observedwith DCMU alone. If 1 mM reduced dichlorophenolindophenol orphenazine methosulphate (DCPIPH2 or PMSH2, respectively)wasadded along with DCMU, the ATP level was 3040% ofthecontrol. Further addition of MV increased the JATP to be7080%of that of the control. These and other resultsconfirm thepresence of both non-cyclic and cyclic photophosphorylationin vivo, the former predominating in Chlorella, and the latterin Anacystis and Synechococcus.
14.
Effect of an ADP analog on isometric force and ATPase activity of active muscle fibers 总被引:4,自引:0,他引:4
Karatzaferi C Myburgh KH Chinn MK Franks-Skiba K Cooke R 《American journal of physiology. Cell physiology》2003,284(4):C816-C825
The role played by ADP in modulatingcross-bridge function has been difficult to study, because it is hardto buffer ADP concentration in skinned muscle preparations. To solvethis, we used an analog of ADP, spin-labeled ADP (SL-ADP). SL-ADP bindstightly to myosin but is a very poor substrate for creatine kinase orpyruvate kinase. Thus ATP can be regenerated, allowing well-definedconcentrations of both ATP and SL-ADP. We measured isometric ATPaserate and isometric tension as a function of both [SL-ADP], 0.1-2mM, and [ATP], 0.05-0.5 mM, in skinned rabbit psoas muscle,simulating fresh or fatigued states. Saturating levels of SL-ADPincreased isometric tension (by P'), the absolute value of P' beingnearly constant, ~0.04 N/mm2, in variable ATP levels, pH7. Tension decreased (50-60%) at pH 6, but upon addition ofSL-ADP, P' was still ~0.04 N/mm2. The ATPase wasinhibited competitively by SL-ADP with an inhibition constant,Ki, of ~240 and 280 µM at pH 7 and 6, respectively. Isometric force and ATPase activity could both be fit bya simple model of cross-bridge kinetics. 相似文献
15.
Effects of adenine, adenosine, AMP, ADP and ATP on the inducedformation of bacteriochlorophyll and carotenoids in cell suspensionsof dark-aerobically grown Rhodopseudomonas spheroides were examinedunder dark-semiaerobic conditions where no significant cellgrowth occurred. Pigment formation was strongly inhibited by3 mM adenine, adenosine, AMP or ATP, but less strongly by ADP.Inhibition by either adenosine or ATP was completely reversible.Addition of 3 mM adenosine resulted in complete inhibition ofpigment formation, while inhibition by more than 10 min ATPdid not exceed 80%. No accumulation of any precursor-like pigmentsof either bacteriochlorophyll or carotenoids was observed incells incubated in the presence of adenine compounds. Amountsof exogenously-added adenine, adenosine, or AMP decreased significantlyduring incubation, whereas the amount of exogeneously-addedATP or ADP did not appreciably decrease. Addition of 3 mM ATPor adenosine also significantly suppressed 3H-leucine incorporationinto bacterial proteins. Nucleosides other than adenosine wereineffective in inhibiting the induced formation of photosyntheticpigments, indicating that the inhibitory action is specificto adenine compounds. It was assumed that both adenosine andATP inhibit chromatophore formation rather than a particularstep(s) in the biosynthetic pathways of the photosynthetic pigment,and that ATP exerts its effect from outside the cells, whereasadenosine does so after being taken up by the cells. (Received July 24, 1972; ) 相似文献
16.
Satoh Hiroyuki; Okada Mitsumasa; Nakayama Katsumi; Murata Teruyo 《Plant & cell physiology》1985,26(5):931-940
Ribulose 5-phosphate (Ru5P) kinase (ATP:D-ribulose 5-phosphate1-phosphotrans- ferase; EC 2.7.1.19
[EC]
), an enzyme in the reductivepentose phosphate cycle, was purified from the green alga Bryopsismaxima and its activity and peptide composition were studied.The specific activity of purified Ru5P kinase was 20 µmoleRuBP formed (mg protein)1 min1 corresponding toa 490-fold purification from the supernatant of chloroplasts.The Km values of Ru5P kinase for ATP and Ru5P were 69 µMand 330 µM, respectively. The molecular size of Ru5P kinase was estimated as 90 kDa bygel filtration and that of its polypeptide as 41 kDa by SDS-polyacrylamidegel electrophoresis. A small portion of the Ru5P kinase wasfound in a large molecular state (500 kDa) which was consideredto be an inactive form of the enzyme. Ru5P kinase activity has been reported in the pyrenoid of Eremosphaeraviridis as well as ribulose 1,5-bisphosphate carboxylase-oxygenase(RuBisCO) and ribose 5-phosphate isomerase activity (Holdsworth1971). In Bryopsis maxima, among the pyrenoid polypeptides otherthan that of RuBisCO, we found a polypeptide of 42 kDa, similarto that of Ru5P kinase in molecular size and ratio to RuBisCO.A peptide map of the 42 kDa pyrenoid polypeptide, however, showedthat it differed from that of Ru5P kinase. In conclusion, Ru5Pkinase may be not involved in the pyrenoid of this alga. (Received January 19, 1985; Accepted May 15, 1985) 相似文献
17.
Recovery of free ADP, Pi, and free energy of ATP hydrolysis in human skeletal muscle 总被引:1,自引:0,他引:1
Wackerhage Henning; Hoffmann Uwe; Essfeld Dieter; Leyk Dieter; Mueller Klaus; Zange Jochen 《Journal of applied physiology》1998,85(6):2140-2145
We measuredsignificant undershoots of the concentrations of free ADP([ADP]) and Pi([Pi]) and the freeenergy of ATP hydrolysis (GATP) belowinitial resting levels during recovery from severe ischemic exercisewith 31P-nuclear magneticresonance spectroscopy in 11 healthy sports students. Undershoots ofthe rate of oxidative phosphorylation would be predicted if the rate ofoxidative phosphorylation would depend solely on free[ADP],[Pi], orGATP. However,undershoots of the rate of oxidative phosphorylation have not beenreported in the literature. Furthermore, undershoots of the rate ofoxidative phosphorylation are unlikely because there is evidence that a balance between ATP production and consumption cannot be achieved if anundershoot of the rate of oxidative phosphorylation actually occurs.Therefore, oxidative phosphorylation seems to depend not only on free[ADP],[Pi], orGATP. Anexplanation is that acidosis-related or other factors control oxidativephosphorylation additionally, at least under some conditions. 相似文献
18.
Shikimate kinase from Phaseolus mungo seedlings was partiallypurified by DEAEcellulose, hydroxyapatite and Sephacryl S-200column chromatographies. The activity was completely inhibitedby EDTA and the requirement for Mg2+ could be partially replacedby Mn2+, Ca2+; Co2+ and Cd2+. Sulfhydryl inhibitor did not inhibitthe enzyme activity. The apparent Km values for shikimic acidand ATP at pH 8.6 were 0.25 mM and 0.38 mM, respectively. Theactivity appeared to be maximal at pH 8.69.0. Shikimate-3-phosphateand ADP inhibited the activity slightly. Aromatic amino acids,quinic acid and dehydroquinic acid had no significant effecton the activity. (Received January 11, 1979; ) 相似文献
19.
The application of a polysaccharide elicitor from yeast extract,YE, to Salvia miltiorrhiza hairy root cultures induced transientrelease of ATP from the roots to the medium, leading to a dose-dependentincrease in the extracellular ATP (eATP) level. The eATP levelrose to a peak (about 6.5 nM with 100 mg l–1 YE) at about10 h after YE treatment, but dropped to the control level 6h later. The elicitor-induced ATP release was dependent on membraneCa2+ influx, and abolished by the Ca2+ chelator EGTA or thechannel blocker La3+. The YE-induced H2O2 production was stronglyinhibited by reactive blue (RB), a specific inhibitor of membranepurinoceptors. On the other hand, the application of exogenousATP at 10–100 µM to the cultures also induced rapidand dose-dependent increases in H2O2 production and medium pH,both of which were effectively blocked by RB and EGTA. The non-hydrolyzableATP analog ATPS was as effective as ATP, but the hydrolyzedderivatives ADP or AMP were not so effective in inducing thepH and H2O2 increases. Our results suggest that ATP releaseis an early event and that eATP plays a signaling role in theelicitation of plant cell responses; Ca2+ is required for activationof the elicitor-induced ATP release and the eATP signal transduction.This is the first report on ATP release induced by a fungalelicitor and its involvement in the elicitor-induced responsesin plant cells. 相似文献
20.
The intracellular pH of an acidophilic unicellular alga, Cyanidiumcaldarium, was determined as a function of external pH by 31Pnuclear magnetic resonance. The algal cells incubated underaerobic conditions or under anaerobic and illuminated conditionsmaintained the intracellular pH in the range from 6.8 to 7.0even when the external pH was changed from 1.2 to 8.4. Underanaerobic and dark conditions, however, the intracellular pHacidified at the acidic pH region of the external medium. Theacidified intracellular pH reversibly returned to neutral eitheron aeration or illumination. The results indicate that, in Cyanidiumcells growing in extremely acidic environments, an active H+efflux (H+ pump) which depends on metabolic activity (respirationor photosynthesis) is essential to maintain the intracellularpH at a constant physiological level against the passive H+leakage due to the steep pH gradient across the cell membrane. (Received March 19, 1986; Accepted July 17, 1986) 相似文献