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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 148 (1987), S. 321-327 
    ISSN: 1432-072X
    Keywords: Cyanophage ; Cyanobacterium (Nostoc muscorum) ; Metabolic changes ; Role of light ; Redox state of thioredoxin ; Glucose-6-phosphate dehydrogenase ; Phosphoribulokinase ; Glutamine synthetase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The development of cyanophage N-1 in the N2-fixing cyanobacterium Nostoc muscorum is dependent on light. The redox state of thioredoxin m was altered in phage infected cells, with the proportion of reduced thioredoxin increasing during the eclipse period. In one step growth experiments, the specific activity of glucose-6-phosphate dehydrogenase increased transiently during the eclipse period, whereas that of glutamine synthetase increased towards the end of the eclipse period (2–4h after infection) then remained high until the end of the latent period (about 7 h after infection). The rate of respiratory O2 uptake was maintained until the end of the latent period. In contrast, the specific activity of phosphoribulokinase and the rate of photosynthetic O2 evolution began to decrease towards the end of the eclipse period and later than the level of extractable protein began to decrease. Nitrogenase activity remained high throughout the eclipse period then decreased rapidly after 5 h. The level of glutamine synthetase protein decreased in parallel with the decrease in total extractable protein, whereas the level of thioredoxin m protein decreased more slowly.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-072X
    Keywords: Blue-green algae ; Cyanobacteria ; Glutamine synthetase ; Light-modulation ; Anabaena cylindrica ; NH 4 + -deactivation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Extractable glutamine synthetase activity of the cyanobacterium Anabaena cylindrica was reduced by approximately 50% when N2-fixing cultures were treated with 10 mM NH 4 + or were placed in darkness. The deactivated enzyme could be rapidly reactivated (within 5 min) by adding 40 mM 2-mercaptoethanol to the biosynthetic reaction mixture. The enzyme could also be reactivated in vivo by replacing the culture in light or by removing NH 4 + . When the enzyme was deactivated by simultaneously adding NH 4 + and placing the culture in darkness, reactivation occurred on reillumination and removal of NH 4 + . The removal of NH 4 + in darkness did not result in reactivation. On in vitro reactivation of glutamine synthetase from dark or NH 4 + -treated cultures the maximum glutamine synthetase activity observed frequently exceeded that of glutamine synthetase extracted from untreated cultures. Anacystis nidulans showed a similar type of reversible dark deactivation to A. cylindrica but Plectonema boryanum and a Nostoc did not. With A. cylindrica, a direct positive correlation between the size of the intracellular pool of glutamate and biosynthetic glutamine synthetase activity occurred during light/dark shifts, and on treatment with NH 4 + . The changes in activity of glutamine synthetase in A. cylindrica in response to light resemble in some respects the light modulation of enzymes of the oxidative and reductive pentose phosphate pathways noted in cyanobacteria by others.
    Type of Medium: Electronic Resource
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