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  • General Chemistry  (85)
  • Crassulacean acid metabolism  (8)
  • 1
    Electronic Resource
    Electronic Resource
    Activity of enzymes of carbon metabolism during the induction of Crassulacean acid metabolism in Mesembryanthemum crystallinum L. (1982)
    Springer
    Planta 155 (1982), S. 8-16 
    Details
    ISSN: 1432-2048
    Keywords: Carbon metabolism ; Crassulacean acid metabolism ; Glycolysis (enzymes) ; Mesembryanthemum ; Photosynthesis (enzymes) ; Salinity and CAM
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The maximum extractable activities of twenty-one photosynthetic and glycolytic enzymes were measured in mature leaves of Mesembryanthemum crystallinum plants, grown under a 12 h light 12 h dark photoperiod, exhibiting photosynthetic characteristics of either a C3 or a Crassulacean acid metabolism (CAM) plant. Following the change from C3 photosynthesis to CAM in response to an increase in the salinity of in the rooting medium from 100 mM to 400 mM NaCl, the activity of phosphoenolpyruvate (PEP) carboxylase (EC 4.1.1.31) increased about 45-fold and the activities of NADP malic enzyme (EC 1.1.1.40) and NAD malic enzyme (EC 1.1.1.38) increased about 4- to 10-fold. Pyruvate, Pi dikinase (EC 2.7.9.1) was not detected in the non-CAM tissue but was present in the CAM tissue; PEP carboxykinase (EC 4.1.1.32) was detected in neither tissue. The induction of CAM was also accompanied by large increases in the activities of the glycolytic enzymes enolase (EC 4.2.1.11), phosphoglyceromutase (EC 2.7.5.3), phosphoglycerate kinase (EC 2.7.2.3), NAD glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.12), and glucosephosphate isomerase (EC 2.6.1.2). There were 1.5- to 2-fold increases in the activities of NAD malate dehydrogenase (EC 1.1.1.37), alanine and aspartate aminotransferases (EC 2.6.1.2 and 2.6.1.1 respectively) and NADP glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.13). The activities of ribulose-1,5-bisphosphate (RuBP) carboxylase (EC 4.1.1.39), fructose-1,6-bisphosphatase (EC 3.1.3.11), phosphofructokinase (EC 2.7.1.11), hexokinase (EC 2.7.1.2) and glucose-6-phosphate dehydrogenase (EC 1.1.1.49) remained relatively constant. NADP malate dehydrogenase (EC 1.1.1.82) activity exhibited two pH optima in the non-CAM tissue, one at pH 6.0 and a second at pH 8.0. The activity at pH 8.0 increased as CAM was induced. With the exceptions of hexokinase and glucose-6-phosphate dehydrogenase, the activities of all enzymes examined in extracts from M. crystallinum exhibiting CAM were equal to, or greater than, those required to sustain the maximum rates of carbon flow during acidification and deacidification observed in vivo. There was no day-night variation in the maximum extractable activities of phosphoenolpyruvate carboxylase, NADP malic enzyme, NAD malic enzyme, fructose-1,6-bisphosphatase and NADP malate dehydrogenase in leaves of M. crystallinum undergoing CAM.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00402925
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  • 2
    Electronic Resource
    Electronic Resource
    Properties of phosphoenolpyruvate carboxylase in rapidly prepared, desalted leaf extracts of the Crassulacean acid metabolism plant Mesembryanthemum crystallinum L. (1982)
    Springer
    Planta 154 (1982), S. 298-308 
    Details
    ISSN: 1432-2048
    Keywords: Crassulacean acid metabolism ; Mesembryanthemum ; Phosphoenolpyruvate carboxylase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Properties of phosphoenolpyruvate (PEP) carboxylase, obtained from leaves of Mesembryanthemum crystallinum L. performing Crassulacean acid metabolism (CAM), were determined at frequent time points during a 12-h light/12-h dark cycle. Leaf extracts were rapidly desalted and PEP carboxylase activity as a function of PEP concentration, malate concentration, and pH was measured within 2 min after homogenization of the tissue. Maximum velocity of PEP carboxylase was similar in the light and dark at pH 7.5 and pH 8.0. However, PEP carboxylase had as much as a 12-fold lower K m for PEP and as much as a 20-fold higher K i for malate during the dark than during the light periods, the magnitude of these differences being dependent on the assay pH. Assuming that enzyme properties immediately after isolation reflect the approximate state of the enzyme in vivo, these differences in enzyme properties reduce the potential for CO2 fixation via PEP carboxylase in the light. A small decrease in cytoplasmic pH in the light would greatly magnify the above differences in day/night properties of PEP carboxylase, because the sensitivity of PEP carboxylase to inhibition by malate increased with decreasing pH. Properties of PEP carboxylase were also studied in plants exposed to short-term perturbations of the normal 12-h light/12-h dark cycle (e.g., prolonged light period, prolonged dark period). Under all light/dark regimes, there was a close correlation between change in properties of PEP carboxylase and changes of the tissue from acidification to deacidification, and vice versa. Changes in properties of PEP carboxylase were not merely light/dark phenomena because they were also observed in plants exposed to continuous light or dark. the data indicate that, during CAM, PEP carboxylase exists in two stages which differ in their capacity for net malate synthesis. The “physiologically-active” state is distinguished by a low K m for PEP and a high K i for malate and favors malate synthesis. The “physiologically-inactive” state has a high K m for PEP and a low K i for malate and exists during periods of deacidification and other periods lacking synthesis of malic acid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393907
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  • 3
    Electronic Resource
    Electronic Resource
    Light and dark CO2 fixation in Clusia uvitana and the effects of plant water status and CO2 availability (1992)
    Springer
    Oecologia 91 (1992), S. 47-51 
    Details
    ISSN: 1432-1939
    Keywords: Chlorophyll fluorescence ; Clusia ; Crassulacean acid metabolism ; Phosphoenolpyruvate carboxylase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In well-watered plants of Clusia uvitana, a species capable of carbon fixation by crassulacean acid metabolism (CAM), recently expanded leaves gained 5 to 13-fold more carbon during 12 h light than during 12 h dark periods. When water was withheld from the plants, daytime net CO2 uptake strongly decreased over a period of several days, whereas there was a marked increase in nocturnal carbon gain. Photosynthetic rates in the chloroplasts were hardly affected by the water stress treatment, as demonstrated by measurements of chlorophyll a fluorescence of intact leaves, indicating efficient decarboxylation of organic acids and refixation of carbon in the light. Within a few days after rewatering, plants reverted to the original gas exchange pattern with net CO2 uptake predominantly occurring during daytime. The reversible increase in dark CO2 fixation was paralleled by a reversible increase in the content of phosphoenolpyruvate (PEP) carboxylase protein. In wellwatered plants, short-term changes in the degree of dark CO2 fixation were induced by alterations in CO2 partial pressure during light periods: a decrease from 350 to 170 μbar CO2 caused nocturnal carbon gain, measured in normal air (350 μbar), to increase, whereas an increase to 700 μbar CO2, during the day, caused net dark CO2 fixation to cease. The increased CAM activity in response to water shortage may, at least to some extent, be directly related to the reduced carbon gain during daytime.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317239
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  • 4
    Electronic Resource
    Electronic Resource
    Induction of crassulacean acid metabolism in Mesembryanthemum crystallinum increases reproductive success under conditions of drought and salinity stress (1992)
    Springer
    Oecologia 92 (1992), S. 475-479 
    Details
    ISSN: 1432-1939
    Keywords: Crassulacean acid metabolism ; Mesembryanthemum ; Reproduction ; Water stress-δ13C ; value
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mesembryanthemum crystallinum L., an inducible crassulacean acid metabolism (CAM) plant, was grown for approximately 5 weeks following germination in well-watered, non-saline soil in a controlled-environment chamber. During this time, plants were characterized by C3 photosynthetic carbon metabolism. After the initial 5 weeks, CAM was induced by a combination of high soil salinity and reduced soil water content. One group of plants was allowed to engage in CAM by being continuously exposed to normal CO2-containing air (about 350–400 ppm). A second group of plants was deprived of ambient CO2 each night (12 h dark period) until completion of their life cycle, thereby minimizing potential carbon gain via dark CO2 fixation. The capacity to express CAM under conditions of drought and salinity stress markedly improved reproductive success: plants kept in normal CO2-containing air produced about 10 times more seeds than plants kept in CO2-free air during dark periods. Seeds from plants deprived of ambient CO2 overnight had more negative δ13C values than seeds from plants kept in normal air.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317838
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  • 5
    Electronic Resource
    Electronic Resource
    Activity and quantity of ribulose bisphosphate carboxylase-and phosphoenolpyruvate carboxylase-protein in two Crassulacean acid metabolism plants in relation to leaf age, nitrogen nutrition, and point in time during a day/night cycle (1982)
    Springer
    Planta 154 (1982), S. 309-317 
    Details
    ISSN: 1432-2048
    Keywords: Crassulacean acid metabolism ; Day/night cycle ; Kalanchoe ; Leaf age and CAM ; Mesembryanthemum ; Nitrogen nutrition ; Phosphoenolpyruvate carboxylase ; Ribulose bisphosphate carboxylase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Activity of ribulose 1,5-bisphosphate (RuBP) carboxylase in leaf extracts of the constitutive Crassulacean acid metabolism (CAM) plant Kalanchoe pinnata (Lam.) Pers. decreased with increasing leaf age, whereas the activity of phosphoenolpyruvate (PEP) carboxylase increased. Changes in enzyme activities were associated with changes in the amount of enzyme proteins as determined by immunochemical analysis, sucrose density gradient centrifugation, and SDS gel electrophoresis of leaf extracts. Young developing leaves of plants which received high amounts of NO 3 - during growth contained about 30% of the total soluble protein in the form of RuBP carboxylase; this value declined to about 17% in mature leaves. The level of PEP carboxylase in young leaves of plants at high NO 3 - was an estimated 1% of the total soluble protein and increased to approximately 10% in mature leaves, which showed maximum capacity for dark CO2 fixation. The growth of plants at low levels of NO 3 - decreased the content of soluble protein per unit leaf area as well as the extractable activity and the percentage contribution of both RUBP carboxylase and PEP carboxylase to total soluble leaf protein. There was no definite change in the ratio of RuBP carboxylase to PEP carboxylase activity with a varying supply of NO 3 - during growth. It has been suggested (e.g., Planta 144, 143–151, 1978) that a rhythmic pattern of synthesis and degradation of PEP carboxylase protein is involved in the regulation of β-carboxylation during a day/night cycle in CAM. No such changes in the quantity of PEP carboxylase protein were observed in the leaves of Kalanchoe pinnata (Lam.) Pers. or in the leaves of the inducible CAM plant Mesembryanthemum crystallinum L.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393908
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  • 6
    Electronic Resource
    Electronic Resource
    Changes in xanthophyll-cycle components and in fluorescence yield in leaves of a crassulacean-acid-metabolism plant, Clusia rosea Jacq., throughout a 12-hour photoperiod of constant irradiance (1990)
    Springer
    Planta 182 (1990), S. 181-185 
    Details
    ISSN: 1432-2048
    Keywords: Crassulacean acid metabolism ; Clusia ; Electron transport rate ; Nonradiative energy dissipation ; Xanthophyll cycle ; Zeaxanthin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The content of the xanthophylls violaxanthin, antheraxanthin and zeaxanthin, which are interconvertible in the so-called xanthophyll cycle in the chloroplasts, was determined in leaves of the crassulacean-acid-metabolism plant, Clusia rosea, at the end of a 12-h dark period and at three times during a 12-h photoperiod of constant illumination (200 μmol photons·m−2·s−1). Whereas the level of violaxanthin was high at the end of the dark period and that of zeaxanthin low, zeaxanthin increased and violaxanthin decreased during the early light period, when atmospheric CO2 was taken up rapidly by the leaves. In the middle of the light period, when net uptake of atmospheric CO2 was not observed, yet when decarboxylation of malic acid allowed for high rates of CO2 reduction in the chloroplasts, zeaxanthin was low and violaxanthin was high. At the end of the light period, when uptake of atmospheric CO2 re-occurred, zeaxanthin increased again and violaxanthin decreased. Measurements of chlorophyll-a fluorescence with a modulated fluorometer showed that the increases in the level of zeaxanthin during the early and late light period were paralleled by decreased rates of electron transport and by increased rates of nonradiative dissipation of excitation energy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00197108
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  • 7
    Electronic Resource
    Electronic Resource
    Gradient in the degree of Crassulacean acid metabolism within leaves of Kalanchoe daigremontiana (1987)
    Springer
    Planta 172 (1987), S. 88-90 
    Details
    ISSN: 1432-2048
    Keywords: Crassulacean acid metabolism ; Kalanchoe ; Leaf surface (lower, upper)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Leaves of the Crassulacean acid metabolism plant Kalanchoe daigremontiana Hamet et Perr., about 3.3 mm thick, showed higher rates of net CO2 exchange through the lower than through the upper surface during day and night, although the lower surface received only a small fraction of the light which was incident on the upper surface. Nocturnal acidification was more pronounced in cells from the lower than from the upper portion of leaves. The lower activity of the exposed side of these long-lived succulent leaves may be related to the potentially adverse effects of excessive light.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00403032
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  • 8
    Electronic Resource
    Electronic Resource
    The relationship between turgor pressure and titratable acidity in mesophyll cells of intact leaves of a Crassulacean-acid-metabolism plant, Kalanchoe daigremontiana Hamet et Perr (1987)
    Springer
    Planta 172 (1987), S. 487-493 
    Details
    ISSN: 1432-2048
    Keywords: Crassulacean acid metabolism ; Kalanchoe ; Tissue acidity ; Turgor pressure ; Water stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Day/night changes in turgor pressure (P) and titratable acidity content were investigated in the (Crassulacean-acid-metabolism (CAM) plant Kalanchoe daigremontiana. Measurements of P were made on individual mesophyll cells of intact attached leaves using the pressure-probe technique. Under conditions of high relative humidity, when transpiration rates were minimal, changes in P correlated well with changes in the level of titratable acidity. During the standard 12 h light/12 h dark cycle, maximum turgor pressure (0.15 MPa) occurred at the end of the dark period when the level of titratable acidity was highest (about 300 μeq H+·g-1 fresh weight). A close relationship between P and titratable acidity was also seen in leaves exposed to perturbations of the standard light/dark cycle. (The dark period was either prolonged, or else only CO2-free air was supplied in this period). In plants deprived of irrigation for five weeks, diurnal changes in titratable acidity of the leaves were reduced (ΔH=160 μeq H+·g-1 fresh weight) and P increased from essentially zero at the end of the light period to 0.02 MPa at the end of the dark period. Following more severe water stress (experiments were made on leaves which had been detached for five weeks), P was zero throughout day and night, yet small diurnal changes in titratable acidity were still measured. These findings are discussed in relation to a hypothesis by Lüttge et al. 1975 (Plant Physiol. 56,613-616) for the role of P in the regulation of acidification/de-acidification cycles of plants exhibiting CAM.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393864
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  • 9
    Electronic Resource
    Electronic Resource
    Synthesis and Structures of (N3)2Ga[(CH2)3NMe2], (N3)Ga[(CH2)3NMe2]2 and (N3)3Ga(NR3) (R = CH3, C2H5) (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2127-2134 
    Details
    ISSN: 1434-1948
    Keywords: Gallium ; Azides ; Chemical vapour deposition ; Gallium nitride ; Single source precursors ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis, properties and X-ray single crystal structure analysis of the intramolecularly adduct-stabilised organogallium bisazide (N3)2Ga[(CH2)3NMe2] (1), the mono azide (N3)Ga[(CH2)3NMe2]2 (2) and the trialkylamine adducts of triazidogallium of the type (N3)3Ga(NR3) (3a-d; R = alkyl) are reported. An unusual isomer 1b of compound 1 is described, which was obtained by slow cooling of the analytically pure neat liquid compound 1 to 0 °C. The new and unusual structure 1b can be regarded as a weak associate of dimers linked together by head-to-tail azide bridges. In contrast, compounds 2 and 3a-b (R = CH3, C2H5) are monomeric in the solid state. The suitability of the volatile compounds 1 and 2 as single source precursors to grow GaN thin films by chemical vapour deposition is compared, showing that preferentially oriented crystalline films can be obtained from compound 2 on sapphire substrates at 600-700 °C in vacuo (0.1 Pa). However the films have a grey rather than a transparent appearance, which is presumably due to N-deficiency owing to the lower N-content of the single molecule precursor 2 relative to 1.
    Additional Material: 5 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Synthesis and Reactions of a Chemical Model of the Urocanase ReactionDedicated to the memory of Wolfgang Oppolzer (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 410-416 
    Details
    ISSN: 0947-6539
    Keywords: enzyme catalysis ; nicotinamide-adenine dinucleotide ; reaction mechanisms ; urocanase ; urocanic acid ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using a convergent synthetic strategy starting from nicotinic acid and imidazole, we have prepared the (E) and (Z) isomers of 1-benzyl-3-carbamoyl-5-[2-(ethoxycarbonylmethylene)-2-(1-(p-to-lylsulfamoyl)imidazol-4-yl)ethyl]pyridinium bromide (21) as models of the urocanase reaction. Domino reactions of both (E)-21 and (Z)-21 led to the same spirocyclic compound, (3aRS)-11-[9-([D7]benzyl)-5-ethoxy-1-(p-tolylsulfamoyl)-1H,9H-furo[2,3-g]imidazo[5,4-f]isoquinolyl]carboxamide (33), which was isolated and spectroscopically characterised. A possible sequence of reactions leading to 33 shows a number of analogies to the conversions catalysed by the enzyme urocanase. Removal of the p-tolylsulfamoyl protecting group of (E)-21 and (Z)-21 under mild conditions led to the highly reactive model compounds (E)-4 and (Z)-4, which were identified by 1H NMR spectroscopy, but could not be isolated, owing to their instability. To facilitate the monitoring of the reaction cascade by NMR spectroscopy (Z)-21 was prepared in which the benzyl group was fully deuterated. Its deprotection to (Z)-4 started a reaction cascade, which led, after purification, to a main product. According to investigations by UV and 1H NMR spectroscopy it seems very likely that 1-([D7]benzyl)-3-carbamoyl-7-(ethoxycarbonylmethyl)-imidazo[4,5-f]isoquinolinium bromide (27) was formed. The presumed mechanism of its formation again shows similarities with the postulated mechanism of action of urocanase.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970030312
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