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  • 1
    Electronic Resource
    Electronic Resource
    Characterization of a malate dehydrogenase in the cyanobacterium Coccochloris peniocystis (1991)
    Springer
    Archives of microbiology 156 (1991), S. 28-33 
    Details
    ISSN: 1432-072X
    Keywords: Cyanobacteria ; Coccochloris peniocystis ; Malate dehydrogenase ; Glyoxylate cycle ; TCA cycle ; Carbon metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A malate dehydrogenase (MDH) was characterized from the cyanobacterium Coccochloris peniocystis. The enzyme was purified approximately 180-fold and had a molecular weight of about 90000. The enzyme had a pH optimum of pH 6.7 to 7.5; a Km (malate) of 5.6 mM and Kms for NAD and NADP of 24 μM and 178 μM, respectively, although similar Vmax were obtained with either pyridine nucleotide. Enzyme activity was inhibited by ATP, citrate, oxalacetate, acetyl CoA and CoA. Enzyme assays with uniformly 14C-labelled malate caused no 14CO2 release, indicating this MDH is not a malic enzyme. Electrophoresis and S-200 gel filtration of the partially purified enzyme indicated a single MDH was present in this preparation. A second, less abundant, MDH was present in crude extracts. The presence of MDH in this organism is consistent with the operation of a glyoxylate cycle which, in the absence of a TCA cycle, would provide organic acids required in secondary carbon metabolism. ATP inhibition of MDH may allow for light regulation of MDH activity since, in the light, oxaloacetic acid is generated by phosphoenolpyruvate carboxylase activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00418183
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  • 2
    Electronic Resource
    Electronic Resource
    Formation and metabolism of glycolate in the cyanobacterium Coccochloris peniocystis (1992)
    Springer
    Archives of microbiology 157 (1992), S. 375-380 
    Details
    ISSN: 1432-072X
    Keywords: Cyanobacteria ; Coccochloris peniocystis ; Glycolate metabolism ; Photosynthesis ; Glyoxylate cycle ; Photorespiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The formation and metabolism of glycolate in the cyanobacterium Coccochloris peniocystis was investigated and the activities of enzymes of glycolate metabolism assayed. Photosynthetic 14CO2 incorporation was O2 insensitive and no labelled glycolate could be detected in cells incubated at 2 and 21% O2. Under conditions of 100% O2 glycolate comprised less than 1% of the acid-stable products indicating ribulose 1,5 bisphosphate (RuBP) oxidation only occurs under conditions of extreme O2 stress. Metabolism of [1-14C] glycolate indicated that as much as 62% of 14C metabolized was released as 14CO2 in the dark. Metabolism of labelled glycolate, particularly incorporation of 14C into glycine, was inhibited by the amino-transferase inhibitor amino-oxyacetate. Metabolism of [2-14C] glycine was not inhibited by the serine hydroxymethyltransferase inhibitor isonicotinic acid hydrazide and little or no labelled serine was detected as a result of 14C-glycolate metabolism. These findings indicate that a significant amount of metabolized glycolate is totally oxidized to CO2 via formate. The remainder is converted to glycine or metabolized via a glyoxylate cycle. The conversion of glycine to serine contributes little to glycolate metabolism and the absence of hydroxypyruvate reductase confirms that the glycolate pathway is incomplete in this cyanobacterium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00248684
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  • 3
    Electronic Resource
    Electronic Resource
    The effect of temperature and oxygen on the CO2 compensation point of the marine alga Ulva lactuca (1984)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 7 (1984), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The CO2 compensation point of Ulva lactuca frond sections has been measured in artificial seawater using a sensitive gas-chromatographic method. Under nitrogen the compensation point remained relatively constant at 3–6 cm3 m−3 at temperatures from 10 to 30°C while in air-saturated medium (0.3 kg m−3 O2) the compensation point rose from 5 cm3 m−3 at 10°C to 11 cm3 m−3 at 30°C. These responses of the compensation point to temperature and oxygen concentration indicate that there is little photorespiratory CO2 loss in this marine macroalga, and the low values of these compensation points indicate that inorganic carbon is actively accumulated by the plant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1365-3040.ep11592150
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  • 4
    Electronic Resource
    Electronic Resource
    Serine synthesis in cyanobacteria by a nonphotorespiratory pathway (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 100 (1997), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The pathway of serine synthesis was investigated in six species of cyanobacteria: Anabaena cylindrica, A. variabilis, A. flos-aquae, Coccochloris peniocystis, Gleo-capsa alpicola and Phormidium molle. Activity of the enzymes phosphoglycerate (PGA) dehydrogenase (EC 1.1.1.95), phosphoserine transaminase (EC 2.6.1.52) and phosphoserine phosphatase (EC 3.1.3.3) was detected in vitro in all species, but no PGA phosphatase (EC 3.1.3.20) or hydroxypyruvate reductase (EC 1.1.1.26) activity could be detected. Metabolism of [1-14C]PGA by cell-free extracts of C. peniocystis resulted in the labelling of serine, alanine and aspartate, which represented 84, 11 and 4% of the labelled amino acid pool, respectively, Labelled serine isolated from these experiments was 100% carboxyl-labelled indicating that it was formed directly from PGA. The labelling of serine was markedly reduced by 5 mM phosphoserine. These in vitro findings indicate that cyanobacteria are capable of synthesizing serine directly from PGA, independent of ribulose-1.5-bisphosphate oxidation, and that the route of serine synthesis via phosphohydroxypyruvate and phosphoserine is the predominant pathway in these organisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1997.tb03463.x
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  • 5
    Electronic Resource
    Electronic Resource
    The inhibition of the carbon concentrating mechanism of the green alga Chlorella saccharophila by acetazolamide (2001)
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 111 (2001), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The effects of the carbonic anhydrase (CA) inhibitors acetazolamide (AZ) and dextran-bound sulfonamide (DBS) on HCO3−-dependent O2 evolution in Chlorella saccharophila were evaluated. Addition of 4 μM AZ or 0.4 mg ml−1 DBS to photosynthesizing cells reduced the O2 evolution rate at low dissolved inorganic carbon (DIC) concentration, decreased the size of the intracellular acid-labile carbon pool, and decreased the apparent affinity of the cells for DIC. Measurement of the whole-cell affinity of cells for CO2 and HCO3− in the presence and absence of inhibitors indicated that active HCO3− transport was inhibited by AZ and DBS. The inhibition of HCO3− transport was independent of the inhibition of external and internal CA. These results suggest that the active uptake of HCO3− occurs initially by the interaction of HCO3− and a CA-like transporter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.2001.1110413.x
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  • 6
    Electronic Resource
    Electronic Resource
    The inhibition of photosynthesis and photorespiration in isolated mesophyll cells of Phaseolus and Lycopersicon by reduced osmotic potentials (1983)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 57 (1983), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Mesophyll cells isolated from Phaseolus vulgaris and Lycopersicon esculentum show decreasing photosynthetic rates when suspended in media containing increasing concentrations of osmoticum. The photosynthetic activity was sensitive to small changes in osmotic potential over a range of sorbitol concentrations from 0.44 M (−1.08 MPa) to 0.77 M (−1.88 MPa). Photorespiration assayed by 14CO2 release in CO2-free air and by 14CO2 release from the oxidation of [1–14C] glycolate also decreased as the osmotic potential of the incubation medium was reduced. The CO2 compensation points of the cells increased with increasing concentration of osmoticum from approximately 60 μ I−11 at −1.08 MPa to 130 μl 1−1 for cells stressed at −1.88 MPa. Changes in photosynthetic and photorespiratory activities occurred at moderate osmotic potentials in these cells suggesting that in whole leaves during a reduction in water potential, non- stomatal inhibition of CO2 assimilation and glycolate pathway metabolism occurs simultaneously with stomatal closure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1983.tb00724.x
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  • 7
    Electronic Resource
    Electronic Resource
    Demonstration of C3-photosynthesis in a bluegreen alga, Coccochloris peniocystis (1980)
    Springer
    Planta 149 (1980), S. 318-320 
    Details
    ISSN: 1432-2048
    Keywords: Coccochloris ; CO2 fixation ; Photosynthesis (bluegreen alga)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Air-grown cells of the cyanobacterium, Coccochloris peniocystis Kutz were exposed to [14C] bicarbonate in the light for periods of 0.5 to 2.0 s followed by longer exposures to unlabelled bicarbonate. Although C4 acids are among the initial products of photosynthesis, the kinetics of tracer movement during the pulse-chase experiments demonstrate that the principal mechanism of CO2 fixation in this alga is the C3-pathway.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00384573
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  • 8
    Electronic Resource
    Electronic Resource
    Light-dependent bicarbonate uptake and CO2 efflux in the marine microalga Nannochloropsis gaditana (2000)
    Springer
    Planta 211 (2000), S. 43-49 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Bicarbonate transport – Carbonic anhydrase – CO2 efflux – Eustigmatophyceae – Inhibitor (DIDS) –Nannochloropsis– (HCO−3 uptake)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract.  Inorganic carbon (Ci) uptake and efflux has been investigated in the marine microalga Nannochloropsis gaditana Lubian by monitoring CO2 fluxes in cell suspensions using mass spectrometry. Addition of H13CO3 − to cell suspensions in the dark caused a transient increase in the CO2 concentration in the medium far in excess of the equilibrium CO2 concentration. The magnitude of this release was dependent on the length of time the cells had been kept in the dark. Once equilibrium between the Ci species had been achieved, a CO2 efflux was observed after saturating light intensity was applied to the cells. External carbonic anhydrase (CA) was not detected nor does this species demonstrate a capacity to take up CO2 by active transport. Photosynthetic O2 evolution and the release CO2 in the dark depend on HCO3 − uptake since both were inhibited by the anion exchange inhibitor, 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid (DIDS). The bicarbonate uptake mechanism requires light but can also continue for short periods in the dark. Ethoxyzolamide, a CA inhibitor, markedly inhibited CO2 efflux in the dark, indicating that CO2 efflux was dependent upon the intracellular dehydration of HCO3 −. These results indicate that Nannochloropsis possesses a bicarbonate uptake system which causes the accumulation of high intracellular Ci levels and an internal CA which maintains the equilibrium between CO2 and HCO3 − and thus causes a subsequent release of CO2 to the external medium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250000254
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  • 9
    Electronic Resource
    Electronic Resource
    Active uptake of CO2 during photosynthesis in the green alga Eremosphaera viridis is mediated by a CO2-ATPase (1992)
    Springer
    Planta 188 (1992), S. 539-545 
    Details
    ISSN: 1432-2048
    Keywords: ATPase ; Bicarbonate transport ; Carbon dioxide ; Carbonic anhydrase ; Eremosphaera ; Inor ganic carbon (dissolved)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mass spectrometry was used to investigate the uptake of CO2 in Eremosphaera viridis DeBary. Upon illumination, cells preincubated at pH 7.5 with 100 μM dissolved inorganic carbon (DIC) rapidly depleted almost all the free CO2 from the medium. Rapid equilibrium between HCO 3 - and CO2 occurred upon addition of bovine carbonic anhydrase (CA) to the medium, showing that CO2 depletion resulted from a selective uptake of CO2 rather than an uptake of all inorganic carbon species. Glycolaldehyde (10 mM) completely inhibited CO2 fixation but had little effect on CO2 transport. Transfer of glycolaldehyde-treated cells to the dark caused a rapid efflux of CO2 from the unfixed intracellular DIC pool which was found to be at least threeto sixfold higher in concentration than that of the external medium. These results indicate that E. viridis actively transports CO2 against a concentration gradient. No external CA was detected in these cells either by potentiometric or mass-spectrometric assay. In the absence of external CA, the rate of photosynthetic O2 evolution in the pH range 7.5 to 8.0 did not exceed the calculated rate of CO2 supply, indicating a limited capacity for HCO2 uptake in these cells. Electrophysiological measurements indicate that CO2 uptake is electrically silent and thus is not a consequence of H+-CO2 symport activity. Microsomal membranes isolated from Eremosphaera showed ATPase activity which was enhanced by CO2. These results indicate that active CO2 uptake is mediated by an ATPase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00197046
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  • 10
    Electronic Resource
    Electronic Resource
    The effect of osmotic stress on the oxidation of glycolate by the blue-green alga Anacystis nidulans (1975)
    Springer
    Planta 124 (1975), S. 125-133 
    Details
    ISSN: 1432-2048
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Anacystis nidulans Richt. was shown to assimilate glycolic acid, and uptake was light-stimulated. In the dark 90% of the glycolate taken up was oxidised to CO2. Both light and dark uptake was completely inhibited by α-hydroxysulphonates but was unaffected by isonicotinyl hydrazide. 3-(3,4-Dichlorophenyl)-1,1-dimethyl urea (DCMU) reduced the rate of light uptake but not to the uptake level of the dark control. Subjecting the algal cells to osmotic stress by incubation in 0.6 M mannitol for 1 h, which reduces the photosynthetic activity of this alga, causes an 80% reduction in both light and dark glycolate uptake although the uptake of glyoxylate, formate, acetate, and glycine is not markedly affected. Osmotic stress had no effect on the uptake and metabolism of glycolate by Anabaena flos-aquae (Lyngbye) Bred. and Oscillatoria sp. The activity of glycolate dehydrogenase in Anacystis was also reduced by osmotic shock while the activity of other enzymes was unaffected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00384754
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