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1.
Changes in ornithine decarboxylase, putrescine N-methyltransferaseand N-methylputrescine oxidase activities in response to sometreatments were investigated using hydroponically grown tobaccoplants. Decapitation of shoots brought about marked elevationof the three enzyme activities, which reached their peaks 24hr after decapitation, then declined. An excellent correlationwas observed between the accumulation of nicotine and changesin the three root enzyme activities. Administration of IAA at2.5 to 5 µconcentration significandy increased these enzymeactivities in roots of decapitated plants but higher concentrationsof IAA prevented the rise in enzyme activities promoted by decapitation.Nicotine strongly inhibited the rise in enzyme activities inroots of decapitated plants in all cases. The results suggestthat these enzymes are under the control of a common regulatorysystem, in which auxin and nicotine are important components.Ornithine decarboxylase was present in all the plants examined,but putrescine N-methyltransferase and N-mediylputrescine oxidasewere detected only in the roots of tobacco, Datura and Atropaplants. 1Part XVI of the series "Phytochemical Studies on Tobacco Alkaloids". (Received August 1, 1972; )  相似文献   

2.
Growth of the Vicia faba seedling is accompanied by a rapid15-day increase in amine oxidase activity of the apical parts.Cotyledons and roots were found to be devoid of activity. Thepartially purified enzyme from leaves readily oxidized putrescine,cadaverine, agmatine and spermidine, while dopamine (3-hydroxytyramine)and L- and D-lysine were oxidized more slowly. The Km valueswere 1.9?10–3 M for cadaverine, 3.7?10–5 M for putrescine,7.8?10–4 M for spermidine, and 5.9?10–3 M for dopamine.Carbonyl reagents and copper-binding agents were effective inhibitorsof Vicia faba amine oxidase. The diethyldithiocarbamate-treatedenzyme could be reactivated specifically by cupric copper. (Received May 25, 1977; )  相似文献   

3.
A novel procedure is described for the chemical synthesis of N-methylputrescine, the product of the title enzyme. This is obtained from putrescine by formylation followed by the reduction of the monoformylputrescine intermediate with LiA1H4. An assay method for putrescine N-methyltransferase was developed which depends on the determination of N-methylputrescine in the presence of an excess of putrescine. This method, which makes use of a radiolabeled substrate unnecessary, is based on dansylation of the product followed by HPLC separation on a reversed-phase column. The enzyme activity of the protein peak extracted from plant material was measured after treatment by gel filtration on prepacked disposable PD 10 columns. The specific enzyme activities determined in the extract from the roots of Nicotiana tabacum and Datura stramonium plants, and from a root culture of D. stramonium, are reported. With an enzyme preparation from the last root culture, Km values for putrescine and S-adenosylmethionine (SAM) were determined as 0.88 mM and 0.15 mM, respectively.  相似文献   

4.
The effects of arginine and urea on the levels of ornithinetranscarbamylase (OTC) were investigated in relation to thephysiological functions of this enzyme in Geotrichum candidum.OTC was repressed in germinated spores to half of its initiallevel when exogenous arginine exceeded 12 mM. The repressionof OTC could not be correlated with intracellular arginine concentration.The addition of urea at the final concentration of 0.035 M increasedthe specific activity of OTC by 5.5 and 2.5 fold as comparedto enzyme levels in arginine-repressed spores and control sporesrespectively. Simultaneous addition of urea and arginine duringgermination prevented either arginine repression or urea inductionof OTC. The enzyme was partially purified from germinated sporesand isolated as a single protein band after disc electrophoresis.Two distinct pH optima for the forward reaction (pH 8.8–9)and backward reaction (pH 7.8) were found. Km values for ornithineand carbamyl phosphate were 5 x 10–3 M and 6.8 x 10–4so respectively. The Km for citrulline in the catabolic directionwas 1 x 10–2 M. Enzymes obtained from cell-free extractsof germinated spores could synthetize ATP from citrulline andADP under physiological conditions by coupling the phosphorolysisof citrulline with carbamate kinase activity. The initial rateof germination was stimulated in the presence of citrullineas the sole nitrogen source, as compared to arginine, glutamineor yeast extract. These observations suggest that citrullinemay be catabolized during germination by means of OTC ratherthan via the energy-consuming urea cycle. (Received June 26, 1971; )  相似文献   

5.
Mannitol-1-phosphate dehydrogenase (EC 1.1.1.17 [EC] ) and mannitol-1-phosphatase(EC number yet unassigned) were detected in the brown algae,Spatoglossum pacificum and Dictyota dichotoma. The enzymes wereextracted from algal fronds and their properties were investigatedusing partially purified preparations. Mannitol-1-phosphatase shows maximum activity at pH 7. The enzymehad a narrow substrate specificity. The Km value for mannitol-1-phosphateis 8.3x10–4 M (30°C, pH 7.0). The enzyme is activatedby Mg++ and Mn++and is strongly inhibited by PCMB, Hg++and NaF. Mannitol-1-phosphate dehydrogenase showed maximum activitiesat pH values 6.5 and 10.2 in reductive and oxidative reactions,respectively. The dehydrogenase also showed narrow substratespecificity; mannitol-1-phosphate and NAD or fructose-6-phosphateand NADH2 are utilized, respectively, in oxidative and reductivereactions by the enzyme. Km values for these substrates andthe coenzymes are 2.5x10–4 M and 7.1x10–5 M forthe first pair and 2.8x10–4 M and 1.3x10–5 M forthe latter pair. This enzyme was strongly inhibited by PCMBand Hg++, but was only slightly affected by adenosine phosphates. Possible roles of these enzymes in the biosynthesis of mannitolin brown algae are discussed. 1 Contributions from the Shimoda Marine Biological Station ofTokyo Kyoiku University, No. 233. This work was supported inpart by a Grant-in-Aid for Co-operative Research from the Ministryof Education, Japan and in part by a grant to one of us (T.Ikawa) from the Matsunaga Science Foundation. 2 Present address: Chemical and Physical Laboratory, HoechstJapan Research Laboratory, Minamidai, Kawagoe, Japan. (Received February 22, 1972; )  相似文献   

6.
Some Properties of the Arginine Decarboxylase in Vicia faba Leaves   总被引:1,自引:0,他引:1  
Growth of Vicia faba seedlings is accompanied by a rapid increasein arginine decarboxylase (EC 4.1.1.19 [EC] ) in the leaves and epicotyl.Increased enzyme activity was observed under saline conditionsin the presence of NaCl and with osmotic stress by mannitol.The partially purified enzyme (about 86-fold) readily decarboxylatedL-arginine, while D-arginine, L-homoarginine, L-ornithine andL-lysine were decarboxylated very slowly, and L-citrulline andL-glutamic acid were not decarboxylated. The Km value was 5.8?10–4M for L-arginine. The optimal pH and temperature for activitywere 8.5 and 45?C, respectively. p-Chloromercuribenzoate andN-ethylmaleimide were effective inhibitors of the enzyme. Inhibitionby spermidine, putrescine and agmatine suggested a possiblefeed-back mechanism in the pathway of polyamine biosynthesis. (Received October 11, 1983; Accepted February 24, 1984)  相似文献   

7.
The uptake of L-leucine into Vinca protoplasts was studied undervarious conditions. The uptake was highly pH-dependent, withthe optimal pH between 3.0 and 4.0. The uptake was also energydependent, since azide, 2,4-dinitrophenol (DNP), carbonyl cyanidem-chlorophenyl hydrazone (CCCP), and iodoacetate inhibited theuptake. Oligomycin, N,N'-dicycIohexyI carbodiimide (DCCD) andvanadate, but not ouabain, inhibited the uptake, suggestingthat ATPase for H+ electrogenic extrusion was necessary to theuptake of L-leucine. The uptake showed stereospecificity, butwas partially inhibited by other L-amino acids. A kinetic studyof the uptake showed that the uptake was multiphasic with threesaturable phases and one unsaturable phase which occurred atconcentrations of L-leucine over 1 mM. The Km values of thethree affinity sites were 1.4 x 10–3 M, 1.3 x 10–4M, 4.3 x 10–5 M; the maximum velocity values were 3.3x 10–8, 4.5 x 10–9, 1.8 x 10–9 mol/10 min/4x 106 cells. (Received April 18, 1981; Accepted August 25, 1981)  相似文献   

8.
Kinetin (4.7 x 10–5 M) and 6-benzyladenine (2.22 x 10–5M) were found to increase ca. 2-fold the putrescine contentin cotyledons of lettuce (Lactuca sativa L.) seedlings grownfor 3 days under fluorescent light. On the other hand, severalinorganic ions (K+, Na+, Ga++, Mg++) at a concentration of 3x 10–2 M reduced the putrescine content. The combinationof kinetin with one of several inorganic ions at the same levelmarkedly increased the spermine content, but the putrescinecontent decreased; calcium and magnesium ions were less effective.The physiological significance of these findings is discussed. (Received July 4, 1982; Accepted November 6, 1982)  相似文献   

9.
Nitrite reductase was extracted from the red alga Porphyra yezoensisUeda and purified through precipitation with ammonium sulfate,column chromatographies, and polyacrylamide gel disk electrophoresis.The enzyme preparation thus obtained showed a single band ondisk electrophoresis. The absorption spectrum had three maxima at 385 nm (Soret band),580 nm (-band), and 278 nm; the ratio of absorbance of the Soretband to the -band was 4.3. The molecular weight and the numberof amino acid residues were estimated to be 63,000 and 601,respectively. The enzyme activity was optimal at around pH 7.5, and its activitywas heat labile as indicated by reduction of activity by about70% when heated at 37°C for 10 min. The enzyme used ferredoxin and methyl viologen, but not NADP+or NAD+, as the electron carriers. Moreover, reduced forms ofthe latter two showed no effect on its activity. Km values ofthis enzyme for NO2, Fd, and MV were 8.1 x 10–4M, 4.3 x 10–8 M, and 3.7 x 10–4 M, respectively.Almost half of its activity was lost when potassium cyanidewas added at a concentration as low as 10–5 M, and theKi value was 1.8 x 10–5 M. Thus, the nitrite reductaseof Porphyra must be systematically grouped in EC 1.7.7.1 [EC] . Itresembled closely that of Chlorella, except for the amountsof some amino acids. 1 Present address: Department of Biological Sciences, Universityof Tsukuba, Sakura-Mura, Ibaraki, 300-31 Japan. 2 Present address: Department of Fisheries, College of Agricultureand Veterinary Medicine, Nihon University, Shimouma, Setagaya-ku,Tokyo, 154 Japan. (Received June 10, 1975; )  相似文献   

10.
L-Tyrosine carboxy-lyase (E. C. 4. 1. 1. 25) was extracted fromthe roots of barley seedlings and purified approximately 25fold. Optimum pH for the enzyme activity was found to be 7.3.The Km value for L-tyrosine was calulated as 4.5?10–4M.D-Isomer did not react with the enzyme. L-DOPA, m-tyrosine ando-tyrosine were decarboxylated to some extent. Pyridoxal phosphateactivated the enzyme 4 fold. Caffeic acid and p-coumaric acidare competitive inhibitors. Ki values were 4.5?10–5M forcaffeic acid and 1.6?10–4M for p-coumaric acid. L-DOPAand m-tyrosine had an inhibitory effect on the decarboxylationof L-tyrosine. Hydroxylamine, semicarbazide, p-CMB, Fe++, Cu++,and Hg++ inhibited the decarboxylation of tyrosine. Enzyme activitywas also found in extracts from Triticum aestivum, Zea maysand Cytisus scoparius. (Received November 30, 1973; )  相似文献   

11.
The NADP$-specific isocitrate dehydrogenase was partially purifiedfrom photosynthetically-grown Rhodospirillum rubrum. The pHoptimum is between 7.5 and 9.0 in phosphate buffer. The apparentKm is 3.1x10–5 M for isocitrate, 5.1x10–5 M forNADP$, 1.7x10–5 M for manganese, 1.5x10–4 M formagnesium, and 3.5x10–3 M for inorganic orthophosphate.Arsenate exerts a slight inhibition. The Q10 between 17.5°Cand 40°C is 1.62, and the energy of activation at 25°Cis 9.74 Kcal/mole. Glyoxylate and oxalacetate cause concertedinhibition of the enzyme activity. Various nucleotides inhibitthe activity. The kinetics of inhibition by ATP was found tobe mixed type with respect to NADP$ and isocitrate, the Ki valuesbeing 1.17x10–3 M and 1.10x10–3 M respectively.The inhibition between ATP and orthophosphate is competitivewith a Ki of 10–4M. Thiol binding reagents are inhibitory;this inhibition is reversed by cysteine or reduced glutathione. (Received October 1, 1971; )  相似文献   

12.
An enzyme, which catalyzes the formation of dihydrofolate fromdihydropteroic acid and L-glutamic acid, was found in pea seedlings.The enzyme was purified approximately 25-fold from the crudeextracts of pea seedlings, and its some properties were investigated.Optimum pH for the enzyme activity was found to be 8.8. Pteroicand tetrahydropteroic acids were not active as substrate. Theenzymatic reaction required as cofactors ATP, divalent (Mg2+or Mn2+) and univalent (K+, NH4+ or Rb+) cations. The productwas characterized as dihydrofolic acid by bioautography. MICHAELIS constants for L-glutamic acid, ATP, dihydropteroicacid and Mg2+ were 7.0x10–4, 9.0x10–5, 3.5x10–6and 1.2x10–3 M, respectively. The MICHAELIS constant forMn2+ was 3.0x10–4. The enzyme was inhibited by PCMB orsilver nitrate and, to some extent, by L-aspartic acid. Inhibitionby PCMB was completely reversed by addition of 2-mercaptoethanol.Enzyme activity was distributed widely among plants. The importanceof magnesium and potassium ions for enzyme catalysis is discussed. 1For the previous paper, Part V, see Reference (30). (Received March 28, 1970; )  相似文献   

13.
Direct somatic embryogenesis can be obtained from epidermaland cortical cells in roots from in vitro Cichorium plantlets.The first embryogenic cells are seen after six days of culturein darkness, at 35 °C, in a liquid medium supplemented withNAA (1 x 10–7 M), 6-dimethylallyl-amino-purine (2·5x 10–6 M), sucrose (0.03 M) and glutamine (1·7x 10–3 M). Embryogenic cells undergo first a linear andthen a globular segmentation, with increasing cytoplasmic density.These cells and young embryoids show aniline blue fluorescence.SEM allows the same microglobular pattern to be seen on thesurface of young embryoids and on young microspores of Cichoriumused as controls. In this root system, callose deposition seemsto be an early marker in somatic embryogenesis. Somatic embryogenesis, callose, Cichorium  相似文献   

14.
Flicker, M. D. and Willmer, C. M. 1986. Vanadate sensitive ATPaseand phosphatase activity in guard cell protoplasts of Commelina.—J.exp. Bot. 38: 642–648. Phosphatase activity was measured in extracts of guard cellprotoplasts of Commelina communis L. using the artificial substratep-nitrophenylphosphate. A pH optimum of 5.8 to 6.3 was determined.Ammonium molybdate (Ol mol m–3) and sodium vanadate (1–0mol m–3) gave almost complete inhibition of phosphataseactivity at pH 60. ATPase assays were, therefore, conductedin the presence of 0–2 mol m –3 molybdate and vanadatewas used as a specific inhibitor of plasmamembrane ATPase activity.Vanadate sensitive ATPase activity showed a pH optimum of 6.6and activity was stimulated by KC1. These properties are characteristicof plasmamembrane proton pumping ATPases in other systems andsuggest that proton extrusion in guard cells could be mediatedby a similar enzyme. The maximum ATPase activity is sufficientto account for all the proton flux observed during the stomatalopening response. Key words: ATPase, Commelina, guard cell protoplasts, phosphatase, vanadate  相似文献   

15.
Membrane-bound Mg++-activated ATPase activity in epidermal stripsfrom tobacco leaves (Nicotiana tabacum L. Samsun NN) was stimulatedby abscisic acid (ABA) when the strips were floated on ABA solutionin light or in darkness. The optimum ABA concentrations in lightand in darkness were 10–5 M and 10–6 M, respectively.Carbonyl cyanide m-chlorophenylhydrazone (CCCP) and N, N'-dicyclohexylcarbodiimide(DCCD) completely blocked the basal level membrane-bound epidermalATPase activity. ABAinduced membrane-bound epidermal ATPaseactivity was completely inhibited by CCCP, but only partly byDCCD. H+-influx into epidermal strips on a solution in light was lowerthan that in darkness. ABA stimulated H+-influx into epidermalstrips in light and in darkness. CCCP suppressed basal levelH+-influx, whereas DCCD did not. CCCP also suppressed ABA-inducedH+-influx, whereas DCCD did not. Interaction between H+-influxand membranebound epidermal ATPase activity is discussed. (Received May 23, 1978; )  相似文献   

16.
L-Tyrosine carboxy-lyase (E.C. 4. 1. 1. 25) was isolated fromroots of germinating barley (Hordeum vulgare). The enzyme requirespyridoxal phosphate for maximum activity. The optimum pH foractivity is about 7.0. The enzyme is inhibited by p-chloromercuribenzoateand hydroxylamine at 10–3 M. Enzyme activity is foundin extracts from young roots, especially from those in earlystages of development, but not in extracts from shoots of thesame plant. Localization and changes in the amounts of L-tyrosinecarboxy-lyase and aromatic amines in developing barley seedlingswere measured. Participation of carboxy-lyase in the formationof aromatic amines in barley roots is suggested. (Received July 17, 1970; )  相似文献   

17.
In adventitious root formation of disbudded epicotyl cuttingstaken from light-grown, 5-day-old Azukia angularis seedlings,indoleacetic acid (IAA), 1 x 10–4 M, applied during thefirst day showed no effect, but enhanced the effect of IAA,1 x 10–4 M, applied during the second day. Treatment duringthe second day promoted rooting by about 70%, and a combinationof treatments for the first and second days promoted rootingsome 200%. p-Chlorophenoxyisobutyric acid (PCIB), 3 x 10–4M, and2,4,6-trichlorophenoxyacetic acid (2,4,6-T), 2 x 10–44M, applied the first day also enhanced the effect of IAA, 2x 10–4 M, applied the second day. When applied the second day, PCIB, 2 x 10–4M, increasedthe number of root primordia or clusters of small cells, butnot die number of protruded roots. Formation of the cell clusterwas inhibited by 2,4,6-T, 3 x 10–4M, applied the secondday. Rooting processes in Azukia cuttings seem to include at leastthree phases: the first phase is induced not only by IAA butalso by PCIB or 2,4,6-T, the second phase is induced by IAAor PCIB and the diird phase depends specifically on IAA. (Received October 28, 1970; )  相似文献   

18.
NADP-specific isocitrate dehydrogenase from the soluble fractionof maturing castor bean endosperm was partially purified (approximately180-fold) and some of its enzymatic properties were studied.Mg++, Mn++, Cd++, Ba++, Co++, Zn++, and Sr++ were activatorsof the enzyme reaction at a concentration of 6.7x10 M. The optimumpH of this enzyme was about 8.5. The enzyme was stable in thenarrow range from pH 7.0 to pH 8.0. Km values for isocitrateand NADP at pH 8.5 were 3.5x10–6 M and 3.6x10–6M, respectively. Enzyme stability was not affected by NaCl concentrationand enzyme reaction was inhibited at 5x10–6 M PCMB (80%inhibition). It is suggested that the condensation product ofglyoxylate and oxalacetate also inhibits the reaction. NADP-IDHin the crude extract from maturing castor bean endosperm washeat-stable but the dialyzed enzyme preparation and the partiallypurified enzyme were labile against heat treatment at 57°C.When Mg++ was added to the partially purified enzyme in thepresence of isocitrate or NADP, the enzyme was stabilized againstheat treatment. Mn++, Ca++, Co++, Sr++ or Ba++ could be substitutedfor Mg++. Addition of only one of the factors, Mg++, isocitrateor NADP, had no effect on the heat stability. Moreover, a combinationof isocitrate and NADP did not establish stabilization. A divalentcation plays a central role, while adenine nucleotide, especiallyATP, may have an important part in stabilization. (Received August 14, 1972; )  相似文献   

19.
Guttation was used as a non-destructive way to study the flowof water and mineral ions from the roots and compared with parallelmeasurements of root exudation. Guttation of the leaves of barley seedlings depends on age andon the culture solution. Best rates of guttation were obtainedwith the primary leaves of 6- to 7-day-old seedlings grown onfull mineral nutrient solution. The growing leaf tissue becomessaturated with K+ below 1.5 mM K+ in the medium, whereas K+concentration in the guttated fluid still increases furtheras K+ concentration in the medium is raised. At 3 mM K+ averagevalues of guttation were 1.4–2.4 mm3 h–1 per plantwith a K+ concentration of 10–20 mM; for exuding plantsthe flow was 4.2–7.6 mm3 h–1 per plant and K+ concentration35–55 mM. Abscisic acid (ABA) at 10–6 to 10–4 M 0–2h after addition to the root medium increased volume flow ofguttation and exudation and the amount of K+ exported. Threeh after addition of ABA both volume and amount of K+ were reduced.There was an ABA-dependent increase in water permeability (Lp)of exuding roots shortly after ABA addition. Later Lp was decreasedby 35 per cent and salt export by 60 per cent suggesting aneffect of ABA on salt transport to the xylem apart from itseffect on Lp. Benzyladenine (5 x 10–8 to 10–5 M)and kinetin (5 x 10–6 M) progressively reduced volumeflow and K+ export in guttation and exudation and reduced Lp. Guttation showed a qualitatively similar response to phytohormonesas found here and elsewhere using exuding roots. Hordeum vulgare L., barley, guttation, abscisic acid, cytokinins, benzyl adenine, kinetin  相似文献   

20.
A cell-wall fraction containing 10.0% dry weight of proteinwas isolated from tobacco (Nicotiana tabacum L.) XD-6 cellscultured in suspension. The fraction possessed high acid phosphataseactivity toward p-nitrophenyl phosphate, phenyl phosphate, inorganicpyrophosphate, adenosine diphosphate, nucleoside triphosphates,and bis- (p-nitrophenyl) phosphate; much less activity towardnaphthyl phosphate, ß-glycerophosphate, glucose-6-phosphate,fructose-6-phosphate, fructose-l,6-diphosphate, thiamine pyrophosphate;and no activity toward glucose-1-phosphate and inositol hexaphosphate.Metallic ions were not required for activation. The enzyme wasextracted from the wall with NaCl solution. The solubilizedenzyme resulted in a single peak on Sephadex G-150 chromatographywith activity toward p-nitrophenyl phosphate, pyrophosphate,and bis(p-nitrophenyl) phosphate. The activity of the solubilizedenzyme toward p-nitrophenyl phosphate was identical with thebound enzyme in its pH optimum, substrate specificity, ion inhibitionand Km value, but it was more sensitive to pH, substrate difference,inhibition, and heat treatment. 1Present address: Department of Biology, Japan Women's University,Mejiro-dai, Bunkyo-ku, Tokyo, Japan (Received September 13, 1972; )  相似文献   

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