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  • Glutathione S-transferase  (2)
  • ATP4−  (1)
  • Chemistry  (1)
  • 1985-1989  (4)
  • 1
    ISSN: 1432-1424
    Keywords: K+ channel ; ATP ; ATP4− ; ADP3− ; RINm5F cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The31P-NMR technique has been used to assess the intracellular ratios and concentrations of mobile ATP and ADP and the intracellular pH in an insulin-secreting cell line, RINm5F. The single-channel current-recording technique has been used to investigate the effects of changes in the concentrations of ATP and ADP on the gating of nucleotide-dependent K+ channels. Adding ATP to the membrane inside closes these channels. However, in the continued presence of ATP adding ADP invariably leads to the reactivation of ATP-inhibited K+ channels, even at ATP4−/ADP3− concentration ratios greater than 7∶1. Interactions between ATP4− and ADP3− seem competitive. An increase in the concentration ratio ATP4−/ADP3− consistently evoked a decrease in the open-state probability of K+ channels; conversely a decrease in ATP4−/ADP3− increased the frequency of K+ channel opening events. Channel gating was also influenced by changes in the absolute concentrations of ATP4− and ADP3−, at constant free concentration ratios. ADP-evoked stimulation of ATP-inhibited channels did not result from phosphorylation of the channel, as ADP-β-S, a nonhydrolyzable analog of ADP, not only stimulated but enhanced ADP-induced activation of K+ channels, in the presence of ATP. Similarly, ADP was able to activate K+ channels in the presence of two nonhydrolyzable derivatives of ATP, AMP-PNP and βγmethylene ATP.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2048
    Keywords: Glutathione S-transferase ; Herbieide detoxification ; Suspension culture ; Zea (herbicide detoxification)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The metabolism of the s-triazine herbicide atrazine has been compared in Zea mays seedlings and cell suspension cultures. The rapid detoxification observed in the shoots of whole plants was not seen in the cultured cells. This difference in metabolism could be accounted for by the varying substrate specificities of the isoenzymes of glutathione S-transferase (EC 2.5.1.18) present in the plant and the cells. A single form of the enzyme isolated from leaf tissue conjugated both atrazine and the chloracetanilide herbicide metolachlor. However, the two isoenzymes present in suspension-cultured cells although active against metolachlor, showed no activity toward atrazine. Following purification, the major form of transferase present in the cells was physically similar to the enzyme isolated from leaf (Mr=55000). Both proteins were dimers of subunit Mr=26300, and with isoelectric points in the range pH 4.3-4.9. The minor form of the enzyme present in culture showed a greater specificity for metolachlor than the major species. In addition the overall activity and ratio of the two isoenzymes varied over the culture growth cycle. These findings illustrate the need for characterizing enzymes involved in herbicide detoxification in plant cell cultures.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Planta 175 (1988), S. 99-106 
    ISSN: 1432-2048
    Keywords: Detoxification (herbicide) ; Enzyme induction ; Glutathione S-transferase ; Herbicide antidote ; Zea (herbicide detoxification)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An antiserum to glutathione S-transferase (EC 2.5.1.18) from maize (Zea mays L.) responsible for herbicide detoxification has been raised in rabbit. The antiserum was specific to the Mr 26000 subunit of the enzyme from maize seedlings and suspension-cultured cells, and recognized the isoenzymes active toward both atrazine and metolachlor. When plants were treated for 24 h with the herbicide antidote N,N-diallyl-2-2-dich-loroacetamide (DDCA), enzyme activities toward metolachlor were doubled in the roots and this was associated with a 70% increase in immunodetectable protein. Translation of polysomal RNA in vitro showed that the increase in the transferase in root tissue was brought about by a ninefold increase in mRNA activity encoding the enzyme. Treatment of suspension-cultured cells with cinnamic acid, metolachlor and DDCA raised enzyme activities but did not increase synthesis of glutathione S-transferase. In cultured maize cells, enzyme synthesis was maximal in mid-logarithmic phase, coinciding with the highest levels of enzyme activity. When callus cultures were established from the shoots of a maize line known to conjugate chloro-s-triazines, enzyme activity towards atrazine was lost during primary dedifferentiation. However, levels of total immunodetectable enzyme and activity toward metolachlor were increased in cultured cells compared with the parent shoot tissue.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 17 (1988), S. 241-244 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The use of fast atom bombardment mass spectrometry has been demonstrated for the qualitative analysis of mixtures of dansylated amines and compared with high-performance liquid chromatography for the quantification of some individual amines from meat products.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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