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  • 1
    Electronic Resource
    Electronic Resource
    Measurement of the glycogen synthetic pathway in permeabilized cells of cyanobacteria (2001)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 194 (2001), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A simple, rapid and reliable procedure for permeabilizing cyanobacterial cells and measuring the glycogen synthetic pathway in situ, is presented. Cells from Anabaena sp. strain PCC 7120 were permeabilized with a mixture of toluene:ethanol (1:4 v/v). Fluorescence microscopy of cells incubated with fluorescein diacetate showed Anabaena non-permeabilized cells as green fluorescents, whereas permeabilized (viable) cells exhibited the intrinsic red fluorescence. Labelled α-1,4-glucan was recovered when permeabilized cells were incubated with the substrates of ADP-glucose pyrophosphorylase or glycogen synthase. The kinetic and regulatory properties of both enzymes could be reproduced in situ. The simplicity of the procedure and the ability to measure in situ glucan fluxes show the methodology as useful for studying the intracellular regulation of storage polysaccharides in a photosynthetic prokaryote.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.2001.tb09438.x
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  • 2
    Electronic Resource
    Electronic Resource
    Interaction of divalent metal ions with the NADP+-malic enzyme from maize leaves (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 81 (1991), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The effect of several metal ions on NADP+-malic enzyme (EC 1.1.1.40) purified from Zea mays L. leaves was studied Mg2+, Mn2+, Co2+ and Cd2+ were all active metal cofactors. The malic enzyme from maize has a moderately high intrinsic preference for Mn2+ relative to Mg2+ at pH 7.0 and 8.0 Negative cooperativity detected in the binding of Mg2+ at pH 7.0 and 8.0 and in the binding of Mn2+ at pH 7.0 suggests the existence of at least two binding sites with different affinity. All of the activating metal ions have preference for octahedral coordination geometry and have ionic radii of 0.86–1.09 Å. The ions that act as inhibitors are outside this range and/or are incapable of octahedral coordination. Ba2+, Sr2+, Cd2+, Ca2+, Be2+, Ni2+, Cu2+, Zn2+, Co2+, Hg2+ showed mixed-type inhibition. The reciprocal of their K1 values follow the order of their apparence in the Irving-Williams series of stability that derives in part from size effects. It is suggested that the size of the ions may play a partial role in determining the strength of the metal interaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1991.tb05085.x
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  • 3
    Electronic Resource
    Electronic Resource
    Oligomeric enzymes in the C4 pathway of photosynthesis (1990)
    Springer
    Photosynthesis research 26 (1990), S. 161-170 
    Details
    ISSN: 1573-5079
    Keywords: NAD-malic enzyme ; NADP-malic enzyme ; NADP-malic dehydrogenase ; pyruvate ; phosphate dikinase ; regulatory protein ; phosphoenolpyruvate carboxylase ; protein structure ; enzyme regulation ; C4 metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This review deals with the factors controlling the aggregation-state of several enzymes involved in C4 photosynthesis, namely phosphoenolpyruvate carboxylase, NAD-and NADP-malic enzyme, NADP-malic dehydrogenase and pyruvate, phosphate dikinase and its regulatory protein. All of these enzymes are oligomeric and have been shown to undergo changes in their quaternary structure in vitro under different conditions. The activity changes linked to variations in aggregation-state are discussed in terms of their putative physiological role in the regulation of C4 metabolism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00033129
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  • 4
    Electronic Resource
    Electronic Resource
    Involvement of thiol groups in the activity of phosphoenolpyruvate carboxylase from maize leaves (1984)
    Springer
    Photosynthesis research 5 (1984), S. 215-226 
    Details
    ISSN: 1573-5079
    Keywords: Cysteine modification ; Maize leaf ; Phosphoenolpyruvate carboxylase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Purified maize leaf phosphoenolpyruvate carboxylase (EC 4.1.1.31) was completely inactivated by several thiol-modifying reagents, including, CuCl2, CdCl2 and N-ethylmaleimide. The inactivation by CuCl2 could be reversed by dithiothreitol, suggesting the involvement of vicinal dithiols in the inactivation process. Complete inactivation of phosphoenolpyruvate carboxylase was correlated with the incorporation of two mol (3H)N-ethylmaleimide per 100-kilodalton subunit. The total protection of the enzyme against N-ethylmaleimide inactivation afforded by the substrate, phosphoenolpyruvate, was correlated with the protection of one mol (3H)N-ethylmaleimide reactive residue per mol subunit. The complete inactivation of phosphoenolpyruvate carboxylase by N-ethylmaleimide and the protection afforded by phosphoenolpyruvate against modification suggest the presence of an essential cysteine residue in the catalytic site of the C4 leaf enzyme.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00030021
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  • 5
    Electronic Resource
    Electronic Resource
    The role of inorganic phosphate in the regulation of C4 photosynthesis (1993)
    Springer
    Photosynthesis research 35 (1993), S. 205-211 
    Details
    ISSN: 1573-5079
    Keywords: C4 photosynthesis ; inorganic phosphate ; metabolic regulation ; carbohydrate metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Inorganic phosphate participates in many fundamental processes within the plant cell. Its broad influence on plant metabolism is related to such key operations as metabolite transport, enzyme regulation and carbohydrate metabolism in general. This review discusses these topics with special emphasis on the role assigned to this ubiquitous anion within the C4 pathway of photosynthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00016551
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  • 6
    Electronic Resource
    Electronic Resource
    Hysteretic properties of NADP-malic enzyme from sugarcane leaves (1992)
    Springer
    Photosynthesis research 31 (1992), S. 89-97 
    Details
    ISSN: 1573-5079
    Keywords: malic enzyme ; hysteresis ; C4 metabolism ; sugarcane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract NADP-malic enzyme highly purified from sugarcane leaves exhibited hysteretic properties. This behavior resulted in a lag phase during activity measurement of the enzyme preincubated in the absence of substrates. The lag was inversely proportional to the protein concentration during preincubation, which suggests that changes in the aggregational state of the enzyme are responsible for hysteresis. The pH conditions as well as the presence of different compounds in the preincubation medium modified the hysteretic properties of the enzyme. Mg2+ eliminated the lag period and increased the enzyme activity by nearly 2-fold. NADP+, 3-phosphoglycerate, ATP and dithiothreitol shortened the lag phase. The substrate l-malate inhibited the enzyme by decreasing the steady state velocity and increasing the lag time in a concentration-dependent manner. NADPH, triose-phosphates and high ionic strength increased the lag phase. Results are consistent with the view that the level of different metabolites and the pH conditions at the chloroplast regulate the activity of NADP-malic enzyme in a coordinate and effective manner.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00028786
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  • 7
    Electronic Resource
    Electronic Resource
    Molecular cloning and expression of the gene encoding ADP-glucose pyrophosphorylase from the cyanobacteriumAnabaena sp. strain PCC 7120 (1992)
    Springer
    Plant molecular biology 20 (1992), S. 37-47 
    Details
    ISSN: 1573-5028
    Keywords: ADP-glucose pyrophosphorylase ; Anabaena 7120 ; Escherichia coli ; gene cloning ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Previous studies have indicated that ADP-glucose pyrophosphorylase (ADPGlc PPase) from the cyanobacteriumAnabaena sp. strain PCC 7120 is more similar to higher-plant than to enteric bacterial enzymes in antigenicity and allosteric properties. In this paper, we report the isolation of theAnabaena ADPGlc PPase gene and its expression inEscherichia coli. The gene we isolated from a genomic library utilizes GTG as the start codon and codes for a protein of 48347 Da which is in agreement with the molecular mass determined by SDS-PAGE for theAnabaena enzyme. The deduced amino acid sequence is 63, 54, and 33% identical to the rice endosperm small subunit, maize endosperm large subunit, and theE. coli sequences, respectively. Southern analysis indicated that there is only one copy of this gene in theAnabaena genome. The cloned gene encodes an active ADPGlc PPase when expressed in anE. coli mutant strain AC70R1-504 which lacks endogenous activity of the enzyme. The recombinant enzyme is activated and inhibited primarily by 3-phosphoglycerate and Pi, respectively, as is the nativeAnabaena ADPGlc PPase. Immunological and other biochemical studies further confirmed the recombinant enzyme to be theAnabaena enzyme.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00029147
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  • 8
    Electronic Resource
    Electronic Resource
    Involvement of arginine residues in the allosteric activation and inhibition ofSynechocystis PCC 6803 ADPglucose pyrophosphorylase (1992)
    Springer
    The protein journal 11 (1992), S. 119-128 
    Details
    ISSN: 1573-4943
    Keywords: ADPglucose pyrophosphorylase ; cyanobacteria ; arginine modification ; regulatory site
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract ADPglucose pyrophosphorylase (EC 2.7.7.27) from the cyanobacteriumSynechocystis PCC 6803 was desensitized to the effects of allosteric ligands by treatment with the arginine reagent, phenylglyoxal. Enzyme modification by phenylglyoxal resulted in inactivation when the enzyme was assayed under 3P-glycerate-activated conditions. There was little loss of the catalytic activity assayed in the absence of activator. Pi, 3P-glycerate, and pyridoxal-P were able to protect the enzyme from inactivation, whereas substrates gave minimal protection. The protective effect exhibited by Pi and 3P-glycerate was dependent on effector concentration. MgCl2 enhanced the protection afforded by 3P-glycerate. The enzyme partially modified by phenylglyoxal was more resistant to 3P-glycerate activation and Pi inhibition than the unmodified form.V max at saturating 3P-glycerate concentrations and the apparent affinity of the enzyme toward Pi were decreased upon phenylglyoxal modification. Incorporation of labeled phenylglyoxal into the enzyme was proportional to the loss of activity. Pi and 3P-glycerate nearly completely prevented incorporation of the reagent to the protein. Results suggest that one arginine residue per mol of enzyme subunit is involved in the binding of allosteric effector in the cyanobacterial ADPglucose pyrophosphorylase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01025217
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