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1.
Saito Tamio; Kwak Sang-Soo; Kamiya Yuji; Yamane Hisakazu; Sakurai Akira; Murofushi Noboru; Takahashi Nobutaka 《Plant & cell physiology》1991,32(2):239-245
Deoxygibberellin C (DGC), a C/D ring-rearranged isomer of GA20,was shown to inhibit the conversion of [2,3-3H2]GA9 to [2-3H]GA4by gibberellin 3ß-hydroxylase from immature seedsof Phaseolus vulgahs. Deoxygibberellin C inhibited the promotionof growth by exogenously applied GA20 of rice (Oryza sativaL.) seedlings. Evidence is also presented that DGC is a competitiveinhibitor of the 3ß-hydroxylase from P. vulgaris.However, DGC only weakly inhibited the conversion catalyzedby the 3ß-hydroxylase from Cucurbita maxima at highconcentrations, and it did not inhibit the promotion of growthby exogenously applied GA9 of cucumber (Cucumis sativus) seedlings.These results suggest that the 3ß-hydroxylases fromP. vulgaris and C. maxima have different structural requirementswith respect to their substrates. 16-Deoxo-DGC also inhibitedcatalysis of the same conversion by 3ß-hydroxylasefrom P. vulgaris, and it slightly inhibited the conversion catalyzedby the enzyme from C. maxima. Application of 16-deoxo-DGC causedthe promotion of the growth of seedlings of both rice and cucumber.
3 Present address: Genetic Engineering Center, Korea Instituteof Science and Technology, Daejeon 305606, Korea
4 Present address: Department of Agricultural Chemistry, UtsunomiyaUniversity, Utsunomiya-shi, Tochigi, 321 Japan (Received September 25, 1990; Accepted December 17, 1990) 相似文献
2.
Naito Satoshi; Inaba-Higano Kumiko; Kumagai Tomoko; Kanno Tatsuo; Nambara Eiji; Fujiwara Toru; Chino Mitsuo; Komeda Yoshibumi; Fujiwara Toru; Chino Mitsuo; Komeda Yoshibumi 《Plant & cell physiology》1994,35(7):1057-1063
ß-Conglycinin, the 7S seed storage protein of soybean(Glycine max [L.] Merr.), is comprised mainly of three subunits,designated , ' and ß. Expression of the gene encodingthe ß subunit is unique because its expression hasbeen shown to be down-regulated by exogenously applied L-methioninein immature soybean cotyledon cultures in vitro. Arabidopsisthaliana strain carrying a mto1-1 mutation overaccumulates solublemethionine. By using this mutant, we analyzed the effects ofmethionine on expression of the ß subunit gene invivo. Reciprocal crosses were made between the mto1-1 mutantand a transgenic A. thaliana strain, designated SNTß3,which carries a ß-glucuronidase (GUS) reporter geneunder the control of the promoter region of the ßsubunit gene. Analysis of GUS activity in F1 seeds indicatedthat the GUS activity was dramatically repressed when the mto1-1mutant plants were used as female parents. We constructed astrain which carries both the transgene and mto1-1 mutationin the homozygous state. Analyses of the GUS activity in seedsof this double homozygous strain indicated that the GUS activitywas repressed to 2.5% of control by introduction of the mto1-1mutation. These results indicate that the ß subunitgene promoter activity in seeds is down-regulated by maternalgenotype and suggest that soluble methionine, or its mobilemetabolite, is translocated from mother plants to repress ßsubunit gene expression in seeds.
5Present address: Division of Biological Sciences, GraduateSchool of Science, Hokkaido University, Kita-ku, Sapporo, 060Japan
6Present address: Department of Biotechnology, Faculty of Agriculture,The University of Tokyo, Bunkyo-ku, Tokyo, 113 Japan 相似文献
3.
The major isoenzymes of -mannosidase (EC 3.2.1.24
[EC]
) and ß-galactosidase(ECf 3.2.1.23
[EC]
) have been separated from cotyledons of gardenpea, Pisum sativum L. (Vicieae), chick pea, Cicer arietinumL. (Cicereae), and cowpea, Vigna unguiculata (L.) Walp. (Phaseoleae).Some of their properties have been determined, including pHoptima, Km values for p-nitrophenyl glycosidc substrates, andthe effects of several inhibitors. Swainsonine, an indolizidinealkaloid, was the most effective inhibitor of mannosidase 1,with I30 values of 5.6 x 108 M (cowpea), 1x 107M (chick pea) and 2.9 x 197 M (pea). The most effectiveinhibitor of ß-galactosidase 2 from all sources wasD-galactonic acid-1,4-lactonwe (-lactone), with Ki values rangingbetween 3.0 and 3.9x 103 M. An inhibitor of the E. coliß-galactosidose, p-aminophenyl thio-ß-D-galactopyranoside,did not inhibit any of the legume ß-galctosidases;rather it enhanced the activites of the enzymes from chick peaand cowpea cotyledons. Etiolated hull and seed tissues frompea pods developing in darkness contained similar acid glycosidaseactivities to normal green tissues, thus the chloroplast isan unlikely location for ß-galactosidase 2. The majorß-galactosidasesdetected with an indigogenic substrate (5-bromo-4-chloro-3-indoxyl-ß-D-galactopyranoside)following gel electrophoresis of extracts from pea hull, seedcoats and cotyledons appeared to be different from ß-galactosidase2. Acid glycosidase, cotyledon, isoenzyme, -lactone, legume, swainsonine 相似文献
4.
Imaizumi Nobuyuki; Usuda Hideaki; Nakamoto Hitoshi; Ishihara Kuni 《Plant & cell physiology》1990,31(6):835-844
Photosynthesis is known to occur in rice panicles, but littlehas been reported about the photosynthetic or biochemical characteristicsof such panicles. The estimated gross amount of photo-syntheticallyassimilated CO2 in a panicle is 30% of that in a flag leaf.This result and the good light-intercepting characteristicsof the panicle in the canopy suggest that photosynthesis inthe panicle may contribute significantly to grain filling. Therice panicle is composed of spikelets and of rachis-branchesincluding rachis which have estimated gross rates of photosynthesisduring the 30-day period after anthesis of 130 to 180 and 50to 100 µmol CO2.(mg Chl)1.h1, respectively.The corresponding rate for the flag leaf is 180 to 230 µmolCO2.(mg Chl).h. On the basis of Chl, spikeletshave a high photosynthetic capability which is similar to thatof the flag leaf. The activities of ribulose-l,5-bisphosphate carboxylase (RuBPCase),phosphoenolpyruvate carboxylase (PEPCase), and pyruvate.Pi dikinase(PPDK) in spikelets were 129, 220, and 87 µmol.(mg Chl).h,respectively. The activities of PEPCase and PPDK in spikeletswere considerably higher than those in the flag leaf or rachis-branches.Oxygen-insensitive photosynthesis was found only in spikelets.The Km of NaHCO3 for photosynthesis by slices of spikelets inan aqueous solution (0.6 mM) was considerably lower than thatfor slices of flag leaf (4.2 mM). All these results indicatethat spikelets have different photosynthetic characteristicsfrom those of the flag leaf and rachis-branches. The possibilityof C3C4 intermediate photosynthesis or C4-like photosynthesisin spikelets is discussed.
4Present address: Department of Biochemistry, Faculty of Science,Saitama University, Urawa, 338 Japan (Received February 14, 1990; Accepted June 12, 1990) 相似文献
5.
Nitrate Effects on Pre-emergence Growth and Emergence Percentage of Wheat (Triticum aestivum L.) from Different Sowing Depths 总被引:1,自引:0,他引:1
The effects of a range of applied nitrate (NO3) concentrations(020 mol m3) on germination and emergence percentageof Triticum aestivum L. cv. Otane were examined at 30, 60, 90and 120 mm sowing depths. Germination percentage was not affectedby either sowing depth or applied NO3 concentration whereasemergence percentage decreased with increased sowing depth regardlessof applied NO3 concentration. Nitrate did not affectemergence percentage at 30 mm sowing depth, but at 60 to 120mm depth, emergence percentage decreased sharply with an increasedapplied NO3 concentration of 0 to 1·0 mol m3then decreased only slightly with further increases in appliedNO3 of about 5·0 mol m3. Root and shoot growth, NO3 accumulation and nitrate reductaseactivity (NRA) of plants supplied with 0, 1·0 and 1·0mol m3 NO3 at a sowing depth of 60 mm were measuredprior to emergence. The coleoptile of all seedlings opened withinthe substrate. Prior to emergence from the substrate, shootextension growth was unaffected by additional NO3 butshoot fr. wt. and dry wt. were both greater at 1·0 and1·0 mol m3 NO3 than with zero NO3.Root dry wt. was unaffected by NO3. Nitrate concentrationand NRA in root and shoot were always low without NO3.At 1·0 and 10 mol m3 NO3, NO3 accumulatedin the root and shoot to concentrations substantially greaterthan that applied and caused the induction of NRA. Regardlessof the applied NO3 concentration, seedlings which failedto emerge still had substantial seed reserves one month afterplanting. Coleoptile length was substantially less for seedlingswhich did not emerge than for seedlings which emerged, but wasnot affected by NO3. It is proposed that (a) decreasedemergence percentage with increased sowing depth was due tothe emergence of leaf I from the coleoptile within the substrateand (b) decreased emergence percentage with additional NO3was due to the increased expansion of leaf 1 within the substrateresulting in greater folding and damage of the leaf. Key words: Triticum aestivwn L., nitrate, sowing depth, seedling growth, seedling emergence 相似文献
6.
Ohta Yoshinori; Yoshioka Tatsuya; Mochimaru Mari; Hisabori Toru; Sakurai Hidehiro 《Plant & cell physiology》1993,34(4):523-529
Tentoxin strongly inhibited the ATPase activity of isolatedcoupling factor 1 (AF1) from the cyanobacterium Anacystis nidulans,with 50% inhibition occurring at 0.3 µM. When thylakoidsfrom A. nidulans were preincubated with 0.3 µM tentoxinfor 30 min, photophosphorylation was inhibited by 50%. Measurementsof fluorescence from 9-aminoacridine indicated that tentoxininhibited the utilization of the proton gradient by ATP formationin thylakoids. These results indicate that tentoxin is a strongenergy-transfer inhibitor of photophosphorylation in A. nidulans.Tentoxin decreased the level of ATP in intact cells both inthe light and in darkness, its effects being much stronger inthe dark. Tentoxin at 50 µM strongly inhibited the growthof the cells.
3Present address: Corporate Research and Development Laboratory,Tonen Co. 1-3-1 Nishi-tsurugaoka, Ohi-machi, Saitama, 354 Japan
4Present address: Technology and Engineering Laboratories, AjinomotoCo., Inc. Suzuki-cho 1, Kawasaki, 210 Japan 相似文献
7.
Photomixotrophic cell suspension culture was established fromthe leaf derived callus cells of Gisekia pharnaceoides L., aC4 dicotyledonous weed. The late log phase cells possessed shade-typecharacters such as low chlorophyll a/b ratio, less pronouncedO2 evolution and CO2 fixation, saturation of photosyntheticCO2 fixation at low intensity. The chloroplasts from these cellscontained granal stacking with high degree of a very few granawhich are characterized by their wide and high degree of stackings. The predominant labelling of 3-phosphoglyceric acid and sugarphosphates (40% of the total 14C incorporated) during 5 s exposureto 14CO2 in light and subsequent decrease in percentage of 14Cin these compounds with increase in exposure time indicatedthe operation of the C3 pathway in these cells. The simultaneoussynthesis of malate (23% of the total 14C incorporated) is relatedto the much pronounced glycolytic and tricarboxylic acid cycleactivities in these cells. The initial proliferation of callimainly from the zones of vascular supplies in the leaf, highstarch content of the cells, presence of large starch grainsin all the chloroplasts, activities of Calvin cycle enzymes,heavy labelling of C3 type intermediates and less labellingof aspartate as early photosynthates and rapid accumulationof radioactivity into starch during 14CO2 assimilation indicatedthat most of the cells in photomixotrophic culture were derivedfrom bundle sheath cells or the leaf cells of Gisekia changetheir function under culture conditions.
1Present address: Tropical Botanic Garden and Research Institute,Navaranga Road, Trivandrum 695 011, India. (Received January 29, 1982; Accepted June 4, 1983) 相似文献
8.
Kamiya Yuji; Kobayashi Masatomo; Fujioka Shozo; Yamane Hisakazu; Nakayama Ishizue; Sakurai Akira 《Plant & cell physiology》1991,32(8):1205-1210
Prohexadione calcium (BX-112) is a novel plant growth regulatorthat inhibits the late stages of the biosynthesis of gibberellinsin plants. Fourteen kinds of gjbberellin, helminthosporol and'helminthosporic acid were applied simultaneously with BX-112to rice seedlings (Oryza sativa L. ), and their growth-promotingactivities in terms of shoot elongation were examined. The growth-promotingactivities of GA1, GA4, GA18, GA22, GA23, GA38, helminthosporoland helminthosporic acid were not inhibited by BX-112, but thoseof GA5, GA9, GA15, GA19, GA20, GA31, GA44 and GA53 were inhibited.These results suggest that 3ß-hydroxylation is animportant and necessary step in the biosynthesis of gibberellinsthat promote shoot elongation in rice seedlings. The weak promotionof shoot elongation by GA22 in the presence of BX-112 suggeststhat the effect of a hydroxyl group at C-18 of GA22 might beable to mimic the effect of the 3ß-hydroxyl groupof GA1. Helminthosporol and helminthosporic acid may promotethe shoot elongation of rice by mimicking physiologically activegibberellins and not by stimulating their biosynthesis.
1Part I is the previous paper by Nakayama et al. (1990a)
3Present address: Frontier Research Program RIKEN, Wako-shi,Saitama, 351-01 Japan. (Received June 26, 1991; Accepted September 4, 1991) 相似文献
9.
Using permeabilized characean cells in which the ionic conditionsat the cytoplasmic side of the tonoplast are easily controlled,effects of Ca2+ ion on tonoplast potential were examined. Whenthe cell was treated with 1 µM Ca2+, the tonoplast potential(EM became positive in a complicated manner in Chara corallinawhile it simply became negative in Nitella axilliformis. Whenthe cell was treated with 9-antracenecarboxylic acid, a Cl-channelinhibitor, Em became more negative and the response of Em toCa2+ was significantly suppressed. It is suggested that Ca2+activates Cl-channel at a low concentration and inactivatesat a higher one in C. corallina while it simply inactivate Cl-channelin N. axilliformis.
1Present address: Biological Laboratory, The University of theAir, Wakaba 2-11, Wakaba, 260 Japan. (Received August 22, 1988; Accepted December 26, 1988) 相似文献
10.
Growth of Pseudomonas stutzeri(VAN NIEL strain) in the presenceof a limiting amount of nitrate under anaerobic conditions ischaracterized by 2 logarithmic phases separated distinctly byan intermediate phase where the growth rate is very low. Inthe first logarithmic phase nitrate is reduced stoichiometricallyto nitrite stage, and in the second phase nitrite is reducedto nitrogen gas. The nitrite reducing activity of cells in the second growthphase is 34 times higher than that of cells in the firstphase. The rise in nitrite reducing activity is correlated witha remarkable increase in the content of cytochromes a2 and c-552.
1Present address: Department of Biochemistry, Hiroshima UniversitySchool of Dentistry, Hiroshima, Japan.
2Present address: Institute of Molecular Biology, Faculty ofScience, Nagoya University, Nagoya, Japan. (Received June 16, 1969; ) 相似文献
11.
Wilson Richard H.; Dever John; Harper Walter; Fry Robert 《Plant & cell physiology》1972,13(6):1103-1111
The effects of valinomycin on the respiration and volume changeshave been studied with isolated mitochondria from bean hypocotyl(Phaseolus vulgaris L.) and cauliflower bud (Brassica oleraceaL.). In the presence of 10 mM K salts of chloride, acetate,phosphate, and sulfate respiration is stimulated by valinomycinconcomitant with osmotic swelling. When swelling declines respirationwith organic acid substrates also declines. In the presenceof the K salts of acetate and PO4 but not Cl the terminationof respiration leads to contraction. The contraction in K-PO4is inhibited by addition to the external medium of between 65to 100 mM K-PO4. The results are interpreted to suggest thatvalinomycin in the presence of KCl facilitated the movementof K down an electrical gradient, with the Cl anion followingand osmotic swelling resulting. However, in a medium containingacetate or PO4 the anions are actively transported against anelectrical gradient at the expense of metabolic energy. Valinomycinfacilitates the influx of K+ with the actively transported anionand swelling follows. When respiration terminates the activelytransported anions move passively back down their electrochemicalgradient and osmotic contraction follows.
1 Present address: Department of Biology, Fort Lewis College,Durango, Colorado 81301, U.S.A. (Received July 21, 1972; ) 相似文献
12.
Kikuyama Munehiro; Hayama Tomio; Fujii Sumiko; Tazawa Masashi 《Plant & cell physiology》1979,20(6):993-1002
The effect of the intracellular concentration of ATP ([ATP]1)on the light-induced potential change (LPC) in tonoplast-freeChara cells was studied. The LPC was hardly affected by loweringthe [ATP]1 by about 1/10 or by raising it to about 10 timesthe normal cytoplasmic concentration (0.51.3 mM). Theinsensitivity of LPC to [ATP]1 excludes the possibility thatan increase in [ATP]1 due to photosynthesis may induce the LPC.However, extreme lowering of the [ATP]1 to about 12 µMcompletely inhibited LPC, although photosynthetic O2 evolutionwas not significantly inhibited. This fact supports the hypothesisthat light stimulates the putative H+pump fueled by ATP. Theuncoupling agents DNP and CCCP greatly depolarized the membrane,and inhibited LPC strongly, but they did not decrease [ATP]1.Photosynthetic O2 evolution was inhibited to some extent by2 µM CCCP and strongly inhibited by 0.1 mM DNP. Sincethe membrane resistance increased significantly, these chemicalsare believed to act on the membrane as an inhibitor of the electrogenicH+ pump not as an H+conductor. Introduction of 1 mM ATP intocells treated with uncouplers, to a large extent restored theirability to produce LPC although the membrane potential in darknesswas maintained at a low level.
1Present address: Niigata College of Pharmacy, 5829 Kamishinei-cho,Niigata 950-21, Japan.
2Present address: Department of Agricultural Chemistry, Collegeof Agriculture, Kyoto University, Kyoto 606, Japan.
3Present address: Department of Botany, Faculty of Science,University of Tokyo, Hongo, Tokyo 113, Japan. (Received March 9, 1979; ) 相似文献
13.
Gotow Kiyoshi; Shimazaki Ken-ichiro; Kondo Noriaki; Syono Kunihiko 《Plant & cell physiology》1984,25(4):671-675
A rapid and convenient procedure was developed for isolatingguard cell protoplasts (GCPs) from epidermal strips of Viciafaba L. The mean rates of O2 uptake in the dark and evolutionin light of the isolated GCPs were 200 and 290 µmol O2mg1 Chl h1, respectively, showing net O2 evolutionin light. Photosynthetic O2 evolution was suppressed completelyby 5 µM DCMU. Addition of 5 µM DCMU to the incubationmedium after 30 min of light exposure also suppressed the light-inducedswelling of GCP, indicating possible participation of PS IIin volume regulation in GCP.
4Present address: Division of Environmental Biology, The NationalInstitute for Environmental Studies, Yatabe machi, Tsukuba,Ibaraki 305, Japan. (Received December 17, 1983; Accepted March 21, 1984) 相似文献
14.
Treatment of suspension-cultured cells of red bean, Vigna angularis,with nigeran resulted in an accumulation of isoflavone glucosides,such as daidzein 7-O-ß-D-glucoside, daidzein 7,4'-di-O-ß-D-glucoside,and 2'-hydroxydaidzein 7,4'-di-O-ß-D-glucoside, whichwas accompanied by a transient increase in the activity of phenylalanineanimonia-lyase (PAL). Similar effects were also seen with otherphytoalexin elicitors, such as RNase A and cell wall componentsof Phytophthora megasperma var. sojae. Interestingly, the accumulation of isoflavone glucosides andthe transient increase in PAL activity were induced also byvanadate, a specific inhibitor of plasma membrane adenosinetriphosphatase. K3PO4 showed similar effects, but this was ascribedto the elevation of medium pH caused by adding this basic salt.In fact, merely raising the pH of the medium was found to besufficient for the induction of PAL activity. Experiments usinginhibitors showed that the induction depends on RNA and proteinsyntheses. The results are discussed in relation to the possiblemechanism of action of phytoalexin elicitors.
1 Present address: Laboratory of Biochemistry, Faculty of Agriculture,Nagoya University, Furocho, Chikusa, Nagoya 464, Japan. 相似文献
15.
Imamura Machiko; Tsuzuki Mikio; Shiraiwa Yoshihiro; Miyachi Shigetoh 《Plant & cell physiology》1983,24(3):533-540
The effect of carbonic anhydrase (CA) on time courses of photosynthetic14C incorporation in the presence of 14CO2 or NaH14CO3 was studiedwith cells of Chlamydomonas reinhardtii which had been grownunder ordinary air (low-CO2 cells) or air enriched with 4% CO2(high-CO2 cells). Experimental data obtained at 20°C andpH 8.0 suggested that the major form of inorganic carbon utilizedby high-CO2 cells was CO2, while that utilized by low-CO2 cellswas HCO3. The cell suspension showed CA activity which was comparableto that observed in the sonicate of cells. Both activities werehigher in low-CO2 cells than in high-CO2 cells. The mechanism by which HCO3 is utilized by low-CO2 cellsof C. reinhardtii is discussed.
3Present address: Department of Biology, Faculty of Science,University of Niigata, Niigata 950-21, Japan. (Received August 4, 1982; Accepted January 19, 1983) 相似文献
16.
To study the wavelength-effect on photosynthetic carbon metabolism,14C-bicarbon-ate was added to Chlorella vulgaris 1 lh suspensionunder monochromatic blue (456 nm) and red (660 nm) light. Thelight intensities were so adjusted that the rates of 14CO2 fixationunder blue and red light were practically equal. Analysis of14C-fixation products revealed that the rates of 14CO2 incorporationinto sucrose and starch were greater under red light than underblue light, while blue light specifically enhanced 14CO2 incorporationinto alanine, aspartate, glutamate, glutamine, malate, citrate,lipid fraction and alcohol-water insoluble non-carbohydratefraction. Pretreatment of the algal cells in phosphate mediumin the dark, which was essential for the blue light enhancementof PEP carboxylase activity, was not necessary to induce theabove wavelength effects. Superimposition of monochromatic bluelight at low intensity (450 erg.cm2.sec1) on thered light at saturating intensity caused a significant decreasein the rate of 14CO2 incorporation into sucrose and increasein incorporation into alanine, lipid-fraction, aspartate andother related compounds, indicating that the path of carbonin photosynthesis is regulated by short wavelengdi light ofvery low intensity. Possible effects of wavelength regulationof photosynthetic carbon metabolism in algal cells are discussed.
1 Part of this investigation was reported at the XII InternationalBotanical Congress, Leningrad, 1975 and the Japan-US CooperativeScience Seminar "Biological Solar Energy Conversion", Miami,1976. Requests for reprints should be addressed to S. Miyachi,Radioisotope Centre, University of Tokyo, Bunkyo-ku, Tokyo 113,Japan.
4 Present address: Department of Chemistry, Faculty of PharmaceuticalSciences, Teikyo Univ., Sagamiko, Kanagawa, Japan. (Received August 6, 1977; ) 相似文献
17.
The penetration of naphthaleneacetic acid (NAA) into pear (Pyruscommunis L. cv. Bartlett) leaves as influenced by selected treatingsolution and environmental factors was studied under definedand controlled conditions. Penetration through the adaxial leafsurface was linear with time, whereas, movement through theabaxial surface was rapid initially and then the rate diminishedwith time. Penetration through both leaf surfaces was proportionalto external concentration and was temperature dependent. MoreNAA penetrated at pH values below than above the pKa. Light(1000 ft-c) stimulated NAA penetration. The light enhanced penetrationof NAA was depressed by 3-tert-butyl-5-chloro-6-methyluracil,3-(p-chlorophenyl)-1,1-dimethylurea, phenylmercuric acetate,2,4-dinitrophenol, carbonylcyanide m-chlorophenylhydrazone andcarbonylcyanide p-trifluoromethoxyphenylhydrazone. We concludedthat NAA penetration was controlled by both physical and metabolicfactors.
1 Journal Article No. 5725 from the Michigan Agricultural ExperimentStation. This investigation was supported-in-part by NIH TrainingGrant No. 5 TOI GM 00246 from General Medical Sciences, PublicHealth Service Grant CC 00246 from the National CommunicableDisease Center, Atlanta, Georgia, and Food and Drug AdministrationGrant FD 00223.
2 Present address: Department of Plant & Soil Sciences,University of Massachusetts, Amherst, Massachusetts, 01002. (Received November 9, 1971; ) 相似文献
18.
19.
Carbonic anhydrase (CA, EC. 4.2.1.1
[EC]
) activity in air-grown Characorallina was detected mainly in the intracellular fraction,most of which composed of chloroplasts and cytoplasmic gel,and not on the cell surface. Only minor levels of CA activity,on the basis of equivalent volumes, were detected in the cellsap and the cytoplasmic sol. The maximum rate of photosynthetic O2 evolution by air-grownChara corallina at pH 6.0 was twice that at pH 7.6, while theapparent Km for external inorganic carbon (Ci) at pH 7.6 wasabout three times that at pH 6.0. However, the apparent Km(CO2)was about three times larger at pH 6.0 than at pH 7.6. The Km(Ci)-valueat pH 7.6 increased severalfold in the presence of acetazolamide(AZA), an inhibitor of CA, but no inhibition was observed atpH 6.0. The pH-dependence may be due to differences in the permeabilityof AZA at the given pH values. Fixation of 14CO2 at 20 µMand of H14CO3 at 200 µM over the course of 5 swas very similar at pH 7.4. Addition of CA significantly suppressedthe photosynthetic 14CO2-fixation but it stimulated the H14CO3-fixation.This result indicates that free CO2 is an active species ofCi that is incorporated into the cell during photosynthesis. These results together suggest the following: (1) Free CO2 isutilized for photosynthesis, (2) CA is mainly located insidethe cell and functions to increase the affinity for CO2 in photosynthesisby facilitating the supply of CO2 from the plasmalemma to thesite of CO2-fixation.
3Present address: Biological Laboratory, The University of theAir, Wakaba 2-11, Chiba, 260 Japan. (Received December 9, 1988; Accepted March 22, 1989) 相似文献
20.
Cloning, Expression, and Characterization of a Root-Form Phosphoenolpyruvate Carboxylase from Zea mays: Comparison with the C4-Form Enzyme 总被引:2,自引:0,他引:2
Dong Long-Ying; Masuda Takao; Kawamura Takao; Hata Shingo; Izui Katsura 《Plant & cell physiology》1998,39(8):865-873
A full-length cDNA for maize root-form phosphoenolpyruvate carboxylase(PEPC) was isolated. In the coding region, the root-form PEPCshowed 76 and 77% identity with the C4- and C3-form PEPCs ofmaize, respectively, at the nucleotide level. At the amino acidlevel, the root-form was 81 and 85% identical to the C4- andC3-form PEPCs, respectively. The entire coding region was insertedinto a pET32a expression vector so that it was expressed underthe control of T7 promoter. The purified recombinant root-formPEPC had a Vmax value of about 28 mol min1(mg protein)1at pH 8.0. The Km values of root-form PEPC for PEP and Mg2+were one-tenth or less of those of C4-form PEPC when assayedat either pH 7.3 or 8.0, while the value for HCO3 wasabout one-half of that of C4-form PEPC at pH 8.0. Glucose 6-phosphateand glycine had little effect on the root-form PEPC at pH 7.3;they caused two-fold activation of the C4-form PEPC. The Ki(L-malate) values at pH 7.3 were 0.12 and 0.43 raM for the root-and C4-form PEPCs, respectively. Comparison of hydropathy profilesamong the maize PEPC isoforms suggested that several stretchesof amino acid sequences may contribute in some way to theircharacteristic kinetic properties. The root-form PEPC was phosphorylatedby both mammalian cAMP-dependent protein kinase and maize leafprotein kinase, and the phosphorylated enzyme was less sensitiveto L-malate.
1These authors contributed equally to this work.
2Present address: Otsuka Chemical Co. Ltd., 463 Kagasuno, Kawauchi-cho,Tokushima, 771-0130 Japan.
3Present address: Sumitomo Pharmaceuticals Research Center,1-98, Kasugade, Naka 3-cho-me, Konohana-ku, Osaka, 554-0022Japan. 相似文献