Ivano Marques - Academia.edu (original) (raw)

Papers by Ivano Marques

Plant Physiology, Oct 1, 1986

Photosynthetic C02-fixation in isolated pea (Pisum sativum L., cv Little Marvel) chloroplasts dur... more Photosynthetic C02-fixation in isolated pea (Pisum sativum L., cv Little Marvel) chloroplasts during induction is markedly inhibited by 0.4 millimolar sulfite. Sulfate at the same concentration has almost no effect. The "C02-fixation pattern indicates that the primary effect of sulfite is

Springer eBooks, 1989

Interactions between plants and microbial pathogens may result in various defense reactions withi... more Interactions between plants and microbial pathogens may result in various defense reactions within the infected plant. Elicitors are important in triggering these reactions. Similar responses may take place in plant cell suspension cultures after addition of pathogen-derived elicitor preparations to the culture medium. An increasing number of studies on the effects of elicitors on secondary metabolism of plant cell cultures may be found in the literature.

Annals of the New York Academy of Sciences, Dec 1, 1988

Les enzymes impliquees dans la synthese de certains alcaloides isoquinoliniques sont inductibles,... more Les enzymes impliquees dans la synthese de certains alcaloides isoquinoliniques sont inductibles, en particulier, la tyrosine decarboxylase de T. rugosum et E. californica. Son induction par un extrait de champignon, est etudiee en fonction de la concentration d'inducteur, du temps apres l'addition de l'inducteur et de l'âge des cellules. Sur les deux types de culture de cellules, l'enzyme est purifiee et analysee

Archives of Biochemistry and Biophysics, Feb 1, 1987

We report here that enzyme activation precedes the rise in metabolite levels, which appear to lim... more We report here that enzyme activation precedes the rise in metabolite levels, which appear to limit photosynthetic COP fixation during induction in pea leaf chloroplasts. Therefore light activation may be required for the build-up of photosynthetic intermediates and hence for photosynthesis in isolated chloroplasts. Analysis of metabolite levels and the known kinetic properties of the chloroplast enzymes indicates that the reductive pentose phosphate cycle is subject to control which fluctuates between several points during induction and when CO, fixation is maximal. The transketolase-aldolasecatalyzed reactions around sedoheptulosebiphosphatase appear to provide a simple and effective primary control for photosynthetic CO2 fixation. When substrate levels and enzyme active site concentrations are taken into account, there is insufficient glyceraldehyde 3-phosphate dehydrogenase, aldolase, and transketolase activity to support photosynthetic CO2 fixation at observed rates. These results suggest that there may be direct transfer of glyceraldehyde 3-phosphate among these enzymes in the pea chloroplast.

In experiments designed to examine the relationship between light activation of reductive pentose... more In experiments designed to examine the relationship between light activation of reductive pentose phosphate cycle enzymes and induction we were surprised to find that the active site concentrations of NADP-1inked glyceraldehyde-3-P dehydrogenase and aldolase exceed substrate concentrations. The potential activity of these enzymes is then not sufficient to support observed rates of photosynthetic CO2 fixation. Since photosynthetic CO2 fixation does occur either our estimates are in error or some mechanism exists for channeling metabolites between enzymes in the chloroplast. Experiments with broken chloroplast extracts are consistent with transfer of P2-glycerate between P-glycerate kinase and glyceraldehyde-3-P dehydrogenase without diffusion into the surrounding medium.

SO/sub 2/ appears to have multiple effects on chloroplast stromal metabolism. What is unique abou... more SO/sub 2/ appears to have multiple effects on chloroplast stromal metabolism. What is unique about metabolism in the chloroplast is reductive modulation of enzyme activity. The evidence summarized here implicates both the components of the modulation process and the light modulated enzymes and ribulosebisphosphate carboxylase in SO/sub 2/-sensitivity. Interference with electron transport, acidification of the stroma, and depletion of phosphates will further complicate metabolism in the photosynthesizing chloroplast when sensitive plants are exposed to SO/sub 2/. 35 refs., 6 figs.

Journal of Experimental Botany, 1985

Duckweed, Lemna minor L~ grown on inorganic nutrient solutions containing either NHt or NO 3 as n... more Duckweed, Lemna minor L~ grown on inorganic nutrient solutions containing either NHt or NO 3 as nitrogen source was allowed to assimilate [1-1-'-CJor [2-14 C]glycollate dunng a 20 min period in darkness or in light. The incorporation of radioactivity into water-soluble metabolites, the insoluble fraction, and into the CO 2 released was measured. In addition the extractable activity of phosphoenolpyruvate carboxylase was determined. During the metabolism of [2-14 C]glycollate in darkness, as well as in the hght, NHt grown plants evolved more 14 CO 2 than NO 3 grown plants. Formate was labelled only from [2-14 C]glycollate and in NH; grown plants it was significantly less labelled in light than in darkness. In NO 3 grown plants formate showed similar rad10activity after dark and light labelling. The radioactivity in glycine was httle influenced by the nitrogen source. Amounts of radioactivity in serine implied that the further metabolism of serine was reduced m darkness compared with its metabolism in the light under both nitrogen regimes. In illuminated NHt plants, serine was labelled through a pathway starting from phosphoglycerate. After [l-14 C]glycollate feeding NHt grown plants contained markedly more radioactive aspartate and malate than NO 3 plants indicating a strmulated phosphoenolpyruvate carboxylation in plants grown on NHt.

Elsevier eBooks, 1996

PDF to Text Batch Convert Multiple Files Software - Please purchase personal license. INTERACTION... more PDF to Text Batch Convert Multiple Files Software - Please purchase personal license. INTERACTION BETWEEN CHLOROPLAST PHOSPHOGLYCERATE KINASE ANDG LYC E RA L DE HY DE-3-PH0sPHATE DEHYDROGENASE Louise E. Anderson, Xiao-yi Tang, Cote ...

Plant Physiology, Mar 1, 1983

Young bean plants (Phaseolus vulgaris L. var Saxa) were fed with three different types of inorgan... more Young bean plants (Phaseolus vulgaris L. var Saxa) were fed with three different types of inorganic nitrogen, after being grown on nitrogen-free nutrient solution for 8 days. The pattern of "CO2 fixation was investigated in photosynthesizing primary leaf discs of 11-day-old plants (3 days with nitrogen source) and in a pulse-chase experiment in 13-day-old plants (5 days with nitrogen source). Ammonium caused, in contrast to nitrate nutrition, a higher level of 14C incorporation into sugar phosphates but a lower incorporation of label into malate, glycolate, glycerate, aspartate, and alanine. The labeling kinetics of glycine and serine were little changed by the nitrogen source. Ammonium feeding also produced an increase in the ratio of extractable activities of ribulose-1,5-bisphosphate carboxylase to phosphoenolpyruvate carboxylase and an increase in dark respiration and the CO2 compensation concentration. Net photosynthesis was higher in plants assimilating nitrate. The results point to stimulated turnover of the photosynthetic carbon reduction cycle metabolites, reduced phosphoenolpyruvate carboxylation, and altered turnover rates within the photosynthetic carbon oxidation cycle in ammonium-fed plants. Mechanisms of the regulation of primary carbon metabolism are proposed and discussed. The effect of NH4' on photosynthetic carbon assimilation has been repeatedly reported (3, 8, 12, 13, 16, 17, 19-23, 27, 29) and the changes in metabolism which occur in response to toxic NH4' concentrations recently reviewed (10). Studies with Chlorella and Medicago sativa suggest that, during NH4' assimilation, photosynthetically fixed carbon is diverted into amino acids at the expense of sucrose synthesis (12, 13, 22). Pyruvate kinase, PEp2 carboxylase, and RuBP carboxylase are all apparently stimulated (8, 12, 13, 20-22), and in isolated spinach cells, photosynthetic 14CO2 fixation increased, in response to the presence of NH4' (29). Supplying C4 and C3 plants with NH4' as compared to NO3 produces, among other effects, changes in the initial carboxylation products, the CO2 compensation point, and the net photosynthetic rate (26), while in maize, NH4' nutrition causes a lower incorporation of label from 14CO2 into malate (3). Further, the addition of NH4' to N03grown cells of Nicotiana tabacum produced an increase in the cellular concentrations of alanine and glutamine, ' This work was supported by Swiss National Science Foundation Project 3.259-0.77.

Plant Physiology, Sep 1, 1988

L-Tyrosine decarboxylase (EC 4.1.1.25) activity was induced in cell suspension cultures of Thalic... more L-Tyrosine decarboxylase (EC 4.1.1.25) activity was induced in cell suspension cultures of Thalictrum rugosum Ait. and Eschscholtzia californica Cham. with a yeast polysaccharide preparation (elicitor). The highest L-tyrosine decarboxylase activity in extracts from 7-day-old cell cultures of E. californica was observed 5 hours after addition of 30 to 40 micrograms elicitor per gram cell fresh weight. The enzyme extracted from cells of E. californica was purified 1540-fold to a specific activity of 2.6 micromoles CO2 produced per minute per millim protein at pH 8A and 30°C. Purified enzyme from T. rugosum showed a specific activity of 0.18 micromoles per minute per milligram protein. The purification procedure involved ammonium sulfate fractionation, anion-exchange fast protein liquid chromatography, ultrafiltration, and hydrophobic interaction chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that the enzyme from the two plant cell cultures had subunits of identical molecular weight (56,300 1 300 daltons. Aromatic amino acids are important precursors of various secondary products in higher plants (e.g. alkaloids, flavonoids, and coumarins). Studies with plant cell cultures have shown that

PLANT PHYSIOLOGY, 1983

Progress in Photosynthesis Research, 1987

PLANT PHYSIOLOGY, 1985

ABSTRACr After dark-light transitions, there is a delay in photosynthetic CO2 fixation by isolate... more ABSTRACr After dark-light transitions, there is a delay in photosynthetic CO2 fixation by isolated pea chloroplasts in the range of some minutes. In order to assess the physiological significance of light modulation of enzyme activity in the control of induction, we made estimates of the kinetic parameters of fructose-1,6-bisphosphatase immediately upon release from pea chloroplasts in the dark and after illumination for various time periods. The Michaelis constant for fructose-1,6-bisphosphate decreased and maximal velocities increased during-induction. It seems likely that light activation of this enzyme is one of the factors contributing to the overcoming of the lag period in photosynthetic CO2 fixation.

PLANT PHYSIOLOGY, 1988

Properties of purified L-tyrosine decarboxylase (EC 4.1.1.25) from elicitor-induced cell suspensi... more Properties of purified L-tyrosine decarboxylase (EC 4.1.1.25) from elicitor-induced cell suspension cultures of Eschscholtzia californica Cham. and Thalictrum rugosum Ait. are described. L-Tyrosine decarboxylase is a dimeric enzyme with a molecular weight of 112,600 ± 600 daltons. The isoelectric point was estimated to be at pH 5.2 and pH 5.4 for the enzyme from E. californica and T. rugosum, respectively. The purified enzymes were stabilized in the presence of pyridoxal-5-phosphate. Optimum pH for the enzyme from both plants was found to be 8.4. Enzyme activity was dependent on exogeneously supplied pyridoxal-5-phosphate. The enzyme decarboxylated L-tyrosine and L-,a-3,4dihydroxyphenylalanine but was inactive toward L-phenylalanine and Ltryptophan. Apparent Km values of Eschscholtziaand Thalictrum-decarboxylase for L-tyrosine were 0.25 ± 0.03 and 0.27 ± 0.04 millimolar, respectively. Similar affinities were found for L-3,4-dihydroxyphenylalanine. Eschscholtzia L-tyrosine decarboxylase was strongly inhibited by the phenylalanine analogue L-a-aminooxy-#-phenylpropionate and largely unaffected by D,L-a-monofluoromethyl-3,4-dihydroxyphenylalanine and a-difluoromethyltyrosine. An enhanced biosynthesis of berberine in cell suspension cultures of Thalictrum rugosum Ait. was achieved by treating

PLANT PHYSIOLOGY, 1986

Archives of Biochemistry and Biophysics, 1987

Plant physiology, 1986

Advances in Molecular and Cell Biology, 1996